Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 260608 AFDCTP Area Forecast Discussion National Weather Service State College PA 208 AM EDT Fri May 26 2017 .SYNOPSIS... An upper low directly overhead will slide quickly away today, leaving northwest flow in it`s wake. Weak ridging will move in but many chances for showers and a few thunderstorms are seen through the holiday weekend. The fast flow aloft will keep it unsettled. A cold front will pass through on Monday. && .NEAR TERM /THROUGH TODAY/... Upper low is over the eastern zones evidenced by the change in storm motion which has occurred over the last few hours there. Short wave dropping SE out of MI/OH will make some light rain in the SW half of the area overnight. This area of showers will likely begin to break up into more-cellular showers as the daylight brings heating under the cyclonic low level flow. Clouds around this morning call for mild temps and muggy air in the morning, and a cooler than normal day on Friday. A slightly confluent flow aloft should keep the showers from growing too tall. Will keep POPs in the SCT range due to the expected areal coverage at any time. But, a good forecast will be that most places may get a little wet. The showers will be moving along and, again, not tall. Thus, the chances for mod or hvy rain and for thunder are very low. Maxes are a tough call due to the clouds and possibility of showers knocking a few degs off. If there can be more sunny breaks, it may rise above the current guidance blend. Will stay close to but just a deg below the locally-produced CTPblend of guidance. && .SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/... As the sun sets Friday, the showers should dissipate nicely except perhaps in the NE cos. However, a ridge runner may drop out of the upper Great Lakes into the state per the GFS. The NAM has some convection just scooting to the south of the area, and it is mainly on Saturday. This is also the rough idea of the 12Z EC. This paints two opposing pictures of Saturday weather. Add in the HiRes ARW and you get yet another. Too many differences on timing and placement of possible convective complex(es) to make a detailed forecast at this point. Will keep continuity strong with chc POPs over the SW/SC cos and lesser numbers in the N. Will peak the POPs during the daytime on Sat vs tonight. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... A lower-amplitude but moderately strong westerly (zonal) mid level flow will set up in the wake of the departing upper trough with modest height rises/weak will ridging aloft into the weekend. A warm front is progged to extend east from surface low in the western Ohio Valley to the mid-Atlantic coast on Saturday. Central PA should reside on the north/east fringe of high instability convective corridor/MCS type pattern expected to evolve from the central and southern Plains to the southern mid- Atlantic coast into Saturday night. The greatest risk for scattered thunderstorms remains over the SW 1/3 of the CWA which is consistent with previous fcsts. SPC has introduced a MRGL risk into this area for D3. The remainder of the area should see a mainly dry start to the holiday weekend but will maintain slight chance POPs. The large scale pattern will evolve into a broadly cyclonic flow regime by Monday with upper trough parked over the Great Lakes and southeast Canada into midweek. The aforementioned warm front will lift north across the area on Sunday followed by a series of weaker cold front associated with shortwave trough rotating around parent upper low centered to the south of Hudson Bay. Ensemble blend still supports max POPs on Sunday/Sunday night into Monday with some additional shower opportunities into midweek as series of shortwaves rotate around mean upper trough. Temps should average near normal/seasonal climo to close out the month of May. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... Relatively cool/moist westerly flow pattern behind low pressure moving up the New England coast will spell MVFR/IFR conditions for the western 1/2 of the airspace. MVFR to VFR conditions will be common over the eastern 1/2 thanks to downslope flow east of the Alleghenies. Lingering rain showers should focus around JST early this morning with widely scattered coverage expected by later today. Expect a gradual improving trend with most sites VFR heading into tonight. Weak wave moving through the Ohio Valley may bring showers into the western airspace by Saturday morning. Confidence is low on the evolution of this system given low predictability and large spread in the model guidance. .OUTLOOK... Sat...Chance of rain with sub-VFR possible. Sun...Showers likely with sub-VFR especially Sunday night. Mon-Tue...Scattered showers and a few Tstorms possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/Gartner NEAR TERM...Dangelo SHORT TERM...Steinbugl LONG TERM...RXR/Steinbugl AVIATION...Steinbugl

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