842
FXUS63 KDTX 171901
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
301 PM EDT Sat Aug 17 2024

.KEY MESSAGES...

* Occasional Showers and Scattered thunderstorms will persist
  through the end of the weekend.

* Dry and seasonally cool weather can be expected Monday into the
  middle of next week.

&&

.DISCUSSION...

The upper low now centered over north central Lower Michigan will
rotate across southern Lake Huron tonight, then drift acros across
Ontario on Sunday. There will be an overall decrease in the coverage
of showers/thunderstorms during the evening will the loss in daytime
heating. The exception will be across the Saginaw Valley and thumb
region where short energy pivoting around the low may sustain better
shower coverage into the night. Ample cloud cover with dewpoints in
the 60s will keep min temps in the mid to upper 60s tonight. There
is respectable agreement among the high res solutions suggesting mid
level short wave features pivoting around the back side of the upper
low will support additonal rounds of showers and scattered
thunderstorms across the thumb region into Port Huron on Sunday.
Deep layer moisture and cyclonic flow across Se Mi will allow
another uptic in showers/thunderstorms across the rest of the
forecast area Sunday afternoon during the peak in the diurnal cycle.
Thunderstorm chances will be higher along/south of the I-94 corridor
where 0-1km ML CAPE is forecast to peak at 1000 J/kg. The cloud
cover and afternoon convective potential will suppress daytime highs
to the 70s.

Increasing northerly flow and mid level subsidence in the wake of
the retreating upper low and associated sfc low will drive much
drier air across Se Mi Sunday night. Despite clearing skies and
respectable low level cold air advection, the increasing gradient
flow will hold nighttime lows in the 50s. 850mb temps down into the
single digits on Monday will allow a respectable growth of the
daytime mixed layer. Moisture flux off Lake HUron will support a
shallow moist layer which will warrant a healthy afternoon cu field.
20 to 25 knots throughout the mixed layer will lead to a rather
breezy day. The airmass will support seasonaly cool daytime highs
ranging from the upper 60s to lower 70s on Monday. Long wave
amplification early next week will feature a building ridge across
the Upper Midwest and troughing/mid level low across eastern Canada
and New England. A strong low level anticyclone/sfc high will reside
across the Great Lakes within this pattern, keep dry conditions with
seasonally cool temperatures through most of the week.

&&

.MARINE...

Numerous showers and thunderstorms are ongoing across all waterways
at issuance, with similar coverage expected to carry into the
evening. Activity will wane overnight at the nocturnal minimum, but
is expected to flare up again on Sunday in similar fashion. All of
this is related to an upper low that is currently passing over
northern lower Michigan. Passage of this low has already shifted
winds in some locations to the NW, with uniform northerly flow
developing across all waterways tonight. This flow regime aligns
directly along the long axis of Lake Huron and will cause in uptick
in winds (25-30 knots) and waves (6-8 feet) from Sunday afternoon
through early Tuesday morning. Small Craft Advisories have been
issued as a result. The upper low will gradually vacate into Ontario
early next week, followed by high pressure which will ensure a
quieter mid-week period for the Great Lakes.

&&

.PREV DISCUSSION...
Issued at 100 PM EDT Sat Aug 17 2024

AVIATION...

Closed circulation centered over northern Lower Michigan is driving
shower development with isolated thunderstorms across much of
Southeast Michigan. There will be a few opportunities for showers at
each terminal through afternoon in the early evening. Only the most
vigorous updrafts will be able to produce lightning - and very
limited capability at that. Generally MFVR cloud conditions will
persist through the forecast period with occasional IFR conditions
with the rainfall activity. West/southwest flow will slowly veer to
northwest as the low slowly lumbers to the east overnight.
Additional shower activity is possible again Sunday.

For DTW/D21 Convection...There continues to be a slight chance for
thunderstorms this afternoon, mainly expect SCT-BKN coverage showers.

DTW THRESHOLD PROBABILITIES...

*  Low for thunderstorms this afternoon.

*  High for cigs at or below 5000 ft today, tonight, and Sunday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 10 AM Sunday to 4 AM EDT Tuesday for
     LHZ421-441.

     Small Craft Advisory from 4 PM Sunday to 4 AM EDT Tuesday for
     LHZ442-443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

DISCUSSION...SC
MARINE.......MV
AVIATION.....Mann


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