textproduct: State College

WHAT HAS CHANGED

No sig changes.

KEY MESSAGES

1) Periods of moderate to briefly heavy rain showers continue across far south central and southeastern PA into later tonight associated with the remnants of Isaias.

2) Big temperature swing forecast for the week ahead

DISCUSSION

KEY MESSAGE 1: Periods of light to moderate rain showers continue across far south central and southeastern PA into later tonight associated with the remnants of Isaias

Rainfall totals have reached the 2-4 inch range across portions of south central PA. A flash flood warning was in effect earlier this evening for Adams and York Counties, but that has since expired and the overall hydro threat is diminishing as rainfall rates come down vs what we saw earlier. MUCAPE is still high enough for a few lightning strikes as moderate rain showers associated with Post-Tropical Cyclone Isaias pivot in from the southeast. Most of the additional rainfall will occur south of a line from Martinsburg to Harrisburg. Rain will wrap up by daybreak for most of the CWA.

KEY MESSAGE 2: Big temperature swing forecast for the week ahead

Noticeably warmer and more humid conditions expected early this week with max temps on Tuesday forecast to peak 10-15 degrees above the historical average for mid October and possibly challenge daily records with highs in the 70-80F range.

Improving weather conditions can be expected Monday as the remnants of Isaias exit the Mid Atlantic. Rain chances on Tuesday appear to be maximized over the northern tier where a shortwave aloft and sfc cold front (infused with moisture from TS Rachel?) streak eastward from the Great Lakes. SPC has highlighted this area with a conditional low risk level 1/5 for severe t-storms. Another period of rain is likely late in the week, but exact timing remains uncertain.

Confidence is increasing in a seasonably chilly cooldown and big temperature swing (vs. early in the week) for the upcoming weekend. The substantial cooldown appears to be delivered in the wake of a strong cold front by gusty west-northwest flow directing the colder air over the Great Lakes. This could setup some lake effect/upslope rain or snow showers (yes, first flakes possible in the Alleghenies/Laurel Highlands) followed by frost and freeze conditions. To quantify the magnitude of the fcst temp swing this week, Bradford could go from 75 degrees Tuesday afternoon to 25 degrees by early Sunday morning (50 degree swing!)

AVIATION /02Z MONDAY THROUGH FRIDAY/

While the bulk of the rain has moved off to the east, expect showers and a few thunderstorms to continue around MDT and LNS through 06Z as a surface low passes to our south and east. IFR/LIFR conditions at BFD and JST are likely to continue through the rest of the night, but there is some uncertainty regarding how low ceilings and visibility stay farther to the east. Even though the LAMP shows quite a bit of IFR at all TAF sites tonight, HREF probs of IFR are fairly low after 06Z. Model soundings from the RAP and HRRR paint a similar picture, showing ceilings rising to MVFR at all TAF sites except BFD and JST as winds become more northwesterly.

Ceilings gradually rise through the day, and VFR is expected at most airfields for much of the afternoon. The exception will be JST where it might take until early evening for the low clouds to finally dissipate. Winds on Monday will be out of the west- northwest at 5 to 10 knots.

Outlook...

Tue...VFR favored, though a front approaching from the north may bring restrictions in -SHRA. AM fog possible.

Wed...Restrictions from low ceilings and -SHRA possible as the front moves southward across the Commonwealth.

Thu...A period of VFR is favored behind the front, with a chance for restrictions and -RA later on Thursday as the front oscillates back northward.

CLIMATE

Daily record high temperatures for October 13th: MDT 85/1954 IPT 83/1954 AOO 82/2024 BFD 78/1969 STC 82/1930

CTP WATCHES/WARNINGS/ADVISORIES

None.