Marine Weather and Tide Forecast for Murrysville, PA

KEY MESSAGES
1) Isolated to scattered showers and thunderstorm possible today and Sunday

2) Severe thunderstorm potential increases Monday into Tuesday

DISCUSSION
KEY MESSAGE 1...
A relatively weak shortwave is expected to cross the Upper Ohio Valley region today. Isolated to scattered showers are expected, though much of the day should be dry. By this afternoon, most of the shower activity should be east of I-79, along a mid level trough. Instability is progged to be minimal, with only an isolated thunderstorm possible. This activity should diminish this evening as the shortwave exits to the east.

Sunday should start with dry weather ahead of another approaching shortwave. This wave should bring scattered showers and thunderstorms to portions of the area, initially north and west of Pittsburgh, by afternoon into the evening. Additional convergence along a lake breeze boundary could also enhance some of the thunderstorm coverage. Low and mid level flow is expected to remain relatively weak, though an upper jet is expected to approach Ohio in the afternoon. Generally a low potential exists for severe storms on Sunday, though DCAPE values around 750 j/kg indicate some damaging wind gusts will be possible. The Storm Prediction Center has included much of Ohio in a Marginal Risk for severe storms.

KEY MESSAGE 2...
Thunderstorm chances are expected to increase by Monday in northwest flow aloft. An MCS is possible across the Midwest to the Ohio Valley region Sunday night into Monday morning.
Current indications are this should stay west of the forecast area following the 500 mb thickness pattern, though this will need to be monitored as details become more certain.

By afternoon, building diurnal instability and a subtle crossing shortwave should result in increasing showers and thunderstorms, and a severe weather potential. ML CAPE is progged from 1500-2500 j/kg, with increasing flow aloft resulting in 40 kt of 0-6km shear. The potential for severe storms is expected to continue into Monday night as a stronger shortwave and surface cold front approach from the Great Lakes region. Again, there will be a potential for an MCS somewhere in the region, though low confidence continues in the location and timing of this potential.

The shortwave and surface cold front is progged to cross the Upper Ohio Valley region on Tuesday. A severe weather potential is expected to continue, though this will be highly dependent on the timing of passage, and any MCS activity Monday night/Tuesday morning.

The latest machine learning guidance indicate the highest potential for severe storms should be from 12Z Monday through 12Z Tuesday. The highest potential on Tuesday is indicated across far SE OH, SW PA, and northern WV. All hazards are possible, with damaging wind, hail, isolated tornadoes and locally heavy rainfall/flash flooding. Low confidence remains in the timing/location, and how these potential hazards will be impacted by previous convection, outflows, etc.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
Mostly MVFR stratocu cigs and some patchy valley fog are ongoing to start the morning, as well as a few isolated showers primarily across the higher elevations east of PIT. Fog should dissipate and gradual improvement to low-end VFR cigs is forecast through mid morning. An upper shortwave trough is still expected to cross the area this afternoon, with continued stratocu and isolated to scattered showers. Instability should remain limited, though an isolated thunderstorm will be possible mainly during peak heating. Most of the afternoon activity is expected to be along and east of the I-79 corridor.
Maintained prob30s for showers for sites east of I-79 and VCSH for the more isolated activity elsewhere. These showers should end this evening as the shortwave exits and heating wanes, with clouds also decreasing.

Outlook...
Isolated to scattered showers/storms are possible again Sunday afternoon during peak heating hours. Thunderstorm chances increase Monday into Tuesday with the approach and passage of a cold front. A few storms could become strong to severe. Low shower/storm chances continue Wednesday with another passing wave, but the potential for severe storms decreases.

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