####018007169#### FXUS61 KCTP 160726 AFDCTP Area Forecast Discussion National Weather Service State College PA 320 AM EDT Fri May 16 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/... With the last of the showers in the northern mountains fizzling out around 930 PM, we are now in a lull in terms of precip with generally clear skies overhead. Valley fog has formed across much of the area where it rained earlier today from Bradford to St. Marys to the forests of Clinton and northern Centre Counties. Fog will also expand over east central PA as the night progresses, first into portions of Schuylkill County and then expanding into the Susq Valley. 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 moving through Michigan and northern Illinois as of 11 PM Thu is progged to drop into OH/wrn PA toward morning. SPC still has the wrn 2/3rds of the CWA in a MRGL risk for SVR (primarily a marginal wind threat - limited by a lack of SBCAPE and DCAPE). The main uncertainty is just how far south the heavy shower/storm activity will reach, given the strongest forcing just clipping our northwestern zones, but a fair number of hires CAM guidance still show convection expanding far south enough to impact even Somerset and Bedford Counties. 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/... 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. Isolated to scattered thunderstorms are possible Friday afternoon as the warm and humid conditions across south central PA provide 1500 to 2000 J/kg of MLCAPE. The missing piece for a more widespread afternoon convective outbreak is a lack of upper level forcing for ascent through the dry midlevels. However, any isolated/scattered cells that do pop up in the afteroon have the potential to become briefly severe, especially if precip cores are lofted up above 3-4 km AGL, yielding more of a downburst potential. Another nocturnal MCS appears possible Friday night into Saturday morning as it moves across Pennsylvania from the Midwest. Severe weather appears a bit more likely with this round as up to 1500 J/kg of MLCAPE lingers into the overnight especially across the Laurels and Alleghenies. 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 additional 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. Even outside of thunderstorms, wind gusts in excess of 30 mph are possible Saturday as westerly winds pick up behind the cold front. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Dry conditions continue into the beginning of the long-term period as an upper-level ridge supplies fair conditions through Tuesday afternoon. Increasing moisture on Tuesday leads to a notable uptick in cloud cover for the second half of the day for most, especially across the Laurel Highlands as the next system pulls closer to the region. Temperatures for Monday and Tuesday are expected to trend slightly below seasonal averages, especially during the daytime hours. Model guidance promotes two different solutions for the area of low pressure approaching central Pennsylvania in the late Tuesday/early Wednesday timeframe. ECMWF/GDPS guidance tend to keep the approaching area of low-pressure west of the area for quite longer and does keep highest chances for precipitation until Wednesday afternoon/evening. Recent GFS/UKMET guidance outline a solution where the surface low-pressure dive further south and station over MD by Wednesday morning, allowing for precipitation chances to increase Tuesday night into Wednesday morning across the area. Given some model differences, have stuck close to NBM guidance while also trimming back timing on precipitation slightly due to some low-level drier air in place. After precipitation onset, generally expect showers to continue through the end of the long-term period given favorable moisture and lift associated with the area of low- pressure. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... Fog and lowered cigs starting to affect multiple TAF sites as temperatures cool over moist ground/lower levels. Once formed expect conds to persist much of the overnight. Next concern for overnight will be a line of thunderstorms that are expected to move 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 Friday behind the line of storms, but additional thunderstorms will likely develop Friday afternoon/evening. Outlook... Sat...Showers/storms especially in the afternoon. West winds gusting 30-35 kts. Sun...Some improvement, as a series of cold fronts move southeast of the area. Mon...Mainly dry with VFR conditions. Tue...VFR with scattered showers across the west 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...Colbert LONG TERM...Beaty AVIATION...Bauco/Gartner ####018006683#### FXUS61 KPBZ 160729 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA Issued by National Weather Service Charleston WV 329 AM EDT Fri May 16 2025 .SYNOPSIS... There is potential for strong to severe storms today and tonight as a cold front approaches. Drier and cooler conditions return Sunday through early next week. && .NEAR TERM /TODAY AND TONIGHT/... KEY MESSAGES: - Several rounds of thunderstorms will be possible today and tonight ahead of an approaching cold front. - Thunderstorms could become strong to severe and capable of producing damaging wind gusts, large hail, and tornadoes. ------------------------------------------------------------------- A narrow mid-level shortwave ridge is passing over the area ahead of an approaching surface warm front. This