Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 162003 AFDCTP Area Forecast Discussion National Weather Service State College PA 303 PM EST Sat Dec 16 2017 .SYNOPSIS...
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High pressure is moving in for tonight and last into Sunday. A weakening wave of low pressure will move in from the midwest late Sunday. Scattered snow showers will be in store for the west during first part of the week. Fast west to east flow aloft will keep the weather unsettled.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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Clouds will likely hold on all night in the NErn half to 1/3rd of the the area with warm advection and lift just above the blyr. However, the moisture will be decreasing through the evening, and the light snow should dwindle to flurries by midnight and little should be left after that. Mins are tricky with clearing in the south but the light SW wind will try to keep temps up a little. Locations to the east of the Susq will likely fall the hardest with snow on the ground.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
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Clouds in the NE half/third should begin to break up, but just in time for a new batch of warm advection to ride in from the west later in the day. So, there will likely be an increase in clouds over the SW, and a waffle from clouds to no clouds and back again in the central/NE. We are expecting some light precip to break out in the SW/SC counties by nightfall. The temps will get into the 40s in the south with sun. without much sun in the NE, it will likely stay below 35F. The low pressure over the mid-MS valley will fall apart as it goes into the OH valley and a loss of moisture will kill much of the precip as the feature fills over us and moves eastward Sun night. The clouds will likely hang low and thick, keeping temps up. Many places should stay above freezing.
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&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... This coming week will see the long-wave upper level trough that has been dominating out weather shift east as a deep trough digs over the Western U.S. Lake enhanced snow showers should be ending by Saturday night with the surface high pressure ridge moving off the coast and the winds becoming move west to southwesterly. The western trough kicks a strong shortwave out across the Plains Sunday into Monday. The associated low center will move northeast across the Great Lakes staying to our North and west. This system will bring in warmer air in southwest flow ahead of it. However, we may be cold air dammed near the surface so the +1 to -2C air at 850 hPa may not translate to a warm boundary layer. The warm advection should bring snow and snow to rain in the south but QPF amounts are light. Will have to watch for potential for some ice also Sunday night. We look to move into a fast moving pattern of weak shortwaves and chances for precipitation (mainly over the northern mountains) through the week. As a northern stream wave zips by to our north by Monday night, it should drag cold air back into the region Tuesday into Wednesday. The northwest flow triggers snow in relatively high POPS in NW PA due to LES. This cold surge should be relatively fleeting and high pressure and a potential surge of relatively warmer air follows Thursday. The warm advection and approaching cold front will likely produce increased potential for snow in NW Thursday into Friday. Farther south any precipitation would likely be mixed or rain. A strong frontal boundary will likely push another surge of cold air into the region Friday into Saturday as the eastern long wave trough tries to re-establish itself. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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Outlook... Mon...Mainly VFR. Spotty SHSN poss W. Tue...Mainly VFR, but possible restrictions in the western and northern mountains in snow showers. Wed-Thu...No sig wx.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 4 PM EST this afternoon for PAZ004-005. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...Watson AVIATION...Dangelo

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