Area Forecast Discussion
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813 FXUS61 KPBZ 190259 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 959 PM EST Thu Jan 18 2018 .SYNOPSIS... High pressure brings dry weather and a warming trend into Saturday. Light rain chances return later in the weekend, before a cold front brings more widespread rain by Monday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Clear skies should continue through the overnight as high pressure remains in control. Decoupling is already starting to occur, but wind speeds are failing to continue their downward trend. With deep snow pack in place, further decoupling could lead to rapid temperature falls, however some wind should keep temperatures largely in the teens overnight. Warm advection is still occurring off the deck, so that should keep the ridges warmer than they have been. Fries && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Mid-level flow becomes increasingly zonal during this period as troughing pulls east of New England, while an upper low tracks across the Deep South. This will allow temperatures to continue to moderate through Saturday, with highs reaching the 30s on Friday and the 40s on Saturday. These temperatures will allow for some snowmelt during the day, while subfreezing temperatures Friday night will help to slow runoff a bit. Clouds will begin to increase on Saturday as southwest flow brings a bit more moisture into the area. 500 mb heights may begin to creep upward Saturday night in response to a trough digging into the western Plains. Over our area, weak isentropic lift may work with sufficient moisture to allow for the development of light rain or drizzle Saturday night. QPF will remain a few hundredths of an inch at most at this point. Soundings indicate too much warm air for snow. However, depending on how quickly temperatures drop during the evening, some light freezing rain or drizzle may be possible near and north of I-80 as values may straddle freezing. This is a low probability event for now and an HWO mention is not planned. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Forcing remains weak on Sunday, and the threat of light rain or drizzle will continue into the night. The models continue to lift a strong, vertically stacked low center across the upper Midwest and Great Lakes Monday and Tuesday, although speed and timing differences remain. It still appears that the highest precipitation probabilities remain Monday and Monday night, and in the form of rain, given the continued above normal temperatures. QPF may not be excessive given the occluding system and the stretching out of the surface cold front, but rainfall amounts will still need to be monitored given the melting snowpack and river ice concerns. Seasonable temperatures return behind the front on Tuesday, with some lingering rain or snow showers. Dry weather is figured for Wednesday and Thursday with developing high pressure. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... VFR will prevail through the period. SW wind will continue through the night and become gusty again on Friday as warm advection continues. .OUTLOOK... Restriction potential returns over the weekend with approaching low pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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