textproduct: Pittsburgh

WHAT HAS CHANGED

Updated aviation forecast, otherwise no significant changes were made to the forecast.

KEY MESSAGES

1) Morning rain will clear to cooler and drier weather through Friday, before more rain chances return over the weekend.

2) Frost remains possible tonight and Friday morning.

DISCUSSION

KEY MESSAGE 1... Rain is expected to persist through this morning, before clearing into the afternoon. With no additional instability expected between now and late-morning, rain will likely remain stratiform, with no additional convective or flooding concerns. The heaviest totals have been observed up in Mercer County (~0.5" as of 1am); ensembles suggest most likely totals by the end of the event in the I-80 corridor will be around 0.75", with a 30% chance of >1". Chances of >1" rapidly decrease to the south and east, with chances generally >15% elsewhere.

Drier and cooler weather is expected Thursday and Friday courtesy of the post-cold-frontal environment and a brief bout of high pressure. Chances of rain increase again late Friday and through Sunday night. Chance Friday and Saturday will be courtesy of a couple of weaker shortwaves. The brunt of rainfall accumulations is forecast Sunday with the next low pressure passage and cold front. Chances of >1" right now are generally <20% and the system seems generally progressive in most scenarios, which would keep flooding concerns low.

KEY MESSAGE 2... There is medium to high confidence in clouds scattering some overnight tonight north of Pittsburgh as high pressure gradually builds in. With it, the pressure gradient will also relax and calm overnight winds with decoupling. NBM probabilities of temps less than 37F tonight are generally 30% to 50% north of Pittsburgh, but chances of a freeze are <5%. Thus, there is a low probability of a frost tonight. Most instances will likely be isolated and patchy depending on micro- scale terrain influence.

A similar regime will linger Friday morning, with a higher chance of low clouds clearing area-wide. This will correlate to a bit higher chances of a frost, with regions north of Pittsburgh and the higher terrain of PA/WV seeing a 50% to 80% chance of less than 37F, and the rest of the region generally between 10% to 35%. Chances of a freeze are, again, low for now, highest at 10% to 25% for Forest County and eastern Tucker County.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Initial light rain will become heavier in the next several hours with crossing surface low and shortwave trough. As expected ceilings have been slow to drop with initial rainfall, but will do so over the next several hours. A brief hour or so of MVFR ceilings are anticipated before continued degradation to at least tempo IFR at most terminals. IFR

Dry advection and subsidence will shift the rain axis east through by mid-morning while area restrictions gradually improve toward VFR through the evening (less than 20% probability of MVFR or lower by 00z Thursday, save for 40% probability of stratus lingering near KMGW). VFR will then continue through the remainder of the TAF period with dry weather.

Outlook... The next round of precipitation and restrictions return Thursday night into Friday, though primarily for terminals in northwest PA. More widespread rain and restriction development occurs Saturday with on and off periods of rain/restrictions continuing into early next week.

PBZ WATCHES/WARNINGS/ADVISORIES

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