####018007895#### FXUS63 KMQT 171725 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 125 PM EDT Sat May 17 2025 .KEY MESSAGES... - Light rain or drizzle possible into Sunday morning, mainly overthe northern half of the U.P. - Dry period expected to begin Monday and linger through at least Wednesday. High temperatures in this period are expected mostly in near or in the 50s to low 60s each day. - Some frost is possible in the interior west next week. && .SHORT TERM /THROUGH TODAY/... Issued at 124 PM EDT Sat May 17 2025 Vertically stacked low is currently positioned over Lake Huron per RAP analysis and GOES water vapor imagery. A few waves are noted rotating around the circulation, which has supported mostly cloudy skies over the region under northwesterly flow. Just upstream, a weak frontal boundary is noted with post frontal temperatures ~10 degrees colder than the 50s observed across Upper Michigan. Spotty showers have also been observed this morning, mainly across the east, but activity has waned through the day. For the rest of the afternoon and into the evening, the upstream cold front will push east, helping to kick the surface low east as well. Pressure rises in the wake of the front will result in increasing northeast winds, particularly in the Keweenaw and by Lake Superior. Suspect ~30mph winds will be common in these spots, with upwards of 35-40mph being possible north of Houghton. Elsewhere, expecting near 20 mph winds. The occasional shower or pocket of drizzle is also expected given the continued moist cyclonic and upslope flow into and over the northern half of the forecast area. Some additional heating may also occur over the interior portions of central and east, but overall temperatures look to have peaked today and should begin to slowly fall west to east. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Issued at 401 AM EDT Sat May 17 2025 The extended period is expected to be fairly quiet as high pressure ridging from a Hudson Bay high dominates the start of the work week, before wrap around moisture from a low lifting into southern Ontario brings some more light rain showers back to the area to end the work week. Because of the northerly air being cycled over our area next week, expect below normal temperatures, although with dry conditions Monday and Tuesday, it is possible we could see elevated fire weather concerns those days, particularly over the interior west. Additional details follow below. The last of the precipitation from this weekend ends Sunday night over the northern tier of the U.P. as high pressure ridging builds in from a descending Hudson Bay high. By Monday, expect mostly sunny to partly cloudy skies as ridging is projected to keep a developing low pressure system over the Central Plains well away from our region. Given the dry Canadian airmass, even though high temperatures are expected to mainly get in the upper 40s to upper 50s, expect RHs to tank into the mid 20 percents across the interior areas; this includes even the interior east, although the driest conditions are currently expected over the interior west Monday afternoon. With the pressure gradient between the Hudson Bay high and developing low pressure over the Central Plains being fairly modest, we could see northeasterly gusts up to 20 knots across the area by Monday afternoon. We have the same song and dance on Tuesday too, although RHs look to be even drier (getting down to around 20% in the interior west), temperatures look to be a couple of degrees warmer, and wind gusts could be a few mph faster. Overall, thinking we will see at least limited fire weather concerns Monday and Tuesday if not elevated concerns (particularly Tuesday over the interior west); will keep an eye on this part of the forecast as we approach early next week. Our next chance at precipitation looks to come beginning Wednesday next week as a mid to upper level low over the Upper Great Lakes attempts to phase with the lower levels of the low moving from the Central Plains to the Mid-Atlantic. While models are trending toward a wetter solution for the end of the work week, a soaking rainfall is still not expected as moisture will be somewhat limited; wouldn't be surprised if most of the precipitation is forced by upslope flow (kind of what we will see today into Sunday). With cloud cover remaining over the area, expect high temperatures to be limited to around 50 (or less) along Lake Superior to generally the lower 60s in the south central. While we do start to see ridging beginning to build in at the end of the work week, we may also see the light precipitation continue until next weekend. One more thing worth noting in the extended period: we may see some frost develop over the interior west during the overnight hours next week. With lows projected to get down into the upper 20s to lower 30s Sunday night and onward, we could see patches to potentially even areas of frost develop over the interior west during the overnight hours; be sure to cover the plants you want to keep safe. