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Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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473 FXUS61 KPBZ 251911 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 311 PM EDT Tue Jun 25 2024 .SYNOPSIS... Remnants of a mesoscale convective system may impact the region after 1pm today. Heavy rain showers and sub-severe wind gusts may occur. The threat for strong storms increases Wednesday with a new disturbance. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - Remnant showers from a mesoscale convective system is currently tracking through the region in eastern Ohio. ------------------------------------------------------------------- A mesoscale convection system (MCS) continues to dive south, within an elongated ridge. Precipitation chances have remained west of Pittsburgh due weak instability. There was a brief period of thunder near Coshocton/Muskingum County earlier, along the edge of the MCS. However the threat has subsided and rain showers remain. With increasing cloud coverage from outflow of the MCS and precipitation chances, temperatures north of I-70 will likely trend near average. Areas south may trend 5 degrees above average. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... KEY MESSAGES: - Showers and thunderstorms are likely Wednesday with a new disturbance. - All threats (flooding, tornadoes, hail, and wind) appear promising early afternoon through late evening. - Storm Prediction Center continues to have a Slight Risk for portions of our region, Weather Prediction Center continues the Marginal risk for flooding. ------------------------------------------------------------------- An ejecting shortwave out of the Midwest will regenerate showers and storms Wednesday across the Ohio River Valley. A few storms may be considered strong to severe if conditions permit, damaging wind gust and hail will be the main threat. However, the tornado threat is considered slightly above the climatological average given directional and vertical wind shear. Based on Hi-Res model ensembles, the joint probabilities of bulk wind shear (>= 30kts) and instability (CAPE >= 500J/kg) are elevated between the period of 1pm to 8pm Wednesday. However, storms could evolve as early as 10am under a warm, moist unstable air mass. The severe threat will likely evolve into a flooding threat as the day progresses, especially late evening with ongoing convection. With PWATS well above the climatological average (1.65" to 1.90") and training showers and storms under zonal flow, swaths of 1 to 2 inches may occur across the region Wednesday night. If these noted high amounts occur over urban areas in a short time period, flash flood products will need to be issued. The severe weather and flash flood threat will likely decrease after midnight as the shortwave tracks east. && .LONG TERM /THURSDAY THROUGH MONDAY/... KEY MESSAGES: - Dry, quiet weather is expected Thursday. - Probability of above average temperatures increase Friday into Saturday. - Shower and thunderstorm chances return Saturday into Sunday with a new disturbance. ------------------------------------------------------------------- In the wake of Wednesday`s shortwave and associated front, temperatures return to normal and dry conditions resume as high pressure builds in across the region. A warming trend in temperatures is forecasted Friday and into the weekend as heights gradually rise, reaching about 588-590dm by Saturday. If showers and storms are absent for a prolonged period of time, apparent temperatures could range from 95F to 100F. However, confidence is still low on heat impacts given long range ensembles tracking a new trough over the Great Lakes and could stir strong to severe storms. Dry conditions and near to slightly above normal temperatures are forecast early next week as high pressure resumes control. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... An MCS will continue to weaken/move SSW of the region this afternoon, with low probability for thunderstorm and moderate rain shower impact at ZZV. Convective cirrus and VFR condition is favored the rest of the afternoon and evening period as subsidence maintains a stable environment. An upper level shortwave will approach the area late tonight into Wednesday with an associated surface cold front. Confidence is high that this wave will help foster increased shower and thunderstorm coverage between 15z-00z Wednesday. Confidence is significantly lower on timing and progression of convection starting as early as 09z. Available convective modeling shows a large range of storm evolutions through this period as they struggle to handle the altered environment the current Ohio MCS is causing. TAF leans a bit into HRRR and HRW ARW modeling given better handling on current weather; but variability in outcomes for both storms and area restrictions is high. .Outlook... Showers and thunderstorms will taper off (with longer delay in restriction improvements) with cold FROPA Wednesday evening. High pressure and rising heights aloft is favored to support VFR and dry weather Thursday/Friday. The next upper level shortwave and surface cold front will increase thunderstorm and restriction chances Saturday. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Hefferan NEAR TERM...Hefferan SHORT TERM...Hefferan LONG TERM...Hefferan AVIATION...Frazier