Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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260 FXUS61 KCTP 151016 AFDCTP Area Forecast Discussion National Weather Service State College PA 616 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 TONIGHT/... Early morning satellite imagery shows fairly extensive valley fog across Central PA. Latest SREF/NAMNest and LAMP guidance indicate the fog will disperse by 12Z-13Z. Canadian high pressure building southeastward into PA will bring fair weather to the area today with a good deal of sunshine, seasonably warm temps and low humidity. Dry air above a weak inversion in the model soundings suggest dewpoints will fall below NBM guidance this afternoon, so have leaned toward the drier MAV guidance. Model guidance indicates there will be some cirrus drifting into PA tonight in advance of a weak shortwave cresting the ridge axis over the Grt Lks. However, model RH profiles indicate it should be relatively thin and not significantly affect radiational cooling, which otherwise looks favorable under the surface high. Have therefore undercut NBM min temps and 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. && .SHORT TERM /SUNDAY THROUGH MONDAY/... 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. A building subtropical ridge along the east coast and the passage of a warm front early Monday will herald the arrival of much warmer early next week. Warm temps aloft should suppress convection and 850mb temps surging to near 17C supports highs Monday afternoon in the mid 80s to low 90s. && .LONG TERM /MONDAY NIGHT 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 later 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. 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 /10Z 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