####018008118#### FXUS65 KRIW 151827 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1227 PM MDT Thu May 15 2025 .KEY MESSAGES... - Another unsettled day today with 30 to 50% chances of scattered coverage showers and thunderstorms. The best coverage will be across the northern half of the area. - Somewhat warmer Friday and Saturday with less coverage of showers and thunderstorms. - A Pacific weather system will bring a 50 to 60% chance of widespread rain and mountain snow from Sunday through Monday. && .UPDATE... Issued at 1224 PM MDT Thu May 15 2025 As of 1200L, the radar remains fairly quiet with only some light showers across western WY. Scattered showers have been steadily increasing in coverage across most areas west of the Divide and across northern WY over the last hour, and these are expected to continue to increase in coverage across the rest of the region through the early afternoon. Precipitation totals are much lower than yesterday, with likely only a few hundredths rather than tenths of precipitation out of the heavier showers. Thunderstorms will be much more isolated today as well, at only 10 to 20% coverage/probability. Though gusty winds and small hail are a possibility with any stronger storms, but those stronger storms are much less likely than in previous days (5 to 10% chance). Friday will see even less coverage of showers and storms with best chances (20 to 30% chance of showers) across the northwest. && .DISCUSSION... Issued at 326 AM MDT Thu May 15 2025 We have had some changes over the past few days. Storm movement was originally south to north on Tuesday, more westerly yesterday, and now we have transitioned to a northwest flow pattern. But one thing has remained constant, the chances of showers during the wettest time of the year across the Cowboy State. And this will continue through much of the next 7 days, although at varying coverages and intensities. The culprit for today's precipitation is a shortwave moving in from the northwest. We already have a few showers out there this morning, and these will increase in coverage as we head into the afternoon. And some of these showers could come with thunder, commonly known as thunderstorms. We do have some decent CAPE this afternoon, topping out around 500 J/Kg, although the lifted indices are not the best I've seen, generally around minus 1. So, I would put the chance of a thunderstorm at any location around 1 out of 4, with a greater chance of showers. And like previous days, the best chance of showers will be in northern Wyoming, with tapering chances further south. Precipitable waters are not terribly high though, generally topping at around 0.40 inches. And, with the storms moving at a decent clip, the threat of flooding looks small. So, the main threat would be gusty wind. I could also see some small hail, given the low wet bulb zero levels and cool temperatures, averaging around 10 degrees below normal. Wind will also be a concern today. The main area of concern looks to be northern Johnson County and the northern Big Horn Basin, with the favored northwest flow pattern behind the shortwave. Low level wind does not look sufficient for widespread high wind though, with 700 millibar wind topping out at around 40 knots when I would like to see 50 knots. Ensembles are giving around a 2 in 3 chance of gusts past 40 mph though, especially at Buffalo. So, it looks like a toupee alert day for many locations. Most showers should end by late this evening. And, there will be some snow in the mountains, with 700 millibar temperatures between minus 1 and minus 3, putting snow levels between 7000 and 8000 feet. Impacts would be minimal since the strong May sun should melt snow off of the roads. Shortwave ridging then moves across the state on Friday. This should cap the atmosphere a bit more and allow for somewhat warmer temperatures. We will still see some showers, but coverage will be less with most locations likely staying dry most of the time. Again, (noticing a pattern here), the best coverage will be across the north with southern Wyoming mainly dry. Saturday looks like the warmest day of the period as flow turns southwesterly ahead of the next weather system. The deepest moisture will stay west of the area on this day, but enough will move eastward and there will be a few showers and thunderstorms late in the day and in the evening. But, this day again looks like most areas will be dry most of the time so if you want do to something this weekend, Saturday definitely looks like the best day to do it. Then on Sunday into Monday, a big atmospheric bowling ball, AKA an upper level low, then moves into the Rockies and brings another period of wet weather. These lows are notoriously fickle with movement so details about timing of precipitation and amounts are still very much in flux. We do know a few things though. One, we have the concern of mountain snow, and potentially a decent amount of it. Models are indicating 700 millibar temperatures may fall as low as minus 3 in portions of the area, which could drop snow levels as low as 7000 feet on Monday. Probabilistic model guidance gives around a 1 in 2 chance of greater than a foot of snow from Sunday morning through Tuesday morning above 9000 feet across portions of the mountains. This is especially so in the ranges East of the Divide, where there would be some wrap around moisture and upslope on Monday. Not a certainly by any means, but something we have to watch. This could be a wet system, with a greater than 2 in 3 chance of over a half an inch or rain across the northern two thirds of the area through the period with favored northeasterly upslope locations having a greater than 1 in 2 chance of at least an inch of precipitation through 6 am on Tuesday. As a result, we will also have to watch for rising rivers. Melting snowpack would not be a concern though, given the cool temperatures though. Things get more muddled past Monday, as there are different solutions in regards to how fast the low will move away to the east. Most guidance shows ridging building behind the system, bringing drier and warmer weather, but when this will occur is still uncertain. