Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 221126 AFDCTP Area Forecast Discussion National Weather Service State College PA 726 AM EDT Mon May 22 2017 .SYNOPSIS... A weak cold front near the Pennsylvania...Ohio border will drift east across the region today and be preceded by occasional mainly light showers. The showers will gradually taper off from west to east across the state this afternoon and evening. Expect an additional 1 to 2 tenths of an inch of rain to fall in most places today. A period of dry and tranquil weather will follow from late today through Tuesday as an area of high pressure drifts northeast and becomes located overhead. Low pressure at the surface moving northeast from the southeast states will team up with a potent, slow-moving and deep upper moving southeast from the Great Lakes to bring periods of showers and below normal daytime temperatures later Wednesday right through the end of this week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Several broken lines of light showers were noted across northwest, and southeastern portions of the state early today. The south-southwesterly llvl jet (25-30 kts) will stay fairly fragmented with slightly diffluent upper boundary layer flow ahead of a cold front pushing slowly east across the state. The far NW and far SE parts of the CWA (closest to the forcing by these 2 moderately stg LLJs) appear to be the locations most likely to see an additional 1-2 tenths of an inch of rainfall, while much of the Central part of the state and Middle Susq Valley will be relatively drier from more infrequent showers. Both the 00Z GEFS and 03Z SREF indicate less than a 50 percent probability for 0.10 of an inch of additional rainfall between 09-21Z across the Central and Western zones, while the Lower Susq region and Western Poconos sees greater than an 80 percent chc of 0.10 of an inch of rain, and even about a 60-70 percent chc of greater than 0.25 inch during this same period. We are forecasting around one-third of an inch or slightly higher across Lancaster county, with slightly lesser amounts closer to I-81. Near sfc-based cape will be quite minimal and located right along the front - in a thin ribbon this afternoon. This fleeting period of instability could account for a narrow line of briefly heavier showers. However, it doesn`t appear nearly enough to produce thunder, so kept mention of precip type exclusively as -SHRA today. Skies will stay primarily OVC across the eastern half of the state through the early-mid afternoon, while the passage of the cold front near and to the west of the RT 219 corridor should mark improving conditions with some sunshine filtering through high clouds during the afternoon hours. High temps today will vary from the mid-upr 60s across the nrn and wrn mtns, to the L70s in the central and southern valleys. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... High pressure builds NE and becomes located over the region tonight and Tuesday with dry conditions, light wind and below normal temps. Periods of high clouds streaming NE will limit the lows from getting too chilly late tonight/early Tuesday. Lows will range from the l-m 40s across the NW mtns...to the l-m 50s in the SE. The center of the high will likely drift NE to the Hudson Valley Tuesday and create a light easterly llvl flow across Central PA...with patchy statocu topped by a bkn layer of cirrus/cirrostratus. High temps Tuesday may display an unusually very tight range from NW to SE of only around 5 deg, thanks to thicker cloud cover, the cool easterly flow and a low prob of a few showers as a weak wave slides up the east coast. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... After mainly dry conditions Tuesday night and Wed morning, the beginning of an extended unsettled weather pattern occurs later Wednesday and it will linger into the weekend, as a deepening and slow moving upper-level low drops into the Great Lakes and surface low pressure develops over the Mid- Atlantic region. Light showers will begin to converge from the south and west during the day Wed, with the dreariest and wettest day being Thursday as a soaking rain looks likely with an occluded front moving through. The synoptic system will be lifting out by Friday, allowing conditions to slowly improve from the SW. Light showers or drizzle may linger as weak surface ridge tries to work in under retreating cool pool aloft. Sat should bring a return of brighter skies, albeit briefly, because clouds increase for the second half of the weekend along an old and sharpening frontal boundary extending from the mid atlantic region westward into the Ohio Valley. This boundary will bring potential for return of showers by Sun and Mon. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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Some showers to the southeast, on the northern edge of the area of showers lifting northward from NC. Main band of showers and perhaps a rumble of thunder is just west of BFD. Minor adjustments made. 12Z TAFS sent. Earlier discussion below. Just a few bands of showers so far, as the airmass is not real moist. More in the way of widespread showers across southern VA at 1 AM may clip far southeast later. Expect a wide range of conditions early today. Conditions should improve from west to east from late morning into the aft, as weak high pressure builds eastward. Models still imply rain approaching our region Tuesday afternoon/eve. .OUTLOOK... Tue...Rain/log cigs possible by evening mainly E/SE. Wed...SCT SHRA poss - mainly W. Thu-Fri...SHRA/low cigs NW, Mainly VFR SE.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert/RXR AVIATION...Martin

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