Marine Weather and Tide Forecast for Whitaker, PA

KEY MESSAGES
1) A Marginal Risk (level 1 of 5) of severe thunderstorms exists for this afternoon and evening, with damaging wind gusts the primary threat. A break in the convection pattern is expected Friday.

2) A stronger cold front is expected to cross Saturday afternoon and evening, with another round of strong to potentially severe thunderstorms. Damaging wind again appears to be the most likely threat.

3) Much above-normal temperatures continue until the Saturday cold front passage. Behind it, temperatures crash to much below-normal levels. Frost/freeze concerns return by early next week, and even a few Sunday night snowflakes are possible.

DISCUSSION
KEY MESSAGE 1...
After a morning lull, another round of strong to potentially severe thunderstorms is forecast this afternoon and evening. Surface low pressure crosses Michigan into southern Ontario today, dragging a weak front across the Upper Ohio Valley. A trailing mid-level shortwave crossing the lower Great Lakes should spark a round of isolated to scattered thunderstorms by mid-afternoon across central Ohio, with coverage slowly increasing into the late afternoon/early evening as activity crosses our region.

The environment will be a little less favorable than Wednesday for severe storms. Although deep-layer shear of around 40 knots will be present, instability should be somewhat less pronounced, topping out in the 500-1000 J/kg range. Factors such as increased cloud cover, lower dewpoints, and weaker mid-level lapse rates all contribute to this lower level of buoyancy. The poor lapse rates point to lower hail potential, while weak to absent low-level curvature to hodographs with uniform column southwest flow suggest little tornado threat. This leaves isolated damaging wind as the most likely impact from the stronger storms, especially if they organize into clusters/short lines. SPC has maintained a Marginal Risk (level 1 of 5) for the forecast area.

A second shortwave digging across the Tennessee Valley will help to dislodge what has been a stubborn southeast CONUS ridge Thursday night as the afternoon and evening showers and storms work their way out after sunset. Behind this wave, a brief period of mid-level ridging should allow for a break from the daily thunderstorm activity for most of Friday and Friday night.

KEY MESSAGE 2...
A stronger cold front is still slated to cross during the afternoon/evening hours of Saturday. This boundary will provide the most focused lift of the past several days, which could be better for convective organization. The main question with this boundary remains timing, which would have implications on how much instability can build across our region. This will depend at least in part on the speed and orientation of the associated 500mb shortwave trough. Ensemble clusters suggest some fairly minor differences in strength and timing with this wave as well as the surface boundary. However, even a 3-6 hour difference has notable effects on the potential location and severity of any associated convection, and thus the overall impact level remains uncertain.
Machine-learning guidance from NCAR and CSU do highlight our region for at least some severe storm potential. Ensemble soundings during that period depict generally poor mid-level lapse rates and modest low-level hodograph curvature, suggesting damaging wind gusts currently appear to be the most likely impact.

KEY MESSAGE 3...
Much above-normal temperatures continue into Saturday ahead of the expected strong cold front. Today, the approaching mid-level trough will begin to knock down the anomalous 500mb heights, which were above the 95th percentile yesterday but will be merely around 90th percentile by afternoon. More abundant clouds will also keep temperatures a bit more in check. High temperatures in the lower 80s remain favored for many areas south of I-80, but records will likely remain a bit out of reach. All climate sites have 30 percent or lower chances of tying/breaking March 16th standards. Meanwhile, record warm minimums for today are more in jeopardy, with all climate locations save ZZV having a 70% or greater chance of occurrence.

Ridging returns Friday, but with lower absolute 500mb heights, thus records are not likely. There may be some modest potential to approach records on Saturday, especially if the front is later than currently projected, allowing for a longer period of warm southwest flow. NBM probabilities of 80 or warmer may be a bit overstated, but much of the area from Pittsburgh south should have at least a 50/50 shot of reaching that level.

Meanwhile, behind the front, the script flips, and northeast CONUS troughing leads to daytime high temperatures some 10-15 degrees below normal for Sunday and Monday, before approaching climatology on Tuesday. Frost/freeze products may need to be issued by early next week, and some Sunday night snowflakes are a possibility.

AVIATION /06Z THURSDAY THROUGH MONDAY/
Areawide VFR is expected under mid-level clouds through the overnight and morning hours. Continued isolated showery activity is expected for FKL/DUJ through about sunrise today. Cloud decks will begin to lower in the afternoon hours in front of an approaching cold front, but VFR CIGs are expected to hold firm.
A line of broken strong to severe storms are expected along the cold front. These storms can bring brief bouts of MVFR restrictions or a few dips to IFR. It is possible for there to be 2 lines of storms, with one along a pre-frontal trough.
Altogether, CAMs are in good agreement on a ~20z approach towards the PA/OH border. Timing has been broken down with prevailing groups showing the greatly increased confidence in timing of these storms as opposed to prior days.

Behind the cold front VFR CIGs can return in VCSH or limited VCTS activity before CIGs are expected to begin to fall as we approach sunrise on Friday.

Winds will be gusty across the region Thursday, with Swerly gusts between 20-25 kts for most ports ahead of the frontal passage. Behind the front, winds shift to more westerly and remain gusty for a couple hours before subsiding.

Outlook...
Friday should be mostly dry following Thursday evening's weak frontal passage. However, another low pressure system and a stronger cold front approach the area on Saturday, returning shower and thunderstorm chances (and associated restrictions) to the region through the weekend. Dry weather and VFR conditions are then favored as we head into early next week with a pattern shift following the weekend cold front.

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