Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 260328 AFDCTP Area Forecast Discussion National Weather Service State College PA 1128 PM EDT Sat Mar 25 2017 .SYNOPSIS... A cold front will sag south of Pennsylvania this evening, then return north as a warm front Sunday night. Unsettled conditions will continue through the middle of next week before high pressure returns with drier air. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Backdoor cold front has pushed south and west of the entire CWA as of late this evening. Parent shortwave and associated large scale forcing has passed east of the region, so no precip is currently falling across central Pa as of 02Z. However, GOES-16 water vapor loop is showing a weak shortwave lifting northward from West Virginia. As this feature and associated southerly low level jet lift into the region later tonight, expect a few showers to result, mainly where WAA is strongest along and north of baroclinic zone across northern Pa. In addition, moist easterly flow is likely to produce some patchy drizzle late tonight, especially over the higher terrain. Overnight lows will range from the mid 30s over the mountains north of Williamsport, to mid 40s in the southern valleys. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... Any rain showers should lift north of the border by early Sunday afternoon, as weak shortwave and baroclinic zone lift into upstate NY. However, persistent, moist easterly flow should result in lingering drizzle/ridge top fog the rest of the day. Upper low will approach from the Ohio Valley late in the day, bringing a renewed chance of showers across the Alleghenies and central mountains toward evening. Can`t rule out a rumble of thunder across the Alleghenies, although any convection will be weakening rapidly as it encounters stable air mass over central Pa. Local experience suggests we lean away from blended model guidance for max temps in such low level cold air damming situations. As such, I lowered tomorrrow`s highs by a few degrees counting on a day not nearly as nice as today, temperature-wise. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... This period starts out with above normal heights over the eastern US. Several lows weaken as they move into this blocked flow and are forced to move to our west. The first wave is comes overnight Sunday into early Monday. It has a good surge of moisture and a boundary related to the cooler weather on Sunday. Thus nearly all guidance shows a very high probability of rain overnight Sunday into Monday. Most of the NCEP guidance shows the peak chance of rain from 0000-1200 UTC Monday. Then things improve during the day Monday. Our POPS Monday may be too high but they are consistent with nearby offices. GEFS implies little or no rain in our CWA much after 1800 UTC. Most rain before than would be in the east. Our 850 hPa temperatures are above normal too so should be a warm later afteroon and evening. The second wave moving up to our west comes in overnight Monday into Tuesday. Clearly the uncertainty with this and the longer forecast length introduces more uncertainty. But at this time peak rain probabilities are during the day Tuesday but lower probabilities than the first event. The second event will push the warm moist air 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. The storm track shifts to our south and some models show a southern stream wave Thursday night and Friday. This could bring clouds to our region. GEFS and CMCE imply we could be on the northern edge of an expanding precipitation shield Friday and Saturday as the southern stream wave slides to our south and east. Thus POPS increase Friday and Saturday. Could be a cold rain across south-central PA Friday and Friday night. && .AVIATION /04Z SUNDAY THROUGH THURSDAY/...
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Could see the cold front on the radar earlier, just south and west of the office. CIGS not real low, even at BFD. For 00Z TAF package, did slow down how fast conditions go downhill. As of 11 PM, not much in the way of low clouds, fog, or showers. IPT did have a MVFR CIG for a brief time earlier. Thus I did back off on lower conditions until late now. Earlier discussion below. Overall expect a wide range of conditions later tonight into Sunday, as colder air just to the north trys to work southward. Conditions could improve some late Sunday afternoon, before a band of showers moves eastward from the Ohio Vly. Things could improve some on Monday, as some models bring the warm front back north of the area. The cold front could sag southward of the area on Tuesday, but perhaps not by much. Outlook... Mon-Tue...Sub-VFR with periods of rain. Wed...Chance of showers across the south early. Becoming VFR. Thu...No sig wx.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Grumm AVIATION...Martin

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