Gale Warning 29, NWS Detroit, MI

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
658 AM EDT Fri Nov 4 2022

.AVIATION...

Very dry low level conditions within a modestly gusty southerly flow
will mark this mild autumn environment. This will ensure VFR
conditions hold through tonight. A brief increase in mid level cloud
will accompany pockets of thicker cirrus at times, particularly this
afternoon and evening. This moisture may prove sufficient toward
generating a few showers invof MBS. A diurnal increase in gustiness
peaking around or just above 20 knots. Winds will remain strong just
off the surface, but enough potential at this stage for adequate
mixing to maintain some gustiness precludes an introduction of low
level wind shear tonight.

DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 330 AM EDT Fri Nov 4 2022

DISCUSSION...

With no fog to start the day, temperatures should reach into the
lower 70s today, as 925 MB temps reach and slightly exceed 16 C.
Increasing clouds during the day will be the main hindrance from
temps going higher, especially across the northwest/Tri-Cities
region where a shower or two is even possible.

Strong height falls ejecting northeast out of the southern Plains
today and tracking through the Western Great Lakes on Saturday. Very
impressive 6 hr height fall center (~200 M) to track through the
upper Peninsula of Michigan. The euro ensemble members are clustered
nicely with the location of the surface low over Wisconsin and
through western U.P, but still some significant differences in the
magnitude of the low as an even deeper low takes shape over the
northern Rockies. The interaction of these two strong storm
systems/upper level jets still needs to be fine tuned. With the
moisture plume/PW values up around 1.5 inches Saturday afternoon,
record setting for early November, showers are expected to develop
with the isentropic ascent/frontal convergence. Fortunately, positive
showalter index with just some modest surface based capes (50-100
J/kg) with the cold front. However, with 50 knots of flow noted at
925 MB, even with the weakening post frontal cold advection, brief
gusts at or above 45 mph appear to be a good bet, even within the
warm sector (assuming the low deepens at or below 985 MB). The 00z
operational Euro coming in with 982 MB low over Lake Superior by 00z
Sunday and a corresponding 26 MB 6hr rise/fall pressure couplet,
supportive of wind gusts aoa 45 mph, with gusts up to 50 mph over
the Saginaw Valley with the favorable southwest flow during the
afternoon. However, the 00z NAM is a bit slower and and argues for
strongest winds late in the day/early Saturday evening. Since this is
a period 3 forecast, will defer to the day shift to issue wind
advisory.

Negative upper level PV advection/height rises for Sunday as the
next strong height fall center tracks just north of Lake Superior
with pronounced mid level dry (40 C dew pt depression) slot tracking
through Great Lakes region. The surface cold front looks to washing
out over southern Lower Michigan Sunday evening, allowing for the
much above normal temperatures to continue into next week.

MARINE...

Ridge of high pressure continues to produce dry weather outside of
northern and portions of central Lake Huron, while southwesterly
flow remains in control. Idealized fetch over central and portions
of northern Lake Huron will bring sustained winds to or slightly
above 20 knots, but otherwise lighter winds hold across the open
waters. Better moisture will fill in over the ridge across northern
Lake Huron, which brings likely rain chances by the afternoon and
evening across northern Lake Huron.

Low pressure will move in across Wisconsin on Saturday, with a very
strong low-level jet filling in ahead of the low, over the Great
Lakes. This will reinforce warmer air over the cooler waters which
will bring stable over water conditions. However, the strength of
the low-level wind field in conjunction with an increasing pressure
gradient brings moderate confidence to see sustained wind speeds
nearing 30 knots, with gust potential to 35 knots, by late morning
Saturday. Once the low pressure system draws north into Lake
Superior late Saturday, a cold front will move from west to east
from Lake Michigan to Lake Huron. This front is expected to quickly
move through Lake Huron between 00Z to 04Z. Mixing depths will
briefly punch into the stronger winds aloft along and immediately
behind the front, which will bring a higher confidence window to see
gusts to gales, including isolated high-end gales, to 40+ knots. A
Gale Watch is in effect for all open water zones as a result, from
Saturday morning to Saturday night.

Winds will quickly mix out behind the cold front through early
Sunday morning which will end any prolonged chances for gales.
Elevated wind speeds will hold on over northern Lake Huron where
westerly flow with cooler air resides, but otherwise dry weather and
well above normal temperatures fill back in over the Great Lakes
through the middle of next week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Watch from Saturday afternoon through late Saturday night for
     LHZ361-362.

     Gale Watch from Saturday morning through late Saturday night for
     LHZ363-421-422-441>443-462>464.

Lake St Clair...Gale Watch from Saturday morning through Saturday evening for
     LCZ460.

Michigan waters of Lake Erie...Gale Watch from Saturday morning through Saturday evening for
     LEZ444.

&&

AVIATION.....MR
DISCUSSION...SF
MARINE.......AM

You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.

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