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 124 PM EDT Sat May 17 2025 Abundant low level moisture will continue to support MVFR and IFR ceilings in this period at all sites. Periods of light rain or drizzle are expected as well, mainly this afternoon and evening, which may result in MVFR visibilities. Overnight, precipitation should come to an end while low ceilings linger. Gusty northwest winds this afternoon near 20-25kts are also expected. As these shift to the north overnight, winds should begin to relax at KIWD/KCMX. && .MARINE... Issued at 124 PM EDT Sat May 17 2025 Surface low spinning over the area with a cold front pressing in from the west will yield mostly northwest winds this afternoon and evening, increasing to near or to low end gale strength. Overall, gale potential looks to be confined between the east end of Isle Royale to the tip of the Keweenaw, but some gales could be observed elsewhere. Confidence in this is low (<25% chance), so the inherited gale warning was left as is. After the front passes tonight, northerly winds will gradually fall into Sunday, reaching <20kts lake-wide by Sunday afternoon. As a high shifts to near Hudson Bay afterwards, northeast winds will predominately prevail early next week. Increases in pressure gradient forces thanks to the high to the northeast and a low spinning to the south, coupled with daytime heating in Minnesota/Wisconsin will result in stronger northeast winds developing across the west half, pressing down into the Duluth Harbor Monday and Tuesday. Most deterministic guidance peaks winds near 30kts, but the latest EC ensemble suggests 10-60% for gales (increasing east to west down to the harbor) Monday and to near 80% for Tuesday. Similar probabilities are noted in the NBM. The stronger winds may yield seas building to 8ft or higher. As a low pressure over the Upper Great Lakes tries to phase with the lower levels of the low moving from the Central Plains to the Mid- Atlantic Wednesday into Thursday, expect northeast winds of 20 to 25 knots to continue over the lake Tuesday night into Wednesday, before the winds turn more northerly later Wednesday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Warning until 8 PM EDT this evening for LSZ264. Lake Michigan... None. && $$ SHORT TERM...JTP LONG TERM...TAP AVIATION...JTP MARINE...JTP ####018007292#### FXUS62 KILM 171726 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 125 PM EDT Sat May 17 2025 .SYNOPSIS... Above normal temperatures near record highs are possible today. A weak cold front, which may be accompanied by a few showers and thunderstorms will move across the area tonight. Next week will start out dry and warm with increasing rain chances Tuesday and Wednesday ahead of a cold front. Drier and cooler conditions return late next week. && .UPDATE... Decaying convection to the west expected to have little impact on the area today, though isolated storms are possible. Overall, going forecast has a good handle on latest expectations but did make small tweaks to max T and winds. Still a warm day on tap but perhaps a shade cooler with debris clouds moving in from the west. && .NEAR TERM /THROUGH TONIGHT/... A strong system/cold front currently moving across the Tennessee Valley and producing significant convection will seemingly have little to work with later today and this evening as it crosses our area. Overall pops remain minimal and if anything near the coast later this afternoon for just a couple of hours. The extensive cloud cover however seems to have taken a toll on guidance with regards to high temperature guidance as even the 90th percentile NBM numbers are trending downward. Still if enough breaks in the cloud cover occur a site or two could thread the needle and tie or break a record. The official forecast has been trended downward as well. