Marine Weather and Tide Forecast for Lake Arthur Estates, PA

KEY MESSAGES
1) Potential for strong to severe thunderstorms tomorrow afternoon and evening with a passing cold front

2) Quiet weather expected Monday through mid-week; monitoring potential hazardous weather on Thursday

DISCUSSION
KEY MESSAGE 1...
Quiet weather will be maintained through the afternoon and evening as high pressure departs the region. Daytime cumulus will collapse with sunset, although mid and upper clouds will be on the increase on southwest flow behind the high.

Rain chances return very late tonight in southeast Ohio and before noon Sunday as a mid-level shortwave lifts from the Middle Ohio Valley into the region by 18Z. Most CAMs do bring at least scattered showers and isolated thunderstorms across the region with this initial wave, with lift provided isentropically. Outflow from overnight convection to our west could also play a role in supporting initiation. This activity should stay below severe limits. The main question becomes the shape of the environment in place behind this morning activity.
This is due to the following main 500mb trough arrival and cold frontal passage expected Sunday evening. CAMs consensus is for a fairly stout line of showers and thunderstorms associated with the front. 0-6km shear of 30-40 knots will certainly be sufficient for storm organization. However, the severity of those storms will be highly dependent on the buoyancy that is present
The 12Z HRRR presents a variety of scenarios here
for instance, the 10th-90th percentile range for surface-based CAPE at 20Z at Pittsburgh ranges from roughly 280 J/kg to to 1340 J/kg. This parameter will likely not be able to be assessed with any appreciable confidence until tomorrow morning.

If the higher-end CAPE scenarios are realized, the main severe threat appears to be damaging wind gusts, given the shear/level of storm organization and cold pool consolidation that could occur. Tornadoes appear to be a secondary threat, tied to the higher-end scenarios where a more robust supercell-like structure can take a more E or even ESE direction, to the right of the more ENE mean storm motion. Hail appears least likely of the severe threats, as the high freezing level and poor mid- level lapse rates (less than 6C/km) limit potential. Rain rates will also be healthy given 1.5-1.7 inch precipitable water values and warm cloud depths of 10-12 thousand feet. However, storm motion should be sufficient to mitigate any flooding concerns other than perhaps isolated urban/poor drainage issues.

Cold frontal passage during the evening will end the severe threat from west to east, with the boundary crossing the ridges likely in the 01Z to 03Z Monday window.

KEY MESSAGE 2...
In the wake of the Sunday cold front, generally quiet weather and below-normal temperatures are forecast early next week, as Great Lakes/northeast CONUS troughing works in concert with surface high pressure. Rain chances may then return Tuesday night/Wednesday as the high departs and a shortwave skirts the eastern Great Lakes. Moisture and flow appear to be weak enough to preclude anything more than minimal severe weather chances.

By Thursday, a warm frontal passage could bring rising 500mb heights and higher dewpoints back to the region. Along with this are indications of enhanced flow, with 45-50 knots at 700mb and 70-80 knots at 500mb on ensemble progs. This combination suggests an increasing risk of severe weather on this day, associated with a potential cold frontal passage from Great Lakes low pressure. Longer- range machine-learning guidance from NCAR and CSU agree with this assessment, with probabilities for severe weather ranging from 15% to 45%. SPC also has already highlighted Thursday for the risk as well. Given the instability/shear combination that could be realized, this is a potentially volatile situation that could present all severe hazards in higher-end scenarios.

In addition to the severe weather threat, multiple embedded shortwaves may promote repeated rounds of precipitation, raising concerns for training storms and localized flooding. At this time, the greatest flood risk appears more likely to focus over areas just west of the Upper Ohio Valley. The evolution of the pattern, and the attendant severe/flooding risks, will need to be monitored closely in the coming days.

AVIATION /00Z SUNDAY THROUGH THURSDAY/
VFR expected through the overnight hours with increasing cirrus replacing diurnal cu that will dissipate with sunset. Ceilings will gradually lower into the morning hours on Sunday as warm advection driven showers work their way up the Ohio Valley. The coverage of these remains uncertain, and the latest suite of hi res guidance has backed off a bit, but have still maintained the PROB30 mentions at all sites covering these. There could be a brief period of MVFR conditions with them, but VFR will predominantly be the theme through the morning.

There is a high probability for a fairly solid line of showers and thunderstorms to develop ahead of a cold front Sunday afternoon in NE OH to NW PA which will then dive southeast through the forecast area through sunset Sunday night. At minimum, users can expect heavy rain with gusty winds between 20kts to locally 35kts in any storm along with dips to MVFR/IFR restrictions. Pending on the degree of heating prior to the line passage, which is dependent on the coverage of morning showers, storms could see an enhancement of both lightning and strong wind potential. Most likely timing is ~21z for ZZV and FKL, ~22z for PIT and surrounding terminals, and ~23z for LBE and MGW. Outside of the convective line, moisture convergence ahead of the cold front may result in patchy MVFR to IFR cigs with light showers.

Outlook...
Dry advection and subsidence favor VFR Monday into Tuesday before the next potential shortwave system advances through the region mid-week.

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