040
FXUS63 KDTX 131859
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
259 PM EDT Tue Aug 13 2024

.KEY MESSAGES...

- Stretch of dry and seasonable weather conditions expected
  Wednesday as daytime highs approach the mid 80s.

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

- Chance of thunderstorms Friday and Friday night.

&&

.DISCUSSION...

Dry and seasonable stretch of summer weather has continued again
today, even in the presence of a shearing mid-level shortwave
overhead. Only evidence of this wave in visible imagery has been a
narrow cloud band extending from roughly Alpena to Erie, PA and a
more agitated cumulus field around the Detroit metro area. Minimal
amount of CAPE (less than a hundred J/kg) concentrated at the top of
the boundary layer may be enough to squeeze out an isolated shower
along the lake breeze, but otherwise expecting a dry evening.

This diurnal cloud response will wane tonight while the departure of
the wave reinforces the present subsidence inversion, supporting
generally clear skies overnight. This sets up favorable radiational
cooling conditions, which will allow overnight lows to drop below 60
degrees in all but urban areas. Considering current dewpoints in the
mid 50s, cross-over temperatures will be within reach to support
shallow/patchy radiation fog across the area Wednesday morning.

CONUS-wide satellite perspective shows the more expansive cloud
cover is still well to our southwest, in association with a stalled
deformation axis at the junction of two distinct anticyclonic
circulations. The northern anticyclone is currently over MN, but
will drift eastward across northern Lower MI on Wednesday, ensuring
one more day of plentiful sunshine and dry weather. Main difference
between today and Wednesday will be a modest warm up owing to a
deeper subsidence response. This contributes to both adiabatic
warming and less cloud cover, boosting daytime highs a few degrees
toward the mid 80s.

Meanwhile, will start to see a breakdown in the western periphery of
the ridge as a series of weak shortwaves blossom into a closed low
over the northern Plains by Wednesday night. This will instigate the
next pattern shift with cloud cover and rain chances increasing by
Thursday evening. Initial theta-e advection will be strong, with
PWAT values forecast to increase by over an inch between Thursday
night and Friday. While the low itself will be vertically stacked
and occluding over the western Great Lakes, this should position SE
Michigan favorably within the warm sector Friday and Friday night.
Nearly all members of the GEFS/EPS/CMCE ensemble suites predict some
degree of instability on Friday, which is not surprising as mid
level lapse rates approach 6 C/km in the deterministic guidance and
dewpoints near 70 degrees. The main uncertainty will be thunderstorm
organization, which will depend on several factors including the
timing and positioning of the frontal boundaries. Friday-Friday
night will thus be a period to monitor for organized thunderstorm
potential.

The upper low lingers over the Great Lakes through the weekend,
sustaining low level moisture overhead and a cooler tongue of
Canadian air through early next week. This equates to daytime highs
in the 70s and at least intervals of showery and cloudy conditions.

&&

.MARINE...

High pressure remains centered over the region through Wednesday
maintaining light and variable winds. This changes by Thursday as
the high is shunted eastward by approaching upper Midwest low
pressure. Southeast winds strengthen in advance of this system with
peak gusts between 20-25kts developing overnight Thursday in Friday.
Shower and storm chances overspread the central lakes during this
timeframe as well. Low slowly moves over the Great Lakes through
this weekend leading to lingering rain chances and modest (10-20kt)
winds that shift to northwesterly by late Saturday.

&&

.PREV DISCUSSION...
Issued at 1224 PM EDT Tue Aug 13 2024

AVIATION...

Light winds will prevail through the TAF period as high pressure
will remain centered over the region. The high based SCT to BKN Cu
field will decrease this evening with the loss in diurnal heating.
Enhanced convergence along lake breeze boundaries will support a
slight chance of an isolated shower around metro Detroit early this
evening. Shallow boundary layer moisture under clear skies and light
winds tonight will support the chance for some radiational fog
development towarad early morning Wednesday.

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...MV
MARINE.......KDK
AVIATION.....SC


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at www.weather.gov/detroit.