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1121 AM MDT Thu May 15 2025 All terminals have a chance (30%) of seeing showers and/or thunderstorms this TAF period. Most terminals chances begin between 19-22Z. KCPR is the outlier with convection chances (30%) beginning after 01Z. Shower and/or thunderstorm chances are a PROB30 group for each terminal given the scattered nature and uncertainty in timing and direct impacts. Heaviest showers in thunderstorms could drop visibilities and ceilings to MVFR flight conditions with very brief periods of IFR visibilities not completely out of question (less than 20% chance at IFR). Thunderstorm chances diminish after sunset at all terminals. However, shower chances (30%) exist longer at KCPR. At KRIW and KLND there is good agreement in light rain between sunset and 05/06Z with a 30% chance at MVFR ceilings with the light rain. There is a greater than 60% chance in MVFR ceilings at KRKS for a few hours overnight. KCOD has a 30% chance at overnight MVFR ceilings and this potential is communicated with a SCT030 group. Gusty winds are expected this afternoon at all terminals except KJAC and KLND before diminishing by sunset. KCPR can expect gusty winds the entire TAF period. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Hensley DISCUSSION...Hattings AVIATION...Gerhardt ####018005567#### FXUS62 KCAE 151827 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 227 PM EDT Thu May 15 2025 .SYNOPSIS... Precipitation chances are low to close out the work week, with much warmer temperatures expected. The weekend looks hot and humid with a few afternoon and evening showers and thunderstorms possible. The next significant chance of rain comes during the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Mostly sunny this afternoon with above normal temperatures. - More mid to high level clouds around tonight with lows around 70 degrees. Upper ridging continues to build into the region from the west this afternoon. This has allowed temperatures to climb into the 80s across the CWA. Adjusted highs up by a few degrees based on recent trends. Mostly sunny skies continue through the afternoon with occasionally breezy winds out of the southwest. Winds diminish after sunset with increasing mid to high level cloudiness possible towards daybreak. Temperatures fall to around 70 degrees by daybreak. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... Key Message(s): - Warm and humid, especially on Friday. - An approaching cold front could spark a few showers or thunderstorms Saturday and Sunday afternoon. Upper ridge axis should be overhead at the start of the period, being replaced by zonal flow for the weekend. This keeps above normal temperatures in the forecast, especially on Friday when heat index values will be in the upper 90s to around 100 degrees. As we have been advertising, this is the first hot and humid day of the year and appropriate precautions should be taken if outdoors during peak heating on Friday. A weak cold front is slated to move into the FA on Saturday but guidance has not been excited about convective development. Regardless, the entire CWA is in a Marginal (1/5) risk for severe weather in the Day 3 SPC SWO and some of the guidance suggests conditions will be favorable for isolated to scattered showers and thunderstorms but the threat should be focused in the vicinity of the cold front, which would serve as the primary trigger for convection. Guidance such as the HRRR and NAMNest indicates showers and thunderstorms will be diminishing as the front moves in on Saturday so PoPs are highest in the north and west. Trends will be monitored to see if the severe threat manifests on Saturday. Regardless, southwest winds may be gusty at times during the daytime hours ahead of the front, especially on area lakes. The cold front may stall in our area for Sunday and could once again trigger a few showers or thunderstorms, this time favoring the southern Midlands and CSRA. In the absence of any upper level forcing, the threat of severe weather should be even lower Sunday afternoon. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... Key Message(s): - Hot and humid conditions continue, with showers and thunderstorms possibly developing middle of next week as a cold front approaches the area. As an upper-lvl low situated over the High Plains continues to make its advancement east-northward towards the region, an associated frontal boundary will linger nearby. A chance of a couple isolated showers could be possible on Monday and Tuesday afternoon as this front meanders back and forth over the region. As this upper-lvl low inches closer, a more impressive setup looks likely on Wednesday and Thursday, bringing a better chance at some showers and thunderstorms to develop. A cold front could possibly pass through on Thursday morning, however confidence remains low on the timing of this being so far out into the forecast. Above normal temperatures should prevail through the extended period. