textproduct: State College

WHAT HAS CHANGED

* No significant changes to previous forecast

KEY MESSAGES

1) Periods of rain today with a marginal thunderstorm wind threat precedes unseasonably cool/very chilly Thursday

2) Significant summerlike weekend warmup ramps into early next week with the highest temperatures of the year so far

DISCUSSION

KEY MESSAGE 1: Periods of rain today with a marginal thunderstorm wind threat precedes unseasonably cool/very chilly Thursday

A seasonably strong upper level trough will dig through the Great Lakes/Ohio Valley today and develop into a closed low over the northern Mid-Atlantic and southern New England region before ejecting to the northeast on Friday. The associated sfc low moving east from Lower Michigan toward northern New York will drag a trailing cold front across the Alleghenies this afternoon and evening. Periods of rain/showers and scattered thunderstorms are expected along and ahead of the cold front. The pre-frontal convective environment will feature weak to conditional instability on 50-55F dewpoints, sufficient (30-40kt) deep layer shear, and steepening low to mid level lapse rates to support a marginal wind threat. The HREF/REFS show the primary frontal band exiting the eastern portion of the CWA after 14/03Z.

Scattered showers linger into Thursday beneath the upper low which will be the coldest day of the week. Max temps will be unseasonably cool and quite chilly for mid May with highs in the 45-60F range or 10 to 20 degrees below the historical average (frequent 20-25 mph wind gusts will only add to the chill).

Rainfall amounts will remain on the light side with fcst QPF generally <0.25 inch through Thursday night. This won't even put a dent in the moderate/D1 to severe/D2 drought conditions across far south central PA.

Conditions will dry out on Friday with daytime highs rebounding +10-20 degrees vs. Thursday.

KEY MESSAGE 2: Significant summerlike weekend warmup ramps into early next week with the highest temperatures of the year

After a cool start to May, guidance continues to signal a significant warmup on the horizon for this weekend into early next week. This large scale pattern shift should deliver a rather sudden and perhaps long-awaited midsummer warm surge with max temps projected to reach well into the 80s and even lower 90s. Daily record highs may be challenged based on the current fcst Monday and Tuesday.

There may be some potential heatrisk considerations looming for early next week. This stems not only with the forecast high temperatures, but also from an acclimation perspective especially after a rather cool stretch of weather during the first half of May. Probabilistic heat risk shows >50% odds for moderate or higher across south central PA with fcst heat index values starting to exceed 95F Monday and Tuesday.

AVIATION /09Z WEDNESDAY THROUGH SUNDAY/

As expected, the showers mainly stayed across the northwest (BFD) sections of PA overnight.

Expect the activity to pick up some speed just after sunrise here. Back edge of the showers just east of CLE and moving along, but expect the back edge to slow down some later today.

More information below.

Low pressure over MI will result in a few showers over the northwest prior to 12Z today.

Most of the showers will be later today, as the warm and cold fronts move into our area. There could be a thunderstorm, mainly across the west. Left thunder out of the east for now.

The cold front will move east of the area later today, followed by a windy and cold day on Thursday. As the upper level low drops to the south on Thursday, moisture will wrap around the low. This will result in clouds and showers across the region, especially across the mountains.

Conditions will improve later on Friday, as the low moves away from the area.

Borderline for LLWS early today, thus removed it. CTPWRKTAF Outlook...

Thu...Lingering clouds and showers with restrictions north/west and improvement southeast.

Fri...VFR likely.

Sat and Sun...VFR is likely much of the time, although brief restrictions are possible with isolated afternoon/evening showers and thunderstorms.CTPWRKTAF

CLIMATE

Record low temperature of 25 degrees was tied (1963) at Bradford yesterday.

CTP WATCHES/WARNINGS/ADVISORIES

None.