Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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824 FXUS63 KDTX 060936 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 536 AM EDT Sun Oct 6 2024 .KEY MESSAGES... - Low chance less than 40% for a shower or thunderstorm this morning across the Tri-Cities and northern Thumb. Low chance (<20%) for a shower for locations south by the mid to late morning hours. - Breezy conditions starting this morning, ramping up through the afternoon. Sustained winds of 20 mph, with gusts around 30 mph, sporadic up to 35 mph. - Dry through the middle of the week with temperatures slightly below normal. && .AVIATION... VFR conditions hold across the area this morning as pre-frontal cloud cover crosses. Some near MVFR possible in the far north over MBS but should vacate within the first hour or two of the new forecast period. Main aviation impact today is stronger winds both pre and post frontal. South-southwest winds this morning peak in the 20-25kt range as the backedge of the overnight LLJ begins to shift east. Cold front then crosses late morning-early afternoon setting up westerly flow in its wake. Efficient mixing particularly as skies clear will allow gusts up around 25kts with some near 30kts possible particularly toward FNT/MBS. Winds gradually weaken tonight as surface high pressure starts to become established. For DTW/D21 Convection... No convection is expected with the front. Stronger westerly winds behind the front expected to hover right around crosswind thresholds this afternoon-early evening. For now, have kept the forecast just below the threshold however any overachieve would reach or exceed that mark. DTW THRESHOLD PROBABILITIES... * Low for a period of ceilings at or below 5000 feet this morning. * Moderate for crosswind thresholds (~270-280deg) this afternoon into early evening. && .PREV DISCUSSION... Issued at 335 AM EDT Sun Oct 6 2024 DISCUSSION... Dynamic upper level trough complex with H5 heights of 540 dam over northern Ontario will rapidly dig through Southeast Michigan this morning. Orientation of the trough axis will result in the main height fall region to extend well southeast of the low pressure center. The net result will keep any chances for shower and thunderstorm activity brief as it flashes across rapidly this morning. Strong prefrontal warm advection is now taking aim over eastern Lower Michigan through 15Z this morning. Main items through midday will be the potential for gusty winds south winds of 20 to 30 mph and a very low chance for showers and thunderstorms invof Saginaw Bay and the northern Thumb. Aforementioned warm advection centered in the 800-700mb layer will introduce steep midlevel lapse rates momentarily, but the significant limiting factor for convection will be very dry air and a lack of moistening. Any convective updrafts that develop this far southward are expected to be elevated with bases at 9.0-10.0 kft agl. Look of the forecast soundings suggests a very transient and short-lived convective updraft potential due to narrow cape densities aloft. Latest regional radar mosaic is lacking with activity and the latest Day 1 SPC outlook has portions of Southeast Michigan designated as General Thunderstorm. Low level thermal progs suggest a disjointed cold front structure with initial cold advection occurring between 14-17Z, then stronger secondary cold advection 21-03Z this evening. This really plays out in the forecast wind directions today with prevailing due west winds this afternoon, turning to the northwest tonight. High mixing heights are modeled at upwards of 6.0 kft agl yielding high temperatures in the middle to upper 70s. Based on the latest trends of hiresolution models did increase land based wind gusts this afternoon into the 30 to 35 mph range. Strong upper level low pressure to the north of the Great Lakes will lead to northwest flow conditions during the early weak period. Forecasted MSLP charts keep the center of surface high pressure to the southwest of the state through at least early Wednesday. There are as many as 3 substantial lobes of absolute vorticity that are forecasted to swing across Southeast Michigan. Low chances for lake effect shower activity will exist across the northern cwa particularly in the Thumb. Will continue to monitor PoP trends as the current northwest flow trajectory is traditionally unfavorable due to downsloping. Surface high pressure and dampening ridge aloft will finally build across the state during the middle to end of the week. Temperatures are forecasted to run approximately 5 to 10 degrees below normal. From this vantage point, frost looks like a good likelihood for some areas Wednesday and Thursday mornings. MARINE... A Gale Warning is in effect for most of Lake Huron this morning. A rapid increase in gust potential is expected toward daybreak as the front sweeps through the region, with wind gusts peaking at 40 to 45 knots. This will be combined with remnant shower and thunderstorm activity that developed over northern Wisconsin last night. Wind direction will veer quickly to the NW as the front passes through, and will diminish through the afternoon which allows the Gale Warning to expire. That said, a weakening wrap around low level jet and cold advection will ramp up wind gusts again to 30 knots over northern Lake Huron. Forecast guidance continues to fall just short of another round of widespread gales (frequent gusts of 30-33 knots), which is reasonable considering the quick dissipation of the jet over western Lake Superior and Lake Michigan this afternoon. Nonetheless, will need to closely monitor observations through the morning for a potential extension or reissuance of the Gale Warning across northern Lake Huron for Sun night-Mon morning. Upper level troughing persists into early next week which will maintain unsettled conditions. FIRE WEATHER... There is an elevated concern for fire weather over most of Southeast Michigan this afternoon. Strong west winds are expected to develop this afternoon behind a cold front with sustained values near 20 mph and peak wind gusts reaching/exceeding 30 mph. Minimum RH values this afternon are expected to range in the upper 20s to lower 30s percent range. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ443. Gale Warning until 10 AM EDT this morning for LHZ361>363-421-422- 441-442-462-463. Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444. && $$ AVIATION.....KDK DISCUSSION...CB MARINE.......MV FIRE WX......KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.