Marine Weather and Tide Forecast for Girard, PA

KEY MESSAGES
1) Daily chances for showers and thunderstorms tonight into the weekend. Highest chances for precipitation will be Tuesday afternoon and late Thursday afternoon through Friday morning.

2) Hot and humid Wednesday and Thursday with heat indices near or over 100 in some areas followed by slightly cooler and less humid conditions Friday through the weekend.

DISCUSSION
KEY MESSAGE 1...
An active weather day is expected Tuesday as a mid-level shortwave and associated vort max lift through the Great Lakes and temporarily create a weakness in the mid/upper ridge. The surface low tied to this feature is currently spinning over the Mid Mississippi Valley, with a warm front extending southeast across the Ohio River Valley. This low will slowly lift through the western and central Great Lakes late tonight and Tuesday allowing the warm front to bulge gradually northeastward into the southern Great Lakes. This warm front will usher in much richer low-level moisture, with PWATs surging to near 2 inches (near max daily climatology for June 9) as dew points rise into the low 70s. This low-level moisture combined with slightly cooler 850-700 mb temps as the mid-level shortwave progresses by will allow for decent coverage of diurnal convection with daytime heating Tuesday.

Initial showers and a few thunderstorms will move SW to NE across the region late tonight and early Tuesday morning as warm air advection and isentropic ascent increase ahead of the warm front. These will be low-impact, but brief heavy rain could occur in the strongest cells. The greatest coverage of convection is expected Tuesday afternoon and evening as weak upper diffluence on the SE flank of the shortwave overspreads the region and interacts with daytime heating (moderate instability of 1000-1500 MLCAPE). Given the very moist environment described above and a skinny CAPE profile, very heavy/efficient rainfall will occur within any thunderstorms.
This could produce localized flash flooding of low-lying and poor drainage areas, particularly if any training occurs. The good news is that antecedent conditions are mostly dry, but training with these types of rainfall rates could still cause localized issues. Contemplated a Flash Flood Watch with neighboring offices, but the location of the heaviest rainfall is highly uncertain. CAMS generally show scattered convection and offer differing solutions on location. In general, the heaviest showers and storms should start in NW and north central Ohio around midday and slowly shift to near the PA border by evening ahead of a weak surface trough/cold front trailing from the low. Given the coverage and location uncertainties, opted to just message the threat in the HWO, Weather Story, and Social Media.

Severe weather is generally not expected Tuesday afternoon and evening, but deep layer effective shear of 20-25 knots and an increase in 0-1 and 0-3 SRH to 100-150 m2/s2 could be just enough to cause some rotation within some of the convection, so cannot rule out a brief spin up tornado somewhere, especially since LCL heights will be low given the water loaded environment.

The mid/upper ridge will become reestablished Wednesday and Thursday over the eastern CONUS ahead of a strong mid/upper trough progressing into the northern Plains. This combined with strong deep layer WSW flow will advect an elevated mixed layer (EML) across the region and reduce the coverage of convection, especially Wednesday. Nevertheless, some widely scattered diurnal convection will develop again Wednesday afternoon, with better chances Thursday afternoon and evening as the ridge starts to break down ahead of the mid/upper trough and associated cold front. As this front crosses the region late Thursday night and Friday morning, a more organized line of showers and thunderstorms is possible. This could produce another round of heavy rainfall in some areas. The overnight and morning timing is not favorable for widespread severe weather, but a decaying squall line with damaging wind potential will need to be monitored, especially for NW Ohio which is currently on the edge of a Day 4 severe weather outlook from the SPC.
Quasi-zonal flow behind this front will cause the boundary to become quasi-stationary near the region late Friday and Saturday followed by a stronger cold front Sunday, so a few isolated showers/storms could continue Friday afternoon through Saturday, then a better chance Saturday night and Sunday with the next cold front.

KEY MESSAGE 2...
Hot and humid conditions are still expected Wednesday and Thursday under the strong mid/upper ridge and deep WSW flow. H85 temps of 20-22 C advecting into the region, decent mixing, and ensemble guidance all support highs in the upper 80s to low 90s.
This combined with dew points in the upper 60s/low 70s will yield heat indices near or over 100F in some areas. Early season heat can be more dangerous, so extra precautions will need to be taken to stay cool and hydrated. Temperatures and dew points will begin to fall behind the cold front Friday, but it will remain seasonably warm and humid until the second cold front brings more significantly cooler and drier air by Sunday and Monday.

AVIATION /06Z Tuesday THROUGH Saturday/
The aviation forecast continues to be tricky, largely because of the fact that the upper level trough and warm front coming through the region during the period will be producing off and on and isolated to scattered convection through much of the period. This creates an issue where it is not nearly enough for prevailing or even TEMPO groups, so the use of PROB30 becomes the best play. However, it could be used in a large portion of the TAF period for most of the terminals, so the attempt here is to isolate the best chance of a terminal experiencing any sort of convective activity. That said, towering cumulus should be expected for most of the period, as should lowering ceilings to largely MVFR, and possibly IFR overnight. Winds become gusty 15-25kts out of the southwest during the daytime heating hours.
AMDs should be expected.

Outlook...Periods of non-VFR likely in occasional showers and thunderstorms through Friday.

MARINE
East to northeast flow around 15 knots continues through early tonight before weakening and become south to southeast tonight ahead of an approaching warm front. The warm front works its way eastward across the lake Tuesday afternoon through Tuesday night, with winds becoming southwest around 10 to 15 knots and persisting through at least Friday morning before a cold front crosses Lake Erie.

CLE WATCHES/WARNINGS/ADVISORIES
OH...None.
PA...None.
MARINE...None.