####018008334#### FXUS61 KOKX 152140 AFDOKX Area Forecast Discussion National Weather Service New York NY 540 PM EDT Thu May 15 2025 .SYNOPSIS... A warm frontal boundary moves in from the south this evening and stalls within the area. Associated weak low pressure moves across late tonight into early Friday. Thereafter a surface trough moves across Friday and another one moves across Saturday. A low to the north sends a cold front through Saturday night. This low lingers in New England and into the Canadian Maritimes through Monday as high pressure pushes in. High pressure remains in control Tuesday into Tuesday night. Another frontal system impacts the area Wednesday into Thursday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Hourly temperatures were running just a tad cooler than forecast thin evening and have been adjusted accordingly. Otherwise, the foecast remains on track. For tonight, with any instability decreasing with the loss of diurnal heating, shower and thunderstorm coverage is expected to considerably decrease with the absence of any significant synoptic lift. Upper level trough will be shifting east of the area, taking the highest positive vorticity advection farther east of the region. Winds become light and variable direction. Another night of low clouds and fog is expected across the area. A relatively warmer guidance for low temperatures tonight using MET/NBM ranging from the mid 50s to lower 60s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/... A subtle mid level shortwave moves across Friday with some associated positive vorticity advection. At the surface, the frontal boundary across the area dissipates, leaving a general weak pressure gradient between low pressure well to the north and west and high pressure well to the south and east. Light southerly flow at the surface is expected. A warmer day is expected. NBM/NBM 50th percentile combination used for daytime high temperatures, well into the 70s for most locations and some locations reaching 80. More instability will be generated at the surface as a result, making for a higher chance of showers and thunderstorms. Marginal risk for damaging winds with these thunderstorms, particularly for areas that have more instability. The convection trends downward Friday night with the loss of diurnal heating. Winds in lower levels increase. This will keep warmer min temperatures Friday night. Again used combination of NBM and NBM 50th percentile, with lows ranging from upper 50s to lower 60s. Fog will be possible but was not put in forecast due to uncertainty with how well mixed boundary layer could be. Upper level low approaches the region Saturday with greater height falls. At the surface, a cold front approaches from the north and west. There is a likely a pre-frontal trough that develops that will be the focus for convective initiation. Chances for showers and thunderstorms increase during the day with highest chances mid afternoon through early evening. The southerly flow increases Saturday and with further increase in winds in 5-10 kft, bulk shear increases. Warmer temperatures are forecast also using NBM and NBM 50th percentile. Outside of Twin Forks and SE Connecticut which have highs more in the lower 70s, rest of area is in mid 70s to near 80 with NYC Metro and parts of NE NJ getting more into the lower 80s. With more low level instability and more bulk shear, there is more of a risk for damaging winds with thunderstorms. SPC has western parts of the region with a slight risk for severe thunderstorms. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Key Messages: * A cold front cuts off precip Saturday night. * Becoming mostly sunny on Sunday with only slight chances for showers. * Dry & quiet Monday into Tuesday. * Another frontal system may bring a return to rainfall Wednesday into Thursday. A surface low in southern Canada/northern New York sends a cold front through Saturday night. Showers and/or any remaining thunderstorms diminish with the passage of the cold front with drier air getting advected in. Mostly sunny skies take over as high pressure gradually builds in from the northwest. To our northeast, low pressure will continue to exit into New England and into the Canadian Maritimes through Monday. This will lead to breezy W/WNW winds from an increased pressure gradient through Monday. An upper-level trough to our west on Saturday passes east SUnday night. As it moves farther away, it takes the surface low with it farther out to sea Monday night and thereafter. This allows a ridge to our west with high pressure at the surface to