textproduct: State College

WHAT HAS CHANGED

* Minor changes to the rainfall forecast for this afternoon.

KEY MESSAGES

1) A few showers linger into the morning, but the potential for additional flooding is low.

2) Scattered showers and thunderstorms this afternoon may lead to isolated flash flooding over west-central PA.

DISCUSSION

KEY MESSAGE 1: A few showers linger into the morning, but the potential for additional flooding is low.

Very heavy rainfall yesterday evening lead to flash flooding across portions of the area. Showers continue to decrease in coverage and rainfall intensities have decreased significantly, so there appears to be very little chance for additional flash flooding through the morning. As a result, we have trimmed back the Flood Watch to only include areas that saw flooding earlier and where rain is still falling. This watch should be able to expire at 7:00 AM for most, if not all of the area that it covers.

KEY MESSAGE 2: Scattered showers and thunderstorms this afternoon may lead to isolated flash flooding over west-central PA.

A shortwave trough tracking through the region today will bring the potential for additional showers and thunderstorms to develop during the late morning and into the afternoon. Similar to yesterday, persistent easterly flow will keep clouds around across much of Central PA. This will mean that the best instability will again be confined to western portions of the forecast area. Precipitable water values are not expected to be as high as they have been the past few days, but values in the 1.5 to 1.7 inch range (approximately the 90th percentile for this time of year) will support heavy rainfall rates.

There is quite a bit of spread in the guidance when it comes to expected rainfall amounts for today, but the HREF 6-hour PMMs show the potential for localized totals in excess of 2 inches across the western Alleghenies. The heavy rainfall from the past few days means that the ground is very saturated and this could be enough rain for isolated instances of flash flooding to occur. WPC has placed southwestern portions of the forecast area in a slight risk for excessive rainfall to highlight this threat and a Flood Watch may be needed for this afternoon if confidence in locally heavy rainfall continues to increase.

Daily chances for showers and thunderstorms will continue through the end of the week, especially Thursday and Friday. Temperatures will be seasonable with highs generally in the low to mid 80s.

AVIATION /09Z TUESDAY THROUGH SATURDAY/

Main impact this morning across central PA will be ceiling restrictions that will be slow to lift. LIFR cigs impacting most of higher elevation locations including terminals of BFD/UNV/AOO while also seeing shorter-lived visibility restrictions that should improve by 13z. MVFR cigs impact the Susq Valley terminals. Overall, these ceilings should very gradually improve into the afternoon, but overall MVFR restrictions will remain in place midday. A brief period of VFR poss late this afternoon in some spots before ceilings drop again overnight.

Showers/Thunderstorms will again bring impacts this afternoon, mainly to the south central mountains (JST/AOO).

Wednesday brings another day that starts with restrictions at most terminals, though MDT/LNS look to most quickly return to VFR. Shower/tstms coverage Wed afternoon will be significantly lower than previous days, again with JST/AOO seeing the highest chance for impacts.

Outlook...

Wed...Restrictions early, with improving conditions by mid morning. Still a chance of showers and storms near JST/AOO.

Thu-Fri...Mainly dry early. Numerous showers/tstorms during the afternoon. Intermittent impacts likely.

Sat...Chance of showers and a few storms.

CTP WATCHES/WARNINGS/ADVISORIES

Flood Watch until 7 AM EDT this morning for PAZ006-011-012- 017>019-024>028-033>037-041-042-045-046-049-050-056.