Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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798 FXUS61 KPBZ 120705 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 305 AM EDT Wed Jun 12 2024 .SYNOPSIS... Continued dry weather and a warming trend is expected through Thursday. Thunderstorms return on Friday. There is medium to high confidence in a heat wave next week that may bring moderate to major heat-related impacts. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - Dry conditions and warming temperatures expected under building high pressure. -------------------------------------------------------------- A fair amount of cirrus can be seen passing overhead on the latest satellite imagery. This may impede the formation of widespread fog this morning, though patches could still form under any breaks in the clouds around sunrise. Any fog that does form will dissipate quickly after sunrise with the onset of diurnal heating and mixing. Dry weather and a warming trend in temperatures are expected today and tonight as high pressure builds over the region. High temps this afternoon will be slightly above seasonal normals. Meanwhile, dry air and calm winds support effective radiative cooling tonight, which should still allow lows to dip down to or slightly below normal. Patchy valley fog cannot be ruled out as well tonight, particularly in and around river valleys. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... KEY MESSAGES: - Warmer temperatures expected, roughly 10 degrees above normal. - A passing shower and rumble of thunder are possible Thursday night mainly north and northwest of Pittsburgh. ------------------------------------------------------------------- High pressure shifts east of the area Thursday, allowing for light southwest winds and subsequent warm air advection to set up, resulting in daytime highs climbing to around ten degrees above seasonal normals. An approaching disturbance and cold front will result in increasing cloud cover and possibly a thunderstorm or two late Thursday night, primarily for areas north and west of Pittsburgh. Model soundings suggest elevated marginal instability and mid-level dry air will be present, supporting a low-probability (but non-zero) threat for hail and strong straight-line winds, though overnight convection should be elevated which would help temper the latter threat. && .LONG TERM /FRIDAY THROUGH TUESDAY/... KEY MESSAGES: - Thunderstorm chances return Friday along a passing cold front, primarily during the morning and afternoon hours. - Growing confidence in a potential heat wave setting up early next week with moderate to major heat impacts possible. ------------------------------------------------------------------- The better chance for showers and storms will occur along the cold front itself as it pushes through the area Friday morning and afternoon. The timing of the cold front will be important, as a faster/earlier passage will mean less available instability as it moves through during the morning before peak daytime heating. A slower/later arrival and passage would allow for greater instability to develop ahead of the front, potentially resulting in more intense thunderstorms in an environment that will also see roughly 30-40 knots of 0-6km bulk shear. At this time, the best chance for better instability (upwards of 1000 J/kg) will be in areas east and south of Pittsburgh. That said, any storms along the cold front will carry at least some low- end potential to become strong or severe. The primary threats would be hail and damaging straight-line winds. The passage of Friday`s cold front brings a brief "cool down" as highs Friday and Saturday remain around or just a few degrees above normal (down from the roughly 10 degrees above normal on Thursday). Dry weather returns Saturday through the weekend as high pressure begins to build back into the region. Long range guidance has been consistent that a ridge will continue to strengthen across much of the central and eastern CONUS Sunday into at least early next week. This will quickly bring hot temperatures back to the area through that time. There is a growing concern that significant heat will be possible with this anomalously strong high pressure ridge, especially as we get into Monday and Tuesday. NBM probabilities for high temperatures reaching 95+ degrees continue to go up, and are now widespread 40-60% across the area, with pockets as high as 80%. These higher probabilities are especially prevalent in lower elevation areas (e.g., river valleys) and urban centers, which tend to be warmer than surrounding areas. In addition, dewpoints are currently forecast to remain in the mid 60s, which would result in high enough humidity levels to support heat indices climbing as high as 100 degrees. If these trends in guidance continue, heat impacts will need to be closely monitored and headlines may need to be considered. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Valley and river fog has begun to develop tonight as calm wind and efficient radiating under a broken shield of cirrus allows for a cool airmass to settle over the relatively warmer waters. It should remain confined to the valleys given the dry airmass overhead with dew points in the 40s, but hi res ensemble probabilities reach near 50% for VIS impacts down to IFR to reach FKL/DUJ in the overnight hours. LBE may see periods of MVFR but confidence is lower there. Elsewhere, VFR will prevail with the SCT to BKN cirrus as upper moisture moves overhead. Fog will dissipate by 14z and give way to a VFR day with light westerly wind as high pressure establishes. .Outlook... VFR conditions are expected under building high pressure through Thursday. Restrictions in showers and thunderstorms return early Friday with another passing disturbance. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Cermak NEAR TERM...Cermak SHORT TERM...Cermak LONG TERM...Cermak AVIATION...MLB