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Front stalls in the area Sun and Mon as the surface boundary ends up parallel to the flow aloft. There is a lone shortwave moving through the zonal flow aloft on Sun, but the timing of the PVA ahead of it is prior to peak heating. The best moisture/dynamics with the shortwave pass to the south, further decreasing the potential for any affects locally. Deep, dry and and mid-level capping (post wave subsidence) will keep the region dry Sun with highs 7-10 degrees above normal. Deep westerly flow will keep the sea breeze pinned near the coast, ensuring much of the area remains on the warm side. Somewhat cooler air follows the passage of the shortwave, which helps push the stalled front a little farther south. This drops Sun night lows close to normal. Front lingers south of the area Mon morning but then starts to work its way north during the next. Flow aloft starts to amplify as weak 5h ridge expands north over the Deep South. Shortwave topping the ridge Mon induces weak surface cyclogenesis which then helps lift the front across the area. Not enthused about rain chances on Mon. Forecast soundings show a lot of dry air below 500mb and even with another day of temperatures well above normal the abundant dry air will keep SBCAPE AOB 200 J/kg. Even the development of a resultant sea breeze will not be enough to generate any convection. Guidance does suggest potential for MCS development Mon evening in the western Carolinas which then migrates east-southeast. If this feature does develop it would be in a weakening state as it approaches the local area. The environment doe not improve much from earlier in the day, the MCS will bring an increase in mid-level moisture with it, but the lack of surface based instability and marginal laps rates will likely be the end of any weak convection trying to move in from the northwest. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Front lingers north of the local area Tue/Wed as stacked low takes shape across the central CONUS. Honest rain chances Tue, although limited moisture will keep coverage in the chance realm. Rain chances ramp up Wed with much more moisture in the region as a cold front approaches. Precipitable water surges to almost 2" which is near 170% of normal, for comparison Tue is "only" about 130% of normal. Frontal convergence and divergence aloft as the 5h trough approaches from the west will further enhance the environmental parameters. Storms will be moving at a good clip and higher LCLs will limit warm cloud layer depth despite a freezing level near 14k ft. Not really a flood kind of event, but given the low level dry air, inverted V sounding, high freezing layer and DCAPE around 700 J/kg cannot rule out a damaging wind gust, but widespread severe seems unlikely, especially with a low level jet struggling to hit 30kt. Cold front moves across the area Wed evening, lagging the convective line, and is followed by a much drier and cooler air mass. Although there will be a cutoff low over the Northeast or Mid- Atlantic region the abundance of dry air will limit any potential shower activity associated with the base of the 5h trough and any associated shortwaves. The week ends dry with temperatures below normal. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... VFR conditions expected through the period. Convective coverage associated with the front moving through this afternoon and tonight looks very limited so no significant impacts expected. Extended Outlook...VFR conditions are expected through much of the period but a frontal system could bring scattered showers and storms with restrictions on Wednesday. && .MARINE... Through Tonight... Southwest winds on the increase this morning as the gradient increases ahead of a significant cold front to the west. Speeds will increase to an eventual 15-20 knots this afternoon and evening. Significant seas will be 2-4 feet for most of the day and increase to 3-5 feet this evening with the slightly stronger winds. Elements should remain below headline criteria. Sunday through Wednesday... Winds will be on the low end of the 10-15 kt range for much of the forecast. Front stalls in the area, weakening the gradient and leading to changeable wind direction. The daily sea breeze will have the biggest impact on the wind field Sun-Tue. On Wed an approaching cold front enhances the gradient with speeds rising into the 15-20 kt range in the afternoon and evening. Seas will run 2-3 ft through the first part of next week before the increase in southwest winds starts building seas. It is possible headlines will be needed for seas later Wed given the 12+ hour duration of enhanced winds. Seas will be a mix of a south to southwest wind wave and southeast swell with the wind wave becoming much more dominant Wed. && .CLIMATE... High temperature records may be challenged again today as anomalously warm air overspreads the region ahead of a cold front. Record highs for our four climate sites are as follows: Wilmington, NC: 92F (1960, 1990) Lumberton, NC: 96F (1941) Florence, SC: 93F (1977) N. Myrtle Beach, SC: 92F (1941) && .ILM WATCHES/WARNINGS/ADVISORIES... NC...None. SC...None. MARINE...None. && $$ SYNOPSIS...ILM UPDATE...31 NEAR TERM...SHK SHORT TERM...III LONG TERM...III AVIATION...SHK MARINE...III/SHK CLIMATE...ILM ####018006550#### FXUS61 KALY 171726 