Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 290318 AFDCTP Area Forecast Discussion National Weather Service State College PA 1118 PM EDT Sun May 28 2017 .SYNOPSIS... A warm front over western Pennsylvania will drift slowly northeast across the state tonight and early Monday. A cold front will push east from the Ohio Valley and cross the state during the day Monday. Low pressure will become stalled over northern Ontario during mid-week and will lead to a period of slightly cooler than normal temperatures and occasionally unsettled weather during the upcoming week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Meso anal shows a stark contrast between the warm-humid air streaming into western PA and the cold dome of cool-air damming stuck over central PA. The warm front has not moved from its north-south position pretty much stalled along and parallel to the Laurel Highlands. Radar shows an MCS, the result of an earlier southward sagging outflow boundary over NWRN PA, now approaching my central zones from the west. The HRRR keeps the convection active well into the wee hours of Monday morning in the warm advection ahead of the approaching front. The airmass is marginally unstable judging by the RAP Cape, and guidance suggests a continued slow erosion of the low level instability as the cold front works into the area later tonight and early Monday. There are also indications of inertial instability looking aloft along the strong jet streak sliding into the lower Gr Lakes. So the radar should remain active with the threat for the next several hours being for additional locally heavy rains. We had some significant flooding in and around Somerset but the rain has finally tapered off to light showers over my SWRN zones. The Flash Flood Watch has been canceled and any additional flooding if it occurs is expected to be minor. Average rainfall is expected to total from around .50" over the far SE to between 1.00 and 1.50" over much of my central and western zones. Locally higher amounts have already been observed in the earlier heavier thunderstorms. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... Cold Front will be slicing through Central PA during the mid to late morning hours, crossing the Susq Valley during the early- mid afternoon hours. It should turn out to be a really nice day with just a westerly breeze in the west, but the slowing front may keep it muggier in the east and isold storms would then be possible in the east early in the aftn. Temps may be a bit higher than currently advertised due to some earlier clearing and the downslope effect (especially near the I-99/Route 220 Corridor. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... The long term period will be dominated by a large upper level low the will slowly moving through the upper Great Lakes and southern Canada. As that quasi stationary low slowly moves to the northeast, it will bring surges of cool moist air across the region. The first surge of cooler air moves across Monday night. This will bring showers in from the W/NW. However, any precipitation will cease as the night continues due to lack of diurnal heating. A reinvigorated boundary should bring a chance of precipitation through the northern half of PA. Several successive shortwave will move through mid to late week which will bring the possibility of 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. Late in the week the models begin to diverge on the location and timing of the upper level low so there is less confidence on precipitation late in the week. However depending where the boundary sets up there could be periods of showers Friday through Saturday, though currently should be mainly along the Southern border. && .AVIATION /03Z MONDAY THROUGH FRIDAY/...
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Adjusted thunder for 03Z TAF package. Poor night for aviation, given low CIGS in spots, showers and still some thunderstorms. Conditions should improve from west to east on Monday, as weak cold front moves across the area. .OUTLOOK... Tue...Chance of showers and thunderstorms. Wed...Chance of showers. Thu...No sig wx expected. Fri...Chance of showers and thunderstorms.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Dangelo LONG TERM...Lambert/Ceru/Martin AVIATION...Martin

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