Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 191117 AFDCTP Area Forecast Discussion National Weather Service State College PA 717 AM EDT Mon Mar 19 2018 .SYNOPSIS... Fair and dry conditions will continue today. A storm system will affect the area for the first day of Spring tomorrow, and will linger into midweek. Cooler than average temperatures will dominate the pattern through the end of the week, with the next opportunity for precipitation coming this weekend. && .NEAR TERM /THROUGH TONIGHT/... Skies are still mainly clear with just some thin high clouds over central areas and a few low clouds associated with a weak cold front over the north. It will remain fair and dry today, but with a gradual increase in clouds late in the day from S to N. The low level flow will start off light from the NW before gradually turn around to the SE ahead of a low pressure system progged to track to our south tonight into Tue. Highs will range from the mid 30s north to around 50 south. Latest timing shows some light precipitation starting to break out over my southern zones around or shortly after midnight. Initially there will be a wedge of warm air aloft over the SWRN part of the forecast area which could lead to a period of a wintry mix, but evaporational cooling should make snow the predominant precip type by Tuesday morning. Surface temperatures over the border counties will remain marginally cool and actual overnight QPF is expected to be light, so we expect little more than a coating of snow by sunrise, and in many locations that will be mainly on grassy surfaces. && .SHORT TERM /TUESDAY/... Most model guidance agrees that the heaviest precipitation will stay south of the PA-MD border on Tuesday. There is agreement that lighter QPF is likely from about I-80 southward. This presents a PTYPE problem as it will be cold enough aloft to favor snow in most areas, but a variety of factors will complicate matters throughout the day. The first day of spring (12:15PM) will bring high sun angles allowing surface temps to rebound into at least the mid 30s over most of the area. Given that daylight QPF is expected to average .25" or less, that implies precipitation rates will not be especially robust which with marginal thermal profiles is normally needed to keep these late season events all or mainly snow. As it stands, we are probably dealing with snow accumulating mainly on the ridges and lower elevation grassy surfaces. We have decided to wait on any headlines as it looks like if anyone gets several inches of snow, it will likely string out over a fairly long duration. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... By daybreak Wednesday the storm is expected to be reorganizing off the Mid Atlantic before tracking off south of Nantucket island. The upper trough/low will keep some light precip lingering Tuesday night and Wednesday morning. An additional coating of snow is possible as surface temperatures chill down into the 20s in most areas Tuesday night. By later Wednesday cool and drier air will begin filtering in. Weak high pressure will keep us fair through Friday before the next approach storm brings a chance of rain or snow Saturday and Saturday night. Tonight the model timing differences are not as stark as they were last night, but now the GFS is notably more south with the low than is the EC. The EC track would make for a widespread late season accumulating snow over much of the region. For what it`s worth, the ECENS loses the low entirely so it`s too early to get excited that the only big snow storm of the year will come as the daffodils start blooming. && .AVIATION /11Z MONDAY THROUGH FRIDAY/...
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Some mid and high clouds over the area as of 7 am. No large changes to the 12Z TAFS. Earlier discussion below. Main change to the 09Z TAFS was to take out low clds for BFD. BUF went sct...and the airmass is very dry. Thus looking at a decent day with light winds and just some high clds. Mid level clouds work into the area from south to north tonight. Some patchy light rain and snow will be possible by sunrise on Tuesday...mainly along the PA...MD border. Outlook... Tue...Snow/restrictions likely southern Pa. Tue night and Wed...more snow at times. Restrictions at times. Thu-Fri...No sig wx expected.
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&& .CLIMATE... The Spring (Vernal) Equinox will be at 12:15 PM on Tuesday, March 20. Sunrise in State College, PA will be 7:14 AM and sunset at 7:23 PM, for a total day length of just over 12 hours. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...La Corte LONG TERM...La Corte AVIATION...Martin CLIMATE...Steinbugl is the U.S. government's official web portal to all federal, state and local government web resources and services.