Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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692 FXUS61 KCTP 121106 AFDCTP Area Forecast Discussion National Weather Service State College PA 706 AM EDT Wed Jun 12 2024 .SYNOPSIS... High pressure will be centered over the Commonwealth today, supplying abundant sunshine and warmer temperatures, followed by a further increase in heat and humidity for Thursday and Friday as the high drifts off the Mid Atlantic Coast. A cold frontal passage on Friday will spark a round or two of showers and scattered thunderstorms, some of which could produce gusty winds, frequent lightning and hail. A ridge of high pressure will bring an increased risk of excessive heat early next week with highs in the 80s and 90s and heat index values possibly exceeding 100F. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The stubborn deck of stratocumulus that hung around much of the CWA on Tuesday (and the Northern Mtns earlier in the overnight) has lifted to our far NE CWA and will be exiting stage right shortly. Some areas of 1/2-1SM Valley Fig will occur across Northern PA, and some of it could even drop the vsby below 1/4SM. An area of mainly thin cirrus is seen on regional satellite imagery drifting east across the CWA. This area of high clouds will exit our eastern zones by about 13Z followed by some scattered Altocu then the development of some flat, fair weather cu this afternoon. As a bubble of 1018 MB high pressure drifts just east of the CWA this afternoon, the light West to Southwesterly flow will combine with the sunshine to advect/vertically mix warmer and quite dry air across the forecast area. Highs will be in the mid to upper 70s across the higher terrain and low 80s in the Lower Susq Valley. These readings will be a few deg F either side of climo Sfc dewpoints in the mid 40s to low 50s will lead to min RH values of 30 to 35 percent this afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... After a tranquil and comfortably cool night (with min temps near 50F in the perennial cold spots across the Northern Mtns and Laurel Highlands and mid to upper 50s elsewhere), we`ll see a further warm up for Thursday and likely Friday across much of the region. Many locations will see their warmest temps on Thursday, except for perhaps portions of southeast PA where temps could be a few degrees warmer on Fri. Temperatures on Friday will depend on the timing of clouds and convection associated with an approaching cold front. Over the past 24 hours, models have generally sped up the arrival time and southward progression of the aforementioned front, now bringing a chance of showers and thunderstorms to the northern Alleghenies as early as Thursday night, and then dropping south across central PA during the day Fri with more numerous showers and thunderstorms. SPC`s new DY3 outlook paints a MRGL risk for SVR TSRA across much of Central PA, while a SLGT Risk covers a small portion of our Eastern zones (the Western Poconos, south through the greater Harrisburg, Lebanon and Lancaster areas). Despite forecast high temps near 90 across southern zones Thu- Fri, relatively low levels of humidity (dewpoints 55-65F) will hold the heat index to just a couple deg above the air temp. Thus not anticipating heat products at this time. However, the +15-20 degree swing from temps well below normal early this week to the warm weather late this week will be noteworthy. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Next weekend looks dry, as a northerly flow of drier air from Canada is advected into our area. Plenty of sunshine and fair weather is expected for Saturday and Sunday with a beautiful weekend in store. Any slight cool down on Saturday will be short- lived, with warmer temperatures progged to build back into the area Sunday into Monday. A few isolated sprinkles could be possible in the northern tier of PA with weak diurnally driven updrafts on Monday afternoon. By Tuesday, the risk for excessive heat will increase as a large ridge builds over the eastern US. There remains quite a bit of spread in model guidance, but potential exists for heat index values topping 100F in southeast PA Tuesday - Thursday next week. The ECENS is more bullish with the strength and northern extent of the ridge of high pressure into PA, which would result in higher temperatures and heat index values. The GEFS is a bit cooler with a weaker high and potential convection associated with a shortwave moving along the ridge, but still indicates the potential for excessive heat. Based on this anomalous pattern, the Climate Prediction Center has placed much of eastern PA in a Moderate Risk for Excessive Heat for the middle of next week (Wednesday - Friday). && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... 12z update... Patchy river valley fog over the northern tier is expected to burn off quickly this morning (by around 13z). We have a fairly high degree of confidence (80-90%) in this scenario. In the meantime, brief restrictions are possible at KBFD and KIPT. Otherwise, VFR will prevail, given the expectation that a very dry air mass will be traversing the region over the next 24 hours or so. Surface winds look light, generally 5 kt or less. Outlook... Thu...Predominantly VFR w/ no sig wx expected. Fri...Restrictions possible in CB/TSRA. Sat-Sun...Predominantly VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Banghoff NEAR TERM...Lambert/Banghoff SHORT TERM...Lambert/Banghoff/Colbert LONG TERM...Banghoff/Evanego AVIATION...Jurewicz/Martin