textproduct: Pittsburgh

WHAT HAS CHANGED

Update to Key Messages

KEY MESSAGES

1) Above-average temperatures and dry weather continue for the next 24 hours

2) Rain returns Wednesday afternoon/evening into early Thursday. Confidence is high that cooler temperatures return late week.

DISCUSSION

KEY MESSAGE 1... A large-scale cutoff low is currently centered over the Great Plains this afternoon. Given its slow progression and upper- level winds running parallel to the frontal boundary, the probability of measurable rainfall remains low over the next 24 hours. Meanwhile, strong southwest flow will support above- average temperatures during the afternoon, along with the potential for record-high minimum temperatures overnight for Wednesday. Wheeling, WV (HLG) and New Philadelphia (PHD), have the greatest potential to tie or break their Wednesday high minimum temperature records, with overnight lows expected to remain in the mid-50s.

KEY MESSAGE 2... As the aforementioned cutoff low transitions into an open-wave trough over the Great Lakes during the next 24-36 hours, an associated cold front will advance eastward towards the Ohio River Valley Wednesday afternoon and evening. Rain chances will increase between 1pm and 4pm in eastern Ohio and 4pm and 9pm for northern West Virgina/western Pennsylvania, bringing an end to the unusually prolonged dry stretch; the last measurable rainfall occurred on October 16th for Pittsburgh, PA. Rainfall amounts are expected to range from 0.25 to 0.50 inches with this new disturbance, with locally higher amounts of 0.50 to .70 inches possible across isolated areas in eastern Ohio due to favorable jet dynamics. Despite the anticipated rainfall, the overall flood threat remains low. The potential for lightning is also low, but not zero, with any isolated strikes most likely occuring south of Pittsburgh between 4pm and 9pm Wednesday due to elevated instability with some noted dry air aloft and slightly higher dew points.

By early Thursday morning, a dry slot, will move into the region from the west. Light rain and drizzle is possible near dawn. Otherwise, drier conditions will prevail into the late morning.

A brief period of dry and quiet weather is expected Thursday afternoon into early Friday. However, as the large-scale trough swings across Lake Erie, a secondary cold front will bring renewed chances of lake-enhanced showers across the region.

Temperatures will trend closer to seasonal averages during this period, with both daytime highs and overnight lows near normal. The 850mb temperatures will fall from around +7 degrees Celsius early Friday to -4 degrees Celsius during the late evening, supporting a transition to colder conditions into the weekend.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

500mb ridging will keep VFR conditions in the forecast through the TAF period, with mid and upper level clouds dominating for most of the period. A few lingering cumuliform clouds in eastern Ohio should scatter out this afternoon. South to southwest wind of 10 knots or less will continue.

Clouds will begin to thicken late tonight ahead of a shortwave and a surface occluded boundary. Ceilings will lower most in eastern Ohio by midday Wednesday, but should stay above MVFR thresholds through 18Z. A few non-restrictive showers may arrive at ZZV by the end of the TAF period.

Outlook... Rain and restrictions should become more widespread late Wednesday into early Thursday. A series of crossing upper troughs will maintain periodic restriction and rain chances Friday and Saturday.

PBZ WATCHES/WARNINGS/ADVISORIES

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