Area Forecast Discussion
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000 FXUS61 KPBZ 201749 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 149 PM EDT Sat May 20 2017 .SYNOPSIS...
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Rain chances will increase Sunday with the approach of a cold front. Temperatures will be at or slightly below seasonal averages for most of next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Stratus deck continues to erode as deeper mixing takes place this afternoon. Thus, while temperatures were slow to warm outside of the nearly cloud free areas in the vicinity of MGW, better warming should take place through the afternoon as the upper ridge builds and warm advection increases. Current mesoanalysis has very little in the way of instability where a small line of showers has developed over east central Ohio. Only reason this area hasn`t fallen apart already would be the support from a weak shortwave aloft. Thus, do not expect much intensification as the showers move into a stable airmass. Will still maintain chance PoPs despite the lack of coverage progged by most of the hi res guidance, as approx 500j/kg will be present by early eve. Strong warming aloft should cap any storms however, so the concern for strong to severe storms is low. Building upper ridge will shift eastward as low pressure in the midwest lifts northeastward toward the great lakes. Sufficient warming aloft and increasing cloud cover will support warmer than average low temperatures. Have slowed increasing PoPs for the overnight until deeper moisture and lift approaches with the advancing cold front.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY/... Rain chances are expected to escalate into Sunday as Great Plains low pressure digs toward the Upper Mississippi Valley and shunts a cold front across the midwest and over the Upper Ohio. No major changes were needed to the current prognosis of categorical PoPs by Sunday, followed by rapid decline with frontal passage early on Monday. Given the positioning well north and west of the immediate area, expect progression and unsustained moisture convergence to offset the influx of moisture. Flood threat looks thus to be local and of poor drainage areas. Warm mid levels, and at best marginal deep layer shear, should limit severe threat along with the nighttime frontal approach. Thus, no hazardous weather mention is necessary at this time. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... Average-or-below temperature is forecast in the wake of the front as broad troughing, with the low center north of the Great Lakes, is projected to entrench for next week. Shortwaves through the base of that low will provide precip chances, and little deviation from the previous forecast was needed given the potential timing issues. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Stratus is lifting to a broken stratocu deck and expect cloud bases to raise through the afternoon as mixing strengthens. An isolated shower or storm could develop but probability is too low for inclusion in any TAF. Best shot appears at ZZV closer to the better instability. Diurnal cu will wane with sunset, however a canopy of broken mid and high clouds will invade from the west associated with upstream convection. This will offset any fog or stratus development overnight. As the cold front gets closer scattered showers are possible by daybreak in eastern Ohio, but a more concentrated area is predicted around early afternoon in ZZV than moving east through the mid and late afternoon hours over PA and WV. High confidence of a line of showers and storms developing and moving through. Confidence is a little lower in the precise timing at this juncture. MVFR conditions will accompany any shower or storm with the ones in the afternoon having a greater chance to drop visibilities to IFR for a short period. Winds from the east will slowly veer to the south by Sunday afternoon. Sustain speeds will be around 10 knots. .Outlook... MVFR and brief IFR restrictions are expected Sunday night with a passing cold front.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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