Area Forecast Discussion
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000 FXUS61 KPBZ 181712 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 112 PM EDT Thu May 18 2017 .SYNOPSIS... Warm weather will continue today, but an approaching front will increase rain chances as the day progresses. && .NEAR TERM /THROUGH TONIGHT/...
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Quick update to handle weakening storms lifting across Ohio. Have added some slightly higher PoPs to portions of southeast Ohio. Expect continued weakening of this activity as it moved into a capped air mass, although outflow from it could help spark some increased activity over the next few hours. Made some tweaks to high temperatures as well, mainly upward in several locations. Rest of forecast on track. Previous discussion... Warm mid level temperature will continue to suppress convection for much of the day despite the eroding ridge; however, progs of increased lift along a southward sagging prefrontal trough still look sufficient to pop some thunderstorms in the warm, moist airmass over the region. Have maintained chance/scattered precip probability which will increase from the northwest as the day progresses. Limitations look to be imposed by the northward track of the low which will result in a poorly supportive mid level forcing for ascent field. Nevertheless, any storms that do develop may become severe, especially in vicinity of the I 80 corridor where deep layer shear and a slowly cooling mid level will reside.
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&& .SHORT TERM /FRIDAY THROUGH SUNDAY/... Fading instability and mid level support is expected to result in a rapid decrease in convection this evening despite passage of the actual cold front, which the deterministic models insist on sending south of the I 68 corridor. Have thus diminished precip probability considerably for the tonight period using the NAM as a general template. For Friday, cooler, albeit still above average temperature is anticipated in the wake of the front with a lack of sustained cold advection under zonal flow. Have maintained chance POPs over southern zones for Friday as any shortwave, or timing deviance could pull the front/convection focus toward the I 70 corridor. Upper ridging is projected to rebuild over the Upper Ohio/Great Lakes Regions by Saturday in response to deep troughing over the Plains. Warmth and moisture will thus quickly return and precip probability will escalate as that trough/associated front system dig eastward this weekend. Cold frontal passage is currently slated for an early Monday passage. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Seasonably cool temperature is anticipated in the wake of the aforementioned front as model-world forecast development of a persistent Hudson Bay to Ohio Valley/Southeast U.S. trough for next week. Low convective thresholds and shortwaves through flow will drive precip chances. Lack of confidence in timing and trough depth dictate that chance POP numbers are prudent at this forecast-stage. && .AVIATION /17Z THURSDAY THROUGH MONDAY/...
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VFR is expected with gusty winds diminishing by early evening. Isolated storms will be possible east of a line running roughly from ZZV to FKL...but chances are not high enough for inclusion in the TAF. .Outlook... Restrictions are possible again late Sat thru Mon with another front.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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