Area Forecast Discussion
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000 FXUS61 KPBZ 161349 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 949 AM EDT Wed May 16 2018 .SYNOPSIS... Warm weather with periodic showers and a few thunderstorms will continue through the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Upper/mid lvl flow magnitude is considerably weaker today as the area is increasingly under the influence of a weak southern-stream shortwave trough and emerging tropical trough. A quick check of the sounding reveals the weakening wind field and a warm, moist column which will result in limited instability, but potential warm rain processes for the next couple of days. For today, a weak shortwave in the wsw flow aloft is expected to support disorganized convective activity as it interacts with the warming airmass and more favorable surface moisture pooled in a weak inverted surface trough, which is actually funneling drier boundary layer air over the northwestern half of the forecast area. The morning sounding reveals a sharp temperature inversion ~H5 which poses a cap on the abundant low-level instability identified by the continued presence of steep lapse rates. As the wave approaches, and upward motion weakens this inversion, strong low-level instability and a very-moist profile may support thunderstorms capable of downbursts. Although an organized severe weather event is not expected, any potent updrafts will need to be monitored today. Seasonable warmth continues.
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Model world is evolving different this morning with the phasing of the subtropical and tropical troughs mentioned above - now progging a mid level cutoff low over the Lower Ohio Valley by Thursday night, with little movement until it is caught up in another shortwave this weekend. Of primary concern is the Thursday night/early Friday scenario of a moist low level (~850mb) conveyer developing off the Atlantic in conjunction with a converging tropical tap. The resulting precipital water with potential warm rain process could spell flood trouble for areas along and south of I 70 - primarily the ridges/Cheat and Mon. basins given expectations of terrain enhancement, which actually may be limited by a capped boundary layer. Either way, confidence is not sufficient to start ringing alarms, so a HWO mention for flooding was confined to upslope areas and those which have received, and are expected to receive the better rain totals today and early Thursday.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Little change to the overall pattern is expected into next week. The front will move little through Monday, until another cold front comes from the northwest and definitively sweeps through. This should finally bring an end to precipitation by Monday night. After a warmup over the weekend, temperatures will fall back closer to average early next week. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... Restriction potential, primarily MVFR, will increase through the morning as an approaching shortwave spawns sct, to nmrs shwrs. Otherwise, lower cigs are expected to be focused south and east of PIT with llvl mstr pooled nr a weak inverted trough. Those restrictions will ease by eve as the disturbances passes, but restrictions in the form of fog and MVFR cigs are expected to reemerge as the night progresses. OUTLOOK... Periodic restrictions are likely for much of this week as a the area remains under the influence of moist upper troughing. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ Update...Kramar is the U.S. government's official web portal to all federal, state and local government web resources and services.