Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 210933 AFDCTP Area Forecast Discussion National Weather Service State College PA 533 AM EDT Wed Mar 21 2018 .SYNOPSIS... Strengthening low pressure east of the Delmarva Peninsula will track northeast and away from Pennsylvania tonight. A ridge of high pressure will build into the region from the Great Lakes late in the week. Low pressure moving out of the Mississippi Valley will likely pass well south of Pennsylvania over the weekend. && .NEAR TERM /THROUGH TONIGHT/... Mid level closed low over the Ohio Valley will shift eastward across Virginia today, placing southern Pa in favored region of best deformation/frontogenetic forcing and anomalous easterly flow. Models depict only very slow strengthening of mid level low, and relatively modest fgen forcing, so have toned down mention of heavy snow. Rather, expect a long duration of moderate snow rates across southern Pa as the 00Z HREF depicts. Very dry air in place across northern Pa should result in a sharp northern gradient to the snowfall today, with locations north of I-80 seeing little if any accumulation. Developing coastal low is progged to track from just east of the Delmarva early this evening to southeast of Cape Cod late tonight, resulting in snow tapering off across southern Pa overnight. A blend of model qpf supports snow accumulation today through this evening ranging from nothing over the northern tier counties, to between 6-9 inches south and east of I-81. A look back at highway webcams across Somerset County from yesterday showed briefly slushy road surfaces during the heaviest of the snow, then a quick return to wet roads as the rates dropped off. Expect a similar situation to play out today, with the high March sun angles helping to melt snow on pavement. && .SHORT TERM /THURSDAY/... Models showing a trailing shortwave diving southeast across the region on Thursday. Upper level diffluence ahead of this feature should result in a fair amount of cirrus. Low PWATS and temps aloft not cold enough to generate moisture flux from the Grt Lks, so not anticipating anything more than scattered flurries across the Laurel Highlands. NBM/Superblend indicating max temps Thursday ranging from the low 30s over the highest terrain of the Alleghenies, to the low 40s in the Susq Valley. However, a tight pressure gradient west of coastal low will produce gusty winds, making it feel even chillier. Bukfit soundings support frequent gusts between 20-25kts. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... All models tracking closed upper level low southeast across Pa on Friday, likely supporting scattered, diurnally-driven snow showers, mainly over the northern and western mountains. After that, focus will shift toward low pressure lifting out of the Miss Valley next weekend. NAEFS/ECENS indicate this system will likely pass too far south to affect central Pa, but will maintain the slight chance for a period of snow. After that, all med range guidance is showing upper level ridging building into the region, supporting a high confidence forecast of fair weather early next week. A dying cold front could approach the area late Tuesday, potentially spreading showers into the state. Temperatures should remain below seasonal normals through most of the long term forecast, as upper trough remains over the northeast conus. However, moderation is anticipated by Tue/Wed, as upper trough lifts out. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
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As of 5 am...starting to see more reports of snow in the obs now. Updated the TAFS as of 530 am. A little more snow reported in the sfc obs now...but it looks more active on the radar. Key is very dry air at low levels from the north is making it hard for much of the snow to reach the ground. Minor adjustments to the 06Z TAFS. Expect some improvement late today into the storm slowly moves eastward off the coast. Outlook... Thu...No sig wx expected. Fri...Cig restrictions poss NW. Sat-Sun...No sig wx expected.
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&& .CLIMATE... The Spring (Vernal) Equinox was at 12:15 PM yesterday, March 20. Sunrise in State College, PA was at 7:14 AM and sunset at 7:23 PM, for a total day length of just over 12 hours. This is normally the time period where the average temperature climbs a degree every few days...and daylight increases upwards of about 3 minutes per day. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 8 PM EDT this evening for PAZ017>019-045-049>053. Winter Storm Warning until 8 PM EDT this evening for PAZ024>028-033>036-056>059-063>066. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald AVIATION...Martin CLIMATE...Martin is the U.S. government's official web portal to all federal, state and local government web resources and services.