478
FXUS63 KDTX 121954
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
354 PM EDT Mon Aug 12 2024

.KEY MESSAGES...

- Seasonable temperatures early this week.

- Isolated showers are possible south of I-96 this evening.

- Mainly dry Tuesday with perhaps an isolated afternoon shower.

- A bit warmer Wednesday and Thursday with dry conditions.

- Rain chances increase Friday and through the weekend.

&&

.DISCUSSION...

Vicinity upper low/trough currently located over southern Quebec
dislodges and gets absorbed into a jet streak over The Northeast
while central CONUS ridge amplification gets underway. Prevailing
geopotential heights remain relatively static over the next 24 hours
with H5 heights hovering near 579 dam, but perturbed flow rounding
the crest of the ridge rolls across southern Lower Michigan and into
the Ohio Valley this evening. This offers a period of weak CVA,
although the tendency for ascent will be rather fruitless given the
absence of meaningful ThetaE convergence into the region. GOES
imagery has highlighted a healthy diurnal cumulus response
along/south of I-96, along with some very minor and sporadic radar
returns per KDTX reflectivity. Opted to maintain Slight Chance (15%)
PoPs through this evening with a reduction in northward extent.
Added mention of patchy fog early Tuesday morning as dewpoints
approach air temperatures, especially if nocturnal clouds are less
prevalent.

Slight eastward progress by the aforementioned ridge results in
stronger low-level stability Tuesday with negligible changes to
moisture distribution. A very slight uptick in dewpoints will be
offset by slightly warmer temperatures while forecast soundings also
suggest warm mid-levels limit CAPE density to the lowest few
thousand feet (similar to today). 12.12Z HREF mean SBCAPE tomorrow
afternoon is actually lower than today`s, and given the poor
convective response thus-far today, did remove PoPs for Tuesday
afternoon. Main caveat regarding rain chances will be impacted by a
marginally higher possibility for a lake breeze response which could
facilitate some convective updrafts along the boundary.

Warming continues Wednesday as the ridge rolls across the Upper
Midwest. The hottest weather will reside much further west, into the
Plains, but with H8 temps expected to rise into the mid-teens, highs
will trend above normal Wednesday, in the low-mid 80s. Subsidence
maximizes Thursday morning with another day of mainly dry weather as
the ridge axis briefly bisects Michigan containing similar
thermodynamics. Shortwave trough arrives on the heels of the
departing ridge (and ahead of the next ridge getting shoved across
the Intermountain West) by Friday yielding the next opportunity for
more widespread precipitation. Potent Gulf moisture feed combines
with a well-develop low and seasonably strong LLJ dynamics leading to
several periods of showers and perhaps some thunderstorms. The
system looks to occlude over southwest Lower by Saturday and stall
out through at least the first half of the weekend while grinding
out additional showers.

&&

.MARINE...

Broad but weak area of high pressure becomes fully established
across the central Great Lakes by this evening maintaining favorable
marine weather through midweek. With the high centered roughly
directly overhead through daytime Wednesday, winds hold mainly light
(less than 10kts) and variable. Pattern change doesn`t look to
arrive until Thursday when low pressure ejects out of the upper
Midwest into the Great Lakes. This system brings the next chances
for showers/storms and moderate (~15-20kt) southeast winds to close
out the week.

&&

.PREV DISCUSSION...
Issued at 1247 PM EDT Mon Aug 12 2024

AVIATION...

SE Mi remains on the eastern fringe of broad Midwest high pressure
this afternoon. Cooler air still over the region gets a boost from a
mid level wave and daytime heating for production of VFR cumulus. An
isolated shower is also possible nearby the terminal corridor but
with low predictability for any specific location. High pressure
then builds more strongly overhead tonight and Tuesday. A brief
period of ground fog is possible around sunrise leading up to
another round of afternoon VFR instability cumulus.

For DTW/D21 Convection... The weather pattern does not support
thunderstorms today through Tuesday.

DTW THRESHOLD PROBABILITIES...

*  Low for cigs at or below 5000 ft this afternoon and evening.


&&

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

$$

DISCUSSION...KGK
MARINE.......KDK
AVIATION.....BT


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