1PM Day 3 Convective Outlook for Wednesday, February 18. NO SEVERE THUNDERSTORM AREAS FORECAST
SUMMARY
Severe thunderstorms appear unlikely on Wednesday.
Synopsis
A deep mid/upper-level trough is expected to persist over the western CONUS on Wednesday, as multiple embedded shortwaves move through the large-scale trough through the period. Low-topped convection will be possible across southern CA early in the period, with multiple rounds of weak convection possible farther north from the Pacific Northwest to central CA coast. Farther east, a negative-tilt shortwave trough will move across parts of the Upper Midwest/Great Lakes, as multiple low-amplitude vorticity maxima eject eastward toward the Lower Great Lakes and Northeast.
MI into the Lower Great Lakes region
Generally weak elevated convection may spread from lower MI into parts of the Lower Great Lakes through the day, in association with an ejecting midlevel vorticity maximum. Some guidance (such as the ECMWF/GFS) depicts modest surface-based destabilization in the wake of this elevated convection, within a favorably sheared environment. However, this occurs within an otherwise drying environment (with PW falling near/below 0.5 inches), with generally limited low-level ascent. The signal for robust deeper convection is currently very limited, but trends will continue to be monitored regarding the potential for any vigorous surface-based development.
Northern Mid-South region into the Ohio Valley
In response to a mid/upper-level shortwave ejecting from the western trough, a surface cyclone is forecast to deepen across the central High Plains during the day, before moving eastward across KS Wednesday night. Guidance varies regarding the magnitude of low-level moisture return within the warm-sector of this cyclone prior to the end of the period. However, MUCAPE may become sufficient for development of elevated thunderstorms late in the period from parts of northern AR/southern MO into much of KY/TN and adjacent Ohio Valley. Strong deep-layer flow would conditionally support some storm organization, but development of sufficient elevated buoyancy for an organized-severe threat remains uncertain.