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... VFR Conditions Continue through the TAF Period.... Afternoon satellite imagery shows passing mid to high level clouds moving in from the northwest and scattered cumulus moving southwest to northeast, though most of the clouds are not over the terminals at this time. VFR conditions are likely to continue with the only consideration being occasionally gusty southwesterly winds at the surface this afternoon. Winds diminish tonight and pick back up again Friday morning though gusts should not be as high tomorrow and the wind direction could be more westerly than today. EXTENDED AVIATION OUTLOOK... Mainly VFR conditions expected through the period barring low end chances for showers and thunderstorm each afternoon which could cause brief restrictions. && .HYDROLOGY... Releases upstream have caused the Saluda River at Chappells to rise into minor flood stage this afternoon. The river is forecast to crest this evening, falling back below flood stage tonight. The North Fork of the Edisto River has crested and fallen slightly below flood stage. If trends continue, the Flood Warning will be cancelled, though we will keep the warning up downstream at Branchville. Elsewhere, the Congaree River points are steady or slowly falling. The river has likely crested and should gradually fall below flood stage later this week. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$ SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM... Dennis AVIATION... HYDROLOGY... ####018005332#### FXUS65 KVEF 151827 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 1127 AM PDT Thu May 15 2025 .SYNOPSIS...Temperatures will continue to warm through Friday before another potent weather system drops into the region over the weekend, bringing strong gusty winds, a chance of precipitation, and a drop in temperatures. Calmer and warmer weather is expected next week. && .UPDATE...Dry, northwest flow on the anti-cyclonic side of an upper level trough sat over the area this morning, which resulted in dry conditions and mostly sunny skies to prevail. This synoptic set up will continue to influence our local weather today with weak height rises expected as the broad upper level trough weakens and shifts east. Expect light winds, mostly sunny skies, and high temperatures 5-8 degrees warmer today than yesterday. -Nickerson- && .SHORT TERM...through Friday night. Midnight satellite loop showed scattered mid level clouds slowly decreasing in coverage over portions of Inyo, Esmeralda, Nye, and Lincoln counties. A band of cirrus was moving east over southern Inyo and northern San Bernardino counties. Surface obs showed generally light winds and mild temperatures. Heights will rise areawide through Friday night, resulting in quiet weather with temperatures rising back to near mid- May normals. Southerly winds will start to increase Friday and Friday night, well ahead of the low pressure system which will be discussed in the long term section. && .LONG TERM...Saturday through Wednesday. Heading into the weekend, a potent trough of low pressure will drop through the western CONUS. Impacts will include strong southwesterly pre-frontal winds, strong northwesterly post-frontal winds, a return of scattered showers / isolated thunderstorms, and a drop in temperatures over the weekend...once again. Details continue to be worked out as we hash out the exact intensity and timing of this system. However, what we know is that PWATs will increase to 125 to 175 percent of normal (generally between 0.50 and 0.75 inches), which will allow for moderate-to-heavy rain rates beneath any thunderstorms that develop, but generally light rainfall elsewhere. Best chances for precipitation currently reside across the southern Great Basin from Saturday afternoon through Saturday night into Sunday, though occasional model runs bring precipitation chances well into the Mojave Desert. Both the ECMWF and GFS ensemble means have this trough entering the Desert Southwest with a negative tilt, which will increase thermodynamic instability and wind shear, meaning severe-level thunderstorms capable of strong winds, large hail, and frequent lightning cannot be ruled out. At this time, it looks like the greatest threat of thunderstorms will be across central Nye and northern Lincoln counties Saturday and across central Nye and the remainder of Lincoln County Sunday. Regarding wind potential, the NBM is slowly trending gustier with both pre-frontal and post-frontal winds. The latest run has 50-70 percent chances of west-southwest gusts in excess of 40 mph across the Mojave Desert (along the Interstate 15 corridor) on Saturday and 30-50 percent chances of northwest gusts in excess of 40 mph across the southwestern Great Basin on Sunday. The LREF has greater probabilities for both times/locations... 