Marine Weather and Tide Forecast for Prospect, PA

NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:

- Locally heavy rain may result in flash flooding again this afternoon/evening, Flood Watch in effect through 10pm.
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A quasi-stationary boundary across the region along with anomalously high PWAT values will continue the broken record daily forecast we have observed the past couple days.
Precipitable water values 2-3 standard deviations above normal, deep warm cloud depth ranging from 11,000 to 13,000ft, and instability will provide an environment ripe for heavy rainfall.
Additionally, storm motion will continue to remain relatively slow. Given slow storm motion, the threat for excessive rainfall and potential flooding remains, and there is a Flood Watch in effect for areas roughly south of Butler,PA where recent rainfall and storm coverage is expected to coincide today.
The probability of rainfall rates reaching to 1-2 inches per hour are above normal, ranging from 20-40%, with HRRR probabilities focused over the previous hit counties of Monongalia and Marion Counties. Similar to Sunday, the highest rainfall potential is expected between 12pm to 10pm. The threat from damaging winds are very low given weak flow aloft and absence of dry air aloft.

Loss of diurnal heating and the environment being worked over by outflow boundaries should result in decreased shower coverage and low rainfall rates. However, generally after 03z (11pm), weak 700mb shortwave movement in strengthening southwest flow may generate enough lift to develop isolated to scattered shower coverage mainly south of I-80. Weak buoyancy should limit shower up growth and keep rainfall rates low while storm motion increases to 15-20kts, which should preclude nocturnal flash flood concerns (though it would be non-zero).

SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/
KEY MESSAGES:

- Flash flood threat spreads areawide, with probabilities highest in locations previously impacted by flooding.
- Increasing shear may allow for isolated instances of a damaging wind threat south of I-68.
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A lower Ohio River Valley trough will start to slide east as embedded 700mb shortwaves within increased southwesterly flow is expected to promote more widespread shower and thunderstorm coverage Tuesday. The environment will remain similar to the setups Sunday/Monday (near record high PWATs, saturated grounds)
save for two points, each which may counter the other: stronger forcing will better aid storm development/coverage (increasing flood threat) and storm motion will be closer to 20kts (lowering the flood threat). Given that the region has be inundated with recent rain and many counties have seen impactful flooding, the messaging remains the same:

Heavy rain showers and thunderstorms pose a flash flood risk with potentially impactful flooding in locations that previously seen flooding.

The weakening trough is now likely to not exit east til Wednesday afternoon. This means additional waves within southwest flow and broad jet induced ascent east of the trough axis may continue rounds of showers and isolated thunderstorms overnight Tuesday into Wednesday morning. Though low probability, the flood risk could further extend into the early Wednesday morning period.

LONG TERM /WEDNESDAY THROUGH SUNDAY/
KEY MESSAGES:

- A mid-week warmup will be followed by increasing late-week severe potential.
- Weekend is likely to be dry and hot.
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By Wednesday, there is some indication of a return to quasi-zonal flow to even weak ridging, with NBM highs back into the mid to upper 80s. On Thursday, a surface low (preceding an upper level trough), is expected to move through the area bringing the chance for severe weather. We will be keeping an eye on severe potential in the transition from heat to weak troughing, with CIPS and CSU machine learning showing increasing probabilities into Thursday and Friday. Into days 7 and beyond, the strength and progressiveness of this trough will determine just how long it takes to warm back up into what could potentially be another ridging pattern with heat returning.

By Saturday, a ridge is likely to move into the area, bringing dry weather and warm temperatures. Temperatures are expected to rise into the mid to upper 80s. The ridge is expected to remain stationary at least through Monday keeping temperatures well above normal into the upper 80s and low 90s

AVIATION /11Z MONDAY THROUGH FRIDAY/
MVFR to IFR cigs will show marginal improvements through the day north of a stagnant boundary thanks to some diurnal heating/mixing. HRRR probabilities favor enough heating/lift to produce showers and isolated thunderstorms focused around KMGW/LBE during the afternoon/evening. Confidence is low on storm coverage extending to other TAF sites given weak flow, but kept mention for nearby terminals (KPIT/KHLG/KAGC) in case storm outflow boundaries initiate farther north/west than model depictions.

The largely stagnant airmass should favor cig lowering overnight towards MVFR/IFR, though weak SE flow could limit drops at KLBE.
The noticeable difference tonight will be weak shortwave movement that could generate isolated to scattered showers mainly after 06z; rainfall rates aren't likely to be high and impact visibility much but it could help drive lower cigs.

Outlook... Periodic restrictions are expected through Thursday as disturbances track along the stalled frontal boundary across the Upper Ohio Valley region. Late night/early morning stratus and fog is likely, along with showers and thunderstorms peaking in the afternoon and early evening. More organized showers/storms are expected with a Thursday cold front.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...Flood Watch through this evening for PAZ021-029-031-073>076.
OH...Flood Watch through this evening for OHZ049-050-058-059-068- 069.
WV...Flood Watch through this evening for WVZ001>004-012-021- 509>514.