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Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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478 FXUS63 KDTX 121954 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 354 PM EDT Mon Aug 12 2024 .KEY MESSAGES... - Seasonable temperatures early this week. - Isolated showers are possible south of I-96 this evening. - Mainly dry Tuesday with perhaps an isolated afternoon shower. - A bit warmer Wednesday and Thursday with dry conditions. - Rain chances increase Friday and through the weekend. && .DISCUSSION... Vicinity upper low/trough currently located over southern Quebec dislodges and gets absorbed into a jet streak over The Northeast while central CONUS ridge amplification gets underway. Prevailing geopotential heights remain relatively static over the next 24 hours with H5 heights hovering near 579 dam, but perturbed flow rounding the crest of the ridge rolls across southern Lower Michigan and into the Ohio Valley this evening. This offers a period of weak CVA, although the tendency for ascent will be rather fruitless given the absence of meaningful ThetaE convergence into the region. GOES imagery has highlighted a healthy diurnal cumulus response along/south of I-96, along with some very minor and sporadic radar returns per KDTX reflectivity. Opted to maintain Slight Chance (15%) PoPs through this evening with a reduction in northward extent. Added mention of patchy fog early Tuesday morning as dewpoints approach air temperatures, especially if nocturnal clouds are less prevalent. Slight eastward progress by the aforementioned ridge results in stronger low-level stability Tuesday with negligible changes to moisture distribution. A very slight uptick in dewpoints will be offset by slightly warmer temperatures while forecast soundings also suggest warm mid-levels limit CAPE density to the lowest few thousand feet (similar to today). 12.12Z HREF mean SBCAPE tomorrow afternoon is actually lower than today`s, and given the poor convective response thus-far today, did remove PoPs for Tuesday afternoon. Main caveat regarding rain chances will be impacted by a marginally higher possibility for a lake breeze response which could facilitate some convective updrafts along the boundary. Warming continues Wednesday as the ridge rolls across the Upper Midwest. The hottest weather will reside much further west, into the Plains, but with H8 temps expected to rise into the mid-teens, highs will trend above normal Wednesday, in the low-mid 80s. Subsidence maximizes Thursday morning with another day of mainly dry weather as the ridge axis briefly bisects Michigan containing similar thermodynamics. Shortwave trough arrives on the heels of the departing ridge (and ahead of the next ridge getting shoved across the Intermountain West) by Friday yielding the next opportunity for more widespread precipitation. Potent Gulf moisture feed combines with a well-develop low and seasonably strong LLJ dynamics leading to several periods of showers and perhaps some thunderstorms. The system looks to occlude over southwest Lower by Saturday and stall out through at least the first half of the weekend while grinding out additional showers. && .MARINE... Broad but weak area of high pressure becomes fully established across the central Great Lakes by this evening maintaining favorable marine weather through midweek. With the high centered roughly directly overhead through daytime Wednesday, winds hold mainly light (less than 10kts) and variable. Pattern change doesn`t look to arrive until Thursday when low pressure ejects out of the upper Midwest into the Great Lakes. This system brings the next chances for showers/storms and moderate (~15-20kt) southeast winds to close out the week. && .PREV DISCUSSION... Issued at 1247 PM EDT Mon Aug 12 2024 AVIATION... SE Mi remains on the eastern fringe of broad Midwest high pressure this afternoon. Cooler air still over the region gets a boost from a mid level wave and daytime heating for production of VFR cumulus. An isolated shower is also possible nearby the terminal corridor but with low predictability for any specific location. High pressure then builds more strongly overhead tonight and Tuesday. A brief period of ground fog is possible around sunrise leading up to another round of afternoon VFR instability cumulus. For DTW/D21 Convection... The weather pattern does not support thunderstorms today through Tuesday. DTW THRESHOLD PROBABILITIES... * Low for cigs at or below 5000 ft this afternoon and evening. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...KGK MARINE.......KDK AVIATION.....BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.