Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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742 FXUS61 KPBZ 210256 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1056 PM EDT Sat Jul 20 2024 .SYNOPSIS... Quiet, dry weather is expected for a large portion of the region under high pressure through Sunday. Precipitation chances increase Monday into Tuesday with an approaching trough from the west. && .NEAR TERM /THROUGH SUNDAY/... KEY MESSAGES: - Dry for much of the area under high pressure ________________________________________________________________ 11PM Update: No major changes to this forecast period. Adjusted temperatures, dew points, and cloud cover to reflect current observations. Previous Discussion: Expect dry weather with diminishing cloud cover for the rest of the region as it remains under the influence of western Great Lakes high pressure. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... KEY MESSAGES: - Seasonable temperature with increasing cloud cover expected through Monday - Thunderstorm chances increase Monday afternoon but favor locales south and east of Pittsburgh _________________________________________________________________ Shortwave ridging traversing the Atlantic high will support dry weather Sunday while moist southwest flow behind it will lead to increase cloud cover late in the day into Monday. Expect area high temperature to run about 5 degrees above the daily average. Ensemble models favor increased shower and thunderstorm chances starting Monday morning in association with a weak trough lifting from the eastern TN River Valley. Jet aided ascent and moisture convergence lends to the higher probability of occurrence along the Laurel Highlands and WV high terrain. However, trends are bearish for the rest of the region as probability of measurable rain is less than 50% (over a 24-hour period) and likely that high as a result of model resolution issues near the terrain feature. Combined with HREF mean CAPE values being near zero, expect limited afternoon storm coverage with many locations remaining dry. More abundant cloud cover due to the shortwave will limit insolation and keep area temperature near the daily average. && .LONG TERM /TUESDAY THROUGH SATURDAY/... KEY MESSAGES: - Periodic shower and thunderstorm chances increase through the week - Above average temperatures expected ________________________________________________________________ The sagging central CONUS trough is anticipated to slowly lift ENE through the Ohio River Valley Tuesday through Thursday while deepening as it phases with another lobe of energy dropping out of Canada. Ensembles favor periodic shower and thunderstorm chances while temperature hovers near the daily average. Severe weather appears unlikely as mean SBCAPE values hover around 500 J/kg (likely a result of residual warm air aloft and weak sfc heating). Tuesday may start out with shortwave ridging while awaiting another shortwave to lift out of the TN River Valley. If forcing remains delayed and farther W/S, then afternoon storm chances may be more isolated and favored natural convergence zones (Erie lake breeze, WV higher terrain). Similar sort of uncertainties may develop for Wednesday as well that lends to lower probability, more isolated convection than currently depicted by ensemble model means. Confidence in widespread convection is highest Thursday due to higher likelihood of surface cold front plus upper trough axis passage that day/evening. Depending on how quickly the upper trough axis exits and high pressure builds in will influence whether lingering showers/thunderstorms are possible Friday and the degree of temperature rise. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... VFR is largely expected through the TAF period with light to variable winds and streams of broken to overcast cirrus. .Outlook... VFR is expected through the Monday under the influence of high pressure, though probabilities increase for isolated to scattered afternoon storms Monday mainly along the WV higher terrain and Laurel Highlands. Scattered shower and thunderstorm chances are expected Tuesday through Thursday with the slow approach of an upper level trough from the west. Current probabilities favor afternoon to evening storm timing, with lower risks during the overnight to morning hours. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Hefferan NEAR TERM...Hefferan SHORT TERM...Frazier LONG TERM...Frazier AVIATION...22/Frazier/Milcarek