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 126 PM EDT Sat May 17 2025 .SYNOPSIS... Scattered rain showers and isolated to scattered thunderstorms will occur ahead of a cold front this afternoon. Some thunderstorms could become strong to severe with damaging winds and large hail. Some lingering showers may persist for Sunday into Monday morning with drier conditions in store through Tuesday. && .NEAR TERM /THROUGH TONIGHT/... Key Message: - Severe Thunderstorm Watch #277 in effect from Schoharie, Albany, Rensselaer Counties and southern VT northward for large hail, damaging winds, and an isolated tornado until 8 pm EDT. - Monitor severe weather threat into early this evening south of the Capital Region and from the Berkshires and NW CT southward. Discussion: Update as of 113 PM EDT...Severe Thunderstorm Watch #277 is in effect from the Schoharie Valley, Great Capital Region and southern VT northward for large hail, damaging winds and an isolated tornado. The Watch may need to be expanded southward into the eastern Catskills, mid Hudson Valley, Berkshires and NW CT if severe weather trends push southward later in time. SPC RAP mesoscale analysis show the best SBCAPE in the 1500-2000+ J/kg range is from the Capital Region north this hour with effective bulk shear of 35-45 KT. Some supercells or multicells may form with damaging winds and large hail the main threats. PWATs are in the 1-1.3" range, so some locally heavy rain is possible especially something trains or back builds. The 700 hPa flow is strong at 30-40 KT from southwest to northeast so storms may be moving along pretty good. Max temps will be in the 70s to around 80F with with some 60s over the southern Dacks. Update as of 1220 PM EDT...Some significant updates to the PoP/WX hourly grids, cloud cover and timing of strong to severe thunderstorms. We retooled the timing with the greatest shear and instability lining up from the northern Catskills, Greater Capital Region and Berkshires north and east. MLCAPEs are in the 1000-1500 J/kg range and effective bulk shear 35-45 KT based on on the latest SPC mesoanalysis. Previous near term... After 8 PM, around sunset, conditions become less favorable for storms to become strong and scattered rain showers are supported to continue throughout the overnight hours as a surface low pressure system moves overhead and a cold front finishes moving through eastern New York and western New England. This cold front will help relieve us of these muggy conditions and bring temperatures to be much cooler in the 50s and 40s for higher terrain locations. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As a surface low pressure system heads north and east that brought the cold front Saturday night, lingering rain showers are in store for Sunday with light rainfall amounts. Breezy conditions and cooler temperatures are in store as well for Sunday afternoon. By early Sunday night, precipitation should become mostly confined to higher terrain locations through Monday morning when drier conditions are in store. Dry conditions return for Monday. High temperatures Sunday and Monday range in the 50s and 60s. Low temperatures range in the 30s for higher terrain locations while elsewhere will range in the 40s. Cool and comfortable temperatures ahead. && .LONG TERM /TUESDAY THROUGH FRIDAY/... High pressure nosing in from the Great Lakes will bring one more day of mainly dry weather to eastern New York and western New England on Tuesday. High temperatures will remain below normal with values in the 50s and 60s. A period of unsettled weather returns by Wednesday and continues through the end of the week. Two separate upper level lows/shortwaves will interact with each another over the Upper Great Lakes/Ohio Valley region and later develop a longwave upper level trough over the region. A cut off upper low may also develop and spin overhead for multiple days. At the surface, low pressure will track from the Ohio Valley to the Upper Great Lakes on Wednesday. By Thursday, the interior low will weaken while a stronger surface low develops off the mid-Atlantic coast and tracks northeastward into New England. Sufficient lift/moisture will result in periods of rainfall beginning on Wednesday and continuing through at least Friday. Latest NBM probabilities for rainfall to exceed 0.50 inches and 1.00 inches spanning Wednesday through Friday are between 60 and 90 percent and 30 and 65 percent, respectively. The clouds and precipitation will keep temperatures below normal for the remainder of the week with highs in the 50s to lower 60s and lows in the upper 30s to mid-40s. