Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 222230 AFDCTP Area Forecast Discussion National Weather Service State College PA 630 PM EDT Thu Jun 22 2017 .SYNOPSIS... A warm front will move through the region today, bringing a return to warmer and much more humid conditions this afternoon right through Friday night. 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/... An area of showers and thunderstorms extends from east of BUF down into NERN Ohio. The HRRR takes this ESE across the area mainly north of I-80 through late afternoon before depicting it as becoming more scattered and disorganized. Dewpoints have surged into the mid and upper 60s rather quickly with the approach and passage of the diffuse warm front. We will stay in the soupy airmass for at least the next 36-48 hours before drier air returns to the region. SPC has much of the northern portion of the region under a Marginal Risk. Instability in the area of the Marginal Risk is limited at best as of mid day, but model guidance does show the development of at least moderate CAPE and shear over much of the western part of the state as the afternoon warms up, and with dewpoints climbing this looks reasonable. RAP depicts 0-1km EHIs between 1 and 1.5 m2/s2 across much of the NW part of my CWA into the evening, so the potential exists for stronger storms to rotate. SPC addressed the convection developing over the area and this tendency for rotation, but at this time a watch is not likely. The biggest threat over the next 36-48 hours will be for heavy flooding rains as we see an almost classic set up for a PRE event developing over the NERN US. Any localized heavy showers and thunderstorms today will lay the groundwork/lower FFG values and additional and potentially training convection that will occur Friday through Friday night as moisture from Tropical Storm Cindy surges into the NE US. Moisture will continue to increase ahead of the remnants of TS Cindy that are surging NE out of the Gulf States. PWATs are forecast to increase to between 1-4 sigma by daybreak Friday and continue into Saturday morning. By late tonight rain and embedded heavy thunderstorms should be overspreading my southern zones. Any decision on Flood Watches 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 /00Z FRIDAY THROUGH TUESDAY/... Outside of ongoing convection, VFR conditions persist over most of Central Pennsylvania. Short term guidance suggests that shower and thunderstorm activity will exit most areas by 01z, and shift mainly into the Lower Susquehanna region after this time. If model and radar trends continue, will introduce this into the 00z TAF issuance. There will be a better chance for more widespread IFR conditions to develop tonight and tomorrow as rain and embedded thunderstorms from the remnants of TS Cindy overspreads the region. .OUTLOOK... Sat-Sun...Mainly VFR. Mon-Tue...Mainly VFR. Chc SHRA/TSRA. && .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...La Corte SHORT TERM...Steinbugl LONG TERM...Steinbugl AVIATION...Jung/La Corte EQUIPMENT...

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