Marine Weather and Tide Forecast for Whitaker, PA

KEY MESSAGES
1) Temperatures warm to well above-normal by early next week prompting some impacts to the heat sensitive population

2) Thunderstorms with non-zero severe threat exists on Saturday as well as the middle of next week with unresolved details at this time

DISCUSSION
KEY MESSAGE 1...
Heights will rise into the weekend as flat ridging establishes overhead which will result in the beginning of a notable warmup into the middle of next week. Highs over the weekend will quickly jump above climatological normals and continue in that direction with the warmest days coming Monday and Tuesday. By then, east coast ridging will amplify in response to a digging trough out west with temperatures by Monday and Tuesday approaching 15 degrees above normal. 500 mb heights are progged to reach right around 588 dam with only +/- 1 to 2 dam of spread in the distribution.
850 mb temperatures surge to 18C with a 90+% chance on Monday and 70-90% chance on Tuesday. While this points toward an abnormal warmup for mid to late May, NBM runs continue to bias correct much too high on both MaxT and MinT with the suggestion of mid 90s for highs and low to mid 70s for lows both Monday and Tuesday. The 850 mb temperature rule, assuming that the potential is maximized with a clear sky day, with ~18C at 850 mb results in MaxTs around 85F. Evaluation of global ensemble distribution, as well as deterministic and ensemble AI guidance, supports mid to upper 80s with the 2/3 or greater of the distribution clustered between 85-90F both days. A tail extends warmer on both days, likely driven by the small membership with slightly higher 850 mb temperatures/500 mb height outliers.
Similarly, a tail extends cooler, mainly on Tuesday, likely driven by solutions with more cloud cover and precipitation. So, while low 90s aren't out of the question, and most likely south of Pittsburgh, the more likely outcome sits in the mid to upper 80s with a conditionally cooler day on Tuesday.

It's still worth noting that with this being the first notable warmup with several days of temperatures well above normal, those who are most susceptible to heat will want to take proper precaution. Even those who aren't may still feel effects with prolonged periods outdoors as the body works on accustoming to warmer temperatures.

KEY MESSAGE 2...
The previously mentioned pattern shift will likely also create two main periods of thunderstorms that offer non-zero severe risks: Saturday afternoon and evening, and somewhere in the Tuesday to Wednesday range.

For Saturday, weak shortwave movement within zonal flow atop the building southeast CONUS ridge is likely to generate a thunderstorm complex near the IA/WI border that travels toward the upper Ohio River Valley. Latest guidance continues to suggest little will be left of this initial complex as it reaches eastern OH late Saturday morning in an unfavorable environment, but it could aide in re- development amid an increasingly warm, moist environment with a northward-lifting warm front. The most likely scenario under this premise favors scattered to locally numerous sub-severe showers/thunderstorms forming near the I-77 corridor and traveling east through the evening as weak shear (20-25kts), lower CAPE (less than 1000 J/kg), and warm mid-levels keep activity mild. But, if surface heating is maximized in conjunction with low 60s dewpoints, enough buoyancy could lend to a lower-end hail and damaging wind threat (with slight higher probability for hail). Confidence is low given environmental state will be heavily influenced by that decay storm complex, and CAMs notoriously struggle to resolve decaying MCSs. Confidence in either scenario may not manifest until we can see how the complex maintains into the overnight hours Friday night.

For Tuesday/Wednesday, shortwave movement within southwest flow is favored by ensembles that shunts the ridge SE and creates enough ascent with surface low passage for widespread showers and thunderstorms. Timing and depth of the shortwave creates variances in when the area of convection reaches the upper Ohio River Valley, resulting in large spreads in environmental parameters used to assess severe risks. This includes large ranges for instability, mid- level forcing, and uncertainties in features like mid-level warm noses or pre-convection cloud cover limiting heating/destabilization.
Thus, it is best to remain cognizant of this period likely featuring showers/thunderstorms and monitor trends into the start of next week to learn what degree severe hazards may be in play or not.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
Areawide VFR begins the TAF period and continues with high confidence through 12z tomorrow.

Today will be dominated by mainly high clouds, with warm advection and a weak shortwave this evening. Light westerly winds will continue to back towards the southwest by tonight.
Clouds thicken and lower overnight ahead of our next shot at rain coming in the form of dissipating thunderstorms near midday on Saturday. At this time, these showers have been included in PROB30 groups near the tail end of the current TAF period for our western ports but have been included as prevailing for ZZV with higher confidence of occurrence further west.

Outlook...
Restrictions and rain chances return Saturday afternoon into Sunday with some shower and thunderstorm chances, especially Saturday night. VFR returns early next week.

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