Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 272301 AFDCTP Area Forecast Discussion National Weather Service State College PA 701 PM EDT FRI MAY 27 2016 .SYNOPSIS... A ridge of high pressure will stay in place over the western Atlantic...bringing very warm and increasingly humid conditions to the region through much of the holiday weekend. Cooler and showery weather may arrive for Memorial Day. && .NEAR TERM /UNTIL 7 AM SATURDAY MORNING/...
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Cells not quite tall enough to generate either large hail or gusts better than 30kts. Loss of heating already starting to diminish the showers. NAM has had a good handle on what has been going on while the HRRR and RAP not very well even with the radar-initialization of the HRRR. Showers over the southern tier will most likely continue for another hour/two and generally weaken as they do so. Wave crossing the NE mountains later this evening may continue to generate some low- topped convection there. Temps lofty and, with high humidity, it will take quite a while to cool off to mins in the u50s NW to m/u60s SE. places that received rain will probably get some fog overnight as well. Previous: Diurnal heating of the very warm and moist airmass/rising parcels are starting to penetrate the weak mid-level cap (with 700 mb temps of plus 4-5C), leading to isolated-scattered showers/tsra forming mainly across the ridges of scent and ncent PA at 18z. This convection will drift east into the more unstable air across the susq valley where sfc based capes around 2000 J/kg are about double what we`re seeing in the area of TSRA genesis. The rather slow moving tsra could create locally isold strong wgusts/hail in best cells. However, wind fields and deep lyr shear are weak, indicating organized svr wx is unlikely. Although aftn Pops are generally blw 50 pct, increased pops across srn penn where convective allowing high res models show some organized TSRA clusters taking shape across the lower susq valley (mainly south of I-81 between 20Z and 00Z). What rain does fall could be locally heavy, due to slow storm motion and high PWATs. Convection- allowing mdls (HRRR) show this potential with highly localized amts in excess of around 2 inches possible in just an hour or so. 18z temps should rise another 1-3F to reach late afternoon highs of 80-82F across the northern and western mtns, and near 90F over the Susq Valley. Diurnally-driven convection will gradually dissipate with the loss of heating this evening. Partly cloudy skies and light wind could yield patchy fog later tonight, especially where the ground is wet from the pm showers/TSRA. High dewpoints will lead to another very warm/rather muggy night with min temps in the mid 60s over much of the area.
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&& .SHORT TERM /7 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Subtropical ridge builds nwwd into Pa on Sat with 500mb height anomalies reaching 2SD across southeast Pa. The assoc warm temps aloft should suppress convection across the se counties Sat aftn. However, sct diurnal tsra again appear likely across the nw half of the state. Thermodynamic/kinematic profiles appear very similar to those on Friday, with moderate sfc-based cape of 1500-2500 j/kg and weak low-mid level shear, suggesting pulse-type convection and a low risk of organized svr wx. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Summertime upper level ridge over the Mid Atlantic and Northeast states is forecast to peak around 29/00z with above normal heights returning to normal by early next week. Temperatures should follow a similar trajectory with positive temp departures trending modestly lower/toward climatology into the first week of June. The tropical disturbance /Invest AL912016/ approaching the Southeast U.S. coast will add additional moisture to an already humid/unstable airmass in place through Memorial day weekend. Some interaction between the tropical disturbance and mid latitude trough crossing the Central Appalachians likely favors the greatest pcpn risk/potential pcpn coverage Sunday night into Memorial Day (Monday) with a decreasing chance for rain into Tuesday. Deterministic and ensemble guidance are in broad agreement in a dry period of weather from Tuesday into Wednesday before pcpn risk gradually increases into the second half of next week. Heights are forecast to rise a bit around the end of the period before the large scale pattern slowly shifts toward a western ridge/eastern trough configuration by June 5th as depicted by the 27/00z NAEFS and ECENS. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Ridge of high pressure remains in control, keeping a genuine summertime weather pattern in place. VFR conditions will dominate much of the remainder of the day. However, there is moderately high low-level moisture/instability in place to generate sct pulse- type thunderstorms with locally gusty winds across mainly the southeastern half of PA. These storms are moving very slow so removed VCTS from MDT and LNS due to them arriving just before sunset. Any flight restrictions should be mainly 15-30 minutes of MVFR cigs and vsbys, though very brief IFR conditions are possible. Vsby reductions to MVFR more likely tonight with humidity increasing...with a few areas of IFR fog mainly confined to places that receive rain today. OUTLOOK... Sat...Early am low cigs/vsby possible. Isold pm tsra impacts. Sun...Sct pm tsra impacts possible...mainly nw half. Mon...Sct pm tsra impacts possible...mainly se half. Tue and Wed...No sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Dangelo/Lambert SHORT TERM...Fitzgerald/Lambert LONG TERM...Gartner/Steinbugl AVIATION...Lambert/Ceru

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