textproduct: State College

WHAT HAS CHANGED

* Leaning warmer with max temperature forecast today * SPC severe t-storm and WPC excessive rain outlooks expanded

KEY MESSAGES

1) Noticeable warmup today will precede rain and thunderstorms this evening followed by a chilly/raw cool down for the end of the week into the last weekend of March

DISCUSSION

KEY MESSAGE 1: Noticeable warmup today will precede rain and thunderstorms this evening followed by a chilly/raw cool down for the end of the week into the last weekend of March

Partly to mostly cloudy and relatively mild start today as south to southwest flow ramps up ahead of strong cold front moving southeast from the Lower Great Lakes. We still expect rain free conditions in most places to last into the afternoon (through 18Z) although can't rule out a passing shower in the increasingly moist warm air advection pattern.

Breaks in the clouds combined with the southwest breeze will support a very warm day relative to late March climo - with fcst max temps in the 65-75F range or +15-25 degrees above the historical average/within 5 degrees or so of daily record highs (see climate section).

The aforementioned strong cold front will provide the primary forcing for a band of rain and thunderstorms to track from NW to SE across central PA this evening through tonight. SPC has extended the MRGL and SLGT risk convective outlooks farther eastward into western and central PA, however calibrated severe storm probs continue to focus the greatest hail/wind/tor risk in the Ohio Valley where CAPE and shear profiles are more insync. Influx of 1-1.5" pwats brings the prospect of locally heavy rainfall more into play and fcst QPF amounts have increased a bit particularly over southwest PA. It's not clear how much fast movement and average soil moisture can be offset by training storms and orographics, but like the severe t-storm risk, the probability of runoff issues has increased on the margin and WPC will be monitoring for a targeted upgrade in the ERO. The highest rainfall totals are 1.50-2.00 inches in the Laurel Highlands.

Behind the cold front, a raw northerly wind will deliver a 24hr maxT change of -20 to -30 degrees for Friday. The early Spring temperature roller coaster reaches a nadir Friday night with lows Saturday morning bottoming in the teens/20s. This will be followed by a rather chilly start the last weekend of March with max temps 10 to 15 degrees below normal. The cool down will not last long with moderating temps/warming trend expected Sunday through the start of April.

AVIATION /08Z THURSDAY THROUGH MONDAY/

VFR conditions will prevail beneath a shield of mid and high clouds, based AOA 8000 FT AGL, that will continue to stream SE across PA today.

The main concern in the near-term will be LLWS concerns with the axis of a 40-45kt swrly 850mb LLJ shifting slowly east across the region during the early to mid morning hours today.

The potential for sub-VFR conditions will begin at BFD after 12Z. Conditions there will steadily deteriorate to IFR after 17Z and stay mainly IFR to LIFR into Thurs night.

A cold front will gradually approach the area and is expected to be stationed east-to-west just north of the PA-NY border around Friday. Showers and scattered storms will be focused along the front; however, recent hi-res model guidance does indicate some storms ahead of the front and have outlined these in PROB30s at BFD given slightly higher confidence.

Further south, SHRA will be introduced in the TAFS prior to 00Z Friday at IPT/JST prior while model guidance suggests that this precip will begin at UNV/AOO in the 00Z-01Z Friday timeframe.

Further SE (MDT/LNS) showers will reach the region around 02-03Z Friday.

Outlook...

Fri...-SHRA become more widespread with a slight chance of TSRA. Restrictions likely.

Sat-Sun...VFR.

Mon...SCT -SHRA with restrictions possible

CLIMATE

Record high temperatures for March 26th:

Harrisburg 80 in 1921 Williamsport 78 in 1939 Altoona 79 in 1998 Bradford 73 in 2007 State College 76 in 1949

CTP WATCHES/WARNINGS/ADVISORIES

None.