Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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388 FXUS61 KPBZ 130645 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 245 AM EDT Thu Jun 13 2024 .SYNOPSIS... Dry weather with above average temperatures for Thursday ahead of scattered thunderstorms on Friday with a passing cold front. 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 and mostly sunny with highs near 10 degrees above average. - Slight chance of a shower north of I-80 after midnight. ------------------------------------------------------------------- Light wind and a mostly clear sky will allow the surface to radiate effectively overnight with again some patchy river valley fog possibly in the pre-dawn hours. Hi res ensemble probability favors south of I-70 and not as widespread as Tuesday night. Any fog will quickly dissipate after sunrise. Surface high pressure will drift to the east today. An increasing gradient on its backside ahead of approaching low pressure will induce a southwesterly wind with warm advection and a mostly sunny sky pushing highs up to 10 degrees above average in the mid 80s. Upper level clouds increase tonight as a cold front approaches from the northwest. Ahead of it, a weak shortwave and surface trough may try to drag some showers/a rumble of thunder north of I-80 just after midnight, but latest hi res ensemble indicates a low probability precip chance. Nocturnal timing with a developed surface inversion should limit any wind threat, and MUCAPE is nothing to write home about with poor mid-level lapse rates, so overall this should be unimpactful. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... KEY MESSAGES: - Cold front will bring showers and thunderstorms on Friday with a Marginal Risk (1/5) for severe weather. - Dry weather and near normal temperatures for Saturday. ------------------------------------------------------------------- The aforementioned cold front will sag through during the day on Friday with showers and thunderstorms developing along it. Its likely arrival time to our northern counties in the morning hours should preclude the bulk of any severe concerns north of Pittsburgh. Even south of Pittsburgh, which will have more residence time ahead of the boundary for daytime heating to drive instability, there`s some uncertainty as to how much destabilization will be able to occur with cloud cover moving in by the morning hours. Shear will not be a hindering factor with probability for >30 knots of 0-6 km at 90%+. The severe threat will be highest south of Pittsburgh where the chance for both 1000 J/kg of CAPE and 30 knots of shear is around 50-60%. Primary threats will be damaging wind and hail, and we remain in a 1/5 risk for severe. With ensemble mean precipitable water values nearing 1.4-1.5", any shower or thunderstorm could bring a brief period of heavy rain with it as well. A renewed push of drier and cooler air will arrive in northwest flow behind the front and drop lows Friday night to a couple ticks below normal. Could see some areas of river valley fog develop. Heights rise into Saturday as upper ridging builds and surface high pressure establishes to the north. Temps won`t rebound much with the northerly component to the flow in the wake of the boundary and dew points will likely mix out some in the afternoon given the dry airmass in place providing a pretty comfortable day. Enjoy it... we won`t be saying that again for a while. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... KEY MESSAGES: - High confidence in a dangerous heat wave setting up early next week with moderate to major heat impacts possible. ------------------------------------------------------------------- Guidance has been consistent that a potentially-historic ridge will continue to strengthen across much of the central and eastern CONUS Sunday into at least early next week. WPC ensemble clusters are highly consistent through Tuesday, indicating high confidence in the temperature forecast. Near-record breaking heat will build in to start off next week. Sunday will bring minor to moderate heat risk across the area as surface high pressure establishes off to our east. Significant heat will be possible with this anomalously strong ridge, especially Monday and beyond, when major heat risk is likely. NBM probabilities for high temperatures reaching 95+ degrees continue to go up, and are now widespread 50-70% 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 to lower 70s, which would result in high enough humidity levels to support heat indices climbing to, and potentially exceeding, 100 degrees. If dew points do hold toward the lower end of that spectrum, we may be able to make a run at 100 degree air temperatures (last time at PIT was 7/15/95); NBM probabilities for that threshold are now up to 50% in spots. Only acting to exacerbate the prolonged heat effects will be a 60-80% chance of low temperatures greater than 70 degrees through the end of the week. Heat impacts will need to be closely monitored and headlines may need to be considered. Three out of four clusters maintain a 594dm ridge through June 21st with the one exception being a much lower probability solution than the others. CPC suggests that excessive heat may last through June 23rd, indicating the potential for a long- duration excessive heat threat. The last comparable, long- duration heat event was from July 1994. Impacts include heightened heat-related illnesses and potential power grid issues with increased demand. It is strongly encouraged to know where cooling shelters are located and stay hydrated. There may be little relief at night. Gather food, water and medication now. Make a list of friends and family to check on and help them prepare. Strongly consider rescheduling outdoor events. Prolonged exposure to excessive heat was the primary cause of weather-related fatalities in 2023. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... Slowly departing high pressure will keep general VFR conditions in place through the TAF period. The exception may be patchy river valley fog, though warmer overnight temperatures will limit coverage. The most likely terminals to experience vis restrictions will be FKL/DUJ. Light and variable winds overnight will becoming southwesterly at around 10 kts with daytime mixing. .Outlook... Restrictions in showers and thunderstorms return early Friday with another passing disturbance. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...MLB NEAR TERM...MLB SHORT TERM...MLB LONG TERM...MLB/Milcarek AVIATION...Rackley/22