


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
42
43
790 FXUS63 KDTX 080353 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1153 PM EDT Mon Jul 7 2025 .KEY MESSAGES... - Dry and seasonable conditions Tuesday. - Shower and thunderstorm potential returns Tuesday evening and Wednesday with temperatures trending toward normal. - Severe weather is not anticipated with the mid-week activity. && .AVIATION... VFR consists of thin cirrus streamers or clear sky as high pressure builds in from the Midwest late tonight. The inbound air mass is cooler and less humid, however radiational cooling is potentially in reach of surface Td stalling the mid to upper 50s by sunrise. This makes a few hours of light/shallow MVFR fog possible toward sunrise that quickly dissipates in early July morning sun. Clear sky or mixed mid and high clouds during the morning transition to cumulus development in the afternoon. These clouds result from warmer and more humid air returning on SW wind as high pressure slides eastward through Tuesday evening. A stray shower becomes possible later in the evening and mainly north of the DTW corridor. For DTW/D21 Convection... Thunderstorms are not forecast tonight and Tuesday. THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 355 PM EDT Mon Jul 7 2025 DISCUSSION... Cyclonic flow lingers behind the surface trough this afternoon, generating mostly cloudy skies over SE Michigan. Despite isentropic downglide aloft and early July daytime heating, cooler northerly flow off of Lake Michigan and Lake Huron has delayed the erosion of this cloud deck compared to model solutions. That said, a scattering trend is noted in GOES-16 visible satellite imagery off to the west which will continue through the evening to support clearing skies. Cold advection has brought H8 temperatures down to 12 to 13 C across the cwa, which in combination with the stratus deck this morning has generally capped temperatures in the upper 60s to low 70s. The thermal trough slides overhead tonight, marking today as the coolest day of the week. Weakening high pressure then briefly fills in Tuesday morning, although SE Michigan remains in the basal portion of the upper level trough. Clearly defined circulation on WV imagery located in SE Saskatchewan reflects a closed 925-700mb low that will track into Lake Superior Tuesday afternoon, occluding in the process. As the system negatively tilts, this sends a warm front into lower Michigan Tuesday evening with the warm sector destabilizing profiles enough to trigger scattered convection as the pre-frontal trough tracks through. Ascent will be reinforced in the background by broad height falls and low level moist isentropic ascent. MUCAPE values are not all that impressive, under 500 J/kg per the SPC HREF, with mid level lapse rates around 5.5 C/km. For any thunderstorms that do develop, storm organization will be minimal as mid-level flow holds below 30 knots. So generally looking at ordinary summertime convection that lingers into the overnight hours. The low will slowly drift east on Wednesday, with the atmosphere eventually becoming capped in the mid-levels as the dry slot streams in overhead. Although the general trend will be towards column stability, the speed at which this occurs is still in question and will be a deciding factor for whether additional thunderstorms are possible Wednesday afternoon. The NBM gridded forecast latches on to the slower solutions which do not bring in the dry slot until Wednesday night, leaving the door open for additional convection Wednesday afternoon in the leftover cyclonic flow. Drier conditions are then anticipated Thursday and Friday with mid-level heights amplifying across the region. Column thickness remains relatively consistent through the period, keeping temperatures right around normal in the mid-80s through the work week. Any fluctations will be the result of diabatic influences like cloud cover and/or convection. Unsettled conditions then arrive this weekend as a Pacific wave pivots across central CONUS. MARINE... Axis of remaining showers (and infrequent lightning) will continue to drift further east across Lake Erie through the early evening hours as high pressure delivers continental Canadian air via northerly gradient flow. Latest observations show afternoon speeds are rather light, generally AOB 10 knots with sub-20 knot gusts. Winds decrease further overnight, becoming more variable into Tuesday as the surface pressure field trends more diffuse. Favorable marine conditions are expected through Tuesday evening before the next low pressure system drags a cold front across Lower Michigan. Winds then organize out of the ESE, ahead of the surface low, with a tightening gradient. Expect a period of showers and thunderstorms within a pre-frontal warm sector for the southern waterways and activity along the cold front further north, moreso for Lake Huron. Ambient dynamics are rather weak which should keep prevailing conditions below Small Craft Advisory criteria, but locally higher winds/waves are possible with some stronger storms. Additional isolated to scattered convection is possible Thursday, particularly south of Lake Huron. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....BT DISCUSSION...MV MARINE.......KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.