textproduct: State College

WHAT HAS CHANGED

* Expanded coverage of patchy fog & frost early this morning * Adjusted dewpoints a bit lower for this afternoon

KEY MESSAGES

1) Dry and warmer start to the last week of April

2) Periods of rain Tuesday and Wednesday will precede a cool pattern shift with below average temperatures into early May

DISCUSSION

KEY MESSAGE 1: Dry and warmer start to the last week of April

The expanded coverage of patchy fog and frost this morning was largely a function of lowering temps by a few degrees across the board. The trend remains evident in sfc obs and mesonet data with recent IR satellite indicating fog formation in the interior central valleys. Patchy frost is most likely in the outlying rural areas where min temps will be several degrees lower than in the nearby cities/towns.

After a relatively chilly start, today will be the pick (warmest/nicest day) of the week with plenty of sunshine sending max temps 10-15 degrees higher vs. Sunday. Departing high pressure sfc pattern along with steep llvl lapse rates supported leaning lower on dewpoints and corresponding minRH.

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KEY MESSAGE 2: Periods of rain Tuesday and Wednesday will precede cool pattern shift with below average temperatures to begin May

The preponderance of model data supports two periods of wet weather Tuesday and Wednesday. QPF amounts are more robust on Wednesday tied to stronger frontal wave with 48-hr totals in the 0.75-1.50" range ending 12Z Thursday. This rain will continue to add to surpluses over the NW half of the area while helping to reduce rainfall deficits in the southern 1/3 of CPA where D1-D2 drought areas have been persistent.

Latest guidance has a good handle on the mid-larger scale pattern evolution from late week into the weekend (end of April into early May) showing a broad upper trough/low over the Great Lakes into the Northeast. This unseasonably cool cyclonic flow pattern will deliver below normal temps (5-15 degrees) and maintain daily shower chances with breezy conditions (wind gusts 25-35 mph) Thursday through Sunday. Odds favor advective freeze over frost risk with wind and cloud cover playing a key factor.

AVIATION /06Z MONDAY THROUGH FRIDAY/

VFR conditions are expected through the rest of the evening as high pressure builds southward into Central PA. Clear skies and light winds overnight will allow for fog to form, some of which could be dense (visibility as low as 1/4SM). The highest confidence in IFR/LIFR restrictions in fog is at IPT and LNS, though it would not be surprising to see periods of reduced visibility at MDT, UNV, and AOO as well.

VFR conditions return areawide by mid-morning under mainly clear skies with winds out of the southeast at 5 to 10 knots. A few gusts of 15 to 20 knots will be possible in the afternoon for western sites. Dry conditions will remain in place for all of Monday. Rain chances return again Tuesday morning with possible showers arriving as early as 12Z Tuesday morning.

Outlook...

Tue...Regionwide VFR in the morning, with MVFR to locally IFR across West-Central PA later in the day as clouds/showers move in.

Wed...VFR/MVFR early, trending toward MVFR/IFR restrictions in the afternoon as rain overspreads the region.

Thu...VFR/MVFR favored as rain ends west to east.

Fri...VFR favored with restrictions possible in showers.

CTP WATCHES/WARNINGS/ADVISORIES

None.