Area Forecast Discussion
Issued by NWS State College, PA

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887 FXUS61 KCTP 241050 AFDCTP Area Forecast Discussion National Weather Service State College PA 550 AM EST Fri Feb 24 2017 .SYNOPSIS... Our extended period of warm, and in some cases record breaking, temperatures will continue into Saturday morning. A strong cold front will plow east across the region on Saturday and create showers and perhaps a narrow line of strong, gusty thunderstorms. Gusty westerly winds, colder temperatures, and snow showers across the western mountains will follow the frontal passage. Chilly but mainly dry weather is in store for Sunday as a ridge of high pressure builds in from the Ohio Valley. One or more weak waves of low pressure moving northeast up the Ohio River Valley Monday into Tuesday may bring some mixed precipitation to the northern half of the area, and mainly rain in the south. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... If you want warmth in Late February, there`s no better way to start the day than in the upper 40s to upper 50s with relatively high dewpoints in the 45-50F range, plenty of clouds and a light southerly breeze. For today, I`ll simply say, toss the winter coat in the closet and sport the shorts and short sleeves, as it won`t get any warmer in February than it gets today (at least within our period of climatological records at observation stations here in PA, that span back into the late 1800s). All-time record highs for February are likely to be broken at many sites across Central PA and the Susq Valley this afternoon thanks to the very mild early start to the day, followed by intervals of sunshine mixed with mid and high clouds, and a warming/moderately gusty southerly breeze. See the Climate section at the end for all time high temps in February. Highs will reach the lower 70s across most of the highest terrain, and soar into the mid and upper 70s in most valley locations in Central and Southern PA. It`s quite possible for a few spots in southern PA to touch 80F this afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Another mostly cloudy and even milder night is on tap for tonight as southerly winds freshen in the tightening pressure gradient ahead of a strong cold front. Temps will only settle into the mid and upper 50s for lows in most places. The cfropa will approach Western Warren county right around daybreak Saturday. Upper ridging over the east coast at the start of the period will be temporarily squashed as a decent northern stream shortwave moves east through the Ohio Valley and across the Middle Atlantic states over the coming weekend. This will bring a pronounced cold front across the region during the day Saturday. A few hundred j/kg of cape along and ahead of this cfront with strong vertical wind shear will bring the threat of one or more lines of heavy showers, and even a quasi NCFRB or QLCS features with embedded strong to potentially svr TSRA. The timing of the Cfront (into the far west between 12-14Z Sat, through Central PA between 14-18Z, and across the Susq Valley and Points east during the mid to late afternoon hours) favors the best chc for marginal svr tsra across the susq valley and points east where ML capes can rebound nicely to several hundred j/kg with temps possibly rebounding to near 70F in the southeast. The aforementioned cold front will return temps to near or closer to near seasonal normals for Sunday into early next week. Brisk winds with gusts over 30 mph will continue Saturday night with partly-mostly cloudy skies and generally flurries SE of the Allegheny front. The depth of the cold air is quite shallow, so accumulations from any snow showers across the NW Mtns and Laurel Highlands will be generally light and only an inch or two. The upper half of the cold air/strato cu cloud deck does dip right into the prime DGZ, so we could see some brief mdtly heavy snow showers across the perennial NW snowbelt and upslope region of the Laurels. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... After some morning flurries and scattered snow showers Sunday, more tranquil conditions with some sunshine area expected for Sunday afternoon, along with decreasing wind and gusts. Heights are forecast to rebuild across the eastern half of the conus early next week on broad southwesterly flow ahead of troffing developing over the Rockies. Several shortwaves within the fast southwest flow aloft will bring several weak fronts across the region next week. This will lead to less than pristine sky conditions...but most of the time period will be generally dry. However, enough low pressure lurking at the surface could lead to a system of more significance sometime during the week. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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For the 09Z and 12Z TAF sets, the main line of showers and isolated thunderstorms is now north of our area. Not much in the way of fog or low clouds at this point, have been backing off on these some. Still possible for some lower clouds and fog around sunrise or just after. Otherwise looking at mainly dry and VFR conditions today and much of tonight. Some strong storms possible, but would mainly track northwest of Bradford. Been watching current activity, which would track activity further west early on. Dynamics lag the cold front Saturday morning, thus much of the shower and thunderstorm activity would be in the colder air, similar to the cold front we had on 11/19/16, which resulted in a 30 degree temperature drop in just a few hours. Windy and colder conditions expected behind the front into Saturday night. Directional shear behind the front would limit snow showers. Highest chance for snow showers would be BFD, as the cold air will be a little deeper there. r concern will come after midnight, when radiational cooling leads to areas of low CIGS/fog. Outlook... Sat...AM fog/LLWS possible eastern PA. Strong daytime FROPA, accompanied by line of shra/tsra. Becoming windy late with evening snow showers/reduced VIS possible at BFD/JST. Sun...Windy. Mon...Slight chance of light snow/reduced VIS northern PA. Tue...Showers/reduced CIGS possible, especially northwest PA.
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&& .CLIMATE... ***February Warmth 2017*** Updated 2/24/17 at 5 am EST Record high temperatures for select sites for Feb. 23-24: ---------------------------------------------------------- Harrisburg 2/24: 75 in 1985; all-time Feb record is 78F Williamsport 2/24: 71 in 1985; all-time Feb record is also 71F Altoona 2/24: 69 in 1985; all-time Feb record is 74F Bradford 2/24: 59 in 1961; all-time Feb record is 64F ----------------------------------------------------------- Most 60 degree days in February at Harrisburg. Based on the latest forecast, add 4 more days to the list and finish tied for second with 7 days. 1. 10 days in 1976 2. 7 days in 1930 3. 5 days in 1991, 1943 5. 4 days in 1997, 1985, 1954, 1939 9. 3 days in 2017, 2016, 1996, 1990, 1961, 1932, 1890 ------------------------------------------------------------ Warmest February on Record (Avg. Temperature through 2/21) Harrisburg: 2017 rank=4 (38.6) 1. 40.4 in 1998 2. 39.6 in 1976 3. 39.4 in 1954 Williamsport: 2017 rank=4 (35.4) 1. 37.0 in 1998 2. 36.1 in 1954 3. 35.6 in 2002 Altoona: 2017 rank=2 (36.5) 1. 37.4 in 1976 Evening cooling will be a little slower than last night. Bradford: 2017 rank=6 (29.3) 1. 32.3 in 1998 2. 30.1 in 2002 3. 29.6 in 2012 4. 29.5 in 1990/1976 ------------------------------------------------------------- && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert/Gartner AVIATION...Martin CLIMATE...Lambert

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