textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry conditions with cool to seasonable temperatures today and Friday; chilly tonight with lows in the upper 30s to lower 40s.

- Much warmer Saturday with temperatures in the upper 70s to around 80 degrees.

- Next significant chance of rain arrives for the second half of the weekend.

DISCUSSION

Latest water vapor imagery clearly shows the upper level trough swinging through the Great Lakes region this morning, modestly amplifying as it moves into New England today. The parent upper level low (539 DAM at 500 MB) over James Bay will slowly track east through Quebec on Friday. This results in cool to seasonable conditions today and Friday before a big warm up occurs on Saturday.

Still looking at 850 MB temps bottoming out at 3 to 4 C tonight. With the center of high pressure over the Ohio Valley, winds may fail to fully decouple, keeping mins elevated in the upper 30s to lower 40s. This is also supported by forecasted surface dew pts holding in that range.

An active warm front over eastern Iowa on Friday, but consensus is is now for the low level jet and instability axis/negative Showalter values to reside northwest of southern Lower Michigan Friday night. Thus, dry forecast generally looks ok, but NBM pops appear to be too low near zero. Trended forecast toward silent 14% pop, as the 3z Rap/00 NAM show concern with for some potential light showers, especially over Tri-Cities region.

Speaking of farther west, warm 20 C 850 MB temps are now progged to track into the Upper Peninsula late Saturday, with 17-18 C progged over southeast Michigan underneath a pronounced upper level ridge axis. With 925 MB temps still advertised at 19 to 20 C per the 00z NAM and surface winds out of the southwest, maxes around 80 degrees still seem likely.

The forecast for the second half of the weekend into Monday will still be determined by what happens to the remnants of the tropical system. Trends suggests the center will reach into the southern Ohio Valley by Sunday evening, before be shunting off to the northeast. This would lead to limited rainfall. However, the forecast can still change based off the track, size, and strength of Hurricane Isaias.

MARINE

Post-frontal airmass in-place across the central Great Lakes features veered west-northwest flow and an uptick in speeds. This stems from an upper level jet positioned over the region and a 25-35 knot low-level below. Stability will decrease with time as diurnal mixing improves to deliver elevated afternoon gustiness. Potential still exists for a period of gusts near 30 knots over portions of Lake Huron this afternoon. Marginal gusts to gales are possible for northern Huron, closer to The Straits, where the low-level jet winds could exceed 35 knots at 3 kft AWL. Lower column winds are expected to hold just below 25 knots, therefore no Small Craft Advisory was issued. If observation trends conflict, a zero lead time product may be needed over The Thumb. Additionally, higher end gusts further north should be infrequent enough to preclude a Gale Warning. Mid/Upper Mississippi Valley high pressure then expands into the area tonight and Friday offering weaker winds with a southerly shift.

PREV DISCUSSION

Issued at 1143 PM EDT Wed Oct 7 2026

AVIATION...

Light winds within a early morning stable boundary layer will give way to modest gustiness (around 20 knots) Thursday afternoon within the onset of daytime mixing. Ample low level dry air courtesy of high pressure across the western Great Lakes will sustain VFR conditions through the TAF period.

D21/DTW Convection...No thunderstorms forecast during the period.

DTW THRESHOLD PROBABILITIES...

* None

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None.