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Through 18z/Sun...Scattered showers/thunderstorms will continue to develop and persist through around sunset, with best chances for multiple rounds of thunderstorms occurring at KGFL and KALB. Brief periods of MVFR/IFR Vsbys will be possible within thunderstorms/heavy downpours. Showers/thunderstorms should decrease from west to east between 23Z/Sat-02Z/Sun. Additional MVFR Cigs should redevelop toward and after 12Z/Sun with increasing coverage of lighter rain showers/sprinkles developing. South to southeast winds 10-15 KT with gusts of 25-30 KT possible through this afternoon, shifting into the west after sunset with the cold frontal passage at 5-10 KT with a few brief gusts up to 20-25 KT possible. West winds 8-12 KT with some gusts up to 20-25 KT expected later Sunday morning. Outlook... Sunday Night: Low Operational Impact. Breezy. NO SIG WX. Monday: Low Operational Impact. Breezy. NO SIG WX. Monday Night: Low Operational Impact. Breezy. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Moderate Operational Impact. Chance of RA. Wednesday Night: High Operational Impact. Likely RA. Thursday: High Operational Impact. Likely RA. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Wasula/Webb NEAR TERM...Wasula/Webb SHORT TERM...Webb LONG TERM...Rathbun AVIATION...KL ####018007423#### FXUS64 KHGX 171726 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1226 PM CDT Sat May 17 2025 ...New AVIATION... .SHORT TERM... (Today through Sunday Night) Issued at 304 AM CDT Sat May 17 2025 Well we may not have broken any record high maximum temperatures yesterday (a few sites fell one degree short of tying their records), but we didn't leave empty handed. ALL FIVE climate sites (College Station, Houston/Bush Airport, Houston/Hobby Airport, Palacios, and Galveston) broke their records for daily high minimum temperatures. Would you believe that the LOW temperature at Houston/Bush Airport yesterday was 81°F?! The normal HIGH temperature is 87°F! The hot and humid conditions will continue throughout the weekend with a mid level high remaining centered over the Gulf. A frontal boundary remains to our northwest and we did see some convection develop off of this line, but by the time it made it into Houston County it was just a couple of isolated showers...but there technically was rain in Southeast Texas! Expecting another similar scenario later this afternoon/evening as the dry line becomes better defined out west. We'll see another round of convection develop and drift towards the Brazos Valley/the Piney Woods as an embedded shortwave provides some additional lift along the boundary. Again...this'll just be a matter of will anything survive long enough to make it here, and the 00Z CAM guidance is a bit more enthusiastic about more than one city up north getting some measurable rainfall. The unfortunate part is that the rain won't occur during the heat of the day when we need it the most for some relief. Speaking of heat, 850mb temperatures will remain firmly in the 90th percentile through the weekend as southwesterly flow aloft prevails. Onshore flow will keep dew points elevated in the mid 70s (we've been mixing out into the upper 60s/low 70s in the afternoon though) and PW values peaking in the 1.5-1.8" range (right around the 75th to 90th percentile). The dew points mixing out along with a decent southerly breeze will help us out a bit in terms of keeping us out of a Heat Advisory, but still expect high temperatures in the low to mid 90s with heat indices reaching into the triple digits both today and Sunday. These won't be a slam dunk for breaking records, but we'll at least be near 'em. The HeatRisk map through Sunday outlines most of Southeast Texas in a moderate to major risk for heat-related impacts (levels 2&3 out of 4), so be sure to take the proper precautions to keep you and your loved ones (including your pets) safe from the heat. I'm sure there's a lot of you with outdoor plans this weekend, so be sure to stay hydrated, take plenty of breaks from the heat, LOOK before you LOCK your vehicle, and to know the signs of heat-related illnesses. Temperatures during the overnight hours won't offer much relief as we remain at least near record territory on that end as well with lows mainly in the upper 70s...and based on last night low 80s aren't out of the question. No rain in the forecast for Sunday, so after tonight our rain chances are back to essentially zero. They'll be back soon though...see the long term section below for more. Batiste && .LONG TERM... (Monday through Friday) Issued at 304 AM CDT Sat May 17 2025 Mid/Upper level ridging will remain parked over the Gulf through the early part of next week. This will continue the streak of hotter than normal daytime temperatures through Tuesday. Increasing humidity combined with hot temperatures will result in heat indices in the 100-107F