Area Forecast Discussion
Issued by NWS State College, PA

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495 FXUS61 KCTP 111549 AFDCTP Area Forecast Discussion National Weather Service State College PA 1049 AM EST Tue Dec 11 2018 .SYNOPSIS... Seasonably cold temperatures will continue through midweek. A fresh coating of snow is likely tonight over the northwest snowbelt and Allegheny ridgetops. A more widespread light snow is likely Wednesday night into Thursday morning. Milder air will return to central PA for late in the week followed by rain to start the weekend. && .NEAR TERM /THROUGH TONIGHT/... Latest GOES-16 IR shows low stratus and stratocu clouds have eroded and drifted slightly northward late this morning as the mean llvl wind has freshened by a few-svrl kts and backed by about 20 degrees - more to the southwest with vertical mixing stretching to 1.5-2.0 kft agl helping to penetrating the cloud layer and entrain drier air aloft. Expect some continued improvement to the clearing this afternoon across all of the CWA except for the NW mtns where the Stratocu deck should be bkn-ovc and fairly persistent. It will be another seasonably cold day with max temps 5 to 10 degrees below average. Shortwave trough moving through the interior Northeast will bring a colder northwest flow aloft tonight. Hires models show lake and orographically enhanced snow showers bringing a fresh coating of snow to the northwest snowbelt and Allegheny/Laurel ridgetops by Wednesday morning. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Narrow ridge of high pressure briefly visits the area early Wednesday, bringing an end to any lingering snow showers or flurries by midday. Another seasonably cold and mainly dry period during the day Wednesday with max temps 30s still about 5 degrees below average. A compact/closed H5 low is projected to weaken as it tracks eastward from the Great Lakes/Ohio Valley into the northern Mid Atlantic Wednesday night into Thursday. A consensus of model QPFs suggest a shot of WAA light snow is probable especially over parts of the northwest Alleghenies/higher elevations and could result in a larger coverage of light snow accums (coating up to 1 inch). This may be just enough for some slippery travel Thursday morning. Confidence (and precip probs) have increased from the previous fcst but still not a slam dunk given weakening system and diffs in the [very light] model QPFs. Light snow may linger into Thursday afternoon before diminishing/shifting southeast Thursday night. && .LONG TERM /FRIDAY THROUGH MONDAY/... Storm system over the southern U.S. will spread milder air and rain into the area by the start of the weekend. Model trends indicate a slower arrival to rain with the most likely wettest period Friday night into early Saturday. There is the potential for heavy rain with a strong southerly LLJ and above normal PWs. Confidence remains low concerning rainfall amounts and flooding risk - something to monitor in the coming days. Also need to watch the thermal profiles at the onset for possible mixed pcpn although it looks like mostly a rain event at this point. There are some big model differences (GFS/EC) in how the system evolves heading into next week, which would have significant implications on the fcst. This appears to be due to phasing issues with the GFS merging the northern+southern stream energy. The 00Z is does not show this which results in a more suppressed system with low scooting off the NC coast and overall warmer solution in the wake of the system. Very low confidence at by the Sun-Mon timeframe given the wide model spread and growing uncertainty. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... Mixing of drier air aloft is expected to increase through this afternoon, causing breaking clouds/rising cigs, and eventually SKC-SCT020-030 conditions across the Central Mtns and Laurel Highlands, while VFR persists in the Susq Valley and SE PA. However, mvfr (to tempo IFR) cigs should hold tough through this afternoon and tonightacross the northwest mountains (KBFD). In the wake of a Cfropa early tonight, a gusty west to NW wind will develop across at least the Central, NW MTNS and Laurels. Prevailing wind speeds should average 10-15kts with gusts into the mid and upper 20s. Gusts of 30-32KT possible INVOF KJST and KAOO. .Outlook... Wed...Early AM low cigs possible W Mtns. Evening light snow possible western half of Pa. Thu...Low cigs possible, mainly central mountains. Fri...Rain/low cigs possible, especially late. Sat...Rain/low cigs possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Steinbugl NEAR TERM...Lambert SHORT TERM...Steinbugl LONG TERM...Steinbugl AVIATION...Lambert/Gartner

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