textproduct: State College

WHAT HAS CHANGED

* Discussed/debated frost mentions.

KEY MESSAGES

1) Clearing. Patchy frost possible in the sheltered valleys of the north.

2) A colder end to what has been one of the warmest April's to date; much below normal temperatures possible to start May along with renewed frost/freeze risk. Also wet at times, especially mid week.

DISCUSSION

KEY MESSAGE 1: Clearing. Patchy frost possible in the sheltered valleys of the north.

Clearing is making steady progress as seen in sat loops, but still cloudy over Happy Valley. Still expect the subsidence inversion to win out early tonight. The wind will be very light for the overnight, perhaps calmer in the east than west. This will allow temps to dip into the upper 30s in the north and isolated cold spots elsewhere. Places N and E of BFD have the best (50%) chc to get some frost form. However, only McKean Co is already counted as being in the growing season, and therefore deserving of Frost Advisories. In this case, not even the whole county/zone is likely to get the 2m temps down to 35-36F (when the near-ground temps are typically first at risk of getting to freezing and frosting up the vegetation). Will hold off on any frost advisories, but there could be pockets of frost along the NY border counties. Fog is also a possibility in the deeper valleys as we dip near dewpoints. When/where fog forms, it usually negates or significantly diminishes the worry for frost.

Previous... Temperatures will get back closer to normal on Monday. Monday likely to be the warmest day of the week.

Monday will also feature a good deal of sunshine. As noted below, April will end on a cool note. Also this week will feature several chances to be on the wet side.

May has a track record the last several years to feature some rather cold conditions.

--------------------------------------------------------------

KEY MESSAGE 2: A colder end to what has been one of the warmest April's to date; much below normal temperatures to start May along with renewed frost/freeze risk. Also wet at times, especially mid week.

Most sites are tracking top 5-10 warmest April-to-date. The much above normal to near-record warmth over the past 3-4 weeks is expected to fizzle out through month-end with increasing confidence in below normal temperatures into early May. This late Spring setback will also feature a renewed frost/freeze risk for a growing season that started weeks in advance of the climatological/historical average.

As noted above, Monday will feature the best day to dry out for outside work, and temperatures near normal.

More wet conditions for later Tuesday into Wednesday, as the next frontal system moves in. Things dry out for later in the week, but temperatures will be well below normal. Frost and even freeze potential for the north if not central zones.

Models hint that the upper level low will be just far enough to the west, to taper the cold some, but also support an increase chance for showers more often now, especially across the east.

AVIATION /00Z 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.

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.