917 FXUS63 KDTX 240442 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1142 PM EST Tue Nov 23 2021 .AVIATION... Despite increasing winds aloft, a stable sfc layer will hold south winds generally around 10 knots. The onset of daytime heating on Wednesday will deepen the boundary layer and will result in an increase in the wind speeds and gusts. Model soundings and latest probabilistic guidance strongly suggests gust Wed afternoon will reach the 20 to 25 knot range. The extensive region of low level dry air across the Lower Ohio Valley and srn Mississippi Valley will keep low clouds at bay through Wed evening with only increasing mid and high level clouds expected. .DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 403 PM EST Tue Nov 23 2021 DISCUSSION... Upper Midwest ridge axis continues to get shoved eastward today ahead of a deepening longwave trough atop western CONUS. What remains of the shearing aforementioned anticyclonic feature will maintain influence across the Great Lakes region through Wednesday as the associated surface high crosses The Carolinas. Surface flow has already responded by backing southwesterly this afternoon and holds through the night. Forecast soundings depict a moderating column overnight with the lowest 10 kft warming above 0C after midnight as a warm sector lifts in with aggregate surface troughiness. Lows rebound to within -1 sigma of climatology tonight (upper 20s) given the warmer profile and periods of insulating mid/high cloud. Dry conditions persist into Wednesday as top-down column saturation ensues once upper levels winds become more zonal. H9-H8 layer confluence establishes a 50 knot LLJ corridor that crosses through the lower Ohio Valley. In light of the strong dynamics, effective mixing depths will generally be too shallow (less than 1000 ft AGL) to tap into the core maintaining gusts in the 20-25 mph range. There could be brief window (19-21Z) as the BL peaks resulting in isolated 30-35 mph gusts. Low-level streamlines in connection with the jet trace back to The Gulf with noted moisture advection arriving during the evening. Flow becomes cyclonic after midnight as the next wave reaches Lower Michigan supporting chances for showers, but probabilities are rather low late Wednesday night as dry air hangs on, delaying saturation. Thanksgiving Day starts off rather dreary as light rain expands across Lower Michigan during the early morning hours. A passing cold front provides a focus for additional development with supporting upper level divergence. Rates look unimpressive given disconnect in phasing and residence time of the primary moisture axis. Turkey Day highs mirror Wednesday's (mid-upper 40s) with west to east clearing during the afternoon. Flow becomes northwesterly in the frontal wake with pronounced dry slot. Subsidence in the mid-levels ensures lingering cloud layer remains shallow, but given modest mixed-layer depth and steep lapse rates, a few flakes will be possible. Not confident enough with coverage of flurries for most of the CWA to include mention in gridded products. However, this cold advection regime and appropriate fetch ensures periods of lake effect snow showers along the immediate southern Huron shoreline into Friday. Additionally, strong mixing potential affords a broad window for +25 mph gusts for much of the region on Friday. High pressure then spills south from central Ontario Saturday bringing dry and cold weather followed by wetter conditions Sunday. MARINE... Central Great Lakes remain under the influence of Ohio Valley high pressure this afternoon and evening. SW winds begin to increase early tonight as the high slides to the mid-Atlantic while low pressure develops over the upper Midwest. Local pressure gradient further tightens Wednesday as the low advances into the upper Great Lakes. Warm air advection with this flow is expected to help stabilize thermal profiles over the lakes limiting mixing down of stronger winds aloft. The window when gusts over central Lake Huron could touch gale-force is still looking to be Wednesday morning between 12-17Z. Profiles during this time are more neutral to slightly unstable before the main surge of warmer air in the afternoon arrive increasing near-surface stability. Overall potential is marginal for both duration and wind strength so have opted not to issue a headline at this time but will monitor in coming forecast packages. Rain showers become possible late Wednesday night through Thursday as the associated cold front slowly drops through the region. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory from 4 AM to 10 PM EST Wednesday for LHZ441>443. Small Craft Advisory until 10 PM EST Wednesday for LHZ421-422. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC DISCUSSION...KK MARINE.......KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.