60-90 percent and 40-70 percent, respectively. Behind the trough, ridging sets up for the start of the work week that will result in Las Vegas chances for 90 degrees rapidly increasing through the week and "Moderate" HeatRisk (Level 2 on a scale from 0 to 4) returning to the low valleys. && .AVIATION...For Harry Reid...For the 18Z Forecast Package...Winds will remain light and variable until after 00Z when west- southwesterly wind below 10kt. These winds will continue through the night before becoming lighter from the northeast in a typical diurnal pattern. Winds pick up Friday afternoon with south- southwest winds gusting at times to near 20kt. FEW-SCT high clouds with bases AOA 15kft will come through at times on Friday. For the rest of southern Nevada, northwest Arizona and southeast California...For the 18Z Forecast Package...Light and variable winds are on tap across the area into early afternoon today. Mainly west to southwesterly winds will pick up this afternoon with speeds below 10kt everywhere except DAG where westerly wind gusting to near 20kt can be expected. Typical diurnal trends can be expected tonight. Gusty southerly wind to 20kt will pick up at the Colorado River TAF sites Friday afternoon. A shield of FEW- SCT clouds will move across the area from northwest to southeast through the day Friday but no significant CIGS are anticipated. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ SHORT TERM...Morgan LONG TERM...Soulat AVIATION...Berc For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter ####018005308#### FXUS64 KAMA 151828 AFDAMA Area Forecast Discussion National Weather Service Amarillo TX 128 PM CDT Thu May 15 2025 ...New KEY MESSAGES, SHORT TERM, LONG TERM... .KEY MESSAGES... Issued at 126 PM CDT Thu May 15 2025 - Temperatures will return to the upper-80s to low-90s across most of the Panhandles this weekend. - Breezy to windy conditions will be possible on Sunday and Monday. - Highly conditional storm chances in the far eastern Panhandles on Sunday. Potential for storms to become severe if they do form. && .SHORT TERM ... (This evening through Friday night) Issued at 126 PM CDT Thu May 15 2025 Currently an upper level closed low is deepening over the Dakotas. Further south the FA is under southwest flow aloft. High clouds are finally pushing off to the east with skies clearing from west to east in the combined Panhandles. A secondary trough axis with this system is progged to move into the area this evening with H5 winds ramping up to 50 to 60 kts over the northwest into SE CO and SW KS. Consequently a closed surface is expected to develop this afternoon leeside of the mountains. Calm winds currently being seen will start to pick up late this afternoon into evening to around 15 to 20 mph in the western combined Panhandles. Tonight as the surface low treks east along southern KS winds will gradually shift to the west with some areas in the north seeing northwesterly winds for a little while. Near normal overnight lows are expected tonight into tomorrow morning. With skies starting out much clearer tomorrow, much of the area should be able to warm a couple to 3 degrees warmer than today. West winds should stay around 15 mph or less for Friday as well with a very quiet but slightly warm day. Tomorrow night, light winds expected with near normal overnight lows once again. 36 && .LONG TERM ... (Saturday through next Wednesday) Issued at 126 PM CDT Thu May 15 2025 For the weekend and into Monday, expecting afternoon highs around 5 to 10 degrees above normal. There after temps should become near normal to slightly below. Otherwise, the extended forecast is looking to be mostly quite with some of the breeziest winds on Sunday. If grasses were not as green as they are some critical fire weather conditions would exist on Sunday in the northwestern combined Panhandles. However, despite RH values tanking to near 10 percent with breezy southwest winds reaching 25 to maybe 30 mph, critical fire weather conditions are not anticipated due to the state of the fuels at this time. The other caveat for Sunday is the chances for severe storms in the eastern combined Panhandles. Based on the current expected track of an upper level low pressure system that is set to be over the PacNW Sat and its associated trough over much of the central to western CONUS, chances for storms in the eastern combined Panhandles remain low at this time. Current model consensus keeps the dryline further east limiting storms in the Panhandles. Storms may still develop in the eastern most stack, but should move into western OK quickly, leaving the Panhandles before becoming severe. It will not be completely out of the realm of possibility that the overall system tracks differently with a potential westward shift of the dry line encompassing more of the FA. Maybe only a 5 percent chance that eastern two stacks of counties in the TX Panhandle hangs on to Tds in the 60s. Will have to watch for trends as we go into the weekend. The only other thing to maybe mention is the possibility of a week cold front for Tue that will bring some relief from warm temperatures. Currently the NBM has a Max T in the mid to upper 70s for much of the FA Tue afternoon. 36 && .AVIATION... (18Z TAFS) Issued at 1131 AM CDT Thu May 15 2025 VFR conditions expected to prevail with high clouds eventually clearing out. Southwest winds should be blowing around 15 kts with slightly higher gusts possible. Eventually those winds are expected to shift to the west later in the period. 36 && .PRELIMINARY POINT TEMPS/POPS... Amarillo TX 51 83 54 86 / 0 0 0 0 Beaver OK 51 84 48 86 / 0 0 0 0 Boise City OK 46 81 45 83 / 0 0 0 0 Borger TX 51 86 52 90 / 0 0 0 0 Boys Ranch TX 46 84 50 87 / 0 0 0 0 Canyon TX 49 83 52 87 / 0 0 0 0 Clarendon TX 53 85 56 87 / 0 0 0 0 Dalhart TX 44 82 45 85 / 0 0 0 0 Guymon OK 49 84 45 86 / 0 0 0 0 Hereford TX 48 84 51 87 / 0 0 0 0 Lipscomb TX 53 85 51 86 / 0 0 0 0 Pampa TX 52 84 54 87 / 0 0 0 0 Shamrock TX 54 86 55 87 / 0 0 0 0 Wellington TX 54 87 56 87 / 0 0 0 0 && .AMA WATCHES/WARNINGS/ADVISORIES... TX...None. OK...None. && $$ SHORT TERM...36 LONG TERM....36 AVIATION...36