Area Forecast Discussion
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000 FXUS61 KPBZ 150914 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 414 AM EST Mon Jan 15 2018 .SYNOPSIS... Low pressure will bring light snow to the region later today and into Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Low pressure will move through the Western Great Lakes today. The low is showing the characteristics of being occluded, with little separation between the leading warm front and trailing cold front. What looks to be the surface warm front will swing northward through the region late in the day and during the evening. Light snow will overspread the area with the surface boundary. Model QPF is light, as the strongest upper level support remains well to the northwest, close to the surface low. Models are in good agreement with the timing and placement of the low, which is now just a bit further north then previous runs. Deep moisture will initially be funneled northward riding ahead of the warm front, so locations south of I-70 may see little to no snow until the evening hours. Warm air advection today will allow surface temps to moderate, but still remain below normal. General accumulations today will be an inch or less, with the higher amounts over my far western counties in Ohio.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
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The trailing cold front will slowly move through the area tonight as it out runs its upper level support. Light snow will overspread the entire region overnight. Models are hinting that a thin band of more enhanced snowfall could develop ahead of the cold front with the passage of an upper jet in the southwest flow aloft and increasing low-level moisture convergence. However, at this time, there is disagreement on where this band may develop. This is something that can be addressed once the hires models get a look at it. Cold front slows over the south-southeast on Tuesday, so the focus for additional snowfall will shift to where the front gets hung up. It may take most of Tuesday until the boundary finally ejects to the southeast. This will necessitate keeping in PoPs through most of Tuesday over Northern West Virginia, Southwest PA, south and east of PIT, and over Northern Maryland. Behind this system, there will be another shot of cold air. Expect little to no lake enhancement/upslope, as winds aloft remain southwest through most of Tuesday. Mid-level flow does shift to the west-northwest late Tues night and Wednesday as the trough axis swings through, but this should lend to no more than scattered snow showers with shallow saturation in the snow growth zone. Temperatures will remain below average.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Upper trough will be replaced with zonal flow through the end of the week before a trough builds over the western CONUS. New runs of the deterministic models have a fast-moving system passing across the region on Friday, but have opted to not make any major forecast changes based on this. Deepening western CONUS trough will support a return of seasonal or above temperature for next weekend. Timing differences between model guidance supports to use of a model blend through the period. && .AVIATION /09Z MONDAY THROUGH FRIDAY/... VFR conditions expected as upper level cloud coverage increases ahead of a clipper system set to arrive late this afternoon. Deterioration to MVFR with intermittent IFR can be expected as snow showers develop late afternoon through the evening. .OUTLOOK... Tuesday through the remainder of the week looks largely dry with VFR conditions. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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