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Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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040 FXUS63 KDTX 131859 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 259 PM EDT Tue Aug 13 2024 .KEY MESSAGES... - Stretch of dry and seasonable weather conditions expected Wednesday as daytime highs approach the mid 80s. - Increasing cloud cover and shower potential arrives Thursday evening and lingers through the weekend. - Chance of thunderstorms Friday and Friday night. && .DISCUSSION... Dry and seasonable stretch of summer weather has continued again today, even in the presence of a shearing mid-level shortwave overhead. Only evidence of this wave in visible imagery has been a narrow cloud band extending from roughly Alpena to Erie, PA and a more agitated cumulus field around the Detroit metro area. Minimal amount of CAPE (less than a hundred J/kg) concentrated at the top of the boundary layer may be enough to squeeze out an isolated shower along the lake breeze, but otherwise expecting a dry evening. This diurnal cloud response will wane tonight while the departure of the wave reinforces the present subsidence inversion, supporting generally clear skies overnight. This sets up favorable radiational cooling conditions, which will allow overnight lows to drop below 60 degrees in all but urban areas. Considering current dewpoints in the mid 50s, cross-over temperatures will be within reach to support shallow/patchy radiation fog across the area Wednesday morning. CONUS-wide satellite perspective shows the more expansive cloud cover is still well to our southwest, in association with a stalled deformation axis at the junction of two distinct anticyclonic circulations. The northern anticyclone is currently over MN, but will drift eastward across northern Lower MI on Wednesday, ensuring one more day of plentiful sunshine and dry weather. Main difference between today and Wednesday will be a modest warm up owing to a deeper subsidence response. This contributes to both adiabatic warming and less cloud cover, boosting daytime highs a few degrees toward the mid 80s. Meanwhile, will start to see a breakdown in the western periphery of the ridge as a series of weak shortwaves blossom into a closed low over the northern Plains by Wednesday night. This will instigate the next pattern shift with cloud cover and rain chances increasing by Thursday evening. Initial theta-e advection will be strong, with PWAT values forecast to increase by over an inch between Thursday night and Friday. While the low itself will be vertically stacked and occluding over the western Great Lakes, this should position SE Michigan favorably within the warm sector Friday and Friday night. Nearly all members of the GEFS/EPS/CMCE ensemble suites predict some degree of instability on Friday, which is not surprising as mid level lapse rates approach 6 C/km in the deterministic guidance and dewpoints near 70 degrees. The main uncertainty will be thunderstorm organization, which will depend on several factors including the timing and positioning of the frontal boundaries. Friday-Friday night will thus be a period to monitor for organized thunderstorm potential. The upper low lingers over the Great Lakes through the weekend, sustaining low level moisture overhead and a cooler tongue of Canadian air through early next week. This equates to daytime highs in the 70s and at least intervals of showery and cloudy conditions. && .MARINE... High pressure remains centered over the region through Wednesday maintaining light and variable winds. This changes by Thursday as the high is shunted eastward by approaching upper Midwest low pressure. Southeast winds strengthen in advance of this system with peak gusts between 20-25kts developing overnight Thursday in Friday. Shower and storm chances overspread the central lakes during this timeframe as well. Low slowly moves over the Great Lakes through this weekend leading to lingering rain chances and modest (10-20kt) winds that shift to northwesterly by late Saturday. && .PREV DISCUSSION... Issued at 1224 PM EDT Tue Aug 13 2024 AVIATION... Light winds will prevail through the TAF period as high pressure will remain centered over the region. The high based SCT to BKN Cu field will decrease this evening with the loss in diurnal heating. Enhanced convergence along lake breeze boundaries will support a slight chance of an isolated shower around metro Detroit early this evening. Shallow boundary layer moisture under clear skies and light winds tonight will support the chance for some radiational fog development towarad early morning Wednesday. For DTW/D21 Convection...No thunderstorms will occur through the TAF period. DTW THRESHOLD PROBABILITIES... * None. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...MV MARINE.......KDK AVIATION.....SC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.