Area Forecast Discussion
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000 FXUS61 KPBZ 222341 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 641 PM EST Thu Feb 22 2018 .SYNOPSIS... Periodic rain chances will continue through Sunday. Conditions should be dry for the beginning of the work week. && .NEAR TERM /THROUGH FRIDAY/... Deeper moisture is exiting the southeastern portions of the area at the moment, but easterly flow is well entrenched over the area, and cold air is oozing down through central Pennsylvania toward the Mason-Dixon line in the higher terrain fairly efficiently. However, above the boundary layer, flow quickly turns southwesterly with warm advection. As this occurs, surface temperatures will continue to fall on the eastern periphery of the forecast area. This will not really be problematic anywhere in the area except for one lone exception...Garrett County, Maryland. In Garrett County, NAM/NAM 4 km nest projections seem to be handling the boundary layer and the layers below 925 mb far better than other guidance. In fact, they are the only pieces of guidance that both show some semblance of an idea with regard to surface temperatures and follow what is the observed temperature persistence pattern based upon boundary layer flow. That said, temperature fall down toward and essentially straddle freezing from later this evening through Friday morning in the interior, eastern, and northern portions of the county. Model soundings suggest +10C above that level, so the cold air will be exceedingly shallow. Thus, any precipitation that falls will be either rain or freezing rain. With that in mind, a winter weather advisory has been issued for this interval for Garrett County alone. All other mountain zones should remain above freezing. In fact, based upon the thermal profile, the majority of Tucker County should remain within striking distance of 50F most of the night. This is due to the fact that low level ESE flow that turns SE does not favor cold air sneaking into that area. Fries Previous discussion follow for Friday...The focus of rainfall on Friday will be along a warm front moving into the region from the west. Many locations could pick up at least an inch of rainfall during the daytime hours, which was enough to cause flooding issues today. The additional waves of rainfall expected Friday and Saturday are the primary reason that earlier today the flood watch was extended to all locations through the end of the weekend. Southerly winds will allow for very mild temperatures tomorrow, with highs reaching the 50s and 60s, with an isolated 70 degree reading not out of the question. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... The second 24 hour period of the forecast should be very similar to the first 24 hour period of the forecast, with a break in precipitation Friday night and reintensification on Saturday. However, Saturday night will remain wet as the region will be in a transition area from warm front impacts to cold front impacts. The cold front will push through on Sunday, bringing some definitive clearing to the region. Highs will reach the 50s and 60s again before the cold front arrives. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The work week should start out dry before a large system moves from the Plains towards the East Coast Wednesday into Thursday. Temperatures will be slightly above normal. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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MVFR/local IFR stratus is expected to continue tonight with low level moisture below a temperature inversion. Widespread IFR and rain is expected again late tonight and Friday as another area of low pressure crosses and lifts a warm front, then a cold front, across the area. With the crossing sfc boundaries, winds should veer through the period. OUTLOOK... Restrictions are expected to continue with a Saturday warm front, and a Sunday cold front.
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&& .HYDROLOGY... Numerous forecast points are already at action stages across the region. Pittsburgh is already over 21 feet. 3 successive disturbances over the next 72 hours will drop rainfall amounts ranging from 1.50 to 4.50 inches across the region. River Flood watches will likely be expanded across the region. With QPF, we expect river flooding to be widespread by 00Z/25 February. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...Flood Watch through Sunday evening for MDZ001. Winter Weather Advisory until 10 AM EST Friday for MDZ001. OH...Flood Watch through Sunday evening for OHZ039>041-048>050- 057>059-068-069. PA...Flood Watch through Sunday evening for PAZ007>009-013>016- 020>023-029-031-073>076. WV...Flood Watch through Sunday evening for WVZ001>004-012-021- 509>514. && $$

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