Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 270647 AFDCTP Area Forecast Discussion National Weather Service State College PA 247 AM EDT Mon Mar 27 2017 .SYNOPSIS... A cool-moist easterly flow will keep it damp over most of the forecast area tonight. A frontal system will move back into the region overnight and remain nearly stationary before a cold front finally ushers in cooler and drier air during the day Tuesday. The drier conditions will continue for mid week before a new storm system approaches for the end of the week. && .NEAR TERM /UNTIL 10 AM THIS MORNING/...
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Low-level cold air damming remains across the region early this morning while several areas of mdtly strong uvvel were support mdt to heavy rain showers (esp across central and western PA) where NAM shows the best 925-700 mb Theta_E convergence via a core of 45-50KT mean winds in the 925-700 mb layer. As this attendant southerly low-level jet continues to overrun the dome of cool air across central Pa, expect rain to continue across/overspread the rest of the region between through 07Z. A blend of near term models support POPS near 100 pct with rainfall overnight of between a quarter and half inch over much of central Pa, with the lower amounts across the Lower Susq Valley and northwest mountains. Although the entire region will remain in stable air east of stationary front, models indicating enough elevated instability ahead of shortwave to perhaps support a few rumbles of thunder overnight, mainly across the western counties.
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&& .SHORT TERM /10 AM THIS MORNING THROUGH 6 PM TUESDAY/...
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Early showers should shift east of the region, as shortwave and associated low lvl jet exit the area shortly after 12Z Monday. Low level stability indices indicate that the surface warm front will lift northeast across the CWA by midday, as it`s associated sfc low moves down the St. Lawrence River Valley. Model soundings support lingering low clouds across the northwest mountains, where southwest flow rises over the higher terrain. Elsewhere, expect brightening skies by midday, with the most sunshine expected over the southern valleys. The partial sunshine, combined with ensemble mean 850mb temps of around 7C, should support max temps in the low 70s across the southern valleys. More cloud cover expected across the northern half of the state, where maxes should be mostly in the 60s.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... This period starts out with above normal heights over the eastern U.S. Several lows weaken as they move into this blocked flow and are forced to move to our west. The first wave is comes overnight tonight into early Monday. It has a good surge of moisture and one or more distinct ribbons of llvl theta-e convergence that should result in some nearly north-south oriented bands of briefly heavier showers. Thus nearly all operational and blended/ensemble guidance shows a very high probability of rain overnight tonight into Monday. Most of the guidance shows the peak chance of rain from 0000-1200 UTC Monday. Then things improve during the day Monday. The second wave moving northeast and right up the Ohio River Valley comes in overnight Monday into Tuesday. Another similar surge of +2-3 sigma Pwat air precedes the passage of this area of low pressure and will once again result in a high probability for showers, but generally light to locally moderate 12 hour rainfall amounts. The second event will push the warm moist air off to our south Tuesday night into Wednesday. Chance of rain should drop overnight Tuesday into Wednesday. Wednesday should be a relatively good day as high pressure builds in from the northwest. The dry air and high pressure are in all the guidance implying Wednesday and Thursday should be relatively nice days. High pressure, dry air, and normal to slightly below normal 850 hPa and 925 hPa temperatures imply near normal daytime highs. Most of the 26/00-06Z U.S. and int`l model guidance (and EFS) indicates more of southern...shearing storm track for late in the week...thanks to a stronger and more wwd position of a deep nrn stream vortex across the Canadian Maritimes. The trend of the big model discrepancy for late this week and this weekend (between the GFS and EC over the past several days) has trended toward the GFS and its ENS members with southern stream energy and its moisture being prevented from amplifying with an associated storm track to our west. Rather, what we see is a shift of the primary southern stream sfc low track to our south as the potent midweek southern stream sfc/upper low (that will be trying to take the turn northeast across the Mid Miss Valley twd the Great Lakes) encounters great resistance from the notably stronger WNW upper jet core defining the northern stream that will be situated from the Upper Glakes to the Mid Atl Coast. With this type of consensus storm track, pops will be somewhat less for Friday and Saturday (compared to a heavily weighted EC/ECENS solution) and limited to mainly the southern half of PA where some rain (or even an elevation-dependent rain/wet snow mix) with expansive cooler and drier air north of PA. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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LMVFR to LIFR conditions will continue through mid-late morning with scattered rain showers moving east across the airspace. Expect improving trend by the afternoon with MVFR to VFR conditions likely after 27/18z. Coverage of rain showers will decrease with time with bulk of precipitation ending 12-15z. VFR should hold for the most part into early tonight with guidance showing restrictions developing into early Tuesday morning. Confidence is low after 28/00z. Outlook... Tue...VFR/MVFR with periods of rain. Wed...MVFR NW 1/3 becoming VFR. Thu...VFR/No sig wx. Thurs night-Fri...Sub-VFR restrictions/rain likely.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte/Lambert NEAR TERM...Fitzgerald/Lambert SHORT TERM...Fitzgerald/Lambert LONG TERM...Grumm/Lambert/Gartner AVIATION...Steinbugl

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