Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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666 FXUS63 KDTX 221942 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 342 PM EDT Sat Jun 22 2024 .KEY MESSAGES... - Flood watch this afternoon-tonight for Midland/Bay/Saginaw counties. - Slight risk of severe thunderstorms this afternoon into tonight over much of southeast Michigan, with damaging winds being the main hazard, but isolated tornadoes also possible. - Hot and humid today with high temperatures in the 90-95 range south of I-69 with heat indices peaking out just under 100 degrees this afternoon. && .DISCUSSION... Severe potential has yet to be realized so far today, but showers and storms still on the way. Hi-res guidance now suggests that the best chances for storms are this evening from 22-02Z. Limited availability of instability continues to be a problem for updraft development, and peak available SBCAPE reaches just over 1000 J/kg in the Thumb. Wind damage is the main threat with this system, and DCAPE values range from 500-1000 J/kg where rain is expected. Bulk shear values of 30-40 knots are currently in place, so if an updraft can develop, it is possible to see a severe storm develop still. Severe hail looks unlikely, but given the combination of 0-1km shear of 20 knots, LCL heights below 1000 mAGL, and long hodograph lengths at the lower levels mean that an isolated tornado cannot be ruled out. Further showers may develop along the stationary front beyond 02Z, which looks to impact Midland and Bay counties but will dependent on how far north the front propagates. Frontal passage brings chances for showers to the entire CWA, but there has been an increasing signal for banding along the front to break apart after sunset. Flood watch remains in effect through 6am tomorrow for Midland, Bay, and Saginaw counties. MRMS analysis has suggested that ~0.25" or less has fallen so far over Midland and Bay counties. PWATs over 2 inches still suggest potential, and if isolated showers still develop, localized downpours can still produce flooding. Ensemble means suggest 0.5" of rain will fall in total, while the latest HREF guidance suggests 0.75-1". Forecasted storm total QPF remains between 1-1.5" in the flood watch due to the aforementioned isolated shower potential and that these totals can occur in a short amount of time. WPC has issued a Marginal Risk for excessive rainfall for this area. As the low pressure moves out early this morning, colder air advection allows overnight temperatures to dip down into the low 60s. Trough axis passes overhead on Monday and weak ridge builds in behind. Setup allows for warm, moist air to return to the region and produce similar 90 over 70 temperature and dew points to toady`s current conditions. Shortwave disturbance is set to move into the region on Tuesday evening ahead of a larger trough on Wednesday. Chances for showers and storms return with this system Wednesday, and a cold front is set to track across the region. High pressure and cool, dry air fills in behind the front and brings high temperatures back down into the low to mid 80s on Thursday and Friday. ThetaE gradient across the front is around 20 degrees K, helping drop dew points down into the 50s. Zonal flow aloft keeps calm conditions before the next system is set to move in over the weekend. && .MARINE... A stalled front will linger across northern Lake Huron the rest of today into tonight with a developing low pressure system over the Midwest tracking along it tonight. This will keep a showers and thunderstorms going across that area through that time as well. This low will then pull a cold front through the region Sunday morning into the afternoon with a secondary low possibly developing along it Sunday afternoon which would track across southern Lake Huron. Increased southwest winds ahead of the front will increase to around 25 knots later tonight thus a Small Craft Advisory has been issued. Winds will become more northwesterly Monday behind the passing system and possible secondary cold front early Monday morning. After that high pressure will quickly build back into the region keeping winds minimized to start the new week. && .PREV DISCUSSION... Issued at 122 PM EDT Sat Jun 22 2024 AVIATION... Stalled frontal boundary has begun to lift north of the area early this afternoon leading to resultant convection likewise occuring north of the terminal corridor. Additional development over central MI is expected through the afternoon with MBS having the greatest chance to see scattered storms. Opted to keep the FNT Prob30 group as confidence is not high enough to make a change either direction (ie tempo or total removal) though trimmed the window given latest radar and model trends. Areas south still expected to remain dry through the daylight hours before the cold front crosses overnight. A decaying line of showers/storms looks favored late evening through overnight, though given the strength of the front, still worthy of tempo TSRA mentions for all sites. MVFR ceilings follow as cooler air filters in with a lift to lower VFR likely during the day Sunday. For DTW/D21 Convection... Showers and thunderstorms track north of D21 this afternoon and this evening. A cold front then generates storms as it sweeps NW to SE across Lower MI late tonight into Sunday morning. DTW THRESHOLD PROBABILITIES... * Moderate for thunderstorms late tonight and early Sunday. * Moderate to high for ceilings aob 5kft Sunday morning. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Flood Watch through late tonight for MIZ047-048-053. Lake Huron...Small Craft Advisory from midnight tonight to 10 AM EDT Sunday for LHZ421-422. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...BC MARINE.......DRK AVIATION.....KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.