textproduct: State College

WHAT HAS CHANGED

* Lowered temperatures today with cold air damming in place * Increasing confidence in dense fog Monday night

KEY MESSAGES

1) Mostly dry today, but cold air damming keeps temperatures chilly again

2) Another slug of rain tonight into Monday morning, then trending drier with some pockets of sun for Memorial Day

3) Warmer midweek with scattered showers before a cooler and brighter end of May

DISCUSSION

KEY MESSAGE 1: Mostly dry today, but cold air damming keeps temperatures chilly again

Weak ridging aloft today will keep us comparatively drier than we were on Saturday. A few isolated showers are possible, but the general idea is that most locations stay dry for most of the day. With low pressure off the DelMarVA coast, southeast flow at the surface will keep us socked in with a classic cold air damming pattern. We'll be noticeably warmer today than yesterday (+10 to +15F), but still -10 to -15F compared to normal. Putting it that way really contextualizes how anomalous Saturday's temperatures were (see Climate section for details about broken climate records). Highs will generally be in the low 60s today.

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KEY MESSAGE 2: Another slug of rain tonight into Monday morning, then trending drier with some pockets of sun for Memorial Day

Another upper level disturbance (mid and upper level troughing) will swing through Central PA tonight, bringing one more round of rain showers to the region. The highest rainfall amounts will be in northwest PA where an additional 0.5-0.75" of rain is possible. Even the Lower Susquehanna Valley should get 0.1-0.25", which will continue to put a dent in ongoing drought conditions.

Hi-res guidance depicts a cold front dropping southeast through the Commonwealth on Memorial Day and bringing an end to the showers. Rain will likely linger in the southeast into the mid afternoon, but a drying/brightening trend can be expected in the northwest. Building surface high pressure also means the stubborn cloud cover will finally mix out/collapse Monday evening across the north. A few peeks of sun could even make an appearance at Memorial Day cookouts across the northern tier. Highs trend much warmer on Monday, generally in the 70s everywhere.

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KEY MESSAGE 3: Warmer midweek with scattered showers before a cooler and brighter end of May

Clearing skies across the north on Monday night in the presence of wet ground will likely to fairly widespread fog formation into Tuesday morning. Many models depict high probabilities in reduced visibility, especially north and west of the I-81 corridor. Dense Fog Advisories may be needed.

Monday's warming trend will continues into the middle of the week, with highs expected to be in the upper 70s and low 80s by Wednesday. The cold front that moves through PA on Monday will stall out across KY/WV/VA for the middle of the week. This could keep some daily shower/thunderstorm chances in place across the southern tier of PA along with more widespread cloud cover there. Wednesday looks like the best chance for storms at this point.

A reinforcing ridge of high pressure will push another cold front through the Commonwealth on Thursday. Behind it, cooler temperatures and brighter skies will follow. High pressure should ensure a much more pleasant last weekend of May than we've had this Memorial Day weekend. Lows in the 40s to 50s and highs in the 60s to 70s will be within a few degrees of average conditions this time of year. It will be a great weekend for planting flowers if you haven't gotten anything in the ground yet!

AVIATION /08Z SUNDAY THROUGH THURSDAY/

Ceilings will continue to lower through the rest of the night, falling to IFR at all airfields before sunrise. Highest chances for LIFR conds are at BFD/JST/AOO (40-50% chc) but nonzero chances at all airfields. Visibility should drop to LIFR at JST and AOO between 09Z and 11Z, while all other TAF sites likely see visibility remain above 6SM.

In terms of winds, breezy winds continue in the Laurel Highlands and NW mountains, with occasional gusts to 30 kts at BFD. Elsewhere, sfc winds have generally weakened. Some LLWS is possible tonight (mainly north of MDT/LNS) as SE to S flow at 1500-2000 ft continues at 35-50 kts.

A modest amount of MUCAPE present this afternoon and Sunday night could lead to a few TSRA mixed in with scattered -SHRA. Restrictions will continue through the day but some minor improvement to MVFR/IFR is possible in the afternoon. Any improvements will be short lived as ceilings will fall to IFR/LIFR once again after 00Z.

Outlook...

Mon...IFR/MVFR early, then MVFR in light rain showers

Tue...Possible morning fog/low visibility, then VFR.

Wed-Thu...Mainly VFR, some scattered SHRA could bring restrictions.

CLIMATE

Several daily record low maximum temperatures were set or tied on Saturday May 23:

LOCATION OBSERVED HIGH PREVIOUS RECORD (YEAR) Harrisburg 54 54 (1982) Williamsport 54 57 (1982) Altoona 50 52 (2005) State College TBA 53 (1968)

CTP WATCHES/WARNINGS/ADVISORIES

None.