Area Forecast Discussion
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000 FXUS61 KPBZ 162013 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 313 PM EST Thu Nov 16 2017 .SYNOPSIS... Scattered rain and snow showers are expected today with an upper-level disturbance. Dry weather should return Friday under high pressure before a second disturbance arrives on Saturday. && .NEAR TERM /THROUGH FRIDAY/... Wind has veered to wnwly in the wake of a morning cold-frontal passage and upper-level trough, with cold advection expected to continue through the day. Amid steep low-level lapse rates, increasing moisture from the Great Lakes and cold air aloft, modest instability will support the persistence of scattered rain showers through much of the day. As cold air filters in, these showers may mix with or change to snow showers, But residual ground warmth and above-freezing temperature will limit snow accumulation. As the upper low responsible for the morning showers exits ewd, shortwave ridging will bring an end to showers. Cloud cover is unlikely to vacate considerably, as steep low-level lapse rates will support prolonged stratocu. Perhaps some cloud breaks are possible tonight, but they will quickly fill on Fri as heating renews the potential for stratocu. Although steep lapse rates will continue amid a cold-air advection regime, the boundary-layer wind field noted in the PBZ 12UTC sounding has decreased with the upper wave`s departure. The wind advisory currently in effect for the ridges of ern Tucker County is likely to be discontinued by mid-afternoon. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... Building high pressure will maintain dry and cool weather Fri. Clouds will increase on Fri ahead of low pressure advancing out of the Plains. Current expectation is that this low will sharpen a warm front across the region Fri night as it tracks to the Great Lakes region. Rain and rising temperature are expected, mainly after midnight after the frontal passage. Occasional rain showers are expected Saturday amid strong swly flow ahead of an approaching upper trough and cold front. The surface low is progged to track into Southern Ontario by Sat evening, and its attendant cold front will move through in its wake. Strong wind aloft is expected on Sat, though forecast soundings show a capping inversion that will prevent the wind from reaching the surface. Gusts nevertheless are possible along and behind the front as lapse rates steepen, but it is unclear whether wind headlines will be needed. Cold advection will help change rain showers to snow showers Sat night as the upper trough approaches. Likely PoPs were maintained in the lake-effect belt along and n of I-80 and in the ridges e/se of Pittsburgh, where upslope flow and enhanced instability will strengthen upward motion. On-and-off snow showers can be expected through Sun night as cold air aloft and a lake fetch maintain low-level instability. && .LONG TERM /MONDAY THROUGH THURSDAY/... Ridging should result in dry weather early in the week before upper troughing returns minimal chances for precipitation n of PIT by midweek. Temperatures should average below seasonal levels. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... MVFR ceilings will dominate through the afternoon into the early evening hours as an upper level trough crosses. Scattered rain and snow showers are possible, most numerous along/north of I-80 and along the ridges. Brief IFR conditions are possible for a few hours at FKL/DUJ with this activity. Gusty WNW winds, with peak values of 25-30 knots, will continue this afternoon before diminishing tonight. Precipitation will taper off during the evening. A gradual transition back to VFR ceilings will occur overnight and into Friday morning, with lighter and more variable wind. .Outlook... Restrictions are likely again with a Sat cold front and with Sun upper troughing and cold NW flow. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ Kramar is the U.S. government's official web portal to all federal, state and local government web resources and services.