FXUS61 KPBZ 201550 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1150 AM EDT Mon Apr 20 2026 .WHAT HAS CHANGED... Freeze Warning in effect tonight into early Tuesday across the region. && .KEY MESSAGES... 1) Cold temperatures through Tuesday morning, Freeze Warning in effect 2) Warmer with periodic shower chances mid to late week && .DISCUSSION... KEY MESSAGE 1... Widespread freeze is expected tonight into Tuesday morning as high pressure builds, resulting in diminishing wind and radiational cooling. With high confidence in low temperatures below freezing tonight into Tuesday morning, a Freeze Warning remains in effect areawide. KEY MESSAGE 3... A weak cold front is expected to move south across the region Tuesday night into Wednesday, with scattered showers. Isolated thunderstorms are possible, though instability is progged to be limited. A number of ensemble models indicate the highest chance for thunderstorms (but still only 15-30%) is south and east of Pittsburgh; lightning will likely be the only threat. Ridging returns dry and warmer weather Thursday into early Friday. The ridge is expected to flatten by late week into the weekend, with a more zonal flow across much of the CONUS, and a closed low across south central Canada. Weak shortwaves embedded in the flow are expected to cross the Upper Ohio Valley region late Friday and into the weekend. Occasional shower and thunderstorm chances are expected. However, the chances of severe thunderstorms is consider very low due to the probability of strong vertical wind shear and instability remaining below 10%. && .AVIATION /15Z MONDAY THROUGH FRIDAY/... Rain and snow showers have moved off to the southeast, with the only potential impacts at MGW briefly before departing by 13Z. Precipitation chances are null through the rest of the TAF period. Winds are expected to gust up to 20 knots by the afternoon. Winds are expected to engage by 15Z to 17Z. The outlier will be ZZV with lighter winds aloft expected and in turn, less winds to mix to the surface. VFR and calming winds persist overnight, with limited impacts to terminals. Outlook... Restrictions and shower potential returns with a cold front Wednesday morning, before VFR returns Thursday under high pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...Freeze Warning from 11 PM this evening to 9 AM EDT Tuesday for PAZ007>009-013>016-020>022-029-031-073>078. OH...Freeze Warning from 11 PM this evening to 9 AM EDT Tuesday for OHZ039>041-048>050-057>059-068-069. WV...Freeze Warning from 11 PM this evening to 9 AM EDT Tuesday for WVZ001>004-012-021-509>514. && $$ DISCUSSION...WM/Hefferan AVIATION...Milcarek/Shallenberger