Area Forecast Discussion

WHAT HAS CHANGED

A slight risk for severe weather has been introduced for Sunday with all hazards possible (wind, hail, tornadoes) for now.

KEY MESSAGES

1) Quiet weather Saturday, followed by potentially another chance at strong/severe storms on Sunday

DISCUSSION

KEY MESSAGE 1... Crossing high pressure will maintain quiet weather on Saturday, along with temperatures around 5 degrees above normal.

The next cold front is expected to cross the region on Sunday, behind which a period of slightly below-normal temperatures is forecast into early next week. While timing of the boundary and an associated mid-level wave might be favorable for a severe storm risk, there are indications of isentropic-fueled rain preceding the boundary on Sunday morning, which could hinder any severe weather potential. However, there are scenarios (like the 12Z NAM Nest for example) where less morning clouds/rain allows for greater destabilization and a chance for more robust convection. The NBM 25th/75th percentile SBCAPE range at Pittsburgh at 18Z Sunday ranges from about 375 J/kg to close to 1100 J/kg, illustrating the uncertainty. Any convection that forms should have about 35-40km of deep shear to work with, so organization is certainly possible in the higher-buoyancy scenarios. SPC currently elevated to a slight (level 2 of 5) severe risk for portions of southwest PA/northern WV on Sunday.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Dry advection and high pressure will erode cloud cover through tonight behind a departing shortwave. Daytime cu will collapse after sunset and leave just a few streaks of FEW to SCT cirrus before that too exits in the late evening and expect skies will go SKC overnight with VFR and light to variable wind. One exception is if surface dry advection arrives too late at MGW while skies clear overnight and potentially allow for localized fog formation near dawn, but latest hi res data and low-level water vapor imagery suggest the dry air advancing and lowering of dew points should arrive in time to preclude near-dawn fog development.

VFR remains with high confidence on Saturday beneath zonal mid- level flow and a quick bout of surface high pressure. A dry boundary layer should support little more than some diurnal cu with light southwest wind.

Outlook... Restrictions associated with showers and thunderstorms likely return Sunday morning and possibly with more widespread stronger thunderstorms in the afternoon as a cold front passes through, though uncertainty with coverage of morning precipitation lends lower confidence to development of afternoon storms, impacts, and restriction probability.

High pressure portends to dry VFR weather conditions to start the next work week.

PBZ WATCHES / WARNINGS / ADVISORIES

PA...None. OH...None. WV...None.