Area Forecast Discussion
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000 FXUS61 KPBZ 220154 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 854 PM EST Sat Jan 21 2017 .SYNOPSIS... Mild weather will continue through the weekend. Rain will move back over the area on Sunday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Mid clouds continue to increase over the area as a short wave traverses nearly overhead at this hour. Radar returns continue to increase with some indication of convective activity in higher reflectivity returns around portions of the area. In these areas, showers aloft will be likely to overcome the relatively deep layer of dry air below the mid-cloud deck and result in a few isolated showers. Regardless, the wave will be pushing northeastward rather quickly, and the window for showers will be fairly brief. Behind this early evening wave, satellite imagery indicates a brief period of partial clearing is translating northeastward. Hi-res guidance has some handle on this with sky cover backing off centered around 03z-06z. Skies were backed down a bit for all locations for a period of 2-4 hours from SW to NE as this area of clearing moves through. With still high surface dewpoints, this may yield a short period of radiational cooling and thus some patchy fog development as it does so likewise. Behind the clearing, mid and high overcast looks to return, however decent lift really does not enter the picture from the south again until well into the daytime on Sunday, so the remainder of the overnight will be dry. Fries && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/... Model depictions of the cutoff low pressure set to dig toward the Upper Ohio Region have deviated from previous days solutions with a more westward track of the center. Increasing ascent via deformed flow and warm advection with increased moisture through the mid levels all support escalating precip probabilities to categorical numbers for the period. With the northern branch of split flow holding colder air north and west of the region, and with warm advection into the mid levels of the cutoff, this looks to remain a rain event although the latest NAM has developed sub-zero air over the region at the 850mb level despite moist advection and an otherwise warm column. QPF was progged using a RFC/WPC blend for the period. An inch to inch and a half is anticipated for the early week with limitations imposed by low pressure progression and mid level dry slotting. Relative warmth will continue, although the diurnal temperature spread will be restricted by clouds and precip. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... The trend of the a slow low-pressure-exit on Tuesday continued in todays deterministic and ensemble depictions. Colder air wrapping into the western flank of the departing low may thus turn rain to snow, before ridging ensues in response to plains low pressure. That system is forecast to interrupt the resulting temperature moderation via a cold front across the Upper Ohio, which will drive temperature back to seasonal readings for the latter half of the week. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... VFR conditions are expected most of tonight as a crossing shortwave maintains mid level clouds across the area, along with a few light evening showers. Local late night/early morning MVFR fog is possible in some locations as the temperatures falls near the dew point, though cloud cover should preclude widespread coverage. VFR is expected Sunday until the approach of another shortwave later in the day results in a deterioration to MVFR conditions in rain. .OUTLOOK... Restrictions are likely through Tuesday with slow moving low pressure, and again with a Thursday cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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