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NWS Forecast Discussion

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FXUS63 KDTX 020457
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EST Thu Dec 1 2022

.AVIATION...

Period of dry low level conditions will exist overnight and Friday,
as environment moderates under prevailing southerly flow. Thicker
mid level cloud will remain prevalent, but with expectation for
skies to remain clear across the lowest 5000 ft until late in the
day. Steady increase in southerly wind magnitude and gust frequency
during the daylight period, peaking near 25 knots late in the day.
Stronger southerly winds persist into Friday night in advance of
strong cold front. Most notable increase in winds will occur with
the frontal passage late Friday night into Saturday morning.

For DTW...No aviation concerns through the daylight hours Friday.
Southerly winds increasing with time, peaking late Friday night into
Saturday with a wind shift to westerly. Potential for gusts in
excess of 35 knots during that time. Lowering cloud bases eventually
dipping below 5000 ft by Friday evening.

 DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 ft Friday evening.

* Medium for westerly winds exceeding crosswind thresholds
  Saturday morning /10z-13z/

&&

.PREV DISCUSSION...
Issued at 321 PM EST Thu Dec 1 2022

DISCUSSION...

Northern periphery of a high pressure system centered over the
northern Ohio Valley will hold over the Great Lakes through the
remainder of the afternoon and evening hours and will maintain dry
weather as afternoon highs in the mid 30s start their descent into
the mid 20s for overnight lows. Advected Layer Precipitable Water
highlights a layer of moisture rich Gulf air extending from the
surface up through h700 over western Texas, which will draw northeast
into Great Lakes through Friday, guided by return flow from the
departing high pressure system. Concurrently, a Pacific Northwest
wave will arrive onshore and will push over the Rockies early
tomorrow morning where a surface low will become better defined on
the lee side of the mountain range as the undulation moves into a
region of better baroclinicity. A strong, deep jet will develop in
the vicinity of the thermal gradient over the plains, which will then
extend into the Great Lakes, Friday afternoon into Saturday morning,
characterized with h850 winds between 50 to 60 knots.

Isolated to widely scattered elevated rain showers will initially be
possible on the nose of the jet Friday evening. The main weather
impact with the extension of the jet over SE MI will be windy
conditions that accompany the initial rain chances. Southwest flow
advecting warm air aloft will reinforce a low-level inversion which
will limit mixing depths and thus surface gust potential. Latest
model guidance supports depths to 1.5 kft which would produce gusts
30-35 mph, barring a neutral to slightly stable profile (see NAM).
Confidence then turns high for both light precipitation chances and
for a smaller window of higher end gust potential (40-50 mph), once
the low pressure system sweeps northeast from Minnesota into the
James Bay late Friday into Saturday morning. This will push a strong
cold front across SE MI between 08-12Z Saturday. Forcing along the
front will produce numerous to widespread light rain showers while
improved mixing depths along and behind the front with deep column
subsidence pulls these stronger wind gusts down to the surface. This
window for better gust potential will last through late Saturday
morning into early afternoon, before gusts quickly ramp down as the
elevated wind field pivots east. There will also be a stark
temperature difference felt after the cold front passage. Warm air
advection ahead of the frontal will actually prop up early morning
temperatures around 40- 45 degrees, with temperatures plummeting into
the 20s in the wake of the front, by Saturday afternoon.

Mid-level subsidence will carry on through early Sunday morning
while very dry air holds over the region with PW values dropping
close to .10-.15 inches through Sunday. Dry weather to then persist
for the remainder of the weekend and likely through Monday with a
weak high pressure filling in over Michigan.

MARINE...

Influence of high pressure wanes tonight/early Friday as it slides
toward the mid-Atlantic states while another low begins to rapidly
develop over the upper Plains. The local gradient tightens over the
course of Friday as the low takes a similar track to the midweek
system (lifting through Lake Superior into northern Ontario) leading
to strengthening southerly flow. Gales become possible by the latter
part of Friday evening over the southern and central portions of
Lake Huron, as a result, Gale Watch is in effect. System sends a
strong cold front through the region late Friday night-early
Wednesday morning setting up strong W to WNW winds for daytime
Saturday. The Gale Watch expands to cover all waters by early
Saturday given the potential for widespread post-frontal gales,
including strong gales over the northern half of Lake Huron. Similar
to midweek, a few sporadic gusts to borderline storms are possible
over northern Huron Saturday morning (~6am-12pm) however not
expecting the need to go with a storm warning. System exits the
central Great Lakes late Saturday allowing for a gradual relaxation
in winds going into Sunday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning from 3 AM to 4 PM EST Saturday for LHZ422-441>443.

     Gale Warning from 3 AM to 7 PM EST Saturday for LHZ361.

     Gale Warning from 4 PM Friday to 7 PM EST Saturday for LHZ362-363-
     421-462>464.

Lake St Clair...Gale Warning from 3 AM to 4 PM EST Saturday for LCZ460.

Michigan waters of Lake Erie...Gale Warning from 3 AM to 4 PM EST Saturday for LEZ444.

&&

$$

AVIATION.....MR
DISCUSSION...AM
MARINE.......KDK

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

NWS DTX Office Area Forecast Discussion