260 FXUS61 KCTP 272258 AFDCTP Area Forecast Discussion National Weather Service State College PA 658 PM EDT Sat Apr 27 2024 .SYNOPSIS... -Occasional showers possible overnight; scattered thunderstorms Sunday, especially across northern PA -Temperatures rise above average Sunday and warmth stays put all week with highs in the 70s and 80s; near-record warmth Monday -Cold fronts Tuesday and Friday-Saturday bring rain and storms. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... The majority of shower activity has moved east of the region this evening. A warm front is moving into southwest PA as indicated by southeast winds ahead of it shifting to the southwest in its wake. The boundary will drift eastward across PA tonight and overrun the relatively cool air in the valleys. Only widely scattered light showers are expected overnight. A rumble of thunder is possible in the northwest where clearing skies have generated a bit of instability, but overcast conditions in southeasterly flow farther east will eliminate any risk of thunderstorms. Dense overcast skies will keep temperatures nearly steady overnight and, if anything, temperatures will creep *up* a few degrees across the west tonight as the warm front moves in. Winds will shift to come out of the southwest by Sunday morning, paving the way for plentiful warm advection and a very mild afternoon on Sunday. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... Surface ridging builds in on Sunday with brightening skies in the south and lingering clouds in the north. The ridge axis will cross Pennsylvania Sunday afternoon, helping focus a ring of fire pattern of showers and thunderstorms in New York and perhaps the northern tier of our forecast area. Scattered showers and thunderstorms could be ongoing Sunday morning and will continue into the afternoon and evening. Although a majority of hi-res guidance keeps showers along and north of I-80, efficient moisture and temperature advection farther south will support showers and thunderstorms all the way to the Mason-Dixon Line. Have added a slight chance of storms there centered on peak heating between 4 and 6PM, with higher probabilities farther north. With Pennsylvania fully in the warm sector southwest of the warm front on Sunday, temperatures will soar into the 70s and 80s. Clouds and showers/storms will be more plentiful in the north, where highs in the low 70s may be a little too high if anything. Farther south, highs in the mid 80s are well within reason barring any significant showers/storms making it toward the I-76 corridor (unlikely at this time). Unlike the previous mild days we've had so far this spring, this warm stretch will be accompanied by a noticeable uptick in humidity. Dewpoints will approach 60F in the Lower Susquehanna Valley, which is usually the point at which you start to notice the humidity. A very mild night is in store for Sunday night thanks to the higher dewpoints that will be in place. Mostly clear skies will allow for efficient radiational cooling such that temperatures fall to near or just above the dewpoint temperatures. In locations that receive rainfall Sunday afternoon, patchy fog is likely Sunday night into Monday morning. Based on the current forecast, locations north of I-80 are most likely to have fog. Lows on Monday morning will be in the 55 to 60F range, which is +10 to +15 compared to average. && .LONG TERM /MONDAY THROUGH SATURDAY/... Fair and unseasonably warm conditions are expected for a majority of central PA on Monday. Recent model guidance continues to suggest MaxTs in the low-to-mid 80s areawide with temperatures pushing the upper 80s across SE PA where some clearing remains possible. RHs in the 40-50% range across portions of the Lower Susquehanna Valley will bring potential for ApparentTs in the 80-85F range during the late afternoon hours extending into interior portions of central PA. Some afternoon convection across mainly northern PA does appear plausible given embedded shortwaves within the ridge axis and have upped PoPs compared to previous forecast cycles mainly for areas north of I-80. If convection manages to occur, MaxTs across northern PA could be limited to the upper 70s but will still be well above seasonable averages. An unsettled pattern is expected to continue into Tuesday as low pressure from the Central Plains moves northwest of the area and brings a weak sfc cold front across the area during the morning and early afternoon hours. Guidance has started to indicate a secondary area of sfc low pressure forming along the DelMarVa later in the afternoon/evening hours before quickly racing off to the northeast. This feature, noted in both GFS/ECMWF guidance has lead to a slight bump up in PoPs Tuesday evening into the early morning hours of Wednesday. The rest of Wednesday trends drier as upper-level ridging takes hold; however, some convective thunderstorms/showers could occur if enough sfc heating takes place. There is low confidence at this time, so have capped PoPs at a SChc (15-25%) in the late afternoon/early evening timeframe. Diverging solutions emerge in deterministic model guidance Thursday and into Friday after the upper-level ridge moves eastward. The European suite of model guidance suggests a stronger ridge axis will provide another stretch of dry and above-average temperatures Thursday and into Friday while the North American suite suggests a weaker ridge axis allowing for shortwaves to bring showers and thunderstorms throughout the end of the week. Model uncertainty does warrant at least a SChc of PoPs Thursday morning through Friday PM with slightly higher probabilities of shower activity across NW PA. && .AVIATION /22Z SATURDAY THROUGH THURSDAY/... A moist south-southeast flow ahead of an approaching warm front is producing stratus across nearly all of Central PA this evening, with the lowest (IFR) cigs noted where the flow is forced to ascend the higher elevations of the Alleghenies. Latest model guidance supports improving flying conditions across the western half of the state later tonight associated with the approach of the warm front and a wind shift to the south. Confidence is most high (80pct) in a return to VFR conditions at JST late this evening. Elsewhere, a lingering upslope flow could lead to persistent stratus with IFR cigs possible across the N Mtns through dawn. Another issue will be the the potential of LLWS across the northwest half of the state associated with increasing southwest winds aloft. Latest BUFKIT soundings support LLWS conditions overnight across the NW Mtns and potentially into the central part of the state. The warm front is expected to lift north of the entire region by late Sunday AM. Shifting winds to the southwest behind the front will result in an end to the LLWS threat with widespread VFR conditions for most of Central PA. However, ensemble prob charts indicate around a 30 pct chance of lingering MVFR cigs along the northern tier of the state. Scattered late day tsra across the northern half of the state could also produce a brief vis reduction north of I-80. Outlook... Mon...No sig wx expected. Tue...Isold PM tsra impacts possible. Wed...Early AM low cigs possible N Mtns. Thu...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Banghoff NEAR TERM...Banghoff SHORT TERM...Banghoff LONG TERM...NPB AVIATION...Fitzgerald