143 FXUS61 KPBZ 062058 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 458 PM EDT Mon Sep 6 2021 .SYNOPSIS... Mainly dry weather and seasonable temperatures are expected through Tuesday under high pressure. Shower chances return Tuesday night and Wednesday with a crossing cold front. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Cu field will diminish due to the loss of heating this evening with a nearly cloud free night in store. Clear skies and light wind will support the development of some river valley fog through the early morning hours. Low temperatures should be close to seasonal normals. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... High pressure shift eastward Tuesday though the region should remain dry until late. Strengthening warm advection in advance of the next system will result in temperatures nearing or exceeding 80, which is right near seasonal averages. Low pressure lifting northeastward from the northern Great lakes to Hudson Bay, will drag a cold front across the upper Ohio valley late Tuesday/early Wednesday. Given the current timing of the cold front, lack of instability will limit any severe threat though some thunder is possible as the front approaches the eastern third of the CWA by early afternoon. Southerly flow and cloud cover in advance of the cold front should keep low temperatures Tue night elevated, followed by high temperatures a touch below average Wed with the daytime frontal passage. && .LONG TERM /THURSDAY THROUGH MONDAY/... Model ensembles indicate the main upper trough is expected to persist across the Ern CONUS through Friday, with the potential for a secondary cold front and vorticity advection to allow for continued shower chance on Thursday before broad ridging ensues. Generally dry weather is then expected through the weekend as sfc high pressure builds under northwest flow aloft. Below average temperatures late in the week should return to or above seasonable levels through the weekend. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... Once diurnal cu diminishes, mainly clear skies are expected tonight with fog development in the river valleys towards dawn. Most of the terminals should escape this fog potential though some brief restrictions may be possible as fog lifts after daybreak. VFR is then anticipated Tuesday with w-sw wind around 10kts with some gusts to 15kts. .Outlook... Restrictions are possible with a Tue night/Wed cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$