Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 261946 AFDCTP Area Forecast Discussion National Weather Service State College PA 346 PM 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 AM SATURDAY MORNING/... Upper low over New England will slowly lift away from the region into the weekend. Nw streamers of light showers will diminish through the evening hours with breaks in the clouds expected overnight. However water vapor imagery shows several short waves within flat flow to the west of PA that will bring several chances of showers into the weekend. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Approaching wave should give way to renewed light rain Sat morning mainly across the southern part of the state. A dry Sat aftn and early Sunday will give way to more rain Sunday afternoon region wide. 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 /SATURDAY NIGHT THROUGH FRIDAY/...
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A shortwave ridge aloft over PA and departing 1016 mb area of sfc high pressure over New England will highlight the start of the extended period, providing dry weather and partly to mostly cloudy skies for us under a light southeasterly llvl flow, topped by increasing mid and high clouds late Sat night and early Sunday. After a mainly dry morning Sunday, a quick transition to increasing deep layer moisture and higher PWAT air of 1-1.25 inches will occur Sunday afternoon through much of Sunday night. A large-scale trough and increasing upper level divergence (associated with a lead upper shortwave in the west/sw flow) will lead to a fairly large area of moderately strong uvvel and a widespread moderate rainfall along and ahead of a cold front. GEFS Probs for GE 0.50 inch of rain/24 hours ranges from 50-80 percent across the wrn mtns of PA...to generally less than 50 percent across the eastern half of the state. This translates into very high POPs for measurable rain (90 percent or more) across the western half of the CWA, to between 70 and 90 percent across the south-central mtns and Susq Valley. 12Z EC and 12z GEFS are in very good agreement on the timing/location of the north/south sfc cold front during the afternoon hours Monday across the eastern half of the state with weak deep- layer ridging and drying for Monday afternoon and night. Dry conditions expected Tuesday morning before significant cooling aloft accompanies a pair of short waves late Tuesday and later Wednesday. POPs during this midweek period will be painted as chc - translating to scattered showers with preference for the majority of the QPF (albeit quite light at that)to be across the typical west-nwrly flow upslope prone areas of the Laurel highlands and NW mtns. The chance for any thunder will be very minimal Tuesday through Thursday. Generally dry NW flow occurs late in the week into next weekend as a 1020 sfc high over the upper midwest Friday evening builds SE twd the region. Pops Thur night through Fri night will be 30 percent or less. After our bout of coolish weather with temps several Deg F below normal Sunday and Monday, GEFS mean temps rebound back to near or slightly above normal (even under slightly cooling 850 mb temps) for Tuesday through at least Thursday. ECENS mean temps are several deg warmer than the GEFS and Nat`l Blend of Models temps. leaned closer to the cooler solutions based on the few-svrl deg C of cooling aloft with near to slightly below 850 mb temps.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... Generally VFR bkn-ovc conds will persist into the overnight as nw flow continues across the airspace. Sprinkles to light rain showers will affect some airfields, but anything heavy enough cause sub vfr reductions will be brief. 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. Wed...VFR early with tsra accompanying a cold fropa late. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Gartner NEAR TERM...Gartner SHORT TERM...Dangelo/Gartner LONG TERM...Lambert AVIATION...Gartner/Steinbugl

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