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Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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172 FXUS61 KCTP 150637 AFDCTP Area Forecast Discussion National Weather Service State College PA 237 AM EDT Sat Jun 15 2024 .SYNOPSIS... Canadian high pressure will push southeast into Pennsylvania this weekend, then an anomalous subtropical ridge will build over the East Coast next week. && .NEAR TERM /THROUGH TODAY/... The upper trough and associated cold front have exited the southeast part of the forecast area as of 06Z. Large scale subsidence behind this feature will ensure fair weather the rest of the night. Breaking clouds, light wind and wet ground from yesterday`s rainfall has resulted in fairly widespread valley fog early this morning. Latest SREF prob charts indicate the fog is likely to persist where it has formed through around 12Z. The driest air and weakest pressure gradient lies over the NW Mtns, where radiational cooling should result in daybreak min temps around 50F. Elsewhere, expect min temps in the 50s to around 60F across the Lower Susq Valley. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... Canadian high pressure building southeastward into PA will bring fair weather this weekend, with a good deal of sunshine, seasonably warm days and low humidity. Dry air above a weak inversion in the model soundings suggest dewpoints will fall below NBM guidance both Saturday and Sunday afternoon, so have leaned toward the drier MAV guidance. Ideal conditions for radiational cooling appear likely tonight under the surface high, resulting in min temps a few degrees below NBM guidance. Have therefore leaned toward the cooler MAV numbers, with lows ranging from the low 40s in the coolest northern valleys, to the mid 50s in the more urbanized locations of the Lower Susq Valley. The surface high should pass east of PA Sunday, resulting in a slightly warmer return southerly flow. Model 850mb temps near 14C support highs a few degrees higher than today, with max temps ranging from the mid 70s over the mountains north of KIPT, to the low 80s most other locations. Warm advection will be underway Sunday night, with low temps in the upper 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 /06Z 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 NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Colbert/NPB AVIATION...Jurewicz/Evanego/RXR