Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 300551 AFDCTP Area Forecast Discussion National Weather Service State College PA 151 AM EDT Thu Mar 30 2017 .SYNOPSIS... High pressure will provide dry weather tonight and early Thursday. A storm system will approach the region from the Ohio Valley on Thursday, bringing showery conditions Thursday night through Saturday. A warm up is then in store over the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Adjusted sky grids for current sateliite trends. Stratocu streets in NE PA is diminishing with the sun setting. Otherwise just a few cirrus patches moving across. High clouds are expected to increase overnight from the west. Lower Susq should remain mostly clear tonight with clouds getting in there Thursday morning. NW mountains may see some lower clouds toward sunrise and an isolated light shower is possible. Temperatures this evening are nicely hanging in there in the 50s and upper 40s. Made adjustments to the hourly grids. Speed of clouds rolling in will effect the morning mins. Wind should die down tonight. High clouds will slowly increase tonight. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... Clouds lower and thicken through the morning. While a few sprinkles are possible in the morning in the west, it is dry under the clouds. Evaporational/dynamic cooling of the airmass *may* help 925-850 mb temps dip to near 0C right as the precip starts across the area Thursday afternoon/evening and Friday. The QPF is really minimal during that brief time, so I will not mention it in the wx grids for now. However, I do expect a pellet or two of sleet or a flake of snow at the beginning of the warm advective precip. Temps will be well above freezing during that time, and column temp profile then rise to entirely above freezing. At the worst a very thin coating of frozen stuff may occur on the grass in the far NE miles of the CWA. Ground/road temps very warm, now. Not expecting any problems. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Model consensus is also for a quasi Miller-B type of low track heading just north of the Ohio River during the day Friday, then a pressure jump and slight intensification of the sfc low (to 996 mb) off the southern NJ and New England Coast Saturday. Under normally colder winter-time circumstances, this low track would be pretty favorable for a significant snowfall across much of central and northern PA. However, a quite warm boundary layer (and 850 mb temps) to begin with, coupled with the lack of a stronger anchoring high over southeast Canada and New England will mean a widespread/soaking rain evening with 24-36 hour rainfall at the majority of places here in Central PA coming in between 0.75-1.00 inch. This rainfall will add a healthy spike to the flow and levels on smaller streams and creeks across the region with broader mdt rises on rivers, but no significant threat for flooding as headwater flash flood guidance is averaging 2-2.5 inches for a 12 and 24 hour period respectively. Periods of light rain, drizzle, and ridge shrouding dense fog will persist Friday night into Saturday as slightly colder air wraps around behind the storm. Some breaks in the cloud cover should occur Saturday afternoon, esp across the Lower Susq Valley where drying downslope flow will be enhanced. Forecast temps Friday may be a bit warm considering the aforementioned storm track just to our south, and amount of rain expected. Max temps Saturday will near to a few deg F above normal in many locations. High pressure building over the region (coupled with the offsetting effect of abundant sunshine and GEFS mean 850 mb temps cooling by 3-4 deg C imply max temps close to what we`ll see Saturday, which is upper 40s to lower 50s across the nrn mtns...and mid to upper 50s elsewhere. Dry and slightly milder conditions are in the forecast for Monday as the ridge of high pressure slides just to our east and ens mean 850 mb temps rebound by a few to svrl deg C (atop a light serly sfc flow). The next, rather potent and moisture laden southern stream wave heads our way for Mon night and Tuesday, bringing a likelihood of a widespread rain. Next Wednesday looks dry in the wake of the early weak system with temps rising above normal. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... 06Z TAFS sent. Some mid level clouds moving toward the northwest as of 2 AM. Earlier discussion below. VFR conditions will continue overnight and most of today, with increasing high-to-mid level clouds/cigs. In the far west, showers become likely KBFD / possible (JST) by noon, and the cigs do lower rapidly during the day in much of the rest of the area. Expect one wave of warm advection rainfall in the afternoon and evening rolling through from SW-NE - and impacting mainly the NW half of CWA. There may even be a few sleet pellets or snow flakes mix in right at the very beginning of the precip in the north. Temps will be much too warm to have this make any kind of trouble on the ground. Wind will be light/variable overnight, and increase over the west later in the morning as the high pressure overhead currently slides to the E/NE and S/SW flow increases. Conditions go downhill Thursday evening and sub-VFR conditions in rain showers and lowered cigs then persist into Friday night. Outlook... Sat: Sub-VFR restrictions early; then gradually improving conditions into Sat night. Sun-Mon: VFR/No sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Watson/Dangelo SHORT TERM...Dangelo LONG TERM...Lambert/Gartner AVIATION...Martin/RXR is the U.S. government's official web portal to all federal, state and local government web resources and services.