Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220102 AFDCTP Area Forecast Discussion National Weather Service State College PA 902 PM EDT Wed Jun 21 2017 .SYNOPSIS... A weak cold front will stall out just south of Pennsylvania tonight, then return north as a warm front on Thursday. A deep upper level trough will approach the region, bringing increasing humidity along with the chance for showers and thunderstorms late Thursday into Saturday. Drier and cooler conditions will return later in the weekend into next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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0030Z radar loop still showing a few isolated showers firing in vicinity of dying cold front across southern Pa. Based on radar/satellite trends, will maintain a low chance of a shower/tstorm south of the turnpike and west of Adams County. Will remove mention of precip across the southern tier after 03Z, as boundary layer stabilizes and dying cold front sags south of the Mason Dixon Line. A push of low PWAT air in the wake of cold front should result in a fair and dry night across central Pa as high pressure builds across the state. Mostly clear skies, a calm wind and wet ground in some places should result in patchy fog late tonight. Temperatures are expected to fall into the upper 40s over the north, where the driest air will reside, to the low 60s over the Lower Susq Valley.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
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Thursday will start out partly cloudy and comfortable with the patchy early fog as a bubble of high pressure slides SE and over us for late morning. The stalled frontal boundary south of Pa will return northward through the state as upper level flow backs to the southwest ahead of deepening trough over the Plains. Diurnal heating of warm and increasingly humid air mass should trigger scattered showers/tstorms by the afternoon, focused primarily along the elevated heat source of the Alleghenies. Moderate CAPEs progged by mid afternoon of around 1500 J/kg, but wind shear looks relatively weak and model downdraft CAPE not very impressive, so the threat of organized severe weather appears low. Well mixed model soundings and mean 850mb temps around 16C should translate to max temps from around 80F over the northwest mountains, to the upper 80s across the Lower Susq Valley.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... From a large scale perspective, the medium range forecast will feature a seasonably strong/amplified upper trough settling over the Northeast U.S into next week. Expect moisture/rainfall associated with the remnants of TS Cindy to exit the area by the start of the weekend. Confidence is low with details (timing) with multiple shortwaves reflecting surface fronts/troughs inducing risk for isolated to scattered showers and Tstorms Mon-Wed. By Friday the tropical airmass will have re-established itself with dewpoints well up into the 60s and lower 70s over the entire region making for a sticky end of the work week. Model consensus continues to signal rain on Friday/Friday night corresponding with a peak in H85 moisture flux and PW. The heaviest rain is fcst to stay to the south of PA. Drier, low PW air arrives by early Saturday and lasts through the weekend. This should translate into comfortable, low- humidity conditions with temperatures near to slightly below late June climatology. Precipitation opportunities will be modulated by several shortwave impulses which have low predictability at this range. Any rains would be generally scattered and on the lighter side given overall lack of deep layer moisture. 21/12z GEFS shows PW values remaining below average into midweek. Temperatures should stay on the cooler side of climo through midweek as the upper level trough shifts east of the area. FWIW the GFS is more bullish vs. EC on heights rebounding/building SE U.S. upper ridging into the second half of next week. That said, there is general agreement in a modest warming trend later next week as the trough moves out and heights return to normal. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... VFR conditions will continue through the evening hours. Any remaining convection will dissipate by an hour after sunset. Initially mainly clear skies and quickly diminishing wind will likely lead to areas of valley fog during the overnight hours (mainly where rain falls today). A warm front will approach the region Thursday triggering showers and scattered thunderstorms, mainly over the west and NW during the afternoon. .OUTLOOK... Fri...Widespread sub VFR likely with rain and embedded thunderstorms. Sat-Sun...Mainly VFR Mon...Mainly VFR. Chc SHRA/TSRA. && .EQUIPMENT... KCCX radar will be offline for approximately 4 days starting Saturday, June 24th for technicians to install the first of 4 major service-life extension upgrades. The work on the radar has been scheduled to minimize potential impacts to operations and will be delayed if hazardous weather is forecast. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Steinbugl AVIATION...La Corte/Gartner EQUIPMENT...

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