Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 141930 AFDCTP Area Forecast Discussion National Weather Service State College PA 230 PM EST Sun Jan 14 2018 .SYNOPSIS...
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A deep cold upper level trough will pass through the region through the middle of next week. This feature will lift out by the end of next week and be replaced by a building upper ridge over the east coast by next weekend. Potential ice jam flooding is a concern along the Lower Susquehanna through Monday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Ice beginning to move on the Susquehanna River. Ice jams are possible and may result in local flooding at points where they potentially form along the Susquehanna River over the next 24 hours. Flood Watch in effect through Monday morning for potential ice jam flooding, mainly for areas extending from just upstream of the confluence near Duncannon southward along the main stem to the MD border. Another very cold night is in store for the area with favorable conditions for radiational cooling beneath surface high. Models do indicate some cirrus spreading into the state ahead of a shortwave lifting northeast up the Appalachians. However, light wind and snow cover should allow readings to fall to around -5F over the northern mountains. Wind chills may again approach -15F along the ridgetops of northern Pa, but most locations should remain sub-advisory.
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&& .SHORT TERM /MONDAY/...
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Clouds increase on Monday ahead of approaching Alberta Clipper It looks like snow will hold off until dark for most except far northwest PA. Thickening clouds and milder flow will allow temps to moderate into the 20s for all.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Med range guidance showing a weakening clipper tracking across the eastern Grt Lks Monday night, a track unfavorable for much snow in central Pa. Weak WAA, combined with orographic enhancement, may produce up to an inch across the northern/western mountains Mon Night, with little further east. However, a weak secondary low tracking from the southern Appalachians to the Mid Atlantic coast, combined with frontogenetic forcing resulting from jet streak entrance circulation, could potentially produce a couple of inches across our southeast counties Tuesday/Tuesday night. A reinforcing shot of cold air will work into the region by Wednesday, as deep upper trough swings through the region. Surface ridging over the area indicates there will be very limited lake effect activity, and mostly sunny skies east of the mountains Wed/Thursday. 00Z NAEFS and ECENS continue to advertise a pattern change by late in the forecast period, with upper trough lifting out and an anomalous upper ridge building over the eastern conus by next weekend. Return southwest flow and above normal temperatures appear very likely by next weekend, as surface high passes off the east coast and anomalous 850 temps surge into the region. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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VFR conds expected through Monday morning as sfc ridge axis builds over the region. Outlook... Mon...PM light snow poss west. PM low cigs poss east. Tue...Morning snow ending. Becoming VFR south and east, lingering snow showers and restrictions over the mountains. Wed...Mainly VFR, but brief reductions in vsby and cigs possible across the Northern and Western mtns as a result of isolated snow showers. Thu...Mainly VFR.
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&& .HYDROLOGY... Complicated hydrology going on across the CWA. The rain from the last couple days is making its way through the river systems. There has been lots of ice movement and there are still active ice jams across some of the area and anyone near rivers and streams should monitor levels closely. With the cold temperatures water will begin refreezing which should lock up shortly. Exception to all this is along the lower Susquehanna. Will be watching a significant rise move downstream towards Harrisburg tonight and Sunday. Expect flows to rapidly increase which will begin moving some of the ice. Fortunately water levels are low and it will take quite a bit of water to produce flooding from any ice jams but this area will be monitored closely. It will certainly be interesting to watch the ice move through the city tomorrow. && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Monday morning for PAZ056-057-063-065-066. && $$ SYNOPSIS...DeVoir NEAR TERM...DeVoir SHORT TERM...DeVoir LONG TERM...Fitzgerald AVIATION...DeVoir/Gartner HYDROLOGY...

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