Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 261948 AFDCTP Area Forecast Discussion National Weather Service State College PA 348 PM EDT Mon Jun 26 2017 .SYNOPSIS... A long wave trough over the Great Lakes and eastern Canada will deepen across the region. This feature will keep it cooler than normal into Wednesday. Scattered showers and thunderstorms will be across the region this afternoon and evening and again on Tuesday, especially across the northern part of the Keystone state during the afternoon hours. A warm up and return of higher humidity levels will occur on Thursday and Friday, as high pressure moves off the east coast. While temperatures will average near to above normal for the second half of the week, there will be occasional showers and thunderstorms. && .NEAR TERM /UNTIL 11 PM THIS EVENING/... Dewpoints have dropped back into the 40s over the entire area this afternoon with deep mixing. Temps aloft are chilly for late June and have allow an expansive cu field to pop. Only a few places of which look like moderate or towering cu have been able to grow - probably due to the lack of moisture. There is also a lack of a trigger to make the low level kick necessary to overcome any CIN. The earlier boundaries from the over-lake convergence are likely what is still helping to puff up the storms in the NW. Coverage will be greatest in the nrn mtns where 70-80 POPs have been painted. Timing will be centered around 21-22Z in the NC/Cent mtns with a bell curve around then earlier in the NW and later in the NE/EC counties. Showers should diminish with loss of heating but they could linger a few hours after sunset in the NE/Poconos. && .SHORT TERM /11 PM THIS EVENING THROUGH 6 PM TUESDAY/... Another round of nocturnal-mid-lake-convergence-driven- convection could POP up overnight. But, guidance also whips a strong short wave trough through the upper Great Lakes and pushes showers and thunderstorms over the second half of the night into wrn PA. These may reach into the Laurels/Alleghenies by morning and have placed low chc POPs there. It will likely be cooler tonight than Mon AM, but the varying cloud cover could help keep temps up. Some fog is possible in the valleys where they do get some rain this evening. Tuesday may hold a few less showers in the aftn with the negative/suppressing influence of the rising heights behind the strong short wave passing overhead (and the related cloud cover and any showers) in the morning. The afternoon heating and cool air aloft will still generate sct showers in the nrn tier. Max temps will be similar to Monday or even a few degs F cooler factoring in chaotic cloud cover in the morning. On the other hand...With the length of the daylight in late June, the sun can can overcome a late start to cook up temps. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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Trough axis moves through on Tue, with secondary trough sliding through Tue night as high pressure builds at the surface. This will keep just very low pops mentioned in the NW mtns during the evening. With clearing skies, NW flow and light winds, and dewpoints in the mid 40s to lower 50s, Wed morning will be the chilliest one of the week as lows should drop to near dewpoints. With plenty of sun, temps will rebound during the day back into the 70s. As the high moves off the east coast by Thursday, a warm front will lift across PA ushering in a southwest flow of warmer and noticably more humid air. Lows Thu morning will be about 10F warmer than the day before, and daytime highs will bump up about 4-8F as well. Upper flow becomes zonal late week as a surface low tracks across the northern Great Lakes and southern Canada, which will focus a stationary front across that region. We`ll remain on the warm/humid side of that boundary (as highs rise to near 80 NW and 90 SE along with muggy overnight), and see convective activity increase Thu heading in the weekend - with highest likelihood over the NW. Convection will be more scattered over the SE. Active pattern continues Sun into Mon as another low rides along the persistent frontal boundary to our west and north, finally nudging that front into/through PA and keeping mention of showers in the forecast while taking some of the edge off of the above normal temps.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/... line of SHRA/TSRA over the nrn tier is along a weak boundary which used to lie over the lower lakes this morning. The convergence is drifting to the east and a short wave trough over OH could add a little forcing to the mix this aftn/evening. But, most of these shra will be diurnally driven, and will die as the heating goes away. The nrn mtns will have numerous SHRA/TSRA until about 00Z when the weak trough aloft scoots to the east. A tail of showers may linger in the NE and even into the central mtns through 01Z or 02Z. The clearing behind these showers and light wind may allow fog to form again in the northern valleys by sunrise. But there are some clouds which will move in later tonight. Next issue will be a much stronger trough aloft whipping around the base of the larger/long wave trough. The timing of the best lift provided by this wave will be before sunrise over the west. But, the remnants/moisture associated with this wave will still make some isold/sct shra over the local through the morning. Limits to vsby will be few, though. Just isold/sct SHRA are then expected for just the nrn mtns/KBFD in the aftn. .OUTLOOK... Wed...VFR. Thu...VFR early, then sct afternoon SHRA/TSRA NW. Thu PM-Sat...sct-nmrs SHRA/TSRA. && .EQUIPMENT... KCCX radar is back on line and in normal operation. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...RXR AVIATION...Dangelo/Ceru EQUIPMENT...

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