Area Forecast Discussion
Issued by NWS State College, PA

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042 FXUS61 KCTP 230933 AFDCTP Area Forecast Discussion National Weather Service State College PA 533 AM EDT Fri Jun 23 2017 .SYNOPSIS... A deep southerly flow and tropical moisture will cover Pennsylvania today ahead of a deepening trough over the Plains states. Showers and isolated thunderstorms with locally heavy rain are expected across central Pennsylvania this afternoon into tonight. 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 /UNTIL 6 PM THIS EVENING/... Latest regional radar mosaic continues to show two concentrated areas of moderate to locally heavy shower activity at sunrise. The first is associated with the standard ring of fire and extends in an arc well north of PA from upstate NY and northern portions of the Eastern GLAKS SW to the Upper Midwest and will not impact the area in the near to short term. The second is associated with a 40-50kt LLJ riding northeastward through the central Appalachians early this morning, with the leading edge of steady showers having pushed into the Laurel Highlands and South Central Mountains overnight. This batch of rain is expected to lift northeast across the forecast area through 15Z, as anomalous 40+ kt southwesterly low level jet arrives. Western half of PA still expected to see the heaviest rain amounts from this feature...with 1+ inch amounts expected over the Laurel Highlands through midday. The batch of morning stratiform rain with embedded heavier convective elements 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 PW will support locally heavy rainfall from any showers/storms that form this afternoon and last into this evening, making some locations more prone to minor flooding as remnant tropical moisture from the prior TS Cindy track across the area throuigh tonight. Kept temps close to Superblend/NationalBlend...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. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... *Heavy rain and short-term flooding risk Friday-Friday night. Local heavy rain threat will last into tonight, but confidence not sufficient for a Watch at this time. Deep tropical moisture (PW locally 2"+) associated with the remnants of TS Cindy will combine with the approaching northern stream trough and cold front to bring a slightly elevated risk of locally heavy rainfall and potential flooding to portions of central PA. Factors arguing against a Watch at this time are fairly narrow window of heavy rainfall and general longer duration of 2"+ rainfall totals...occurring over a 12 hour plus timeframe. If one area has a greater risk of minor would be the Laurel Highlands where a multi- model blend incorporating HIRES models/CAMs remains fairly consistent with location of max QPF. Enhanced terrain lift will also be a factor over a region that has the lowest ambient short-term FFG in the CWA. HWO continues to highlight lower end +RA/FF risk at this time - later shifts should consider a FF watch at shorter ranges with increasing confidence. Heavy rain threat winds down late tonight as deepest subtropical moisture is shunted east of the region after midnight. Expect lingering moisture/rainfall associated with the moisture remnants of TS Cindy to exit the area by Saturday afternoon. && .LONG TERM /SATURDAY NIGHT 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. Drier, low PW air arrives behind the cold front later Saturday 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 /10Z FRIDAY THROUGH TUESDAY/... Only some isolated showers across the north remain across Central Pennsylvania as of 03z. While mainly VFR conditions exist, some isolated fog is beginning to develop in areas that say early rainfall. Short term guidance suggests that mainly rain free conditions will persist for several more hours, 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. Rain from the 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...DeVoir NEAR TERM...DeVoir SHORT TERM...DeVoir 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.