Area Forecast Discussion
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000 FXUS61 KPBZ 190740 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 340 AM EDT Mon Mar 19 2018 .SYNOPSIS... Low pressure will bring a wintry precipitation mix to the Upper Ohio Region tonight, Tuesday, and Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... No major changes were needed for todays forecast as eroding high pressure will maintain dry weather under northwest, to westerly flow aloft. High temperature is thus expected to moderate just a couple degrees over the seasonal average with neutralized temperature advection under an increase in high cloudiness. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... A weather-plethora, winter-spring battle is setting up to engage over the Upper Ohio Region for the short term period. Problems include model discrepancy and run-inconsistency as well as incidents of apparent feedback with overblown omega in the developing warm advection regime. Obs. and model world do agree that a southern stream low will dig over the Lower Ohio shunting relative warmth and moisture across WV and MD tonight, and finally over PA early on Tuesday. The warm surface (after another 50+ degree day) will be an inhibiting factor for travel issues for most areas in the event of light snow, or should warm advection be sufficiently strong for light freezing rain. The focus for problems thus remains on the ridges where dynamic cooling via falling pressure and southeasterly upslope is likely to support a temporal combination of freezing rain and snow development. As the aforementioned warm advection into the mid levels should inhibit dendritic growth potential, have limited potential snow amounts to advisory levels. In addition, the warm surface and eventual mid March sun angle should limit ice accumulation, especially after daybreak Tuesday; have thus lowered the ice from QPF ratio for the tonight/early Tuesday time frame. The bottom line is that advisory level winter precip is anticipated for the ridges, with much lesser confidence for other areas. A Hazardous Weather Outlook mention was thus included as per collaboration with neighboring NWS offices. For at least a portion of Tue, shortwave ridging in advance of the digging Lower Ohio storm system should diminish PoPs, while temperature rises into the 40s amid warm advection ahead of low pressure encroaching upon the Lower Ohio. Thereafter, the Lower Ohio low-center is progged to trundle slowly across the Mid Atlantic region through Wednesday, with coastal surface development enhancing boundary layer cold advection over the immediate area. Periods of light snow and snow showers are thus envisioned as the Upper Ohio is enshrouded on the northern flank of the mid level low, with inhibitions provided by daytime sun angle and a lack of mid level frontogenesis in a weakening wind field. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The ECM, GFS and ensembles are in general agreement on the gradual filling of the Eastern CONUS trough during the late week period. A dry, but cool period is thus expected to close the work week as surface high pressure builds under the resulting northwest flow over the Upper Ohio. A damp/seasonable weekend seems likely with another trough passage in amplified flow. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... VFR conditions are expected through the TAF period as high pressure slides E, though clouds should increase today/tonight ahead of approaching low pressure. OUTLOOK... Restriction potential returns with low pressure late Mon night thru Wed. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.