Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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000 FXUS61 KPBZ 251758 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 158 PM EDT Mon Mar 25 2024 .SYNOPSIS... Fire weather danger is expected today due to gusty conditions and low relative humidity, a Special Weather Statement was issued in collaboration with our partners. Downslope wind gusts this evening into tomorrow have prompted a Wind Advisory for areas east and southeast of Pittsburgh. Rain chances increase after 6am Tuesday, ahead of a cold front. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - A Special Weather Statement (SPS) was issued in collaboration with our Ohio and West Virginia partners for fire danger today. Low relative humidity and gusty conditions will result in an increased risk of fire start and spread. - A Wind Advisory has been issued for downslope potential late this evening and into Tuesday. ------------------------------------------------------------------- This 12Z PIT sounding suggests that very dry air at 1,000ft to 4,000ft will mix to the surface with diurnal heating and prompt a second day of very low relative humidity values. MinRH values will range from 20% to 25% for West Virginia and eastern Ohio; 30% to 35% for PA counties. Along with dry conditions, wind gusts between 15mph to 25mph will be observed throughout the day as a disturbance over the Plains strengthens and increases the gradient wind field. Therefore, fire weather danger will be a concern throughout the evening and it is advised to exercise caution if handling open flames or equipment that creates sparks. A Special Weather Statement was issued in collaboration with surrounding WFOs and the State Foresters in West Virginia and Ohio. Despite low relative humidity in Pennsylvania, the 10 hour fuel moisture was measured above the 10% threshold level of concern. Therefore, no Special Weather Statement was issued for western PA. A Wind Advisory was issued along the ridges of Pennsylvania and West Virginia after 7pm this evening due to downslope winds. Probabilities are high that localized wind gusts over 50mph from the southeast could create impacts: unsecured objects may blow away, tree limbs could be blown down, and power outages may increase early Tuesday morning. Otherwise, dry and above normal conditions are likely today with a building ridge over the Ohio River Valley. Temperatures will 10 to be 15 degrees above the climatological normal. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... KEY MESSAGES: - Strong wind gusts (+50mph) along the ridges of West Virginia and Pennsylvania is expected tonight into Tuesday afternoon due to downsloping; Wind Advisory continues into early Tuesday afternoon. - Rain chances return to the region Tuesday with an approaching disturbance. - Scattered light showers continue Wednesday with the slow crossing of a cold front. ------------------------------------------------------------------- Upper level ridge will remain parked over eastern PA tonight. This will slow the eastward movement of an upper level wave rotating northeastward on the eastern side of the massive central US trough. This should keep the area dry tonight. A tight surface pressure gradient, and crossing low-level jet, will increase the risk for strong wind gusts over the ridges tonight. Hi-Res guidance probabilities are considered high (above 80%) over the ridges for 50mph wind gusts from the southeast through 1pm Tuesday due to downsloping. The Wind Advisory continues for the Laurel Highlands and West Virginia ridges. Still seeing some timing issues with the onset of rain on Tuesday and how far east it will push before either stalling or dissipating. The amplified ridge over the east coast will begrudgingly move eastward on Tuesday. The shift will be in response to a shortwave trough that will eject eastward from the central US trough. Much of the energy from the shortwave may be spent fighting the ridge. Models are showing a descent moisture plume passing through the region on Tuesday, which will aid in bring widespread rain to the area. It does appear that as the rain moves eastward, it will decrease in coverage and intensity. Probabilities for >0.25 inches for the eastern half of the forecast area are 40% to 60% while over the western half are 60% to 70%. Looking at probs >0.50 seeing around 15% to 45%, with the higher numbers over Ohio. Rainfall will be generally light with the higher QPF mainly over Ohio. With rain and increased cloud cover, highs on Tuesday will drop a few degrees, but still remain above normal. With the slow eastward movement of a cold front, due to the stubborn east coast ridge, the risk for scattered showers will continue on Wednesday. However, a large upper level dry slot will spread across the region ahead of the front, greatly limiting rainfall amounts. Its not out of the question that much of the rain directly along the front will dissipate Wednesday afternoon. Temperatures remain above normal on Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... KEY MESSAGES: - Dry conditions are favored Thursday and Friday. - Unsettled weather returns for the weekend. ---------------------------------------------------------------- Dry conditions are more likely with the reestablishment of high pressure Thursday and Friday. Although an isolated shower cant be completely ruled out over the ridges on Thursday. Eastern CONUS ridge will try to amplify over the weekend. However, it appears as if we will be located right at the top of the ridge. Shortwaves, riding over the ridge, will keep in the risk for scattered showers both Saturday and Sunday. Above normal temperatures will remain through the weekend. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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VFR conditions will prevail through early Tuesday afternoon. Scattered to broken upper level clouds will continue to slide across the area ahead of approaching low pressure still centered well off to our west. A tightening pressure gradient has resulted in southeasterly wind gusting to 15-25 knots this afternoon. Later tonight, as a 40-50 knot low level jet moves overhead after 00z, all sites aside from LBE will likely have decoupled and a strong inversion will prevent gusts from mixing down resulting in just a 10-12 knot gradient wind. However, downsloping with southeasterly flow will increase gusts overnight at LBE as probabilities increase to ~70% for >40 knots, primarily between 02z-06z; this will preclude a low level wind shear threat at LBE. However, with limited gusts at the surface at other sites and the strong low level jet overhead, low level wind shear will develop after 06z and continue overnight until the boundary layer begins to mix in the morning, increasing surface gusts to 15-20 knots and ending the wind shear threat. Rain will arrive from the west beginning late Tuesday morning, but will be battling a lot of surface dry air at onset. Hi res ensemble probabilities indicate most likely precipitation onset around 11z for ZZV, 16z for FKL to PIT to MGW, and after 18z for LBE/DUJ, which may even be a bit aggressive given the extent of the dry air in place. Probabilities look to remain <50% for ceiling restrictions in rain, but MVFR visibility restrictions are possible (~50% chance) toward the end of the TAF period. .Outlook... Restrictions may linger into early Wednesday with lingering boundary layer moisture before the passage of a cold front in the morning, but VFR then returns with high confidence for Thursday and Friday under high pressure.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... PA...Wind Advisory from 7 PM this evening to 1 PM EDT Tuesday for PAZ073>078. OH...None. WV...Wind Advisory from 7 PM this evening to 1 PM EDT Tuesday for WVZ510>514. && $$ SYNOPSIS...Hefferan NEAR TERM...Hefferan SHORT TERM...22 LONG TERM...Hefferan/22 AVIATION...MLB

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