Expert Forecast Opinion

324
FXUS63 KDTX 130402
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1202 AM EDT Mon Jul 13 2026

.KEY MESSAGES...

- Heat builds during the early half of the week with highs in the
90s Monday through Wednesday.

- Peak heat expected Tuesday with highs in the upper 90s and heat
indices near or above 100 degrees.

- Potential for showers and thunderstorms exists late in the week
into next weekend.

&&

.AVIATION...

High pressure will govern the quiet aviation conditions through the
TAF period. This will allow VFR conditions to prevail with limited
cloud cover and light winds. Only some mid-high clouds to speak of
from a decayed thunderstorm complex that moved across northern Lake
Michigan and northern Lower Michigan. Winds will be light and
variable winds through remainder of the night. VFR conditions also
expected to prevail through rest Monday with a developing light W-
SW.

D21/DTW Convection...No thunderstorms are forecast.

.DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 242 PM EDT Sun Jul 12 2026

DISCUSSION...

1023 mb surface high pressure is entrenched overhead this afternoon,
which has led to another day of dry and seasonable mid-July weather
for SE Michigan. Fair weather cumulus is observed extends from the
Thumb into northern OH/IN in the anticyclonic flow pattern, but is
shallow and ultimately expecting a dry and pleasant evening for SE
Michigan.

Instability bubble is still confined to the U.P./Upper Midwest, but
will gradually pivot around the ridge and into Lower MI early Monday
morning. There are some model solutions (the most aggressive being
the HRRR) that initiate convection over central Ontario and send it
south toward the progressing instability plume overnight. Given that
instability is already being worked over by Lake Superior convection
at issuance, do not think this convection will be able to survive
into central/southern MI for very long. Slight chance PoPs however bump
against the northern border of our cwa Monday morning as a result.

Heat begins to build across the state Monday, with the hottest
conditions arriving Tuesday as a 600 dam mid-level ridge stalls over
the Upper Midwest. Downsloping effects over the Saginaw Valley and
metro Detroit (plus urban effects) will lead to a local boost in
highs by a couple of degrees. So while most locations see highs in
the mid-upper 90s, high temperatures in these locations will be
closer to 100. Heat indices remain in the 100-105 range at best
given sub-par moisture quality as dewpoints barely reach 70 degrees
Tuesday, which may require a Heat Advisory. Overnight lows then
remain seasonably warm, in the low-mid 70s through Wednesday
morning. The ridge establishes a strong capping inversion that
limits thunderstorm chances for the first part of the work week.

In contrast to our last heat stretch, this one will be shorter-lived
with the ridge breaking down mid-week and folding into SE CONUS as a
strong low carves into Quebec. This leads to a period of height
falls Wednesday and a flip in column winds from NE to NW, while also
establishing a deformation axis across northeast CONUS/Canada late
in the week. Higher confidence item in this pattern is a drop in
temperatures closer to normal: upper 80s-low 90s by Thursday. Much
lower confidence in thunderstorm chances though, which will depend
on how the deformation axis behaves. Nebulous signal in the ensemble
guidance is due to the variability in individual members, ranging
from aggressive high pressure pushing all moisture/instability into
the Ohio Valley to a surge of return flow/instability into the Great
Lakes for the end of the week. About 15% of ensemble members have no
instability building into the region until next weekend, although
most stall the instability axis north of the state line. To sum it
up, the pattern late week-next weekend is low confidence and
unsettled when it comes to rain/storm chances.

MARINE...

High pressure will continue to hold over most of the Great Lakes
region today and going into the beginning of the week. The one
caveat will be across northern portions of Lake Huron where there
will be a slight chance for showers and storms this evening going
through the overnight hours. Any precipitation will diminish by
early Monday morning and dry conditions will prevail though much of
the week. Lighter northeast winds will continue to be variable as
the high passes overhead this afternoon before becoming more
southerly going through the evening.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....AA
DISCUSSION...MV
MARINE.......SS


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