range. Tuesday will feature a transition in the pattern as a mid/upper trough over the western CONUS tracks eastward. Low pressure at the surface will move across the Great Plains and across the Ohio River Valley, ejecting a cold front in the process. This front is projected to move southward towards the Gulf. This may trigger convection; however, there remains uncertainty on how capping will impact convective initiation and whether or not there is enough lift to initiate upward movement of air. In any case, the hot and humid conditions look to continue through at least Tuesday with the potential for conditions to be drier behind the FROPA (how much less humid we will experience varies between guidance). Adams && .AVIATION... (18Z TAF Issuance) Issued at 1222 PM CDT Sat May 17 2025 Generally a fcst of persistence with overnight and morning MVFR stratus, followed by lifting ceilings as we head into the late morning and afternoon hours. We'll need to keep an eye on our northern terminals late in the day/evening as some highres guidances suggests the potential for some iso-sct tstms in the area in the 22-03z timeframe. Also showing the brief potential for iso activity for the metro terminals in the early afternoon. Run- to-run consistency has been somewhat poor, however, so opted not to mention at this time. Will monitor trends and amend as necessary. 47 && .MARINE... Issued at 304 AM CDT Sat May 17 2025 Generally light to moderate onshore flow is expected over the next several days. A steepening pressure gradient is expected to result in somewhat higher winds on Monday into Tuesday, especially at night and during the morning hours. Caution flags may be warranted. Considering the long fetch, we cannot rule out seas reaching Small Craft criteria over Gulf on Monday and Tuesday. Winds may shift more north to northeast by Wednesday and Thursday thanks to a passing frontal boundary. Self && .CLIMATE... Issued at 304 AM CDT Sat May 17 2025 With multiple days of near-record to record-breaking heat possible going into early next week, here's a look at the daily high temperature records through Tuesday (May 20th). May 17th High Temperature Records --------------------------------- - College Station: 96F (1925) - Houston/IAH: 96F (2018) - Houston/Hobby: 94F (2018) - Palacios: 93F (2003) - Galveston: 90F (2020) May 18th High Temperature Records --------------------------------- - College Station: 98F (2022) - Houston/IAH: 95F (2022) - Houston/Hobby: 94F (2022) - Palacios: 89F (2022) - Galveston: 90F (2022) May 19th High Temperature Records --------------------------------- - College Station: 94F (2022) - Houston/IAH: 95F (2003) - Houston/Hobby: 94F (2008) - Palacios: 89F (2024) - Galveston: 90F (2022) May 20th High Temperature Records --------------------------------- - College Station: 96F (2022) - Houston/IAH: 95F (2020) - Houston/Hobby: 95F (2008) - Palacios: 95F (1943) - Galveston: 91F (2022) Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 95 75 93 75 / 30 20 10 0 Houston (IAH) 95 77 93 77 / 0 0 0 0 Galveston (GLS) 86 79 85 79 / 0 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through late tonight for TXZ436>439. GM...None. && $$ SHORT TERM...Batiste LONG TERM....Adams AVIATION...Batiste MARINE...Self ####018003714#### FXUS63 KUNR 171726 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1126 AM MDT Sat May 17 2025 .KEY MESSAGES... - Widespread frost is likely early this morning as temperatures drop into the mid-30s under light winds and clearing skies. - Another storm system moves through Sunday into Monday, bringing appreciable rain to the region. - Unsettled weather to continue through next week && .DISCUSSION...(Today Through Friday) Issued at 306 AM MDT Sat May 17 2025 Nighttime microphysics RGB imagery shows the strong storm system has finally moved off to the east, leaving clearing skies and light and variable winds in its wake. The low is centered over the Great Lakes region with an impressive line of convection arcing from Ontario to the gulf coast. Colder air has filtered into the Northern Plains as a surface high slowly slides south from Canada. Temperatures across the CWA are in the 30s to low 40s with some spots hitting the freezing mark. On track to see widespread frost development through this morning across much of the western SD plains into northeastern WY. Today will be mild as a weak upper ridge builds into the region and return flow brings warm temperatures back into the CWA. Positive theta-e advection and approaching weak shortwave energy will support chances for thunderstorms this afternoon and evening. Weak upper level winds, marginal buoyancy (100-300 J/kg SFC CAPE per NAM), and low shear will keep severe risk slim to none. Bulk of lift and moisture arrives late