Area Forecast Discussion
Issued by NWS State College, PA

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767 FXUS61 KCTP 251444 AFDCTP Area Forecast Discussion National Weather Service State College PA 1044 AM EDT WED MAY 25 2016 .SYNOPSIS...
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A ridge of high pressure will build over the northeastern U.S. bringing a noticeably more summer-like pattern through at least the first half of the upcoming holiday weekend. Cooler and showery weather may arrive for Memorial Day.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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a veil of cirrus and cirrostratus clouds streaming in from the west will dim the sunshine at times through this afternoon (mainly across central and southern PA). Summer-like temperatures are in store again today. Diurnal ranges may be 30 to 40 degrees in some places today with highs more like mid-July. Afternoon RH`s will dip into the 20 to 30 pct range. Thus, it will be tough to get any cu to pop (especially with the aforementioned cirrostratus deck trimming the insolation and sfc temp by a tad). If they do develop, the cu will be over the ridges and very sparse in coverage. One exception may be over the NE as some deeper convection could make a weak/isolated shower or two over central NY and drop it down through the Endless Mountains late in the day. Otherwise, POPs will be near zero. Mid to late afternoon max temps should be 1-3 degrees warmer than Tuesday thanks to the sunshine and a slightly milder start to the day in most places.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Clouds start to increase from the west late tonight. But, it should remain clear in the eastern half of the area all night. The wind never quite dies off, so very mild mins are expected. The low level moisture/dewpoints should be on the rise. A spot or two in the southern tier may not go below 60F. Will keep POPs low for the overnight, but a stray shower is possible by sunrise in the Laurels. Muggy is the word for Thursday. Most guidance brings dewpoints into the 60s all over the region. The limiting factors for convection will probably be the presence of a capping inversion around 12kft at the top of some morning mid-level clouds. But, the clouds may slide to the east a bit and allow the heating to bring the W/NW into the 80s. This results in CAPE near/over 1000J/kg. All the convection should be diurnally-driven, but the GFS does ride a very weak short-wave trough right overhead at peak heating time, too. Thus, it is more bullish on the QPF/POPs than the NAM and ECMWF which make very little precip. POPs will be held at 50 pct over the Alleghenies and 20-40 pct in the rest of the region for the afternoon and early evening. These numbers may be too a few pct points too high, but the cap may seriously limit deep convection. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... The extended guidance continues to show a strong ridge over the mid Atlantic and the Great Lakes region through the weekend. This will bring the arrival of the first extended period of summer- like temperatures and humidity. By Thursday we will be embedded in a broad WSW flow aloft. Slightly above normal PWATS support the idea that humidity will become noticeable over most of the area for the first time this warm season. It also means we will be susceptible to mainly afternoon convection pretty much on a daily basis into the weekend. However the strong ridge should provide enough subsidence to keep any convection at bay Thursday and Friday. The GFS is very aggressive poking the Bermuda ridge strongly up over the eastern U.S. Saturday while the ECMWF is a little flatter. However given the southerly flow of moisture, the warmer temperatures and the possibility of a mid level trough advecting through, Saturday should have a decent chance for some afternoon convection. The trend is for the ridge to break down late in the weekend and for cooler air to move into the region early next week. This could bring temperatures to slightly below normal. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
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High pressure will provide the region with a warm and sunny day with just varying amounts of high-level cirrus and cirrostratus. VFR conditions will prevail. 500 mb heights rise a little today and the llvl pressure gradient weakens a bit this aft...so I am not expecting the west to southwest wind gusts to exceed 12-15 kts. Still with the high late May sun angle...the airmass will likely still mix to about 7000 feet. There could be a few showers and thunderstorms late Thursday. Not totally sold on this...as the mid and upper wave potentially triggering the convection will be weakening as it approaches, and dewpoints are relatively low to begin with (and have to come up a lot higher) for any appreciable convection to fire. Somewhat a better chance for scattered afternoon shra/tsra on Friday. OUTLOOK... Thu-Sun...Isold...mainly pm tsra impacts possible.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/Lambert NEAR TERM...Dangelo/Lambert SHORT TERM...Dangelo LONG TERM...Ceru AVIATION...Lambert/Martin

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