fully take hold, if briefly, Tuesday into Tuesday night. Dry conditions continue with winds becoming light under a weak pressure gradient. A frontal system from the Great Plains then moves into the Ohio or Tennessee River Valleys on Tuesday, moving through or in the vicinity of our region Wednesday into Thursday. Expecting showers during this timeframe. Too soon to call chances for thunderstorms. MOdel guidance still varies with timing, magnitude, and track of this frontal system. Have gone with chance POPs Wednesday into Thursday, as a result. Temperatures look to cool each day in the long-term period. Highs on Sunday will be in the low/mid 70s with all highs in the mid/upper- 60s by Wednesday. Nightly lows will range from the mid-50s to the mid-40s. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... Low pressure weakens and passes near or just south of Long Island tonight. Another weak low approaches late Friday morning. Conditions vary significantly across the region from LIFR to VFR as breaks in the overcast have developed along the south coast of Long Island. Periods of VFR are possible along the coast into early this evening. Toward sunset conditions lower again to LIFR and IFR, and at times late tonight VLIFR. Conditions will be improving to MVFR Friday morning. There will be a chance of showers with thunderstorms Friday afternoon. Low confidence forecast with timing and conditions for tonight. Winds light E/SE to light and variable become light and variable throughout during this evening. A light south flow develops Friday morning. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Amendments expected for changing flight categories throughout the TAF period. .OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY... Friday afternoon: MVFR with showers and a slight chance of tstms. Saturday: MVFR. possibly IFR in the morning, becoming VFR in the afternoon with showers likely, and a chance of thunderstorms with MVFR. Sunday: Mainly VFR. Slight chance of showers inland. W winds G20- 25kt. Monday - Tuesday: VFR. Monday NW winds G20-25kt. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90 && .MARINE... Generally weak pressure gradient in place in the short term through Saturday with conditions remaining below small craft advisory thresholds. Winds and waves are currently expected to fall below SCA criteria Saturday night through Tuesday. However, wind gusts may near SCA criteria on all waters Sunday under an increased pressure gradient. && .HYDROLOGY... Basin averaged amounts with showers and thunderstorms is expected to be near quarter to a half inch with locally higher amounts through Saturday. Thunderstorms could result in areas experiencing minor flooding, especially within urban, low lying and poor drainage areas. With increasing translational speed to thunderstorms, flash flooding is not expected. There are currently no hydrologic concerns Saturday night through the middle of next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JM/BR NEAR TERM...JM/BR SHORT TERM...JM LONG TERM...BR AVIATION...MET MARINE...JM/BR HYDROLOGY...JM/BR ####018004045#### FXUS65 KFGZ 152140 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 240 PM MST Thu May 15 2025 .SYNOPSIS...Warm temperatures continue on Friday with cooler weather returning over the weekend and into early next week. A storm system over the weekend and into Monday will bring chances for showers and gusty southwest winds. && .DISCUSSION...Friday...Dry conditions continue with near average temperatures expected. Winds will be primarily out of the west to southwest and around 5-15 mph with afternoon gusts around 20-25 mph. Saturday through Monday...A deepening trough across the Great Basin will bring increasing winds through the weekend. The winds on Saturday will increase out of the southwest to 10-20 mph with gusts 25-35 mph, increasing to 15-25 mph with gusts 30-40 mph on Sunday. It will still be fairly dry on Saturday, and with the very dry conditions across eastern parts of the forecast area, we could see some fire weather concerns. The strongest winds look to be more over western and northern areas while the driest conditions look to be over eastern areas. Still looks marginal but near critical to critical fire weather conditions are expected. The approaching trough will drag in some cooler air on Saturday as a cold front moves through but the colder air arrives for Sunday and Monday as the trough redevelops on the western side and dives down through the state. We should also see moisture increasing on Sunday which may allow for some showers and isolated