Saturday night into Sunday as upper level low moves into the western US with negatively tilted lead shortwave swinging through the region. Sfc low ejects into the eastern CO/NE with strong south-southeasterly flow advecting ample moisture into the region. Elevated instability across the southern tier of the FA (500-1000 J/kg MU CAPE per NAM) and 30-40kt shear could support rotating updrafts and a marginal severe hail threat along the SD/NE border Sunday afternoon. Upper low stalls out over the Northern Plains late Sunday into Monday with TROWAl supporting a long duration rain event Sunday afternoon into Monday night with gulf moisture continuing to advect into the region. LREF QPF probs depict 70+% chances for 1+" QPF over western SD by Tuesday morning. Upslope enhancement will support medium-high probs (40-70%) for 2+" of QPF along the eastern slopes of the Black Hills. Colder air aloft will support high elevation snow in the Black Hills, especially in areas over 6kft which may pick up a few inches. The upper low will finally slide off to the east with weak upper ridging/quasi-zonal flow developing over the region by Wednesday into Thursday, resulting in seasonably cool temperatures and slightly drier weather. Occasional disturbances along the flow will bring near daily chances for showers through the end of the week. && .AVIATION...(For the 18Z TAFS Through 18Z Sunday) Issued At 1126 AM MDT Sat May 17 2025 VFR conditions are expected to persist area-wide through 00z. After 00z, regions of MVFR CIGS (and potentially locally IFR/LIFR over higher terrain) may develop over portions of northwestern SD and the Black Hills. More widespread sub-VFR conditions in RA will likely develop near the end of the period. Areas of LLWS may emerge after 03z as strong low-level southerly flow develops. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...Wong AVIATION...Sherburn ####018008242#### FXUS65 KVEF 171728 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 1028 AM PDT Sat May 17 2025 .SYNOPSIS...Widespread gusty winds are expected across the region today as a weather system moves in. A few showers and thunderstorms are possible across the southern Great Basin as well. Temperatures will cool slightly today through Monday with northwesterly breezes hanging on through Monday afternoon. A warming trend will commence Tuesday onward with temperatures climbing well above normal. && .UPDATE...Satelite imagery through the morning showed an upper level trough digging into the region. Ahead of the trough, a shield of abundant cloud cover developed and blanketed the area. Scattered showers and thunderstorms were noted through the northern half of Nevada which is where the strongest forcing and weak instability was situated. Further south closer to our neck of the woods, it remained dry under mostly cloudy skies. Southwest winds were beginning to respond to the incoming system, with widespread gusts of 20-30 MPH reported this morning. This upper level trough will continue to deepen and dig into southern Nevada through the day, bringing gusty winds and chances for precipitation the region. Did not need significant changes to the afternoon forecast as everything seems to be on track. Winds will be the main and most widespread impact with Wind Advisories in effect where there is the best chance for wind impacts today. Gusts over 40 MPH will set up through the typical gusty southwesterly belt through San Bernardino, southern Nevada, and western Arizona. Weak downsloping will also bring 40 MPH+ gusts and strong crosswinds to the Eastern Sierra Slopes and the Owens Valley. An increase in probabilities for gusts over 58 MPH is noted on HREF DESI after 3 PM this afternoon south of Olancha on Highway 395 as well as around Independence, and meteograms do show a few members over 60 MPH. NBM is much lower. Compared to the previous 60MPH+ downslope wind event that occured last week in the Owens Valley, this set up is much less favorable. Higher winds are possible in the Owens Valley this afternoon and early evening, but confidence is too low at this time. Drivers on Highway 395 should be prepared for strong crosswinds this afternoon either way as west winds will likely gust 40-50 MPH. Precipitation will be less impactful as scattered showers and isolated thunderstorms move through the Southern Great Basin this afternoon and evening. The highest risk for precipitation will be in Esmeralda county early, then spread through central Nye and Lincoln County through this afternoon and evening, with lightning and brief gusty winds possible with any showers and storms as weak instability and low end DCAPE develop ahead of the incoming trough. There is a low chance for isolated showers in Clark County and northern Mohave