textproduct: State College

WHAT HAS CHANGED

* Did add a mention of localized severe storms with strong winds late this afternoon and early evening, mainly for northwest and north-central PA.

KEY MESSAGES

1) Noticeable warmup this afternoon will precede rain and thunderstorms this evening, followed by a chilly/raw cool down for the end of the week into the last weekend of March.

DISCUSSION

KEY MESSAGE 1: Noticeable warmup this afternoon will precede rain and thunderstorms this evening, followed by a chilly/raw cool down for the end of the week into the last weekend of March.

Strong warm and moist advection is well underway this afternoon across the Commonwealth, with temperatures climbing into/through the 70s in many locations. With surface dew points also on the rise (should reach the 50s by late afternoon, at least across northwest PA), we will destabilize the environment, to the tune of 300-600 j/kg of MLCAPE by later in the day. Shear profiles will also be strengthening, as 925-700 mb flow increases markedly into the early evening.

Buoyancy and shear profiles alluded to above will create an environment supportive of at least isolated severe thunderstorms from roughly 4-9 pm, as a strong cold front pushes from north- south across the state. Damaging wind gusts will be the primary threat, with areas north of US-22/I-78 having the most risk.

One good thing with this system is the probability of 0.5-0.75" rainfall, with locally higher amounts possible, particularly across the Alleghenies. Given long-term dryness in many parts of the state, such rainfall is certainly welcome.

Later tonight and early Friday, the front should make its way south of the Mason-Dixon line, with strong low-level cold advection ensuing. As a result, Friday will be a much chillier day, with afternoon high temperatures a good 25-35 degrees lower than on Thursday, along with a stiff N-NW breeze.

For much of the weekend, uneventful weather is foreseen, as a large surface high pressure system builds into the eastern states to bring dry weather. Temperatures will start out chilly on Saturday, with daytime highs only in the 30s and 40s across central PA. Sunday will begin a moderating trend, once the aforementioned high pressure system pushes off the east coast, and winds shift into the S and SW.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Active period for the next 24 hrs as a cold front moves through from N to S. TSRA just N of BFD as a shortwave trough is passing over LE. The front seems to be near DTW and through YYZ, marching steadily but slowly southward. Have placed VCTS at BFD starting at 20Z, but TS could (50%) arrive before, then have a couple hour break before more TS threatens. Have timed TS thru each site with a rough 3 hr window. LLWS threatens most sites for 4-6 hrs before the front moves through with the worst WS at JST with wind field around 50KT FL020. Some of the TS will contain hail and make significant downdrafts as they move through. The storm motion will be more west to east, likely riding along the front. Not dissimilar to a few days ago.

The strong llvl winds will keep moisture flowing over the front and make numerous SHRA and a few TSRA behind the front. Cigs probably (60%) lower to IFR across the N at BFD shortly aft 00Z, and remain in place for most of the night. Drying N wind will help many other sites stay MVFR behind the front when it is not raining. The drier air and wind will also keep BR from becoming FG. The highest chance for IFR will be at BFD and JST. The morning should help all sites improve to VFR and be there for the rest of the day.

Outlook...

Fri...Gusty AM wind diminishing aftn. Otherwise VFR.

Sat-Sun...VFR.

Mon...SCT -SHRA with restrictions poss, mainly W.

Tue...NMRS SHRA. TSRA poss W.

CLIMATE

Record high temperatures for March 26th:

Harrisburg 80 in 1921 Williamsport 78 in 1939 Altoona 79 in 1998 Bradford 73 in 2007 State College 76 in 1949

CTP WATCHES/WARNINGS/ADVISORIES

None.