549
FXUS63 KDTX 141944
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
344 PM EDT Wed Aug 14 2024

.KEY MESSAGES...

* Dry weather hold through tonight with lows falling to around 60.

* Increasing cloud cover and shower potential arrives Thursday
  evening and lingers through the weekend.

* Chance of thunderstorms Friday and Friday night.

&&

.DISCUSSION...

Sunny and dry today under the center of a large area of high
pressure. A few diurnally drive cu developed this afternoon which
should scour out quickly this evening with the subsidence in place.
Upper level ridge axis will remain just to the west tonight before
drifting east through the first part of the day Thursday. This will
mark the beginning of the moisture advection and more active stretch
of weather that will carry through the weekend.

A low amplitude jet stretched from northern California eastward to
Illinois will direct several shortwaves toward the area while
steadily deepening the mid level trough already taking shape exiting
the northern Rockies. The low will strengthen further over the
northern Plains Thursday while drawing in moisture from the deep
south. The leading warm advection arm of the system will lift across
the area Thursday afternoon bringing the first round of precip
chances. There`s really no instability to speak of but a band of
showers is expected to move into the area. The increasing high
clouds tonight and early Thursday will help mute temps a bit but
highs should still make it into the 80s. Thursday night we do get a
little elevated instability (couple hundred J/kg) to work with while
the next spoke of PV rotates around the low through the area. In
addition mid level deformation and the left exit region of the jet
slide through so expectations are for continued showers and embedded
thunderstorms overnight into the morning.

The upper low and attendant surface low will be positioned over the
western U.P. but a secondary low is expected to develop over
southern MI  which will pass over SE MI Friday afternoon. We briefly
get warm sectored by this low during peak afternoon heating while
still under the left exit region of the jet with deformation aloft.
Early model solutions advect in between 1500-2000 J/kg of MUCAPE
with around 30 knots of bulk shear so organized storms will be
possible. Mid level lapse rates aren`t the greatest due to the
wealth of moisture in the column once again with PWATs around 1.75"
but CAPE and shear with the surface low and cold front should be
sufficient for good coverage of storms. SPC currently has us in a Day
3 Marginal Risk for severe chances. We are also in a Marginal Risk
for Excessive Rainfall due to the ample moisture and multiple round
of storms/showers possible.

Shower and thunderstorm chances continue through the weekend as the
upper low slowly passes over the Great Lakes sending several
additional troughs through the region. 850mb temps will hover around
13C in the thermal trough with ample clouds and showers so high
temps are expected to hold in the 70s.

&&

.MARINE...

Light and variable winds persist through tonight as a high pressure
center passes directly overhead. A more organized southeast flow
pattern then emerges on Thursday ahead of the next low pressure
system which will impact the Great Lakes Thursday night through the
weekend. Initial indications of the low arrive Thursday evening with
an uptick in rain shower activity and cloudiness, but the main
precipitation window occurs Friday and Friday night with the arrival
of the low`s frontal boundaries and warm sector. Warm sector
instability on Friday will be supportive of organized thunderstorm
potential. Aside from the precipitation, wind gusts may approach
Small Craft Advisory thresholds late Thursday night through Friday
amidst a nocturnal uptick in the low level jet. Cooler, showery
conditions continue through the weekend although wind and wave
potential looks to subside.

&&

.PREV DISCUSSION...
Issued at 1238 PM EDT Wed Aug 14 2024

AVIATION...

A large high pressure system centered over Lower Michigan today will
slowly drift into the eastern Great Lakes by Thursday afternoon.
Very dry and stable conditions associated with this system will
limit cloud cover to just FEW to SCT high based afternoon cumulus,
focused mainly along lake breeze convergence zones. Winds will also
remain light given the weak sfc gradient.

For DTW/D21 Convection...No thunderstorms will occur through the TAF
period.

DTW THRESHOLD PROBABILITIES...

*  None.


&&

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

$$

DISCUSSION...DRK
MARINE.......MV
AVIATION.....SC


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