FXUS61 KPBZ 070530 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 130 AM EDT Thu May 7 2026 .WHAT HAS CHANGED... -Frost Advisory continues for Forest, Venango, Clarion, and Jefferson Counties this morning. -An additional frost advisory will likely be needed again tonight for northwest Pennsylvania and higher terrain. -Models are more consistent with period of areal rain this weekend; totals Saturday and Sunday have a 70% chance of >0.25". && .KEY MESSAGES... 1) Frost chances this morning and Friday morning. 2) Rain chances increase this weekend. && .DISCUSSION... KEY MESSAGE 1... Clouds are expected to continue to clear from the west through the morning, leaving northern parts of the area susceptible to efficient radiative cooling. New HREF guidance suggests that frost probabilities have increased, with a 60% to 90% chance of an area-wide frost within the advisory, and even a 30% chance of a freeze in Forest County. Patchy frost is possible for isolated areas outside of the advisory with areal frost chances generally 30% to 50% in eastern Ohio and areas north and east of Pittsburgh. Our course, micro-scale terrain influence will generally determine who sees and doesn't see frost in any given location. Given the 50% probability contour matches fairly close the the current advisory area, opted to not expand the current advisory. For tonight, there is higher confidence in mostly clear conditions early before low-moisture may increase clouds later into the night. This adds some uncertainty as to whether frost will be fully possible late overnight, and if the temperatures get below 37F before the clouds arrive. Overall, HREF probabilities do favor a brief period of frost potential overnight in northwest Pennsylvania and the higher terrain (>50%). Chances of a freeze are highest in Forest County and eastern Tucker County at 20% to 35%. As to avoid confusion with current frost headlines and allow more time to resolve the cloud and temperature potential overnight, opted to postpone any frost advisory issuances for tonight until the day-shift in coordination with neighboring offices. KEY MESSAGE 2... A digging trough is expected to approach the east coast from the northwest. Along with it, model guidance has come into agreement that rain chances will peak with ascent associated with two shortwaves rounding the trough base. These have become better resolved over the last 24 hours. The first is increasingly likely to pass Saturday morning through the early afternoon, bringing areal rain chances. The second is a bit more uncertain, but most likely to arrive with a cold front around and south of Pittsburgh Sunday afternoon through the overnight hours. Sunday high temperatures will vary greatly based on the cold front position, with areas north of Pittsburgh favoring cool temperatures, and areas south of Pittsburgh more seasonable. Chances of >0.25" of rain in any 6hr period are only 25% for now, with NBM showing a ~70% chance of >0.25", ~45% chance of >0.5", 15% chance of >1", and 0% chance of >2" for both Saturday and Sunday respectively. Therefore, flooding concerns remain low to none. Drier and cooler conditions are favored to follow this system and start off the next work-week. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... Dry advection and brief surface ridging will allow for partial clearing through mid-morning. This will ensure mainly VFR areawide, save for MGW where IFR fog is possible. VFR continues during the day, with high based cu/stratocu by this afternoon. A crossing shortwave trough could force a few showers or sprinkles in the afternoon, but these should stay north of PIT. NW wind will gust to around 20kt today, diminishing once again this evening. Outlook... Periods of rain and restrictions are expected late Friday into early Saturday, and again Saturday night into Sunday, as shortwaves rotate through a broad upper trough across much of the eastern CONUS. General VFR is expected in between these systems. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...Frost Advisory until 8 AM EDT this morning for PAZ008-009-015- 016. OH...None. WV...None. && $$ DISCUSSION...Milcarek AVIATION...WM/Rackley