Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 261057 AFDCTP Area Forecast Discussion National Weather Service State College PA 657 AM EDT Fri May 26 2017 .SYNOPSIS... An upper low is sliding off to the northeast and leaving a cool 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. A cold front will pass through on Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Rain on radar is aloft in some places, as it is to the east of the office, but to the west it is hitting the ground. A big clear slot has developed over the eastern counties. No sweat, the clouds are headed that way, and it may just help develop some instability to generate the isolated showers in the forecast. Have tweaked POPs in the next few hours for recent radar and meso model trends. Prev... A short wave over OH will continue to drop SE and generate showers for the next few hours. As the forcing wanes/moves away, the showers there will break up and dissipate until more- cellular showers develop in the day time heating. Cool air aloft will both make it unstable and keep temps down through the day. Clouds from the upper forcing and llvl cold advection are also going to contribute to the keeping max temps about 10F cooler than normal today. A 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 will have at least a sprinkle. The showers will be moving along and, again, not tall. Thus, the chance for hvy rain is very low.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/... 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 other operational models are also generating what looks to be an MCS upstream. The 06Z NAM has some convection just scooting to the south of the area, and it is mainly on Saturday. The EC is also placing a high QPF over the upper OH valley and into the Mid-Atlantic on Sat morning. There is a little better consensus on the timing and placement of convection for the short term, so we will nudge the POPs up a bit in the SW for the late tonight and Sat time frame. && .LONG TERM /SUNDAY 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 /12Z FRIDAY THROUGH TUESDAY/...
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Relatively cool/moist westerly flow pattern behind low pressure moving up the New England coast will spell MVFR/IFR ceilings for the western 1/2 of the airspace. MVFR to VFR conditions will be common over the eastern 1/2 thanks to downslope flow in the lee of the Alleghenies. Expect isolated to widely scattered rain showers through the afternoon but coverage and probs are too low to mention in TAFs. Anticipate a gradual improving/decreasing cloud trend with most sites VFR heading into tonight. Remnant meso/convectively enhanced wave tracking east across the Ohio Valley should thicken clouds back up by Saturday morning. Confidence remains low on the evolution of this system given limited predictability and continued above avg. spread in the model guidance including high-res CAMs. Models are usually too far north with MCS type activity so it looks like the best chance for light showers would be over the far SW airspace 06-12z. .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.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...RXR/Steinbugl AVIATION...Steinbugl

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