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 /12Z SUNDAY THROUGH THURSDAY/

A mix of MVFR and IFR restrictions are being observed this morning across Central PA. While ceilings have been slow to lower across the region, the expectation is still that IFR conditions will develop at all airfields within the next few hours. Once they do, most guidance suggests that IFR will persist through the end of the TAF period. The exception will be at JST and maybe AOO where a period of MVFR ceilings will be possible this afternoon. There is even a low (less than 30 percent) chance that JST sees a brief period of VFR conditions. Any improvements will be short lived as ceilings will return to IFR/LIFR across the entire forecast area tonight.

A relative minimum in shower activity is expected this morning and into the afternoon, but rain becomes more widespread once again this evening over western PA. This shower activity will spread eastward into the overnight hours, eventually reaching all TAF sites. Some weak elevated instability will be present as these showers move in, so a few rumbles of thunder cannot be completely ruled out.

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.