Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 271558 AFDCTP Area Forecast Discussion National Weather Service State College PA 1158 AM EDT Mon Mar 27 2017 .SYNOPSIS... An area of low pressure will be moving northeast across the Upper Great Lakes region this morning, pushing a warm front northward across the District. Unseasonably mild conditions are expected this afternoon through Tuesday. Cooler and dry weather will follow for Wednesday and Thursday. A new storm system will approach for the end of this week with the potential for more inclement weather. && .NEAR TERM /TODAY/... Drier air can be seen invading from the west. So far much of it is overshooting the low clouds/moisture trapped in the cool air damming regime over central PA, but the mixing down is starting to become evident over the SW where JST and AOO have both skycover improve rapidly. LAV and MET MOS guidance shows more of a mix of sun and clouds developing today. The model guidance also indicates a quick rebound/warmup in temps back into the 60s to near 70 deg F in the south this afternoon. RAP guidance shows us developing a modest amount of instability over about the southern 1/3 of the CWA this afternoon, and the meso-anal shows this already beginning over SWRN PA where the sun is breaking through the clouds. I kept small chance pops over the south to cover the potential for an isolated shower or thunderstorm. It will tend to become cloudy with a renewed chance of showers once again tonight as the next wave of low pressure moves into Ohio. Lows will be very mild in the 40s to lower 50s. && .SHORT TERM /TUESDAY/... The storm will pass just south of PA Tuesday with periods of light rain that will tend to taper off during the afternoon. It will be another mild day in the 60s in most locations. && .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 through early today. It has a good surge of deep layer moisture preceding it, and one or more distinct ribbons of llvl theta-e convergence that have resulted in some quasi north-south oriented bands of briefly heavier showers. Most of the guidance shows the peak chance of rain ending from SW to NE across the region between 0900-1400 UTC today. improving conditions will follow for the midday and afternoon hours today. The second wave moving northeast and right up the Ohio River Valley comes in overnight tonight across the western part of the state, and Monday into Tuesday over the eastern half or so of the state. 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. This second ares of low pressure 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 nice day (though with some mdt northerly wind gusts at times, as high pressure builds in from the northwest. The dry air and high pressure are in all of the most recent 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 /16Z MONDAY THROUGH FRIDAY/... MVFR/IFR conditions are already beginning to improve over SWRN PA. Expect the improving trend into the afternoon with MVFR to VFR conditions likely by mid to late afternoon. VFR early will deteriorate once again overnight as a new storm system spreads showers our way. 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. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte/Lambert NEAR TERM...La Corte/Lambert SHORT TERM...Lambert LONG TERM...Lambert/Gartner AVIATION...La Corte/Steinbugl is the U.S. government's official web portal to all federal, state and local government web resources and services.