Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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359 FXUS61 KCTP 040148 AFDCTP Area Forecast Discussion National Weather Service State College PA 948 PM EDT Wed Jul 3 2024 .SYNOPSIS... Warm and humid conditions will prevail through week`s and into the start of the coming weekend. A weakening cold front will push in from the Great Lakes tonight, then stall out over the area late this week. Low pressure tracking north of Pennsylvania will drag a cold front through the state Saturday. Drier and more comfortable conditions are expected for Sunday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... The focus tonight will be on a an approaching, slow-moving cold front, which lies from Western Lk Erie into Northern Indiana at 02Z. A band of convection along the attendant low level jet/plume of highest pwats has largely dissipated as it pushed into Northwest PA this evening. However, modest instability and convergence along the low level jet could still support a few showers overnight across the northwest part of the forecast area. Mostly cloudy skies over the northwest counties and increasing clouds elsewhere, combined with surging humidity, will result in a much warmer night than we`ve seen recently, with low temperatures in the mid 60s to lower 70s. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/... Latest model guidance indicates the cold front will stall out over Northern PA Thursday, resulting in a warm and sultry 4th of July for Central PA. Isolated showers are possible during the morning hours, primarily in the vicinity of the front over Northern PA, then expect convection increasing in coverage by afternoon, as a weak shortwave approaches from the Southern Grt Lks. Model RH profiles suggest mostly cloudy skies are likely. However, even modest diurnal heating of this high-pwat airmass should yield moderate capes of near 1000 J/kg south of the front. Deep layer shear profiles are not especially impressive Thursday, but the combination of instability and shear yields decent updraft helicity values across the southern tier of the state, where isolated late day severe weather appears possible. The combination of instability and +2-3SD pwats could yield torrential downpours in some parts of Southern PA Thursday afternoon. The 12Z HREF indicates localized amounts to 3 inches are possible across the southern tier, but dry ground in this part of the state will limit the flash flood threat. Highs Thursday afternoon will generally be in the 80s with a few spots potentially reaching 90 degrees in the southeast before convection arrives. Passage of the shortwave and nocturnal cooling should result in dwindling convection Thursday night. Slightly cooler air may work into the N Mtns, as the front sags into the central part of the state. Otherwise, expect a very warm and muggy night with min temps in the upper 60s to low 70s. The stalled front over Central PA is progged to return north as a warm front Friday PM ahead of low pressure lifting across the Grt Lks. Falling heights and surging pwats ahead of an upstream shortwave and associated surface low lifting across the Grt Lks should bring a round of showers/tsra in the Friday PM to Saturday AM timeframe. Model shear/instability profiles indicate strong to severe tsra can`t be ruled out Fri PM. The trailing cold front should clear most of the region by Sat morning, but could take until afternoon clear the southeast counties, where the threat of a tsra will linger. Current guidance suggests the mid level shortwave and bulk of the large scale forcing will pass north of PA, leading to unimpressive mean qpf in the ensemble plumes of 0.25 to 0.50 inches Fri PM to Saturday. However, locally heavier amounts will accompany stronger convection. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Deterministic guidance continues to outline fair and seasonable conditions on Sunday and into early Monday with surface ridging and drier air working in behind the frontal passage. There is a bit of uncertainty into the later hours on Monday as ECMWF guidance outlines drier conditions prevailing across all of central PA, with GFS outlining some showers and thunderstorms Monday late afternoon/evening across mainly southern Pennsylvania where moisture and lift will be slightly more favorable. Given some uncertainty, have mainly kept PoPs confined along the Turnpike and the higher elevations of Schuylkill County for this forecast cycle, slightly cutting back from NBM PoPs in this timeframe. Both ENS and GEFS plumes begin to outline greater chances for precipitation into Tuesday, as a low pressure north of the area continues to push eastwards and drag a cold front across the region. Some instability will bring some potential for storms especially in the afternoon/evening hours, but cannot rule them out throughout the morning hours during this forecast cycle. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... A few showers have developed across the northern tier and will continue to push eastward over the next few hours. More showers and thunderstorms ahead of an approaching cold front are expected to move into the region tonight, with the bulk of the overnight activity expected to remain across the northern half of the area. Ceilings will gradually lower at BFD as these showers and storms move in, and a period of MVFR ceilings is likely afer 06Z with IFR ceilings expected after 09Z. There is fairly high confidence that the low clouds extend down to JST with the HREF showing a 60-70% chance of MVFR ceilings there. Elsewhere, VFR conditions are anticipated. As the front progresses through the area, thunderstorms will become more focused across the south. While all sites will likely see thunderstorms at some point during the TAF period, the exact timing of thunder will have to be adjusted in the forecast once we have a better idea of the exact placement of storms. Brief visibility restrictions and gusty winds will be possible in any of the stronger thunderstorms. Outlook... Fri...Sct TSRA w/ possible impacts; Mainly PM w/ highest coverage across the west. Sat...Sct to Nmrs TSRA areawide, highest chances SE in PM. Sun...AM fog possible; otherwise, no sig wx. Mon...SHRA possible SE late PM; otherwise, no sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir/Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald/NPB AVIATION...Bauco