376
FXUS63 KDTX 242326
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
726 PM EDT Tue Sep 24 2024

.KEY MESSAGES...

- Scattered thunderstorms are expected this evening. There is an
isolated risk of severe storms along/south of an Ann Arbor to
Detroit line.

- There is a low chance for showers Wednesday, with dry weather
forecast Thursday and Friday.

- Daytime highs will mainly be in the 70s for the rest of the week.

&&

.AVIATION...

Low pressure will track from southwest Lower Michigan this evening to
the central Lake Huron basin by Wednesday morning. Low to midlevel
thetae content will quickly lift northward through Metro Detroit
during the first 3 hours of the taf period along a warm front before
stalling and stretching out north of I 69 late tonight. Convective
trends have weakened but will continue to call for a TEMPO group of
tsra at the beginning of the taf period out of respect for the warm
frontal forcing. A lack of an organized cold front and dry air
advection will keep the low levels saturated overnight. The forecast
remains fairly pessimistic for IFR and LIFR conditions in lower
ceiling heights the latter half of tonight. Daytime heating will
bolster MVFR ceilings Wednesday before a cold front and
northwesterly flow clears things out Wednesday evening.

For DTW/D21 Convection...TSRA still remains possible the first 2
hours of the taf period.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 feet tonight.

* Medium for thunder to 02z.

* Low for ceiling below 200 feet overnight from 08 to 12z.

&&

.PREV DISCUSSION...
Issued at 259 PM EDT Tue Sep 24 2024

DISCUSSION...

A mid level short wave and associated sfc low will lift northward
across Lower Mi tonight. This short wave is ejecting away from the
ongoing development of a closed mid level low over the Mid
Mississippi Valley. Respectable moisture transport/isentropic ascent
combined with the northward advection of instability will support
numerous showers and scattered thunderstorms this evening. The
associated sfc warm front is forecast to lift into Se Mi this
evening. ML CAPE values of 500 to 1000 J/kg are forecast to lift
into the I-94 corridor and points south this evening. This combined
with modest deep layer shear and at least a short period of good low
level cyclonic curvature on the hodograph suggests some mini
supercells are possible this evening, mainly in the south.

While the upper low meanders across the Mid MS and TN Valleys on
Wednesday, northern stream trough amplification will evolve into
another closed mid level low to the northeast of Lake Huron by
Wednesday night. Lingering low level moisture and sfc troughing
overhead Wednesday combined with weak larger scale ascent via the
northern stream trough will support a low chance for light showers.
Diurnal heating support afternoon highs into the upper 60s to low
70s. Mid level subsidence and sfc high pressure will then expand
across Lower Mi from the west Wed afternoon and evening and will
usher in a much drier airmass. Mid level ridging and sfc high
pressure will then hold across the Great Lakes region through the
end of the work week. Despite the north-northeast flow, the airmass
will not be very cold. Diurnal heating should allow highs to be in
the 70s while the dry air will promote nighttime lows down into the
40s and 50s.

The upper low meandering over the TN valley and the remnants of
Helene lifting inland from the Gulf Coast is forecast to
interact/phase by the weekend. There is ample ensemble spread with
respect to how quickly this system drifts northward toward the Great
Lakes. Some members even struggle to bring the moisture into Se Mi
in light of the strong ridging over the northern lakes. At this
stage in the forecast, a chance of showers will be maintained
through the weekend.

MARINE...

Low pressure over southern Lake Michigan this afternoon will
continue to track northeast, moving through central Lake Huron
tonight. Mainly light winds in and around the low, but both
waterspouts and thunderstorms are possible with the cyclonic low
level flow and instability through tonight. Behind the low on
Wednesday, northwest winds still look to be mostly light, but
locations over northern Lake Huron look to briefly top out in the 20-
25 knot range. Winds then dropping at or below 15 knots Wednesday
night into Thursday as high pressure builds back into the region.
Winds becoming northeast to end the work week as the high moves off
into Eastern Canada and low pressure lifts north out of the
Southeastern United States. The pressure gradient will be tightest
over Lake Erie, and gusts of 25 to 30 knots appear likely Friday-
Saturday morning.

&&

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

$$

AVIATION.....CB
DISCUSSION...SC
MARINE.......SF


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.