828
FXUS63 KDTX 222259
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
559 PM EST Fri Nov 22 2024

.KEY MESSAGES...

- Dry weather returns for the weekend as weak high pressure builds
in. Lingering cloud cover will be difficult to dislodge however.

- Another low looking to develop over the region Monday bringing
additional rain chances and brief shot at milder air.

- Confidence is increasing in several days of below normal
temperatures Tuesday through next weekend.

&&

.AVIATION...

Low level cyclonic flow and ample moisture has resulted in an
extensive stratus deck across the entire Great Lakes region. This
cyclonic flow will weaken during the day Saturday, while the low
level flow slowly backs toward the west. However, a deepening
subsidence inversion is likely to hold stratus in place through the
TAF period. Ceilings have trended above 2k feet this afternoon.
Current observational trends and some of the 18Z model guidance has
also trended toward higher probabilities of ceilings holding in the
2-3k foot range through the night. For this reason, a persistence
forecast will be warranted through the TAF period with just some
subtle weakening of the sfc winds as the gradient slowly relaxes.

DTW THRESHOLD PROBABILITIES...

*  High in ceilings at or below 5000 ft tonight and Saturday.

&&

.PREV DISCUSSION...
Issued at 345 PM EST Fri Nov 22 2024

DISCUSSION...

A closed and vertically stacked low has drifted over New England
while slowly drifting northeastward through the weekend. Broad
cyclonic flow will hold over the region tonight into Saturday before
broad low amplitude ridging slides into the central conus and takes
over influencing the weather across the Great Lakes.

Heading into tonight the cyclonic flow and moist boundary layer (up
through 7kft) will keep the region cloud with a blanket of stratus.
The winds over Lake Huron turn more northwesterly tonight which will
end the moisture advection into the Thumb in lieu of drier flow from
northern lower which should help start bringing an end to the
drizzle/light rain thats been prevalent most of the day, but there
does look like one more lobe of vorticity that will pivot around the
upper low while another arm of vorticity on the leading edge of the
ridge pushes through the region which should be enough forcing to
keep some precip around through part of the night.

The leading shortwave ridge ridge should move in enough early
Saturday to result in drier conditions but with models locked in
with low level moisture hanging around, stratus will likely remain
through most of the weekend. Little in the way of thermal advection
and continued cloud cover will result in only subtle temperature
increases Saturday and Sunday.

The longwave ridge axis passes over the area Sunday night which
opens the door for some warm air advection and likely the warmest
temperatures of the week as high reach into the low 50s. This warm up
will be short lived as an active pattern then sets up for the coming
week. A shortwave trough dipping into the Midwest looks to phase to
some degree with a fast moving shortwave racing across the central
Plains Monday. Trough amplification from this interaction will
excite surface cyclogenesis overhead with most models offering rain
chances Monday and Monday night. Though the longwave pattern goes
nearly zonal across the area in the wake of this trough, we look to
fall on the cool side with northwesterly flow ushering in 850mb
temps around -5 to -10C through the latter half of the week
resulting in highs in the 30s. Reinforcement to the trough over the
region will stall and deepen it overhead heading into next weekend.
THis would lead to several days of cold temperatures and wintry
precip with lake effect rain/snow showers possible.

MARINE...

Shoreline observations and buoys continue to report wind gusts
between 30-34 knots from Port Austin to Port Huron and adjacent open
waters. Not expecting much change to the ambient wind field or
instability over the next few hours, so will keep the Gale Warning
going as observations warrant for most locations. The exception to
this is over Saginaw Bay where gusts have held aob 30 knots, so will
convert the Gale Warning to a Small Craft Advisory for the outer
bay. The pressure gradient relaxes gradually tonight and most of the
day Saturday, requiring a transition to Small Craft Advisories for
all zones ahead of quieter conditions Saturday night and Sunday. The
next low pressure system to impact the Great Lakes ejects out of the
Plains early next week. Precipitation will likely stay all rain
early on as the warm front surges low level temperatures well above
freezing for Monday. Cold advection behind this system Tuesday-
Wednesday creates more efficient mixing conditions and gusty
northwest flow just before the Thanksgiving holiday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EST this evening for LHZ422.

     Small Craft Advisory until 4 PM EST Saturday for LHZ421.

     Gale Warning until 7 PM EST this evening for LHZ441>443-462>464.

Lake St Clair...Small Craft Advisory until 10 PM EST this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EST this evening for LEZ444.

&&

$$

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


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