312
FXUS63 KDTX 191933
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
333 PM EDT Sat Oct 19 2024

.KEY MESSAGES...

- Warming trend will continue into early next week with highs 10 to
  15 degrees above average.

- Dry weather will also continue through at least Tuesday.

&&

.DISCUSSION...

Upper level ridging positioned to the southeast of the region will
maintain dry and mild conditions through the weekend into the first
part of next week. In fact, this ridge is expected to expand a bit
further north through the region during the Monday time frame as
upper heights rise in advance of a southern stream system now cutoff
over the southwest CONUS.

This cutoff upper low pressure system will begin ejecting from the
southwest CONUS Sunday night into Monday as a significant stream of
Pacific shortwave/jet energy sweeps onshore over the Pacific
northwest. This system evolves into an open wave as it crosses the
Great Lakes region Tuesday. No precipitation is expected as the
atmosphere remains very dry from the central portion of the CONUS on
into the Great Lakes during the period this system transits.

The first impulse of the aforementioned Pacific energy bypasses the
region to the north, but subsequent energy sweeps into the area in
the wake of this initial southern stream system by Wednesday. There
is even a suggestion that a portion of the polar jet stream phases
into this belt of westerlies driving the Pacific wave train. This
will lead to an amplifying shortwave as it passes over and then east
and southeast of the region. While there will be some rain chances
with this system, the atmosphere does remain rather dry so no real
impacts are anticipated.

Cooler conditions are anticipated by week`s end after this midweek
system passes with maximum temperatures dropping back into the 50s
area wide. Before that, expect a warming trend into Monday with
maximum temperatures building into the mid 70s by that time with
temperatures then settling back into the upper 60s to around 70
midweek before the cooler late week conditions arrive.

&&

.MARINE...

Composite ridging across the eastern half of CONUS maintains
formidable surface high pressure influence across the central Great
Lakes through Tuesday. This supports light to modest south-southwest
flow and generally benign wave heights. Flow aloft has become more
zonally oriented this afternoon, before the next ridge axis emerges
west of the Mississippi River tomorrow. Increasing confluence within
the low-levels lends potential for gusts to approach 25 knots (and
waves to exceed 4 feet) over Saginaw Bay tomorrow afternoon
warranting a brief Small Craft Advisory. Will likely issue the
advisory with this evening`s marine update. No precipitation
concerns anticipated until Tuesday night, upon arrival of a cold
front extending from deepening low pressure that will work across
central Ontario.

&&

.PREV DISCUSSION...
Issued at 1230 PM EDT Sat Oct 19 2024

AVIATION...

Morning fog and low clouds dissipated completely around 15z, and
mixing/low level drying will continue to take place this afternoon.
Surface dew pts are still running above guidance, which draws
concern for some fog development once again tonight. However, do
think dew pts will drop into the upper 30s to lower 40s by day`s
end. The pressure gradient will also be tighter tonight, and 925 MB
southwest wind speeds look to increase to around 25 knots. Although
surface wind speeds will attempt to decouple/go calm, the influence
of Lake Erie should be less tonight. However, still a difficult
call, as HRRR is indicating SFC southeast-south flow this evening
over Monroe/Wayne counties before winds veer very light southwest
overnight. Ultimately, this should be enough to moisten up
surface/near surface to support at least light MVFR fog development,
and that is the direction this forecast will go for the southern
TAFS.  Still, would not rule out lower visibilities. Otherwise,
expect clear skies through tonight, with just some increase in mid
to high clouds tomorrow.

For DTW/D21 Convection... Thunderstorms are not in the forecast
through the weekend.

DTW THRESHOLD PROBABILITIES...

*   Very low in ceilings below 200 ft and/or visibilities below 1/2
    mile 7-14Z.


&&

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

$$

DISCUSSION...DG
MARINE.......KGK
AVIATION.....SF


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