Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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549 FXUS63 KDTX 141944 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 344 PM EDT Wed Aug 14 2024 .KEY MESSAGES... * Dry weather hold through tonight with lows falling to around 60. * Increasing cloud cover and shower potential arrives Thursday evening and lingers through the weekend. * Chance of thunderstorms Friday and Friday night. && .DISCUSSION... Sunny and dry today under the center of a large area of high pressure. A few diurnally drive cu developed this afternoon which should scour out quickly this evening with the subsidence in place. Upper level ridge axis will remain just to the west tonight before drifting east through the first part of the day Thursday. This will mark the beginning of the moisture advection and more active stretch of weather that will carry through the weekend. A low amplitude jet stretched from northern California eastward to Illinois will direct several shortwaves toward the area while steadily deepening the mid level trough already taking shape exiting the northern Rockies. The low will strengthen further over the northern Plains Thursday while drawing in moisture from the deep south. The leading warm advection arm of the system will lift across the area Thursday afternoon bringing the first round of precip chances. There`s really no instability to speak of but a band of showers is expected to move into the area. The increasing high clouds tonight and early Thursday will help mute temps a bit but highs should still make it into the 80s. Thursday night we do get a little elevated instability (couple hundred J/kg) to work with while the next spoke of PV rotates around the low through the area. In addition mid level deformation and the left exit region of the jet slide through so expectations are for continued showers and embedded thunderstorms overnight into the morning. The upper low and attendant surface low will be positioned over the western U.P. but a secondary low is expected to develop over southern MI which will pass over SE MI Friday afternoon. We briefly get warm sectored by this low during peak afternoon heating while still under the left exit region of the jet with deformation aloft. Early model solutions advect in between 1500-2000 J/kg of MUCAPE with around 30 knots of bulk shear so organized storms will be possible. Mid level lapse rates aren`t the greatest due to the wealth of moisture in the column once again with PWATs around 1.75" but CAPE and shear with the surface low and cold front should be sufficient for good coverage of storms. SPC currently has us in a Day 3 Marginal Risk for severe chances. We are also in a Marginal Risk for Excessive Rainfall due to the ample moisture and multiple round of storms/showers possible. Shower and thunderstorm chances continue through the weekend as the upper low slowly passes over the Great Lakes sending several additional troughs through the region. 850mb temps will hover around 13C in the thermal trough with ample clouds and showers so high temps are expected to hold in the 70s. && .MARINE... Light and variable winds persist through tonight as a high pressure center passes directly overhead. A more organized southeast flow pattern then emerges on Thursday ahead of the next low pressure system which will impact the Great Lakes Thursday night through the weekend. Initial indications of the low arrive Thursday evening with an uptick in rain shower activity and cloudiness, but the main precipitation window occurs Friday and Friday night with the arrival of the low`s frontal boundaries and warm sector. Warm sector instability on Friday will be supportive of organized thunderstorm potential. Aside from the precipitation, wind gusts may approach Small Craft Advisory thresholds late Thursday night through Friday amidst a nocturnal uptick in the low level jet. Cooler, showery conditions continue through the weekend although wind and wave potential looks to subside. && .PREV DISCUSSION... Issued at 1238 PM EDT Wed Aug 14 2024 AVIATION... A large high pressure system centered over Lower Michigan today will slowly drift into the eastern Great Lakes by Thursday afternoon. Very dry and stable conditions associated with this system will limit cloud cover to just FEW to SCT high based afternoon cumulus, focused mainly along lake breeze convergence zones. Winds will also remain light given the weak sfc gradient. 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...DRK MARINE.......MV AVIATION.....SC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.