Area Forecast Discussion
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258 FXUS61 KPBZ 071600 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1100 AM EST Wed Dec 7 2016 .SYNOPSIS... Building high pressure should maintain dry weather today. A Thursday cold front will bring much colder temperatures and snow shower chances to end the work week. && .NEAR TERM /THROUGH TONIGHT/... Building high pressure should maintain partly cloudy skies across the area this afternoon. A shortwave and surface trough should cross the area overnight with an increase in clouds, though with a lack of deep moisture available little or no precip is expected. Temperatures should average near seasonal levels. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... An upper-level low will advance east into Quebec Thursday, allowing much colder air to wrap in behind, invading our area from the west. Very little moisture exists along the mid-level cold front, so initial precipitation chances will be minimal through Thursday afternoon, but a slight wind shift will bring lake-effect and upslope snow that could extend into the early weekend. Although cold advection will be ongoing, the coldest air will pour in later Thursday afternoon with a mid-level trough. This will steepen lapse rates through the mid-levels and increase the boundary layer height. Veering winds behind the trough axis will seep Great Lakes moisture in across the northern 1/3 of the forecast area, eventually extending southward into the Ridges. Deep northwest flow will spread snow showers initially confined to our northern reaches southward, nearing the Pennsylvania Turnpike Friday afternoon. Snow showers will be ongoing through much of the day Friday for the northern 1/3 as well as into the Ridges. These areas stand to see the best chance of accumulating snowfall, albeit over a fairly long duration. For now, will carry a mention of accumulating snow in the HWO for these counties. With a less favorable wind setup and less moisture availability for most of the event, eastern OH, northern WV (outside of the mountains), and much of southwestern PA should see little to no accumulation. The shot of much colder air will hold temperatures 5-10 degrees below the averages. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Surface high pressure will briefly settle over the area Saturday, bringing an end to any remaining light snow showers. Drier weather will remain fleeting, however, as zonal flow aloft will quickly advance the next system into the lower Great Lakes. Models currently having a difficult time latching onto this system, leaving the track in limbo. The track of the low will play a vital role in determining the level of warm air advection and subsequent precipitation types Sunday into Monday. Regardless of the exact path, the setup is favorable for tapping into Gulf moisture to spread along the trailing boundary. Superblend was largely utilized for this system, including the inclusion of likely PoPs Sunday night. After the early week system, models differ slightly on smaller disturbances through the upper-level pattern. One thing that is fairly certain, however, is that the cold air will stay through next week, continually re-enforced by mean northwest flow aloft. Middle of next week should feature temperatures that are well-below average. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... Patchy MVFR CIGs will improve to VFR through the day, and continue through tonight. Expect west to southwest winds under 10 KTs ahead of an approaching cold front through Thursday morning. .OUTLOOK... Periodic restrictions in snow showers are likely for the rest of the week as a strong cold front sweeps the region Thursday, with cold advection through the weekend. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.