Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 141138 AFDCTP Area Forecast Discussion National Weather Service State College PA 738 AM EDT Mon Aug 14 2017 .SYNOPSIS... 1018mb sfc high pressure centered over southeastern New York early today will drift off the southern New England Coast this afternoon. A weak southerly flow of warm and increasingly moist air will interact with a compact upper air disturbance lifting NE over the Ohio River to bring scattered showers thunderstorms to the central and western mountains of PA later this afternoon and evening. A weak ridge of high pressure will move over the state Tuesday morning and early afternoon, accompanied by mainly dry conditions. Another surface and upper trough will move quickly to the east across the Great Lakes region and bring some isolated showers and thunderstorms, mainly across the northern mountains Tuesday afternoon. Mainly dry conditions are expected across Pennsylvania Wednesday into early Thursday. A warm front will move into the area on Thursday, followed by a cold front late in the week. Both of these weather features will trigger scattered to numerous showers and thunderstorms. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Patchy dense fog will impact parts of the region through the mid morning hours, mainly in the deep river/stream valleys north of I-80. Water temps running well into the 70s in this area, resulting in a near 25F air/water departure by dawn. Weak to moderately strong, south to SW 850 mb jet of 20kts will and a WSW wind of 20-25 kts at 700 mb will help to transport increasing llvl moisture (and the nose of higher PWATs of 1.5 to 1.75 inches into southern and central PA today). Widespread cirrus and cirrostratus, along with some altocu will be spread across the CWA for much of the day thanks to the persistent though somewhat weak mid/high-level uvvel beneath the right entrance region of a jet draped from New England to the Mid Atl region. The variable thickness of the cloud cover should have some impact on the amount and strength of any convection that develops today. The triggering mechanism for the scattered SHRA and TSRA comes in the form of a compact 60-70 kt 300 mb jetlet that will be lifting NE through the broader scale 300 mb jet. Painted POPS greater than or Equal to 20 percent over the wrn half of the CWA, with chcs for precip at 10 percent or below across the Susq Valley and points east today. Basin Average rainfall today through 00Z Tuesday should amount to 0.20 of an inch or less across the central and western mtns. High temps this afternoon will range from the mid 70s across the mtns or the north and west, to the L80s in the southeast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... After some clouds and the chance for a few showers this evening through about midnight across mainly the SE half of the CWA, the late night hours tonight should turn quiet with just some patchy valley fog. A sfc and upper trough will slide acrs upstate New York during the day Tuesday. The southern edge of some slightly greater mid level lapse rates will brush northern PA and could be associated with one or more clusters of SHRA/TSRA. Elsewhere, conditions will be generally dry and warm. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Wednesday continues to look dry for now. However, the remnants of a weak cold front from the north drops southward toward the area. 00Z EC showed a low with strong warm advection for Thursday. The EC was deeper than faster with the low on Thu. Some variation with guidance with the end of the week. For now, did edge the POPS up some for Sunday and Sunday Night, to line up with others, the blend, and timing of the front better. Did not want to go too high, as events lately are largely clusters of convection. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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Some localized visibility restrictions in fog did manage to develop beneath high cloud shield. Expect visibility to improve to VFR by mid morning. VFR conditions are expected into tonight. The latest hires guidance is now focusing more shower activity across south-central PA from mid-late afternoon into the evening but overall confidence is low. Did add VCSH to KJST/KAOO where hires ensemble nearest- neighborhood probs indicate max pcpn potential. Another question mark concerning low stratus and fog development tonight into early Tuesday morning which seems tied to clearing trend. Persistence and steady to gradual increase in low level moisture would tend to favor some restrictions. For now, will show downward trend in flight cats to MVFR/IFR with low confidence. .OUTLOOK... Tue-Wed...VFR. No sig wx. Thu-Fri...VFR. Sct Tstm impacts likely.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Fitzgerald/Lambert SHORT TERM...Fitzgerald/Lambert LONG TERM...Lambert/Martin AVIATION...Steinbugl

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