Area Forecast Discussion
Issued by NWS State College, PA

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664 FXUS61 KCTP 251655 AFDCTP Area Forecast Discussion National Weather Service State College PA 1255 PM EDT WED MAY 25 2016 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 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. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... 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 /FRIDAY THROUGH TUESDAY/...
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The large scale pattern has a decidedly summertime look and feel to it through Memorial Day weekend and into next week with light winds aloft and a prevailing ridge across the northeast CONUS. Temperatures will average above normal with the core of the `hot` weather front-loaded Friday-Sunday before trending modestly toward late May/early June climatology. Precipitation risk early in the period should be characterized by diurnal convection with the highest probs occurring during peak afternoon heating, augmented at times perhaps by weak disturbances drifting through aloft. Max POP may be centered on or around Memorial Day as weak shortwave suppresses heights as it passes by to the north and some interaction takes place with `tropical` system migrating toward the southeast U.S. coast. Latest NHC forecast this area of disturbed weather has a 50% chance of development within the next 5 days.
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&& .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... 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. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/Lambert NEAR TERM...Dangelo/Lambert SHORT TERM...Dangelo LONG TERM...Steinbugl AVIATION...Lambert/Martin

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