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County Warning Area [CWA]: PBZ
Regional NWS Weather Office: Pittsburgh, PA
County Warning Area [CWA]: PBZ
Regional NWS Weather Office: Pittsburgh, PA
000 FXUS61 KPBZ 261744 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 144 PM EDT Tue May 26 2020 .SYNOPSIS... A strong area of high pressure will maintain dry weather for the area through Thursday with well-above average temperature. Rain chances come back Thursday morning and again on Friday with a series of low pressure systems. Cooler and drier weather will then return for this weekend. && .NEAR TERM /THROUGH TONIGHT/... GOES satellite imagery and forecaster observation shows a virtually cloudless sky across the NWS Pittsburgh Forecast Area as of 120PM-- which is quite a rare feat for one of the cloudiest areas in the country. A rather amplified ridge remains in place across the eastern CONUS with the axis of this 590dam ridge just to our east. Subsidence and very warm mid-level air has essentially suppressed any convective clouds thus far today. With plenty of heating and just enough boundary layer moisture, a CU field may still develop over the next few hours... but updrafts will have difficulty sustaining/growing. A stray shower cannot be completely ruled out, but the coverage/probability is quite low. As far temperature, temperatures well into the 80s this afternoon (70s for the mountains and around 90 for the city) will fall back into the 60s at night.. but may plateau towards dawn as high clouds spread across the Upper Ohio Valley. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Similarly warm and humid conditions will continue through mid-week as the amplified synoptic pattern remains in place with the Upper Ohio Valley (~the Pittsburgh forecast area) located in southerly flow between an anomalously strong ridge off the east coast and a stacked upper/mid-level low across the Mid-South. For Wednesday, an upper-level trough originating from the southeast will rotate around the aforementioned low and move into the Ohio Valley. While the sensible surface response and precipitation features will be focused towards Indiana, models are signaling an associated upper-level cloud deck crossing the region in the morning hours that will then deepen through the day with the approach of another, more substantial, shortwave trough and associated surface low moving northward through the Appalachians. The temp diurnal range for Wednesday will hinge on the depth of this upper-level cloud layer and the amount of insolation that is let through. Still, expect a warm and humid day given the underlying summer-like airmass. If the upper-level cloud deck is indeed as deep as some model guidance is hinting at, am not expecting much in the way of convective lower clouds or showers... especially with a very dry 600- 800mb layer and poor lapse rates outside of the boundary layer. By Wednesday night, the second shortwave trough and sfc low mentioned above will continue its northward track into the Upper Ohio Valley. Light stratiform precipitation (perhaps initially broken as the mid-level dry air saturates) will overspread our southern counties after midnight and slowly lift northward through the morning along the convergent axis on which it`s centered. Adjusted POPs forward in time from the previous forecast based on the latest model timing. It would appear now as if the latter half of Thursday should be mostly dry in wake of this trough. However, scattered, diurnally-driven showers or even a tstorm Thursday afternoon may develop despite lack of upper forcing or strong buoyancy in the mid-levels. Coverage will ultimately depend on how fast that trough and associated cloud cover move out. The quicker the sun returns, the more instability and shower/tstorm coverage we can achieve. Conversely, if cloud cover lingers around longer... the latter half of Thursday may remain dry with slightly cooler temperature. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Pattern flip alert. By Friday morning, northern stream troughing will dig into the Great Lakes region and help kick the meandering aforementioned mid-south low eastward into the Atlantic. An attendant cold front will stretch from the surface low in the Ontario/Quebec region southwest into the Ohio Valley. While some precipitation may occur before the frontal rainband given the warm, moist air, the bulk of the precipitation on Friday will occur late afternoon and into the evening hours near/along the frontal zone itself as it moves across the forecast area. The strongest areas of synoptic lift will be displaced closer to the vort maxima of the northern and southern stream troughs, with Pittsburgh in between these. As a result, this front doesn`t look to be a big rain-maker at this time. A marginally unstable environment may be just conducive enough for a couple embedded thunderstorms and heavier rain rates-- but nothing appears rather eye-catching at this time. Precipitation should be clear of the forecast area by daybreak Saturday as comparatively cooler, drier air filters in behind the front. Each day from Saturday through Tuesday appear to be either near or below-average as far as temperature-- or about 15(or more!) degrees cooler than what we`ve experience this week. No major precipitating-features seem to be present in the pattern, though cannot rule out some light showers in this stretch as any pronounced shortwave troughing rounding the base of the longwave trough could produce something light. Confidence in this extended period is greater than usual given run- to-run consistency and agreement in the models. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Expect VFR conditions to remain in place across the area through the TAF period as high pressure will remain the dominant weather feature. Expect a few TAF locations to see some southerly wind gusts up to 15 knots with the max heating of the day until they subside by or just after 00Z. Overnight, expect some mid and upper level cloud cover to begin to enter the area. This will keep fog development at a minimum, even over the rivers. .Outlook... Outside of some early morning fog each day, no widespread restrictions are expected until Wednesday night and the rest of the work week. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$
| Forecast Discussion from: NOAA-NWS | Script developed by: El Dorado Weather |
