Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240319 AFDCTP Area Forecast Discussion National Weather Service State College PA 1119 PM EDT Tue Apr 23 2024 .SYNOPSIS... -Periods of rain showers tonight through Wednesday afternoon (mainly across the NW Mtns tonight) -Rain-free late this week with a renewed frost/freeze risk early Thursday and Friday mornings && .NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/... Rain did manage to make it to the ground at BFD. Dewpoint rose into the u30s-l40s across the N where it did rain more than a sprinkle. However, the very dry (20s) dewpoints continue for much of the rest of the CWA> The next volley of showers moving across wrn PA does have some gusty wind with it, as it is probably mixing the wind down as the rain-cooled air reaches the ground, too. Our local stability/dry air will break down some, but not across the entire CWA. The SE/Lower Susq is more likely to go without getting the ground wet overnight. Will leave 20-30 PoPs there. Low temps tonight in the low 40s/50s are +10-15 degrees warmer than the last two nights (no frost) thanks to an active southwest to westerly breeze along with clouds/rain showers. && .SHORT TERM /7 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Looking at the accumulated Growing Degree Days (base 50F), it appears that more of the CWA has hit the growing season. Thus, we`ve expanded the Freeze Watch for Wed night/Thu morning into more of the area - despite keeping the minT forecast as is. We have kept the Laurels (Cambria/Somerset/Bedford) out of the watch for the time being since current fcst is for mins in a general 32-36F span. Note: Cambria and Somerset have been deemed to be "in" the growing season, now. The areas not yet in the growing season in Central PA are Schuylkill, Potter, Tioga, Sullivan, northern Clinton and northern Lycoming Counties. Prev... The main upper level shortwave trough swings through the area early Wednesday, followed by a secondary cold frontal passage during the afternoon leading the way for a pool of slightly anomalously cold air aloft (about -25C at 500 mb or about -1 sigma). Latest hires model guidance shows scattered low-topped diurnal convective showers developing during the late morning (Mainly over the NW Mtns) and through the afternoon across the Central and SE zones with the potential to produce locally gusty winds. SPC continues to indicate non- severe t-storm probs over the southeastern portion of the CWA for Day 2 where HREF shows a few hundred J/kg of CAPE. Highs on Wednesday will trend cooler and range from the upper 40s in the northern tier to mid 60s in the southeast. Expect rain shower activity to fade quickly toward sunset/into early Wednesday night or shortly after 00Z Thu. 1030+mb Canadian high pressure building over the region Wednesday night below normal pwats will bring dry wx/rain free conditions into late week. The main focus will return to potential for frost/freeze conditions which remain highlighted in the HWO. && .LONG TERM /THURSDAY THROUGH TUESDAY/... We will have a chilly but tranquil start to the extended period Thursday morning, with widespread freeze/frost expected courtesy of sprawling Canadian high pressure ridging into the northeastern United States. Plenty of sunshine is expected on Thursday, helping temps rebound through the 50s to low 60s. Another chilly night is expected Thursday night (especially over eastern areas), before moderating return flow on the backside of departing high pressure begins on Friday and brings milder temperatures and increasing high cloudiness. The weekend appears somewhat unsettled, with a warm front approaching Friday night and the warm sector struggling to overspread central PA. It won`t be raining all the time, but periods of rain or showers cannot be ruled out from the Friday night through Sunday. Upper ridging may eventually win out by Sunday night and Monday, allowing for drier wx and warmer temps with highs surging through the 70s and perhaps topping 80F across the south on Monday. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
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High and mid-level clouds continue to thicken over central PA heading into the overnight hours. There are some light radar returns moving in from western PA, but the low-levels remain quite dry so precip is having trouble reaching the ground. The south to southwesterly breeze has diminished a bit, but we continue to see occasional gusts of 15-25 kts in some locations. Cigs will continue to gradually lower overnight, with the western highlands (BFD, JST) dropping to MVFR, if not IFR, by daybreak on Wed. The central mtns will likely drop to borderline MVFR/VFR by daybreak, with the Lower Susq Valley remaining VFR. We should eventually see light rain showers make it to the ground across the western highlands, but this activity is likely to diminish as it progresses eastward overnight. There could also be some LLWS during the early overnight hours, with a 35-45 kt southwesterly wind a couple thousand feet above the sfc. Surface winds will become northwesterly overnight, and become gusty again by Wed afternoon. Spotty showers remain possible on Wed as well. Outlook... Wed...Spotty -SHRA with MVFR cigs west and predominantly VFR east. Thu-Fri...Predominantly VFR conds under high pressure. Fri night-Sat...Patchy rain developing from west to east. Sun...Scattered SHRA/TSRA possible.
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&& .FIRE WEATHER... Low humidity (20-30% minRH) and breezy conditions (20-30 mph wind gusts from the south/southwest) will result in an elevated risk of wildfire spread late this afternoon. However, dead fuel moisture values per latest PABOF/DCNR sitrep and ongoing Spring green-up are both limiting factors offsetting the wind+RH fire wx risk to a large extent in CPA. && .CTP WATCHES/WARNINGS/ADVISORIES... Freeze Watch from late Wednesday night through Thursday morning for PAZ004-005-010-011-017>019-025>027-045-046-049>053. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert/Dangelo SHORT TERM...Lambert/Dangelo LONG TERM...DeVoir/Evanego AVIATION...Evanego FIRE WEATHER...Lambert

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