12AM Day 1 Convective Outlook for Wednesday, July 16. THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ON WEDNESDAY OVER PARTS OF THE CENTRAL HIGH PLAINS AND PORTIONS OF THE GREAT LAKES REGION .
SUMMARY
Scattered strong to severe thunderstorms are possible Wednesday afternoon and evening from parts of the central High Plains to the Great Lakes and Mid-Atlantic states.
Upper MS Valley
A large but weakening linear MCS is tracking slowly eastward into western MN/IA. 00z model consensus shows a convectively enhanced upper trough and MCV will emerge from this activity, tracking into parts of WI and northern IL by Wednesday afternoon. Strong heating and ample low-level moisture will be in place over the warm sector of this MCV, but weak mid-level lapse rates will limit CAPE values to around 2000 J/kg. Present indications are that thunderstorms will intensify by mid-afternoon across this region and spread eastward toward Lake Michigan and western Lower MI by evening. The strongest cells will pose a risk of damaging wind gusts. Enhanced vertical shear near the MCV may also result in a tornado or two.
WY/CO
The belt of primary mid-level westerlies will extend across WY later today, with the southern fringe of stronger flow aloft over northern CO. Ample mid-level moisture will encourage scattered afternoon thunderstorms over the mountains and foothills of CO/southern WY, with storms moving into the adjacent plains by mid-afternoon. Backed low-level winds will result in favorable deep-layer shear for a few organized/supercell storms capable of large hail and damaging winds through the afternoon and early evening.
NY/PA/WV
Current water vapor loops shows a subtle shortwave trough and weak mid-level jet max over southern IL. This feature will track northeastward up the OH Valley and into parts of OH/WV/PA by Wednesday afternoon. Forcing associated with this feature, combined with a warm/humid air mass will promote multiple clusters of thunderstorms affecting the region. Forecast soundings show rather weak mid-level lapse rates, weak winds in the lowest 4km, and considerable mid-level moisture limiting downdraft potential. Will therefore maintain only MRGL at this time, but acknowledge some risk of scattered wind damage across this region later today.