textproduct: State College

WHAT HAS CHANGED

* No significant changes, severe weather risk continues this evening

KEY MESSAGES

1) Late summer surge of heat and humidity continues severe thunderstorm and excessive rainfall threat through Thursday

DISCUSSION

KEY MESSAGE 1: Late summer surge of heat and humidity continues severe thunderstorm and excessive rainfall threat through Thursday

A series of mid level impulses tracking eastward along the northern periphery of an expansive 500mb ridge will continue to interact with anomalous moisture/instability and strong WNW flow aloft to promote severe storm and excessive rain risk through Thursday.

After a round of severe storms this morning, robust destabilization is occurring across western and central PA with plenty of heating and very rich dewpoints in the 70-75F range. More thunderstorms are expected this afternoon through the evening in an convective environment highly supportive of organized storms capable of all severe weather hazards. There is also the potential for heavy rain and flash flooding especially were storms repeat over the same area.

Increased southwest to westerly flow on Thursday will push the will continue to pump in the late summer heat and very high dewpoints. Heat advisory remains in effect from 11a-8p Thursday across a portion of south central PA where max heat index values are projected to reach/exceed 100F.

The severe risk will be focused more across the southwest quadrant of central PA Thursday, and south of the PA-MD border on Friday. An upper trough passage favors one final round of showers and storms on Friday, but fortunately the Labor Day weekend is trending dry. The upper ridge is forecast to retrograde by the end of the week which allows for a return to more seasonal temperatures and lower humidity this weekend into early next week.

AVIATION /00Z THURSDAY THROUGH MONDAY/

With scattered storms taking shape over Central PA, have included mentions of thunderstorms over northern and western terminals this evening. Exact timing of when exactly any of this scattered activity could impact a site remains uncertain, but any impacts to terminals could see lightning and IFR visibility drops in heavy rain.

Another round of forcing has kicked up storms in New York which is dropping southward. Most guidances continues this line southward into our area overnight with further development along its western flanks. Have included PROB30s for most confident timing of activity overnight, IFR restrictions in heavy downpours are possible.

Fog remains possible but guidance has backed off prevailing fog conditions at JST and AOO so adjusted visibilities there. Visibility restrictions remain possible though in any thunderstorms that cross paths with the terminals. Prevailing IFR ceilings look most likely in the eastern terminals starting around tomorrow. Morning thunderstorm activity may lead to these restrictions persisting at MDT and LNS later into the morning. Afternoon thunderstorm activity looks most likely at JST and AOO tomorrow but seeing how these storms tonight unfold may change timing/other sites that may see impacts.

Outlook...

Thu...Scattered-Numerous SHRA/TSRA with brief restrictions possible; morning fog.

Fri...Scattered SHRA/TSRA SW. VFR elsewhere after morning fog.

Sat-Mon...VFR favored; morning fog possible.

CTP WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 11 AM to 8 PM EDT Thursday for PAZ026>028- 035-036-056-057-059-063>066.