Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 261114 AFDCTP Area Forecast Discussion National Weather Service State College PA 714 AM EDT Wed Apr 26 2017 .SYNOPSIS... A moist east-northeast inflow from the Atlantic Ocean will provide a cloudy and misty start today, followed by clearing through the afternoon. A few strong to severe storms are possible across the Northwest Alleghenies Thursday afternoon and evening. Warmer temperatures are expected through the end of the week. && .NEAR TERM /THROUGH TONIGHT/... Low pressure off the Delmarva/NJ coast this morning will track north-northeast today to a consensus position located southeast of Cape Cod by the end of the period. Moist east-northeast flow and residual low level moisture will provide a cloudy and misty start to the day with even some light rain at times into mid morning across the Susquehanna Valley where current radar and HRRR shows rain band wrapping NWWD - but the overall trend by later today should be toward improving conditions with increasing sunshine especially over western areas as the system moves slowly away from the area. It will be warmer than yesterday with highs ranging from the low 70s west to mid 60s east. Cloud trends will be key with the potential for cooler readings if clearing is slower to evolve. Low clouds may redevelop over the southeast overnight into AM Thursday with mild readings in the 50s. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Lead shortwave trough will pivot through the Great Lakes with an attending surface low occluding into Ontario, while its trailing front pushes eastward through the OH Valley. Latest model data shows at least marginal instability (MLCAPE >500 J/kg) developing within a strongly sheared pre-frontal environment from the upper OH Valley into western PA. The SPC D2 outlook expanded the marginal risk into NW PA and this area is being monitored for possible increase in thunderstorm risk level to SLGT (2/5) in later updates. Utilized a multi- model blend for this period which remained consistent in placing the highest POPS over the NW Alleghenies Thursday afternoon/evening, shifting EWD into north-central PA early Thursday night. Lingering showers should push east or dissipate as the front becomes quasi-stationary and oriented more west- east over CPA into Friday. The precip potential increases into Friday night based on NBM/ECENS blend as SW flow aloft directs higher moisture/PWs along the frontal zone. Temperatures will average well-above late April climatology with Thursday most likely the warmest day when many locations could reach 80F. The placement of the frontal boundary suggests the warmest temperatures on Friday will be across southern PA with another run at 80F. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Model and ensemble guidance remained in good agreement with large scale pattern amplification this period with a vigorous closed H5 low ejecting northeast from the southern Rockies into the upper Great Lakes/Canada and deep surface cyclone expected to lift out of the MS Valley. Meanwhile, an anomalous upper ridge centered over the Southeast U.S./western Atlantic will gradually weaken and shift east. The details of weekend forecast are still uncertain with rain risk likely focusing along/north of quasi-stationary frontal zone progged to shift south of PA by early Sunday before lifting back to the north as warm front. Therefore continued to utilize a NBM/ECENS/WPC blend for max/min temps and POPS which maintained good continuity with previous fcst. While unsettled with a period of rain likely at some point, the fcst does not look like a washout. Temperatures should remain above late- April climo but could be too warm/cool depending what side of the boundary you are on. Max POPS remain centered on Monday/May 1st as the aforementioned cold front crosses the Appalachians and continues toward the Atlantic seaboard. A severe weather threat may evolve downstream from the OH Valley into the Mid Atlantic, but at this time it is unclear whether instability will be sufficient to support severe storm risk. Temperatures will decline to near normal behind the cold front by next Tuesday May 2nd. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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The focus of moist and rather deep east to northeasterly flow off the Atlantic, in conjunction with low pressure lifting north from the Delaware coast, will maintain IFR to LIFR cigs into the late morning hours today (based on SREF Prob charts) with areas of MVFR to IFR Vsbys in -DZ and BR (especially over the east facing slopes and crests of the ridges). The early low CIGs/area of light rain and drizzle across the Susq Valley and points east will give way to gradually improving conditions during the late morning and afternoon hours today, as the storm system weakens and moves northeast twd Cape Cod. Model RH profile support VFR conditions at BFD/JST by midday, while more gradual clearing takes place across the eastern half of the state during the afternoon. Poorest flying conditions will likely hang on the longest (perhaps until 16-17Z) across the Lower Susq Valley invof KMDT, KLNS and KMUI. Outlook... Thu...AM fog possible. Isolated PM tsra impacts possible west. Fri...No sig wx expected. Sat...Rain/low CIGs possible NW Mtns. Isolated tsra impacts possible southeast. Sun...Low CIGs possible east. Isolated PM tsra impacts possible west.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Steinbugl SHORT TERM...Steinbugl LONG TERM...Steinbugl AVIATION...Lambert

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