FXUS61 KPBZ 100008 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 808 PM EDT Fri May 9 2025 .SYNOPSIS... Building high pressure will keep the region dry through the weekend. After a chilly start with the potential for frost tomorrow morning, a warming trend is expected into next week. Rain chances return by the middle of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... KEY MESSAGES: - Frost Advisory in effect from 2am-8am - Dry conditions and seasonal temperatures expected Saturday ------------------------------------------------------------------- Weak northwest flow and high pressure inching up the Ohio River Valley will finish eroding lingering stratocu and allow for clear skies overnight. The combination of clear skies, light wind, and lingering cold airmass (with low dewpoints) should result in area temperature around 10 degrees below the daily average and pose a risk for frost formation. An areawide Frost Advisory highlighting this potential impact remains in effect, though the effects of heating within urban areas likely will mute frost development. Additionally, hi-res modeling suggests a potential for enough of a surface pressure gradient to maintain some BL mixing for areas east of I-77 in Ohio that could limit the degree of cooling and frost formation. This could also cause stark differences in valley versus ridgetop temperature, which the latest forecast attempts to capture. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... KEY MESSAGES: - Quiet conditions with moderating temperatures Sunday ------------------------------------------------------------------- Dry conditions are expected as we remain in a fold-over ridge, wedged between the cutoff low over the gulf states and troughing over Nova Scotia/Newfoundland. Subsidence will generally keep skies mostly clear and warming aloft will support low temperatures closer to average as well, which will limit additional frost concerns. && .LONG TERM /MONDAY THROUGH FRIDAY/... KEY MESSAGES: - Warming trend continues through next week. - Next rain chances return Tuesday - Potential for strong to severe thunderstorm Thursday/Friday ------------------------------------------------------------------- The aforementioned cutoff low will begin to be absorbed back into the upper flow Monday with southerly flow and moisture returning to the region. At this juncture, ensemble guidance does want to start introducing the chance for showers and possible thunderstorms by Monday afternoon but this will be contingent on how quickly the low levels saturate. By Tuesday afternoon, confidence increases in the generation of showers and storms, but some discrepancies remain in amount of instability and shear present. Showers and thunderstorms are again possible on Wednesday as the trough passes across the upper Ohio valley. A brief reprieve is expected Wednesday night as the upper low shifts off to the east. The break is short lived however as chances for showers and thunderstorms return for Thursday and Friday. As noted previously, joint probabilities of effective shear >=30kts and MUCAPE >= 500J/kg exceed 30% in Ohio on Thursday and 50% across much of the region on Friday, which suggests the potential for strong/severe storms given the timing and lift from a cold front tied to low pressure over the northern Great Lakes. Cluster analysis flattens the ridge by the end of the period but even so, temperatures will remain above average through the period. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Clear skies tonight and light winds open the door for the chance of fog formation, especially in the river valleys. ZZV and MGW seem to have the greatest chance for fog development, however, there is less than 10% probability of occurrence which is why it is not included in the TAFs. Otherwise, VFR continues Saturday under largely clear skies with light to moderate winds. Outlook... High pressure will continue VFR through early Monday night. Restrictions are likely to return Tuesday/Wednesday with an upper level trough moving into the region. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...Frost Advisory from 2 AM to 8 AM EDT Saturday for PAZ007>009- 013>016-020>022-029-031-073>078. OH...Frost Advisory from 2 AM to 8 AM EDT Saturday for OHZ039>041- 048>050-057>059-068-069. WV...Frost Advisory from 2 AM to 8 AM EDT Saturday for WVZ001>004- 012-021-509>514. && $$ SYNOPSIS...34 NEAR TERM...Frazier SHORT TERM...34 LONG TERM...34 AVIATION...Lupo/AK