ridge was not well resolved by convective-allowing models, resulting in stronger mid-level subsidence than forecast which is helping to suppress convective initiation south of the I-80/90 corridor in Ohio. The last couple runs of hi-res models are finally beginning to correctly initialize with this lack of storms and as a result, are now showing a lesser coverage over the local area through morning. The best chance for thunderstorms between now and roughly 8am will be north of Pittsburgh and more so north of I-80. There is certainly still some potential for storms farther south to the I-70 corridor, but confidence there is decreasing at this time. A special 06z PIT sounding shows a weak capping inversion in place around 700mb (owing to the aforementioned mid-level subsidence above that level), but otherwise steep lapse rates, dry air aloft, and roughly 40 knots of deep-layer shear are present and would support a severe weather threat should any storms form. Initial thinking was that the environment would need to recover during late morning and early afternoon hours today in the wake of the early morning round of storms. However, if less coverage is in fact observed, this recovery may no longer be needed which could shift the start time for the next expected round of thunderstorms up a few hours to mid afternoon. This will need to be monitored, as previous messaging was for storms to develop after 6pm while some convective models are now showing initiation as early as 2pm. The environment will remain potent with ample instability and wind shear, supporting a severe threat with any storms that form. All hazards would be possible, including damaging wind gusts, large hail, and tornadoes. The final round of thunderstorms is still expected to push through during overnight hours tonight into Saturday morning. Once again, there is newly added uncertainty to the timing and intensity of that final round as that will depend on whether thunderstorms form in the afternoon or not. If they do, the environment could be worked over enough to lower the intensity of overnight storms, whereas the opposite would hold true if storms don't form in the afternoon. This too will need to be closely monitored. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... KEY MESSAGES: - A cold front crosses the area, ending thunderstorm activity and ushering cooler and drier weather into the region. ---------------------------------------------------------------- Showers and storms depart the area to the east on Saturday as a cold front sweeps through the area, ushering in cooler and drier weather under deep-layer northwesterly flow. Showers could linger in the ridges through Saturday evening with weak upslope occurring in the wake of the front, but by overnight hours that activity too should wane, with temperatures then dropping into the low to mid 50s by early Sunday morning. && .LONG TERM /SUNDAY THROUGH THURSDAY/... KEY MESSAGES: - Cooler and drier pattern returns Sunday through Tuesday. - Precipitation chances return Tuesday into Wednesday with another low pressure system - Potential for heavy rain mid-week that warrants monitoring ------------------------------------------------------------------- Models have been consistent that troughing over the Great Lakes and northeast CONUS will maintain northwest flow over the local area Sunday into Monday, keeping temperatures seasonable and the weather dry through that time. Probability of precipitation increases again late Tuesday into Wednesday with a new low ejecting out of the Rockies and tracking east across the Plains. A few model scenarios note a stationary boundary straddling south of Pittsburgh with this passing low. If that scenario plays out, heavy rain could pose a threat for portions of the region around mid-week. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... A shortwave trough will continue to track across the Upper Ohio Valley region early this morning. Mid level capping has limited the southern extent of a line of thunderstorms. It appears some erosion to this cap is likely as the trough approaches, though the southern extent of the line of storms remains in question. Included IFR restrictions for FKL and DUJ, where the more favorable conditions for convection exist. A brief period of MVFR is possible after the passage of the wave this morning, though VFR should quickly return by mid morning. Scattered diurnal cu is expected to develop through the day. With the thunderstorms not developing as far south as expected early this morning, this will result in more destabilization later today as another shortwave crosses the region. Added a prob30 mention of thunder for most airports south of Rt 422, though considerable uncertainty exists in this scenario. Another round of thunderstorms, possibly an MCS, is expected to cross the region late this evening with a crossing cold front. Models differ on the northern extent of this potential, which could also be impacted by any afternoon convection. Included a prob30 for thunder for now until forecast details become more clear. Outlook... Patchy restrictions in scattered showers are expected Saturday and Saturday night under a crossing upper trough. VFR returns Monday under high pressure. Restriction and rain potential returns with a Tuesday warm front. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Cermak/Hefferan NEAR TERM...Cermak SHORT TERM...Cermak LONG TERM...Cermak/Hefferan AVIATION...Shallenberger