Scientific Forecaster Discussion
000 FXUS61 KPBZ 202016 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 416 PM EDT Sun Oct 20 2019 .SYNOPSIS... Warmer conditions are expected Monday before the passage of a Tuesday cold front. Near-average temperature and dry conditions are then expected by mid week under high pressure. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Shortwave ridging in the wake of the exiting Nestor will maintain dry weather and seasonably warm conditions for tonight. A clear sky and light wind will support patchy, shallow fog as crossover temperature will likely be achieved. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY NIGHT/... A deepening, closed upper low will advance toward the Upper MS Valley, promoting strong sly flow over the Ohio Valley. Despite increasing cloud cover, warm advection will enable daytime high temperature to reach 10-15 degrees above average. Rain coverage should expand from west to east Monday night as the boundary layer saturates with increasing low level jet support ahead of an encroaching cold front. Strong forcing for ascent of precipitable water in excess of 1.40" (+ 90% climatological average) should support periods of moderate rainfall through Tuesday morning as the cold front quickly advances through the forecast area. Subsiding air in building high pressure will support a drying trend Tuesday behind the cold front. Lingering low level moisture should fuel the development of a cumulus deck under broad upper troughing Tues afternoon, with strong wind mixing to the surface via steep low-level lapse rates and a decent gradient wind. Cold advection behind the front will return daytime high temperature to near average values. Similarly, as dry air and clearing sky ensue Tue night in the wake of the upper wave, minima will also end up near seasonal average. Quasizonal flow aloft and surface high pressure should support a dry and seasonably cool Wed. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Although long range models diverge on details, the consensus suggests return flow ahead of a deepening Plains trough, supporting at least seasonable temperature in the long term. Precipitation chances will be dictated by shortwave activity in SWly flow aloft ahead of the aforementioned trough. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... Shortwave ridging wl maintain VFR through Monday with the only interruption being the potential for peri-dawn fog. .Outlook... Restrictions are likely Monday night into Tuesday with a frontal approach, subsequent passage, and coincident rain. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None.