Area Forecast Discussion
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000 FXUS61 KPBZ 182301 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 601 PM EST Sun Feb 18 2018 .SYNOPSIS... A warm front will approach from the south late tonight, and rain will overspread the area Monday morning. Drier weather is expected for Monday night and Tuesday. Much warmer temperatures will take hold for the first half of the week. && .NEAR TERM /THROUGH MONDAY/...
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A gap in cloud cover is advection from the SW through most of the area this evening as thicker clouds depart NE and isentropic ascent lurks to the SW. This will yield a brief mostly clear period this evening before thicker clouds return. That said, increasing clouds and southerly flow should preclude much in the way of a diurnal temperatures downward trend, and temperatures may indeed start to rise as clouds further increase overnight. Models have continued to slow the approach of a zone of isentropic lift tonight, and therefore warm-frontal precipitation as well, keeping most of it after 09Z. Have continued with this trend in the grids, with no likely values for now.
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Light rain will overspread the entire region after sunrise on Monday as the warm front advances. Better upper support from low-level convergence and right entrance region jet dynamics will reside across the northern counties into early afternoon, and kept the higher categorical PoP values here. The advancing warm sector will allow rain to taper off from south to north staring during the mid-afternoon hours, with chance PoPs remaining across the far north by evening where the final resting position of the boundary remains in doubt. Up to three quarters of an inch of rain may be realized across the north by evening, with less to the south. Despite the saturated ground, this will not be enough to raise a new flooding threat. The remainder of the forecast remains mostly dry along the western edge of a ridge centered around a 500mb high off of the southeast U.S. coast. Have some minimal PoPs across the north and west from time to time as the boundary wavers from time to time, but the area should get a period of drying following the frontal rain. Another big story will be the warming temperatures, which will push much above normal values underneath the ridge. Of particular note is Tuesday, with 500mb heights poking above 580 dam for much of the area. Values above 70 degrees are likely for many, levels which have not been reached in over three months.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... There are still some timing differences regarding the timing of the next cold front, but a passage in the late Wednesday/early Thursday period still is expected. This will bring the next chance of rain as well as cooler temperatures, but above-normal warmth will remain. The end of the forecast remains problematic, as several shortwaves may track across the area from Friday into the weekend, bringing a potentially healthy rainfall. Given the still wet ground, this situation will need to be monitored over the next few days for a possible renewed threat of high water. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... MVFR stratocu will continue to dissipate under building high pressure with nearly clear skies overnight. Some wind shear is possible as a warm front lifts across the region early Monday, with restrictions in rain also likely. Will trend toward low MVFR cigs as the rain spreads northeastward, though did not want to go as pessimistic as the guidance suggested. Winds will remain light until late in the TAF period tomorrow, with a wind shift to the south expected. OUTLOOK... Occasional restrictions are possible through much of the week as several systems cross the Ohio Valley. && .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.