Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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000 FXUS61 KPBZ 230035 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 835 PM EDT Fri Mar 22 2024 .SYNOPSIS... Rain is expected to overspread the region tonight through early Saturday with crossing low pressure. Dry weather is then expected through early next week under high pressure. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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KEY MESSAGES: - Rain tonight with crossing low pressure ------------------------------------------------------------------- Wet-bulbing effects north of I-80 have began to reduce as air approaches saturation and a warm nose has began to advance, changing over all snow to rain. In isolated patches, brief bouts of freezing rain are possible before complete recovery to rain as temperatures warm slightly overnight. Temperatures near- freezing and marginally warm road temperatures will not allow for ice accumulation on roadways. This "warm period" will be short lived before a cold front moves in and drops temperature below freezing again with a brief changeover back to snow possible before the system departs in the morning. By then the late March sun will reemerge and hinder any accumulations. Further, any winter impacts will remain limited to none. .. Previous Discussion .. A surface trough was analyzed from southern OH through southwest PA. Dry air remains in place in the lower levels, though warm, moist advection should eventually result in dew points increasing through this evening. A northern stream trough advancing across the Upper Midwest is expected to phase with a SE CONUS trough tonight, as a surface low tracks NE along the East Coast. Rain is expected to overspread the region tonight, as an inverted surface trough extends northward across the Upper Ohio Valley region. The latest mesoanalysis shows 850mb temps still -1 to -3 deg C across Venango and Forest counties. A brief period of snow, or rain/snow mix, is possible at the onset of the precip this evening in that area, before enough warm advection occurs to change the precip to rain. The region will also be under the entrance region to an upper jet, enhancing ascent. Rainfall amounts are expected to range from 0.25 to 0.5 inches west of I 79, with 0.5 to 0.75 east of I 79. NBM probabilities of 0.5 inches are highest (50-60%) north and east of PIT. The inverted surface trough/cold front will shift east of the area toward morning, as the surface low continues its track along the East Coast. The rain could mix with or briefly change to snow north of PIT, though most of the moisture and ascent should be exiting the region as colder air moves in.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... KEY MESSAGES: - Precipitation ends Saturday as low pressure exits - Dry weather is then expected through Monday under high pressure - Warmer temperatures Monday ------------------------------------------------------------------- Rain will end from west to east Saturday as the surface low tracks NE the East Coast, and the surface trough/cold front exits the Upper Ohio Valley region. A brief mix or changeover to snow is possible north of PIT and in the ridges, though no accumulation is expected. North wind is expected to gust to 30-35 mph during the day, with a tight pressure gradient between the East Coast low and high pressure to our west. Shortwave ridging is then expected to build across the Upper Ohio Valley region through Monday, with dry weather expected. Seasonable temperatures are expected Sunday. A warming trend is expected by Monday as the ridge axis shifts east of the area, and the flow veers to the south. Highs are expected to be 10 to 15 degrees above average by Monday. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... KEY MESSAGES: - Rain chances return Tuesday and Wednesday with a cold front - Mainly dry and seasonable to end the week ---------------------------------------------------------------- Model ensembles indicate a trough across the central CONUS will advance slowly eastward toward the Upper Ohio Valley region Tuesday and Wednesday. Increasing rain chances are expected as the trough and its associated surface cold front track east across the area. The front is expected to move east of the area by Thursday, though some uncertainty exists in how far east it will progress before a wave of low pressure tracks north along it. Maintained slight-low chance pops due to the uncertainty. High pressure is expected to build across the region Thursday night and Friday, with dry and seasonable weather expected. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... Broad ascent ahead of an incoming shortwave trough (and associated surface cold front) is leading to widespread light rain and VFR cigs due to the drier antecedent conditions. The exception is a brief period to begin at FKL with a wintry mix of snow and sleet (lower probability of freezing rain) as surface warm advection was limited prior to precip onset. Continued 850mb warm advection and lack of reinforcing cold surface air will aid a transition to rain by 04z. Approach of the trough axis and surface cold front will increase moisture convergence across the area (NW to SE), resulting in a rapid reduction toward IFR cigs after 06z. Lifting cigs and deterioration of rain is likely after frontal passage while a strengthening surface gradient increases N to NNW wind (favoring 13z-16z time period). Dry advection and subsidence should favor a west to east erosion of stratocu, returning area terminals to VFR toward the end or just after the TAF period. .Outlook... Height rises and surface high pressure will promote dry weather and VFR conditions until the next low pressure system arrives late Tuesday into Wednesday. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...WM NEAR TERM...WM/Milcarek SHORT TERM...WM LONG TERM...WM AVIATION...Frazier

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