Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 130211 AFDCTP Area Forecast Discussion National Weather Service State College PA 911 PM EST Thu Jan 12 2017 .SYNOPSIS...
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A cold front is exiting the southern tier of PA. High pressure will build into the region on Friday. An anomalous upper level ridge will build over the southeast United States this weekend into early next week. At the surface, a quasi-stationary frontal boundary will oscillate in the vicinity of PA through early next week. Milder conditions will work back into the area for mid week.
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&& .NEAR TERM /UNTIL 8 AM FRIDAY MORNING/...
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Wind has switched to the NW at most sites. However, the light wind in the eastern valleys is allowing fog to form. As of yet, no M1/4SM obs. But, if the wind does not pick up a few knots, it may get dense. Rain band breaking up and getting lighter. Rain has ended in the NW, but some flooding is still on-going. Latest reports indicate few if any new areas of flooding have developed in the last couple of hours. Have therefore canceled the flood watch. What is on-going should start to recede soon - but the larger waterways, esp the Conewango Creek in Russell, will rise a bit more. Prev: Front is through 85% of the area at 7pm/00z. Precip is holding together slightly better than expected, but is on the wane. Wind is still light in the ern valleys and some fog has started to form. while winds will not be all that strong overnight, the fog should not get dense as there will be some gradient wind. Temps will be getting cool enough by midnight in the NW that if something were to fall, it could be flurries or sprinkles or some fzdz. Will have to watch for that possibility. Prev: Radar continues to show moderate to heavy rain moving across my NWRN counties. Flood advisories continue for reported minor flooding as snow melt, rainfall and frozen ground conspire to cause rapid runoff. The latest HRRR shows the heaviest rain beginning to move southeast out of the northern mountains by mid afternoon so conditions should begin to improve over the next 3-6 hours. Will maintain POPs at or around 100% across the northwest counties, while the southern half of the state should see no more than a passing shower at times through 3PM. With the showers expected to diminish as they enter the central counties and lower Susq, I tapered the POPS to cover this. Guidance further suggests the rain that makes it into my southern counties will taper off rapidly between about 6 and 9 pm tonight, leading to a mainly dry overnight. As of right now I expect enough post frontal cloudiness to keep fog from becoming a widespread problem. But if we scatter out, that will change. Another threat will be for an isolated severe storm. Meso anal shows a nose of meager Cape but with intense windshear nosing into western Pa along and just ahead of the surface front. Lightning data shows an occasional cluster of strikes indicating thunder is occurring. SPC has a marginal risk up into western Pa so the potential for a strong wind gust cannot be ruled out with any potentially well organized convection. Lows will range from the mid 20s over the NW to around 40 over the SE.
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&& .SHORT TERM /8 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... Friday looks basically dry with brightening skies as cooler and drier air works in from the north and west. Highs will be 20 to 30 deg cooler than today. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Did not change much for the weekend. Colder air at low levels this weekend will keep the risk of mixed precipitation across the area on Saturday, and again by the later part of Monday. Main area of concern will be the southern part of central PA. Not looking at much QPF with either system, but type of precipitation being the concern. More detail below. This weekend, central PA will be in between an anomalous upper ridge over the southeast conus and shortwave traversing southeast Canada. At the sfc, a weak wave of low pressure is progged to pass south of PA along a quasi-stationary front. A period of light snow or wintry mix will likely accompany this feature Sat/Sat evening, mainly across the southern counties. Fairly good agreement among med range guidance for a dry/seasonable Sunday, as high pressure builds southeast into the region. Main change was to edge a little precipitation a few miles further north. Next week looking mild and showery, as bulk of med range guidance shows a building ridge along the east coast with a surface low track west of PA. It looks like there will be enough low lvl cold air to support some ice ahead of first low on Monday. For Tue-Thu, med range guidance placing PA in deep southerly flow ahead of a trough over the midwest. Plume of anomalous PWATS over the region supports the idea of warm and showery weather. GEFS temp plumes showing no below freezing temps (even at BFD) Tuesday- Thursday. Some variation with potential waves on the front by late next week, thus did not want to take mention of showers out for late Thursday at this point. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... A cold front will exit the southern tier of PA this evening. High pressure will build into the region on Friday. Rain band in association with the cold front was earlier much more notable with a period of heavier rain and gusty winds, but at 02z it is quickly diminishing as it pushes across the southern mountains and Lower Susquehanna Valley. LLWS also coming to an end as parent low tracks further into New England and low level flow weakens a bit as it turns to the west. Winds at the surface will pickup as the night wears on - they already have across portions of the west. But until they do, the light winds and plentiful ground moisture will bring areas of fog - some dense - to the valleys of the east (including KIPT). This should mix out overnight as winds increase with drier air moving in. Over the west, upslope flow should keep IFR/MVFR in place through much of the overnight before gradual improvement Fri morning - as KBFD looks to be the last to improve to VFR. Developing downslope flow will bring improvement to VFR early overnight to the central mtns. Outlook... Fri...Mainly VFR with decreasing winds. Sat...Sub-VFR likely with wintry mix southern 1/2 airspace. Sun...Mainly VFR Mon-Tue...Sub-VFR likely with another period of mixed pcpn psbl. && .CLIMATE... Daily max temperature records for today... Harrisburg 60/1890 == 65 today Williamsport 57/1986 (55 today) Altoona57/2006 == 66 today Bradford 53/2013 == 56 today Johnstown 66/1898 (63 today) && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo/La Corte SHORT TERM...La Corte LONG TERM...Fitzgerald/Ceru/Martin AVIATION...RXR CLIMATE...

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