Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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000 FXUS61 KPBZ 282132 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 532 PM EDT Thu Mar 28 2024 .SYNOPSIS... High pressure building over the Upper Ohio River Valley will bring seasonable temperatures and mainly dry weather through Friday. A series of low pressure systems are expected to bring several rounds of showers and thunderstorms Saturday through Wednesday; hazardous weather may develop. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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KEY MESSAGES: - Cooler conditions are expected today in the wake a cold front. - Dry weather and clearing skies with building high pressure. ---------------------------------------------------------------- Made some minor updates to sky cover into the evening hours, but otherwise no changes were made as the forecast remains on track at 530 PM. Previous discussion... A series of vigorous shortwaves will traverse the western edge of the upper trough as the axis crosses the region this evening and overnight. The second of these waves may spawn a few light showers or sprinkles late tonight into Friday morning. Any precipitation that does fall will remain generally south of Pittsburgh and focused along the ridges with upslope flow. Given thermal profiles and limited moisture mostly below the DGZ, precipitation should mainly fall as light rain, through a few flakes and flurries are possible in the higher terrain. Accumulation (rain or snow) will be minimal and end Friday morning.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... KEY MESSAGES: - Dry Friday save for the WV ridges with early wintry mix possible. - Wind Advisory in effect for eastern Tucker County Friday. - Widespread rain showers return Saturday. ------------------------------------------------------------------- Shortwave troughing exits Friday morning as heights rise, albeit briefly, and dry weather returns to close the week save for the West Virginia ridges where upslope flow acting on a moist, conditionally unstable boundary layer will likely support low clouds and some light precipitation into the late morning. Ensemble probabilities lean toward snow as the primarily precip type for the morning hours, though wouldn`t entirely rule out a brief mix with some rain or freezing rain depending on surface temperatures as forecast soundings show the depth of the moisture cutting off below -10C. Spread in ensemble temperature is small, but hovering right around the freezing mark. Any impacts would most likely be confined to elevated surfaces, bridges/overpasses given warm antecedent conditions. Most likely end time of precip is around 10-11am as dry air finally wins out. The other note for the West Virginia ridges will be the potential for high wind gusts in eastern Tucker County on Friday. As flow turns more westerly, models continue to show a 55-60 kt mountain wave at 850 mb just east of Tucker County Friday morning into the evening. NBM probabilities for Advisory criteria (>46 mph gusts) continue to sit around 75-95% in eastern Tucker. Strongest gusts should remain downstream given that this is a northwesterly flow event, but expect the ridges to get quite windy with 45 to 55 mph gusts likely at the Dolly Sods Mesonet site. For these reasons, have issued a Wind Advisory for eastern Tucker County from 4am-8pm Friday. Otherwise, it will be a seasonable day with plenty of sun under transient high pressure and warm advection driving high temperatures into the mid 50s (60-70% chance southeast Ohio tops 60 degrees). The upper ridge quickly flattens on Saturday as the first in a series of shortwaves slide in from the west. A warm front lifts through on Saturday and resultant warm advection drive rain showers will arrive early in the morning continuing through the day as the cold front follows quickly behind it and sinks through Saturday night. Rainfall amounts for this batch look to be contained to half an inch or less, though a deeper trough could push them closer to 0.6-0.7". && .LONG TERM /SUNDAY THROUGH THURSDAY/... KEY MESSAGES: - A series of weak low pressure systems will keep showers and thunderstorms in the forecast for much of the period. - Probabilities increasing for rainfall totals Saturday to Wednesday greater than 2", highest from Morgantown to Tucker County WV. - Above-average temperatures are expected. ------------------------------------------------------------------- The aforementioned cold front then stalls just to our south and keeps low chance precipitation primarily south of I-70 into early Sunday morning. Uncertainty remains on how far south it stalls with some ensemble solutions still holding rain chances up to Pittsburgh, so will maintain slight chance mention further north until better agreement comes in. The front then lifts back north again Sunday night as warm advection in southerly flow renews. Widespread rain again returns as low and mid level flow will parallel the east-west oriented boundary as it sits across our area into Monday. Rich moisture arrives with PWAT values nearing 1.1" pushing the daily max climatological value. Another deeper upper wave ejects out of the Plains late Monday as low pressure forms and plagues the area through mid-week. Uncertainty comes into play with the timing and strength of the trough and the track of the surface low with most ensembles holding downstream ridging strong, but a lower probability chance exists that a more zonal and progressive pattern unfolds. In terms of rainfall totals, WPC has placed our CWA in a Marginal (1/5) risk for excessive rainfall on Monday. Ensemble probabilities for >2" are increasing (40-70%), especially across West Virginia, with high end amounts of 3-4" not out of the question. In addition, machine learning shows increasing severe weather risk Monday and Tuesday across the Ohio Valley. This will largely be a question of how much instability can materialize as overall dynamic parameters are sufficient to support the potential for severe weather. At this time, analogs hold the threat just to our southwest, but uncertainty as mentioned above could shift the threat further into our area. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... VFR conditions are expected across the region day until a mostly clear sky as high pressure builds from the west. Winds will prevail from the northwest/west into the evening as a shortwave lifts out of the Great Lakes. Stratocu cigs are expected to increase tonight as a weak shortwave crosses the region. A few light rain or snow showers are possible south of PIT, where slightly more favorable moisture is expected with the wave. A brief period of MVFR is possible at MGW, though the latest model probabilities of occurrence are less than 50 percent. .Outlook... VFR is expected through Friday night under high pressure. Widespread restrictions and showers return Saturday with crossing low pressure. VFR briefly returns Sunday under high pressure, before restrictions in showers/possible tstms return Sunday night and Monday with a warm front. && .HYDROLOGY... Widespread round of rainfall are expected beginning Saturday and continuing into the middle part of next week. Ensemble probabilities for >2" of total rainfall are increasing (40-70%) areawide, but especially across West Virginia, with high end amounts of 3-4" not out of the question there. This may result in areas of flooding or flash flooding, especially on Monday, when our area has been placed in a Marginal Risk (1/5) for excessive rainfall. Rises on area rivers from prolonged excessive rainfall are also looking increasingly possible as ensemble probabilities continue to trend higher by the beginning of next week. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...Wind Advisory from 4 AM to 8 PM EDT Friday for WVZ514. && $$ SYNOPSIS...Hefferan/Rackley NEAR TERM...Hefferan/Rackley SHORT TERM...Rackley/MLB LONG TERM...MLB AVIATION...WM/Hefferan HYDROLOGY...

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