textproduct: State College

WHAT HAS CHANGED

*Dense Fog Advisory expanded to Lebanon County

KEY MESSAGES

1) Feeling more like early Spring than late Winter this week

2) Periods of rain Wednesday, Thursday night into Friday

3) Mixed/wintry precipitation Thursday night into Friday and plowable snow possible on Sunday

DISCUSSION

KEY MESSAGE 1: Feeling more like early Spring than late Winter this week

Following one of the coldest first 2 weeks of February on record, mild weather for this time of year will be in place this week with daily max/min temperature anomalies running 10-20 degrees above the historical average. Conditions will feel more like early Spring than late Winter. Depending on the time of arrival and coverage of precipitation later this week, daytime temps may not get as quite as warm as currently forecast, but will still be above normal.

The transition to a milder pattern this week is accompanied by low clouds and fog as stagnant, warmer air moves over the colder/snow covered ground. The lower Susquehanna Valley has been socked-in and also experiencing poor air quality due to the inversion and very weak sfc flow/calm wind. 07Z observations indicate a blend of shallow stratus and fog with visibility generally 1-3 miles. Schuylkill County (and vicinity) is a common exception in this pattern due to elevated terrain and often times more prone to locally dense fog particularly along the I-81 corridor. RWIS data indicates dense fog with visibility around 500ft (~1/10th of a mile) has also backed into Lebanon County at the I-81/I-78 interchange and therefore we expanded dense fog advisory.

KEY MESSAGE 2: Periods of rain Wednesday, Thursday night into Friday

Following one of the driest first 2 weeks of February on record, much needed periods of rainfall are likely on Wednesday and again Thursday night into Friday. Total QPF during the mid to late week period ranges between 0.50 to 1.00 inches with the highest amounts shaded toward the NW portion of the fcst area. While we do not expect the rainfall to cause flooding, the warmer temperatures and increased flows on rivers and streams should increase the risk of ice jams at least on the margin. KEY MESSAGE 3: Mixed/wintry precipitation Thursday night into Friday and plowable snow possible on Sunday

Model guidance continues to indicate a overrunning wintry/icy mix on the leading edge of returning precip late Thursday night into Friday. This would impact travel conditions for the Friday morning commute. We may begin to message the risk of slippery travel in the HWO.

There is an emerging risk of plowable snow on Sunday, although the specifics on the strength and track of the associated low pressure/coastal system are still very uncertain. Continue to monitor the forecast.

Guidance signals continue to favor a seasonably colder end to the weekend and start to the last week of February. The cool down appears to be transitory and not long lasting heading into the second half of next week/end of the month.

AVIATION /08Z TUESDAY THROUGH SATURDAY/

A few to several Deg C of warm advection streaming in from the West-Northwest (within the 2-5 kft AGL layer) will create broad scale, gentle upward vertical motion across the bulk of PA.

This will help to maintain plenty of layered clouds with low bases (IFR to LIFR CIGS with IFR to MVFR VSBYs) across much of Central PA through this morning.

Conditions should be mainly VFR at KJST and KAOO for the bulk of the TAF period. However, periods of MVFR CIGS are expected there.

Conditions today will be slow to improve with VFR not likely area wide. The best chance for VFR will be over the southeast at MDT and LNS after 18Z.

Outlook...

Wed...IFR -RA/cigs N, MVFR -RA/cigs elsewhere.

Thu...Dry early, then rain later in the day with restrictions possible.

Fri...Rain with restrictions likely. Some snow may mix in over northern PA.

Sat...Lingering rain and snow showers.

CTP WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 9 AM EST this morning for PAZ058-059.