Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 280546 AFDCTP Area Forecast Discussion National Weather Service State College PA 146 AM EDT Sun May 28 2017 .SYNOPSIS...
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A warm front will approach from the south today as a cold front approaches from the west. The cold front will pass through later tonight and early Monday morning. Low pressure stalled over northern Ontario during mid-week will create a slightly cooler than normal and unsettled stretch of weather.
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&& .NEAR TERM /UNTIL 8 AM THIS MORNING/...
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Fog and some low stratus have already formed in the SW and clouds cover the NE mtns now, as well. The flow at cloud level will be more from the E/SE through the night and clouds will expand a bit more through the night under weak high pressure and it`s subsidence inversion. A few patches of drizzle are possible if the fog/stratus can get a few kft thick.
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&& .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM MONDAY/...
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The mean sfc-850 mb flow becomes more southerly during the daytime. This should help bring more-mild air in, but the mountains tend to thwart good mixing and make it difficult to really get temps cranking. However, there will be some breaks start to for in the morning. Some of the higher terrain may then be ripe to pop a few showers. the column is not all that unstable at first, but the chance for storms increases during the afternoon. Again, they will be popping off the higher terrain/elevated heating surfaces at first, then expand some. Initial strom motions may be slow, and they may kill themselves off before they get too tall. CAPE will be limited due to the limited heating/sunshine in lots of places. The destabilization will be easiest in the east where less low clouds are expected, but the deeper moisture is off to the west and the dynamics are even farther to the west. PWAT goes above 1.5 inches in the west by the end of the day Sunday. Will ramp POPs up in the west through the aftn, leaving the east in chc or less POPs. Have made a slight tweak earlier in time for some showers/storms over the Laurels and Alleghenies. Temps will get into the m70s for the eastern valley cities, but only near 70 elsewhere. Widespread showers and storms will occur this evening and through the night. The NAM is trending quicker with the CFROPA and others are following suit. The SREF is also aggressive with the FROPA. Even if the slower models come to fruition, the front will be to the Susq River by 12Z and little if any showers are expected after 15Z in the east. It should turn out to be a really nice day with just a westerly breeze. Temps may be a bit higher than currently advertised due to some earlier clearing and the downslope effect.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Dry conditions expected Tuesday morning before significant cooling aloft accompanies a pair of short waves late Tuesday and later Wednesday. POPs during this midweek period will be painted as chc - translating to scattered showers with preference for the majority of the QPF (albeit quite light at that)to be across the typical west-nwrly flow upslope prone areas of the Laurel highlands and NW mtns. The chance for any thunder will be very minimal Tuesday through Thursday. Generally dry NW flow occurs late in the week into next weekend as a 1020 sfc high over the upper midwest Friday evening builds SE twd the region. Pops Thur night through Fri night will be 30 percent or less. After our bout of coolish weather with temps several Deg F below normal Sunday and Monday, GEFS mean temps rebound back to near or slightly above normal (even under slightly cooling 850 mb temps) for Tuesday through at least Thursday. ECENS mean temps are several deg warmer than the GEFS and Nat`l Blend of Models temps. leaned closer to the cooler solutions based on the few-svrl deg C of cooling aloft with near to slightly below 850 mb temps.
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&& .AVIATION /06Z SUNDAY THROUGH THURSDAY/... Weak ridge of high pressure will build across the region tonight, resulting in a calm wind and conditions favorable for fog formation. GOES 10.3-3.9um imagery already showing developing low clouds/fog across the southern tier of Pa at 04Z and dewpoint depressions suggest IFR/LIFR conditions could begin as early as 05Z at AOO, while much of the remainder of central Pa is likely to experience fog formation between 06Z-09Z. At this point, would categorize IFR/LIFR conditions as likely at JST/AOO/LNS/UNV/MDT overnight and around 30 pct at IPT. Early low clouds/fog will begin to lift after 12Z, with VFR conditions expected in most locations by afternoon. However, there is at least some potential of a moist sse flow into the mountains creating a MVFR stratus deck along the east slopes of the Appalachians from BFD south through UNV,AOO and JST. The other area of concern will be isold tsra impacts across the western airfields associated with a warm front pushing into the region. .OUTLOOK... Mon...AM showers/low cigs possible. Tue...No sig wx expected. Wed...Slight chance of showers/reduced cigs. Thu...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/La Corte NEAR TERM...Dangelo/La Corte SHORT TERM...Lambert LONG TERM...Lambert/Ceru AVIATION...Fitzgerald

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