Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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280 FXUS61 KCTP 150517 AFDCTP Area Forecast Discussion National Weather Service State College PA 117 AM EDT Sat Jun 15 2024 .SYNOPSIS... Lingering showers over the southeast will come to an end after midnight with the passage of a cold front. This will be followed by Canadian high pressure building in for this weekend, bringing lower humidity. After that, the big story will be building heat as a subtropical ridge builds over the eastern United States next week. && .NEAR TERM /THROUGH TODAY/... Any evening showers/storms will exit the Lower Susq Valley by early morning, as the cold front pushes east of the commonwealth. High pressure building in behind the front should bring clearing skies, cooler air and lower humidity overnight. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... Canadian high pressure building southeastward into PA will bring fair weather this weekend, with abundant sunshine, seasonably warm days and comfortable humidity. Dry air above a weak inversion in the model soundings suggest dewpoints will fall below NBM guidance, especially Saturday, so have leaned drier than guidance. Ideal conditions for radiational cooling appear likely Sat night under the surface high, resulting in min temps several degrees below mid June normals. Temps at daybreak on Sunday will range from the mid 40s across the nrn mtns to the mid 50s in the Lower Susq Valley. Expect another pleasant afternoon Sunday with low dewpoints and highs in the upper 70s to mid 80s, about 5 deg warmer than Saturday. Warm advection will be underway Sunday night, with low temps in the 50s to low 60s. && .LONG TERM /MONDAY THROUGH FRIDAY/... Little change with the late evening update outside of limiting chances of diurnal showers/storms on Tuesday. Have kept chances into the middle/end of the week due to some uncertainty. Prev.. Confidence is increasing for a heat wave next week with the potential for 4-6 consecutive days of MaxT 90F+ across much/all of central PA. The prolonged nature of this heat wave may have cumulative adverse effects on vulnerable populations exposed to heat, with heat related illnesses possible if proper precautions are not taken. Outdoor workers and individuals with preexisting health conditions will be among those most at risk. Moisture may be slow to advect into the region initially, with dewpoints Monday afternoon expected to be in the range of 60-65F. Thus Mon heat index values are forecast in the mid to upper 90s, with some valley locations across central/southern PA pushing close to the 100F mark. Tuesday through Thursday (and potentially Friday-Saturday) are progged to be the warmest days of the week, with most guidance showing a 595-600 dm 500 hPa ridge centered over the area. Southerly flow will usher in higher dew points Tuesday that will allow for heat index values to reach 100-105 degrees over a large portion of the area. With the large high pressure system overhead, winds will be light and clouds will be few. Keep in mind that the sun angle will be at its max next week as we approach the summer solstice. The intense sun and lack of a breeze will exacerbate the impacts of heat. Beyond Thursday, uncertainty begins to develop regarding the shape of the ridge and the possibility of convection firing along the periphery of the high pressure system, but the potential for highs in excess of 90F continues through Saturday. && .AVIATION /05Z SATURDAY THROUGH WEDNESDAY/... 06z update... Now that a cold front has pushed to the south and east of the Commonwealth, skies have cleared out for the most part. However, satellite imagery and surface observations have depicted patchy valley fog in the pre-dawn hours, especially where heavier rainfall occurred Friday afternoon and early evening. For this reason, we have moderate confidence (40-60%) in at least MVFR visibility restrictions through about 12z. At this time, KUNV and KIPT seem to be the most likely sites to see at least brief IFR restrictions. Any fog patches should burn off quickly by 12-13z, given a deep layer of dry air aloft and the expectation of large-scale sinking motion. There is high confidence of VFR conditions (90+%) for the remainder of the valid TAF period (through 06z Sunday). Surface winds should be light (mostly under 5 kt) through 13-15z, then pick up out of the NW to 8-10 kt, before diminishing again by/after 00z. Outlook... Sat-Wed...Predominantly VFR, with building heat next week. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald/Evanego/RXR NEAR TERM...Evanego/RXR SHORT TERM...Evanego/Colbert/RXR LONG TERM...Colbert/NPB AVIATION...Jurewicz/Evanego/RXR