Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 230216 AFDCTP Area Forecast Discussion National Weather Service State College PA 1016 PM EDT Thu Jun 22 2017 .SYNOPSIS... A deep southerly flow of high PWAT air will overspread Pennsylvania tonight and Friday ahead of a deepening trough over the Plains states. A cold front will push east across the region during the morning or early afternoon hours Saturday, followed by drier and cooler air with comfortable humidity that will last through much of next week. && .NEAR TERM /THROUGH FRIDAY/... Dwindling batch of convection over the Lower Susq Valley should push east of the forecast area by around 04Z. In it`s wake, cooling/stabilizing boundary layer and weak large scale forcing argue for a period of quiet weather late this evening. Batch of rain over the Ohio Valley should lift northeast across the forecast area between 08Z-15Z, as anomalous southwesterly low level jet arrives. Latest model data continues to indicate the western half of Pa will get the heaviest rain from this feature. GEFS 850hpa mflux values approach +5SD across the Laurel Highlands, where up to an additional inch of rain could fall Friday morning. Batch of stratiform rain in the morning should give way to scattered afternoon convection, as nose of low level jet lifts past the area and model soundings support a bit of brightening/increasing instability by the PM hours. High PWATs and will support locally heavy rainfall from any showers/storms that form during Friday afternoon and make those locations more prone to flooding as remnants of TS Cindy track across the area Friday night. Superblend/NationalBlend high temps ranging from the low 70s over the northwest mountains, where overcast skies are expected, to the mid 80s over the Lower Susq Valley, where model RH profiles support partly sunny skies by afternoon. Any decision on Flood Watches for remnants of TS Cindy Friday night will be made by later shifts. && .SHORT TERM /FRIDAY NIGHT/... *Heavy rain and short-term flooding risk Friday-Friday night. A significant influx of deep tropical moisture (PW 1.50-2"+) associated with the remnants of TS Cindy will combine with an approaching northern stream trough and cold front to bring an elevated risk of heavy rainfall and potential flooding to portions of central PA. The deep moisture will focus along/ahead of an emerging frontal zone and interact with the westerlies aloft and weak instability to support the heavy rain/FF risk. The area that appears to be most susceptible/at greatest risk would be over SW PA (southwest Alleghenies/Laurel Highlands) where a multi-model blend incorporating HIRES models/CAMs has been fairly consistent with location of max QPF. Enhanced terrain lift will also be a factor over a region that has the lowest short-term FFG in the CWA. Updated WPC D2 ERO shows a MDT risk for excessive rain over SW PA clipping Somerset Co. with SLGT risk encompassing the rest of the area. We will continue to highlight +RA/FF risk via HWO at this time - later shifts will likely consider a FF watch at shorter ranges with increasing confidence. Expect some consolidation of pcpn along the frontal boundary as it pushes southeast across the area Friday night with max POPs generally shifting from west to east by the 06-12z Saturday period. && .LONG TERM /SATURDAY THROUGH THURSDAY/... From a large scale perspective, the medium range forecast will feature a seasonably strong/amplified upper trough settling over the Northeast U.S into next week. The theme continues to be above avg confidence in the pattern but low confidence in the details. Expect moisture/rainfall associated with the remnants of TS Cindy to exit the area by Saturday afternoon. Drier, low PW air arrives behind the cold front with decreasing clouds and lowering humidity providing a nice start to the weekend. An extended period of comfortable, low-humidity conditions with temperatures near to below late June climatology are expected to last through the early part of next week. A few cool nights early next week with min temps 40-55F. Precipitation opportunities will be modulated by shortwave impulses reflecting weak surface fronts/troughs which have low predictability at this range. Any pcpn would be generally scattered in nature and on the light side given below normal moisture levels for late June. The 22/12z GEFS shows PW values remaining below average through midweek which would tend to favor mainly dry wx. Temperatures should stay on the cooler side of climo through midweek as the upper level trough shifts east of the area. Differences continue with the trough evolution later in the week with the GFS initially more amplified before building SE U.S. ridge. The EC generally maintains a mean trough over the Northeast CONUS into the second half of next week. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Showers and thunderstorms now confined to the Lower Susquehanna region of Central Pennsylvania. These storms continue to trek off to the ESE and are slowly weakening with time. Outside of some isolated restrictions under the core of the storms, VFR conditions persist across the region. Short term guidance suggests that mainly rain free conditions will persist into the overnight, before another wave of rain approaches from the Ohio Valley. This will rapidly overspread western and central portions of the region prior to 12z, and the rest of the area shortly after sunrise. It appears that the most concentrated and heavier rain will be confined to western areas, with more showery activity to the east during Friday. Remnants of Cindy then overspread the area later Friday and overnight Friday Night. This should bring widespread rain, embedded thunder, and low ceilings to the entire region. Rapid improvement Saturday as the front and remnant tropical moisture slide off to the east. VFR conditions should return for the most part by morning, but some lingering showers could keep spotty restrictions in place in some areas. .OUTLOOK... Sat...Scattered restrictions in AM showers...otherwise VFR. Sun...Mainly VFR. Mon-Tue...Mainly VFR, but with a chance of SHRA/TSRA. Tue...VFR. && .EQUIPMENT... KCCX radar will be offline for approximately 4 days starting Saturday, June 24th for technicians to install the first of 4 major service-life extension upgrades. The work on the radar has been scheduled to minimize potential impacts to operations and will be delayed if hazardous weather is forecast. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Fitzgerald SHORT TERM...Steinbugl LONG TERM...Steinbugl AVIATION...Jung EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.