Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 152003 AFDCTP Area Forecast Discussion National Weather Service State College PA 403 PM EDT Sun Oct 15 2017 .SYNOPSIS... A rather strong cold front will push east through the region late today and early tonight. Blustery and cool weather is in store for Monday. Temperatures will rebound to near normal on Tuesday, then continue to gradually rise to well above normal right into this upcoming weekend, as a large area of high pressure builds east over Ohio Valley and Mid Atlantic states bringing an extended period of dry conditions. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Regional radar mosaic loop shows several bkn lines of fast moving, briefly heavy showers and even a few low-topped tsra from NE Ohio and Western Lake Erie, north into the SW Peninsula of Ontario. A preceding area of strato cu was streaming northeast within a belt of strong llvl warm advection via a 50-60 KT LLJ across eastern Ohio and NW PA - just ahead of these lines of prefrontal convection. Models generate a few to several hundred J/KG of cape this afternoon into early this evening, so some tall, gusty showers and even a few low-topped TSRA are expected across the NW third to half of the state along and just ahead of the Cfropa. SPC 16Z update has maintained the Day1 SLGT risk area across the NW mtns of PA and its MRGL risk area a few layer of counties further to the SE...to near the I-99/RT 220 corridor. High Res CAMs data indicates the potential for a quasi-NCFRB feature consolidate from, or forming just ahead of the current bands of showers and isolated low-topped TSRA. The timing of this convective feature, with potential embedded mini bow echoes and damaging microburst wind gusts of 50 to 60kts will be along a KBFD to KPIT line between 21Z and 2230Z...before march on to a KBGM to KIPT...KUNV and KCBE line between 00Z and 01Z Monday...then reaching a KAVP to KMUI...KMDT and KTHV line between 02Z-03Z Monday. This convection should maintain its strength easily through 00Z Monday before slowly weakening as the front crosses the central counties, and slips away from the core of the strongest low-mid level SW-WSW flow across Nrn PA and New York State. Temps are closing in on their forecast max values - in the low to mid 70s across the nrn and wrn mtns....and 75 to 80F in the central and SE zones. QPF should be low in the SE (generally 0.10 of an inch or less, but between one-quarter and one-half of an inch in the NW. Winds will become increasingly gusty (peaking in the 25 to 30kt range across the Laurels and NW Mtn) out of the SW in advance of the cfront. After the front clears the area early this evening, the cold NW flow will make quite a dramatic difference in the temps, and especially the apparent temps considering a brisk breeze from the WNW overnight. After becoming so Again, we have become acclimated to the persistent above normal temps early this autumn, the drop (albeit a brief 36 hours or so) to much below normal temps and cold, cross-lake flow...strato cu and sprinkles/light showers will be a shock. Min temps early Monday will vary from the U30s to L40s across the NW mtns and Laurel Highlands, to the lower 50s in the SE. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... For Monday, we expect to see maxes about 5-10F below normal with highs ranging from the U40s to L50s across the mtns, to around 60F in the SE. As the mid-level thermal trough crosses the region Monday, isolated to scattered instability (and lake effect) showers will occur across the NW Mtns and Laurel Highlands, with just some sprinkles accompanying expanding MDT cu clouds in the afternoon elsewhere. The NW wind gusting between 20-25 mph will trim another 8-10 degrees off what the air temp should feel like on our skin. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
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As the upper level trough deepens as it moves eastward, cold air, with readings of around 6C at 850 mb will move over the region by Tuesday morning. Temperatures will be slightly below normal with readings in the mid 30s. Frost across much of Central and Northern PA remains likely with even sub- freezing conditions across the perennial cold spots INVOF KBFD. For the mid to late week period, heights gradually rise with a multi-model consensus indicating a string of dry and increasingly warm days and mainly clear/cool nights. We could have a period true Indian Summer weather with high temps in the in the low to mid 70s from mid week into next weekend.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/... The western edge of the stubborn low stratus has eroded to near a KAVP to KLNS line as of 1830Z, and will be followed by a several hour period of mostly sunny skies across the Central Mtns and much of the Susq Valley. The nw part of the CWA will see a quick increase in dual to mult-layered strato/alto cu clouds in a zone of strong low to mid level winds 60-65 KTs and warm advection ahead of a potent cold front racing east from Ohio. A well-mixed, gusty southwesterly flow of 15-20KTS as of early this afternoon will increase by another 5 kts or so preceding the late day early evening cfropa across the NW mtns and Central Ridge and Valley Region. The lingering/recent clearing of the low clouds across the Lower Susq Valley, and greater separation from the main core of the strong Swrly low-level jet at 4-7 kft AGL (over far nwrn PA and Lake Erie), will lead to light moderate winds and gusts out of the 200-220 deg range for the rest of this afternoon and early this evening there. A sharp cold front will cross the area late this afternoon (NW) and mid to late evening (SE), accompanied by showers and isolated strong to potentially severe tsra across the NW mtns of PA with brief MVFR CIGs and VSBYS. This front will be followed by MVFR cigs across the western mountains later tonight and Monday, as residual low level moisture ascends the Alleghenies, with sct-bkn VFR Cigs elsewhere later tonight and much of Monday. Outlook... Mon night...No sig wx expected. Tue...Patchy AM fog possible. Wed-Sat...A few hours of patchy dense valley fog is possible each morning, otherwise No sig wx expected for the bulk of the time as a large are of high pressure builds east over the region. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Ceru AVIATION...Lambert/Gartner

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