


Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
591 FXUS63 KDTX 162001 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 401 PM EDT Thu Oct 16 2025 .KEY MESSAGES... - Warmer air arrives Friday and Saturday with scattered rain showers mainly north of Metro Detroit Friday mid morning. - A strong low pressure system is forecasted to track across the Great Lakes late Saturday to Sunday. It remains highly uncertain what the duration of heavy rainfall activity will be for any one location across Southeast Michigan. Low confidence exists in the forecasted rainfall amounts for this system across all of Southeast Michigan. There is a potential for rainfall amounts to exceed 2.0 inches. && .DISCUSSION... Strong H5 ridge amplification will occur over the central Great Lakes region during the next 24 hours with 580dam heights briefly brushing up against Southeast Michigan. Feature of interest late tonight/early Friday period is a strengthening warm front aloft with an active upright 850-500mb frontogenetic circulation tucked under right entrance region dynamics. Best time window for forcing is 12- 15Z from Midland and Bay counties eastward to Huron County. Low confidence exists in footprint of measurable precipitation with significant amount of dry air in the lowest 6.0 kft agl. Messaging is good with 40-65% chance PoPs after 12Z. Warm air aloft will lead to low mixing heights, highs Friday in the 60s some 5 degrees above normal. First part of Saturday will be influenced by the heart of the upper level ridge and warm sector. The first question for Saturday will be the race between warming daytime temperatures versus the amount and arrival of high cloud to limit any insolation. Current forecast has a respectable temperature gradient forecast across the area with near 70 north to near 80 degrees Detroit southward. High confidence exists that a dynamic Autumn storm system will impact the region, including Southeast Michigan late Saturday through Sunday. Latest deterministic global solutions and ensemble systems support a +140 knot upper level jet and full latitude trough resulting in a powerful cyclogenesis event in proximity of Southeast Michigan. Will state outright that exact sensible weather impacts will be difficult to pinpoint leading up to the event as exact storm track and timing relative to daytime/nocturnal instability environments highly matter. With regards to this particular system, a high amount of uncertainty persists with a large variance amongst the model suite with the phasing, or lack thereof of severe potential vorticity anomalies. For instance, the GFS/ECMWF solutions suggest a two piece double barrel low Saturday and Sunday, whereas the EC-AIFS/GEM solutions suggests one primary surface cyclone lifting invof Detroit Sunday. The potential sensible weather impacts to monitor for this system include: 1. Potential for a line of showers and weak thunderstorms late Saturday afternoon and evening (questionable with the NAM one of the only solutions bullish) with an environment of 500 J/kg MLCAPE and an inverted V sounding. 2. Potential for a long duration, very heavy rainfall axis on a shearing deformation axis Saturday night/Sunday. Cluster analysis with the separate QPF EOFs suggests an overwhelming amount of spread explained by the positioning of the heavy rainfall over Lower Michigan. Some difference continue to exists, primarily with the GFS type solution that ejects two separate pieces of energy/two distinct low solutions. The d(prog)/dt of the ECMWF has been trending away from the more northern/GFS solution towards a more primary low/CMC solution. Regardless, given the magnitude of dynamical support and potential longer duration need to highlight the tails of the ensemble distribution. Current 90th percentiles of the EPS has 2.50 inches of rainfall at all 3 sites, KMBS/KFNT/and KDTW. Monitor future forecasts for expected rainfall amounts. 3. Potential for high winds with this storm system. Too much uncertainty exists in track and character of the low ejection to suggest any precision. Will say based on the EPS data that a period of breezy conditions of 25 mph and greater is expected. Really not seeing much ensemble signal for potential duration of 45 mph greater for the land areas. && .MARINE... A high pressure system now situated over the Great Lakes will wash out across the western Atlantic through the end of the week as a low pressure system moves from the northern Plains into western Ontario. This will strengthen and maintain a moderate pressure gradient over the Great Lakes late tonight into Friday, accelerating the passage of a warm front. The passage of this front will veer wind direction to south-southwest with wind speeds and gust potential picking up shortly thereafter. Sustained winds in excess of 20 knots are expected tomorrow across Lake Huron, with gust potential ranging between 25 to 30 knots. Small Craft Advisories may be needed for portions of the Saginaw Bay and the Lake Huron shoreline. Some showers with embedded thunderstorms will also be possible across Lake Huron Friday morning and afternoon. A second low pressure system is then expected to move over Michigan through Sunday morning and afternoon. There is still uncertainty regarding the exact track of the low pressure which will have big implications on both wind direction and wind speed and gust potential through the day on Sunday. At present time there is somewhat of a bimodal solution space, with solution one favoring a track that moves over northern lower Michigan. This would bring a period of stronger southwest flow across portions of Lake Huron with potential to reach gales, before veering wind direction to the northwest, where gale potential will again be possible. The second solution favors a more southern track into lower Michigan and the Ohio Valley. This will preclude any stronger southwest flow on Sunday morning, but still brings high chances for gales later in the day with the flip to northwest flow. Forecast adjustments are expected leading into the event. && .PREV DISCUSSION... Issued at 126 PM EDT Thu Oct 16 2025 AVIATION... High pressure remains in place over lower MI today promoting VFR skies and light winds. Drier airmass and active subsidence keep any diurnal cu to a minimum with clouds generally confined to transient cirrus. Mid/high cloud fills in late this evening ahead of an approaching elevated warm front. Said front then lifts through the region Friday morning offering a period of `lower` cloud (6-8kft). While some elevated showers are expected with the front, with drier air still in place near-surface, most of these are expected to become virga or only a sprinkle. For now have only added a Prob30 shower mention to MBS which is closest to the main moisture pool. For DTW/D21 Convection... Thunderstorms are not in the forecast for today or tonight. DTW THRESHOLD PROBABILITIES... * None. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...CB MARINE.......AM AVIATION.....KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.