County but with no instability- thunderstorms are currently not expected and this correlates with HREF and HRRR lightning models which show no lightning this far south. If showers were to impact the Las Vegas area, it would be between 5PM and 11PM and while rain would be light, sudden gusty winds would still be possible given the dry low levels. Again, its a low risk for rain and any associated impacts that far south, but a few hi-res models do show showers in the area and with 0.50in PWATs and strong forcing with the trough, it's not out of the question. Further south where it will remain dry, mostly cloudy skies will persist much of the day. High temperatures today will be cooler than yesterday. -Nickerson- && .PREVIOUS DISCUSSION...1022 AM PDT Sat May 17 2025 .SHORT TERM...through Monday. Morning satellite imagery depicts our next weather system making its way onshore along the Pacific Northwest Coast, and will continue to dig south into the Great Basin through this afternoon. Ahead of this trough, the main story will be the wind with a belt of strong southwest winds forming from the Western Mojave Desert near Daggett, eastward into Southwest Utah and Northwest Arizona. Widespread gusts of 35 to 55 mph are expected across the Mojave Desert and Northwest Arizona and this remains well covered by the wind advisory for today. A few gusts near or around 60 mph are possible near Barstow this afternoon and evening as the pressure gradient maximizes. Further West, high resolution guidance remains fairly insistent on strong downslope winds in the Sierra and Owens Valley this afternoon, despite a somewhat suboptimal flow pattern lacking a strong cross-barrier component of the flow aloft. Given the trends in model support, went ahead and added the Sierra/Owens Valley/White Mountains to the wind advisory as well. In addition to the winds, a belt of showers and isolated thunderstorms are expected to develop along the cold front and base of the trough axis this afternoon and evening across the southern Great Basin. These storms will traverse from west to east, and exit our region late this evening. While a stray shower may form as far south as Las Vegas, chances are greatest across mainly central Nye and Lincoln Counties. Temperatures today will cool a few degrees from yesterday and remain cool through Monday as the trough moves through and additional disturbance drops southward Sunday night reinforcing cool temps and northerly breezes. .LONG TERM...Tuesday through Friday Temperatures increase through the workweek as the trough exits to the east and heights aloft rise. The probability of reaching 100 degrees in Las Vegas on Thursday is now 75 percent. On Thursday and Friday, expect widespread Moderate (Level 2) HeatRisk across the desert valleys, a level of heat that affects anyone sensitive to heat, especially those without adequate cooling or hydration. There is also the potential for some Major (Level 3) HeatRisk along the Colorado River, which affects anyone without effective cooling or hydration. Zonal flow aloft should help maintain non-impactful winds through at least Thursday, but may have to watch an approaching shortwave towards the end of the week. && .AVIATION...For Harry Reid...For the 18Z Forecast Package...Gusty southwest winds continue through the evening hours with gusts 30-40 knots. After sunset, winds begin to weaken until they shift to the northwest. The exact timing of this wind shift remains uncertain and will likely be tied to the strength/coverage of shower activity to the north of the valley. Most guidance brings the northwesterlies in between 04z and 09z tonight, but if the aforementioned precipitation is very weak/sparse, it is possible that the wind shift holds off until sunrise tomorrow (20% chance). Chances of precipitation in the Las Vegas Valley are rather low at ~15%. While some fluctuations back to the west are possible overnight, winds should be predominantly from the northwest with gusts 20-25 knots. SCT-BKN clouds at or above 10kft. For the rest of southern Nevada, northwest Arizona and southeast California...For the 18Z Forecast Package...Gusty southwest winds persist across most of the area today with the exception being BIH where winds will be more northwesterly. Gusts this afternoon in the 25-40 knot range, with the strongest winds out at DAG. After sunset, winds will begin to weaken. In the Las Vegas Valley, a shift to the northwest is expected between 04z and 09z, though the wind shift may struggle to reach or persist at HND. VFR conditions prevail with SCT- BKN clouds at or above 10kft. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ SHORT TERM...Outler LONG TERM...Meltzer AVIATION...Woods For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter