Marine Weather and Tide Forecast for Prospect, PA

KEY MESSAGES
1) Potential for severe weather exists today through Friday, but large uncertainty exists in timing/coverage/threats

2) Low probability flash flooding concerns exists through Friday due to warm, moist environment

3) Above-average temperature with potential for record high minimums possible through Friday, pending storm outcomes

DISCUSSION
KEY MESSAGE 1...
The region will remain within a warm, humid environment through portions of Friday conducive to convective activity before a more well-defined front and upper trough cross by Friday evening that provide at least a brief period of more seasonable and dry weather.

For today, latest mesoanalysis shows a clear exiting of a mid- level shortwave trough and axis of enhanced PWATs as of 17z while satellite-noted dry air arrives in its wake amid shortwave ridging. Confidence is higher at the moment that these features, dry mid-level air and ridge subsidence, will suppress convective activity for a large portion of the afternoon. Thereafter, hi- res model guidance notes a corridor of surface temp/dewpoint convergence near CLE that is the most likely area for thunderstorm development between 6pm-10pm, with these storms moving southeast (before weakening) during the late night hours.
The highlighted Marginal Risk by SPC remains conditional on these or any other thunderstorms developing prior to midnight, which remains on the lower end of probabilities; if they do form within the proper evening window, the risk for damaging wind and heavy rain rises due to SBCAPE values approaching 2000 J/kg, DCAPE values around 1000 J/kg, and weaker shear.

Thursday's outlook shows similar to higher severe potential due to maintenance of high SBCAPE/DCAPE values but confidence is significantly lower in storm development/coverage/timing. Like today, these facets will be predicated on storm evolution overnight plus any influences from western Great Lake activity that may or may not provide sources of lift/convergence to help the initiation process.

Friday features a more well defined mid-level shortwave and surface frontal boundary that offers a lifting mechanism, but model guidance remains spread on timing differences that could result in more bullish precipitation/severe chances (afternoon passage) or more bearish precipitation/severe chances (overnight to mid morning Friday passage). Early hints from the most recent hi-res modeling seem to lean toward the latter ideal, meaning overall precipitation chances and associated severe risks trend lower while favoring areas east of Pittsburgh.

KEY MESSAGE 2...
Despite fluctuations in mid-level moisture content, area PWAT values will remain in the 90th and higher percentile ranges through Friday while thermal profiles remain warm. These factors alone create non-zero flash flood risks as they favor warm-rain processes that result in higher and more efficient rainfall rates. Add in generally weaker mid-level flow (though storm motion quickens Friday), the risk for flash flooding exists each day.

However, fairly dry surfaces plus low confidence in storm coverage/occurrence dampens the likelihood of flash flooding actually developing for any of these periods. The most likely outcome is minimal flooding occurrences, with issues only developing in poor-drainage locations that see prolonged 1-2"/hr rates or areas that happen to see multiple rounds of these efficient rains in a short amount of time.

KEY MESSAGE 3...
The combination of area dew points remaining in the upper 60s to lower 70s while seeing enough periods of sunshine means increased heat concerns today into Friday morning, with impacts more acutely impacting heat-sensitive populations within urban environments. Though a brief hour of heat indices near to matching Heat Advisory criteria can't be ruled out, but are unlikely to be prolonged enough for headline issuance. Even still the lack of significant overnight cooling can act to exasperate any heat-related impacts until a cooler airmass arrives Friday night into Saturday morning.

The biggest caveat to this heat potential is that convective activity could act to limit diurnal heating (or further limit overnight cooling) if it results in rain over a given location and/or maintains thicker cloud cover than anticipated.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/
Confidence is medium in thunderstorms forming in warm advection zone over northern OH and Lake Erie 22-00z and then turning southeast toward western PA later this evening. Current best timing of thunderstorms would be about 03z BVI FKL, 04z PIT AGC DUJ, and 05z LBE. Close call at HLG and MGW and likely to stay northeast of ZZV.

Would expect mainly MVFR ceilings to return later tonight in moist environment, with DUJ likely to go to IFR again and FKL a close call.

Confidence in thunderstorms and related restrictions for Thursday and Thursday night is low. Unstable airmass will be in place, but there is a lot of variability in how clusters of thunderstorms may evolve upstream from MI to IN and IL Thursday and Thursday night and that will impact what happens in the upper Ohio River Valley area. Predictability in these patterns is usually only good for next 6 to 12 hours.

Outlook...
Friday thunderstorm chances and possible restrictions are low confidence as weakening storms push through first thing in the morning and there is an attempt at redeveloping in the afternoon but odds favor this being east of the Appalachians.

Saturday looks relatively quiet with another possibility of thunderstorms on Sunday.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...None.
OH...None.
WV...None.