thunderstorms (even some snow showers across the higher elevations) late Saturday through Sunday. Areas along and north of the I-40 corridor look to have the best chances for a shower. The increasing moisture should help to tamp down the fire weather concerns. Though the southern portions of Apache and Navajo counties will still have near critical conditions as winds will be gustier on Sunday. As the secondary trough pushes into the region, we will see another influx of moisture to the region and more chances for showers and thunderstorms, especially along and north of the Mogollon Rim. An active start to the week for sure. As the second trough exits the region late Monday, we should see a rather quick recovery across the state. Temperatures will warm to near average by midweek and then 5-10 degrees above average for the second half of the week. Winds are expected to become lighter through the rest of the week. && .AVIATION...Thursday 15/18Z through Friday 16/18Z...VFR conditions expected. FU layers near area fires. Light and variable winds to west 5-15 kts. Variable/terrain driven winds return after 02Z generally 5-10 kts. OUTLOOK...Friday 16/18Z through Sunday 18/18Z...Mostly VFR conditions expected through the period. SW winds 5-15 kts on Friday, becoming stronger on Saturday with gusts near 40 kts. Overnight winds expected to be light and variable Friday into Saturday, but likely remain elevated Saturday into Sunday. -SHRA/-SHSN possible after 06Z Sunday along and NW of a KGCN-KPGA line. Showers will extend SE beyond this outlook period. && .FIRE WEATHER...This afternoon through Saturday...Dry conditions will continue with minimum RH values mostly below 15%. Southwest to west afternoon winds 10 to 20 MPH today and Friday. Southwest winds increase on Saturday 15 to 20 mph gusting between 25 and 35 mph. Near critical fire weather possible Saturday. Sunday through Tuesday...Cooler, windy, and chances for showers on Sunday and Monday. Southwest winds 15-20 mph gusting between 30 and 40 mph on Sunday, becoming lighter westerly winds on Monday. Warmer, less wind, and drier on Tuesday. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...Meola AVIATION...MAS FIRE WEATHER...MAS For Northern Arizona weather information visit weather.gov/flagstaff ####018005962#### FXUS61 KCTP 152140 AFDCTP Area Forecast Discussion National Weather Service State College PA 530 PM EDT Thu May 15 2025 .SYNOPSIS... * Daily chances for thunderstorms continue through Saturday with potential for damaging winds and localized flooding. * Temperatures trend warmer Friday and Saturday with a notable uptick in humid/sticky weather. * A cold front will bring much cooler temperatures and less rainy/more sunny weather Sunday and early next week with breezy conditions. && .NEAR TERM /THROUGH TONIGHT/... Convection this afternoon and evening has generally been confined to a narrow band of sfc confluence across west-central PA from the Laurels to the northwest mountains. Thermal and shear profiles suggest these storms will remain non severe. The waning instability with loss of daytime heating will result in much of the convection dissipating later this evening. Lingering SHRA may stick around thru midnight. The next issue of note is later tonight as forcing associated with the left-exit region of a jet max over the OH valley approaches. A complex of storms should develop thru the night over Upper Great Lakes and drop into OH/wrn PA toward morning. SPC still has the wrn 2/3rds of the CWA in a MRGL risk for SVR (mainly hail/wind threat, but a very minimal tor threat in the SW). Precip arrives late tonight, perhaps a little earlier in the SW. Rain rates should not be excessive, but could be briefly heavy. A flood watch has been issued for Somerset and Bedford Counties where it's been very wet and stream flows are running high. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Newest guidance is highly aligned with prev forecasts. There should be a lull after the morning convection. Don't have much to add to the disc below. Prev... Latest guidance indicates a lull in the precipitation during the late morning and afternoon on Friday following the passage of the warm front. Southwest flow will continue to funnel moisture up into the northeast US as dewpoints reach their highest values so far this year (in the mid to upper 60s). It will feel noticeably humid as well. Highs in the 80s across the area appear likely with the only exception being if thunderstorms can fire up in the afternoon. Another round of convection appears likely Friday night into Saturday morning (yet again decaying as it moves across Pennsylvania from the Midwest). Severe weather appears a bit more likely with this round as 2500J/kg of MLCAPE overlaps with sufficient shear in the evening. The SPC Slight Risk gets into southwest PA, but would not be surprised to see an eastward expansion across southern PA with subsequent updates. By Saturday, a cold front will approach the Commonwealth with a convective outflow boundary likely surging out ahead of it from the previous night's convection. The outflow boundary will encounter a warm and moist airmass that could lead to development of sustained strong thunderstorms on Saturday afternoon. Still some uncertainty with how quickly a line of thunderstorms will congeal Saturday afternoon, but southeast PA would be favored for a primarily damaging wind threat, as outlined by SPC's Slight Risk (level 2 out of 5) that covers York and Lancaster County. With all 3 rounds of storms, progressive storm motions should limit the risk of significant flooding, but cannot rule out some isolated issues for locations who's soil moistures/creeks are already running high. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Latest guidance is consistent with prev, with a dry period for Sun thru Tues. Some SHRA may pop up in the nrn mtns Sun aftn, but these would be isolated. Mon and Tues are certainly dry. A storm system gathers over the mid-MS and OH valleys during that time. The system looks like it should broaden to the west and make us wet for another few days straight. && .AVIATION /10Z THURSDAY THROUGH TUESDAY/... Ceilings are gradually rising this afternoon across Central PA, with VFR conditions expected area-wide after 20Z. Scattered showers and a few thunderstorms have developed over western Pennsylvania and could produce brief periods of heavy rain at BFD into the early evening. Model soundings suggest that IFR ceilings will return tonight for much of Central PA and there is around a 30% chance of LIFR ceilings developing at MDT and LNS. There also appears to be at least some potential (< 30%) for fog to develop at those two sites as well. The main concern for tonight will be a line of thunderstorms that will track through the region in the 09-14Z timeframe. PROB30 groups have been added to all sites except MDT and LNS to highlight the most likely timeframe for impacts. These thunderstorms will likely be weakening as they move in from the west and encounter a more stable environment, but we can't rule out a few strong wind gusts, especially at western airfields. Conditions gradually improve during the late morning behind the line of storms, but additional thunderstorms will likely develop Friday afternoon/evening. Outlook... Sat...Mainly VFR, isolated PM showers/storms. Sun...Some improvement, as a series of cold fronts move southeast of the area. Mon...Mainly dry with VFR conditions. Perhaps a shower early at BFD and JST, with MVFR CIGS early at these sites. Tue...VFR with showers developing late. && .CTP WATCHES/WARNINGS/ADVISORIES... A flood watch is in effect form late tonight through Friday morning for Somerset and Bedford counties. && $$ SYNOPSIS...Jurewicz/Banghoff NEAR TERM...Colbert SHORT TERM...Jurewicz/Banghoff/Dangelo LONG TERM...Jurewicz/Banghoff/Dangelo AVIATION...Bauco ####018008060#### FXUS65 KRIW 152143 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 343 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 /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 341 PM MDT Thu May 15 2025 Shower and/or thunderstorm chances (30%) continue through sunset (at the latest) at all terminals except KPNA and KBPI. At KPNA and KBPI, showers or thunderstorms should remain over the mountains. Shower and/or thunderstorm chances are a PROB30 group for the terminals given the scattered nature and uncertainty in timing and direct impacts. Heavier showers in thunderstorms could drop visibilities and ceilings to MVFR flight conditions; however, confidence in this occurring is not high enough to include in TAF. Otherwise, thunderstorm chances diminish after sunset at all terminals. At KRIW and KLND there remains around a 60% chance in light rain between sunset and 05/06Z with a 30% chance at MVFR ceilings with the light rain. Shower chances (30%) increase again after 20Z Friday at KJAC and KCOD. Chances in MVFR ceilings have dropped to around 30% at KRKS overnight so both KRKS and KCOD have a 30% chance at overnight MVFR ceilings. This potential is communicated with a SCT030 group. Gusty winds should diminish at all terminals 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