textproduct: State College

WHAT HAS CHANGED

* Posted and now expanding a dense fog advisory for much of the area. * Keeping with the trend of holding temps down vs NBM for Friday over much of the area, and have also done so for Thursday.

KEY MESSAGES

1) Fog tonight is getting worse now, but may improve toward sunrise as the rain moves across.

2) Periods of beneficial rainfall expected into this weekend.

3) Warmest temperatures since late last Fall poised to arrive areawide by Saturday. But, cool air will probably hang on Thurs and Fri.

DISCUSSION

KEY MESSAGE 1: Fog tonight is getting worse now, but may improve toward sunrise as the rain moves across.

High moisture in/on the ground and air have again begun to drop visibilities, especially across the higher terrain early tonight. But, the fog is also getting thick in many valley locations in the SE, now, too. We have posted and now expanded a dense fog advisory for much of Central PA. We are not entirely confident in how long to run the advisory. The fog may dissipate/visbys improve as the rain to our west moves in and spreads across most of the area and even starts to taper off. We'll limit the run of the advy to 09Z for the time being, but could easily see the mid shift having to expand and extend the advy.

KEY MESSAGE 2: Periods of beneficial rainfall expected into this weekend.

On the heels of one of the driest winters on record, periods of beneficial rain are expected into this weekend. Patchy light rain will linger across southern PA today, before a more robust moisture surge spreads widespread steadier rain into central PA overnight through Thursday. Rainfall of 0.75-1.25" is expected through Thursday evening.

PoPs and QPF for Friday look comparatively low. The next good chance for widespread rainfall will arrive Saturday into Saturday night, ahead of and accompanying a cold frontal passage.

KEY MESSAGE 3: Warmest temperatures since late last Fall poised to arrive areawide by Saturday. But, cool air will probably hang on Thurs and Fri.

Cold air damming will delay the arrival of the warm air for much of central PA until Saturday. We have continue to bump temps down from NBM middle of the road numbers for Friday, and we've done similarly for Thursday, now, too. The cloud cover, mainly light but deep easterly flow in this damming scenario make it tough to scour out the cooler air. The western hills may get up closer to NBM maxes for Thurs and Fri, but we've brought temps down a deg or two there, too. However, the persistent and amplified upper level ridging over the Southeast U.S./Western Atlantic will (eventually) provide a significant springtime warming trend Saturday. Fcst max and min temperatures will be 15-30 degrees above average on Saturday.

Even with a cold frontal passage Sat night, it should remain unseasonably mild into early next week.

AVIATION /06Z THURSDAY THROUGH MONDAY/

IFR/LIFR ceilings and visibility will continue at all Central PA TAF sites through the day on Thursday and into Friday. Multiple rounds of rain will move through the region over the next 24 hours, with most guidance keying in on two periods of steadier rainfall. The first is beginning now and will continue into the early morning. After a relative minimum in shower coverage for the late morning and early afternoon, expect another round of rain to move through for into the evening. Pockets of weak elevated instability embedded within these waves could result in rumbles of thunder, though MUCAPE values look too meager (0 to 200 J/kg) for prevailing thunderstorms at any one site.

Outlook...

Fri...Stationary front across the region. Restrictions possible, especially across central/eastern airfields.

Sat...Restrictions remain possible, especially in the north and east. VFR most likely from KJST south and west, where winds could get gusty in the warm sector. Afternoon/evening showers and thunderstorms likely with cold FROPA.

Sun...Trending towards VFR.

Mon...Restrictions possible as low-level moisture increases.

CTP WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 4 AM EST early this morning for PAZ006-012-018-019-025>028-034>037-041-042-045-049-050-056>059- 063>066.