Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 221609 AFDCTP Area Forecast Discussion National Weather Service State College PA 1109 AM EST Mon Jan 22 2018 .SYNOPSIS... A warm front over the Interstate 80 corridor this morning will lift slowly north today. A potent area of low pressure moving across the Great Lakes will push a trailing cold front through the Commonwealth on Tuesday. Temperatures will rise well above normal today and stay there through early Tuesday, before falling back to near or slightly below normal Wednesday and Thursday. A rebound to above normal temperatures will occur again by next weekend. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... Still awaiting WFROPA here in Happy Valley. Right now, it`s still Murky Valley, but visby is coming up. Expect to see the wind do an about face soon. Batch of showers sliding through the central mountains will take a few more hours to clear out of the NE. However, a decent break of 10-12 hrs should occur until more significant precip returns (from the west). Temp fcst still looking solid for a decent rise as the lower clouds are almost gone from the south. Prev... Surface warm front extended near the RT22/322 corridor in south-central PA early this morning with weak isentropic lift from the southwest producing widespread low stratus to its north and east, and a dual-multi layer of stratocu and alto cu in the warm sector across the southern tier of PA. Expect occasional light rain, drizzle through much of this morning, before some improvement with just some isolated-sctd showers leftover this afternoon as the warm front lifts across the northern mtns and eventually into New York State by late today. The weak low-level isentropic...and orographic lift over the mtns and interface of the shallow cool air and warmer moist air aloft will yield areas of dense fog through about 14-15Z today across the higher terrain - AOA 1800 ft MSL. Temps will remain relatively mild for late January and mainly in the upper 30s to lower 40s. A few pockets of cooler air around 35F will persist across the Middle Susq Valley early today. Blended model guidance points toward a very mild afternoon with temps ranging from the mid-upper 40s across the NE to the balmy upper 50s over the southern tier counties. These highs will depart from normal by 13-15F across the NE and by nearly 30 degrees over the Laurel Highlands. && .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM TUESDAY/... Mild weather will continue overnight. A few showers early on will rapidly expand in coverage from SW to NE across the region for the second half of the night as deepening uvvel develop with the approach of the left exit region of a 130 kt upper jet lifting NE from the tenn Valley. The rain could fall heavy at times for brief periods just ahead of an approaching cold front. Cold front crosses central PA Tuesday morning with weak secondary low forming in the lee of the Appalachians supporting a period of enhanced rainfall over the eastern 1/2 of PA on the order of 0.50-0.75" (as front occludes into early Tuesday afternoon). A rather potent, SW 50kt LLJ could also generate a rumble of thunder. River ice concerns are addressed in the hydrology section. Gusty WSW winds, possibly as high as 40 to 45 mph occur in the wake of the cold front Tuesday afternoon and evening. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... The progressive pattern will keep the mid/late week cool-down rather brief before temperatures moderate/trend warmer into the upcoming weekend. Gusty westerly winds with top values between 35 and 45 mph will continue Tuesday night, before gradually decreasing through the day Wednesday. Occasional snow showers are likely downwind of Lake Erie Tuesday night and Wed but should only amount to light accums of a coating to 2 inches in most places. Dry wx under high pressure Thu- Fri with chilly starts to the day (especially in the east) with moderating temperatures heading into the weekend as the next (weaker) low pressure system lifts across the Great Lakes bringing chances for rain on Sat increasing into Sunday. && .AVIATION /16Z MONDAY THROUGH FRIDAY/... JST is now VFR and upstream obs indicate that it should continue to be VFR for many hours. AOO, MDT and LNS all have VFR CIG, but light fog. Rest of the srn airfields should be up to VFR VISBY, soon. Prev... Moist flow, along with calm winds and will continue to have VLIFR cigs across the northern mountains (KBFD) while progressively higher cigs are expected further south. Trapped low level moisture along with calm winds has allowed fog/mist to develop overnight. These reduced vsbys, along reduced cigs at UNV and IPT will continue through the morning. Light precipitation south of the front continues with light showers at times at MDT and LNS with scattered showers moving in from the west. While IPT and SEG are LIFR, areas across southeast Pa (KMDT/KLNS) at 13Z, are MVFR. The latest model soundings and MOS guidance support the idea of a possible period of the MVFR cigs/vsbys continuing through mid morning. Expect predominantly MVFR cigs at KJST and AOO through the day, where a southerly flow results in drying/downsloping off of adjacent higher terrain. Warm front is progged to lift through western Pa on today, resulting in a return to VFR conditions along the spine of the Alleghenies, including KJST and AOO. Elsewhere, modest improvement will come slowly across the eastern half of Pa on the cold side of the front. Cigs and vsbys should decrease again tonight with more widespread showers possible out ahead of a cold front tonight into tomorrow morning. Along with this front will be a LLJ which will bring a LLWS problem that will become a concern Monday evening into Tuesday morning. Outlook... Tue...AM rain/low cigs poss, then windy with PM shsn poss w mtns. Wed...AM shsn possible w mtns. Thu-Fri...No sig wx expected. && .HYDROLOGY... Marietta gage /MRTP1/ pretty much steady right now, although ice effects continue. The Flood Watch for this area lasts into Monday afternoon. Due to the mild temperatures, there is a potential for ice movement, but also deterioration/thinning with time. All locations along rivers and streams that have significant ice buildup should monitor water levels closely for the next several days. The anticipated rainfall totals of 0.5 to 0.8 inches over the next 48 hrs is much less than we had a few days ago, and the ice is less pervasive/extensive due to our relatively mild temps (versus the period leading up to our previous significant rainfall). && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Tuesday afternoon for PAZ065-066. && $$ SYNOPSIS...Dangelo/Lambert NEAR TERM...Dangelo/Lambert SHORT TERM...Lambert LONG TERM...Lambert/RXR AVIATION...Dangelo/Ceru HYDROLOGY... is the U.S. government's official web portal to all federal, state and local government web resources and services.