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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 161843
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
243 PM EDT Tue Apr 16 2024

.KEY MESSAGES...

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- Red Flag Warning in effect until 8 PM today for a portion of SE
  MI.

- Shower chances will increase this evening into tonight as a warm
  front encroaches on the area.

- Showers and thundestorms are expected Wednesday as low pressure
  tracks into the Great Lakes.

- There is a slight chance of severe weather generally south of the
  I-69 corridor mainly on Wednesday afternoon.
-- End Changed Discussion --

&&

.AVIATION...

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High pressure influence lingers today with variable easterly flow
and modest coverage of high cirrus. Clouds thicken and lower
overnight as a low pressure system near the Upper Midwest dislodges
drawing increasingly moist air into Southeast Michigan once the
system`s LLJ situates overhead. Expect varying coverage of showers
after midnight with lower ceilings into Wednesday morning. Some
additional showers and perhaps a stray rumble of thunder are
possible as another round of activity develops under the strong
dynamic forcing which could also lead to some reduction in
visibilities through 14Z Wednesday. A brief drier period lingers
into the midday hours before the arrival of pre-frontal storms
around/after 18Z Wednesday.

For DTW/D21 Convection...Low confidence in the development of
thunderstorms tonight and Wednesday morning as shower activity
should predominantly remain scattered due to lagged moistening and
limited elevated instability. A cold front is then expected to move
through Wednesday afternoon which generates a line of thunderstorms
oriented from north-south. This line of storms should become
increasingly organized ahead of the boundary resulting in a 1-2 hour
window for thunder, reduced visibilities from heavy rainfall, and a
burst of strong winds. Some potential exists for a brief spin-up
tornado along the line. Models suggest timing is currently favored
between 19Z and 21Z. Some discrete single-cell thunderstorms within
the warm sector could also lift north ahead of the line between 16Z
and 19Z, but confidence in this activity is low.

.DTW THRESHOLD PROBABILITIES...

* Medium for ceiling below 5,000 ft after midnight and Wednesday.

* Low for thunderstorms from 07-12Z and 16-19Z Wednesday, then
  medium from 19-21Z Wednesday.
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&&

.PREV DISCUSSION...
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Issued at 1058 AM EDT Tue Apr 16 2024

UPDATE...

In coordination with neighboring offices and the MDNR, we have issue
a Red Flag Warning for a portion of southeast Michigan this
afternoon into the evening until 8 PM. The combination of decreasing
humidities, sustained winds, and dry fuels support increased risk of
fire danger.

PREV DISCUSSION...
Issued at 330 AM EDT Tue Apr 16 2024

DISCUSSION...

A surface ridge extending south from a large high center near Hudson
Bay will retreat eastward today as a strong low pressure over the
central plains ejects into the midwest. In between these systems,
east to northeast flow will gradually increase throughout the day.
This will impact temperatures immediately downwind of the Great
Lakes with highs hold in the 50s to near 60 over the Thumb as well
as locations east of Saginaw Bay and western Lake Erie. The rest of
the area will climb into the lower/mid 60s as increasing cloud cover
leads to slightly cooler readings overall than those on Monday. The
area should remain dry throughout the day with the first sporadic
light showers associated with the outer reaches of aforementioned
low pressure to the west not making inroads into the area until this
evening.

Shower chances will increase Tuesday night as a lead vorticity spoke
pivots northeast across the area in advance of the approaching low
pressure with a distinct surge of higher theta-e air working into
the area during this time frame. Low level instability will still be
confined well south of the area along and south of an encroaching
warm front so this activity should be largely thunderless with
little more than a rumble or two possible within this elevated
activity. Shower/thunderstorm chances continue into early Wednesday
as the warm front lifts north through the area as low pressure
tracks into Wisconsin.

The trickiest portion of the forecast will come later Wednesday as
this lead activity lifts north of the area and some degree of a warm
sector shifts north and northeast into parts of the region as the
surface low continues east through northern Lake Michigan into far
northern lower MI and the eastern UP. A pocket of modest instability
(MUCAPE 1250-1750 J/kg in some spots) looks to develop within this
relatively warm and moist area south of the warm front to the west
and southwest of the forecast area with this area then translates
east and northeast into the region during the afternoon/early
evening.

A cold front pivoting west to east around the low pressure center
will encounter this unstable pocket and provide the necessary lift
to force a line of vigorous line of convection across southern lower
MI with this activity eventually shifting into the forecast area
late in the day. Increasing southwest flow into the mid levels (40
to 55 knots from H85 to H5) will provide moderate deep shear and
line up pretty well to encourage any line of convection that does
develop to bow eastward with time. The main question will be how
much instability is able to feed this line of storms east into the
region.

SPC has increased risk to a Slight over the southern half of
the area which aligns pretty well with timing/location of this warm
sector and advancing cold front as compared to yesterday`s forecast.
Favor a wind threat locally in the DTX area as potential convective
line should be rather mature by the time is gets this far east. In
addition, there will be some large hail potential and possible a
rouge tornado embedded within the line given the relatively strong
(but veered) low/mid level flow.

Showers will end Wednesday night as the low lifts into the northern
Great Lakes and the cold front pushes east with time. Mild weather
will persist into Thursday within largely westerly flow with lower
to mid 60s common. A large northern stream upper low pressure system
will be translating across southern Canada during this time frame. A
cold front will shift southeast through the area Thursday night as
this low (actually phasing to a degree with the southern system)
arrives/deepens north of Lake Superior. This will provide another
round of showers mainly Thursday evening/night with cooler air then
funneling into the area from Friday on into Sunday as a large high
pressure system builds into the CONUS from Canada in the wake of
this northern stream system. Highs will settle into the 50s for much
of the rest of the forecast with lows down into the low 30s in many
locations by Sunday and Monday mornings.

MARINE...

A ridge of high pressure extending southeast from Ontario maintains
light northeast wind and dry conditions today. Low pressure tracking
in from the Midwest causes winds to shift to easterly and strengthen
tonight into Wednesday morning. Northern and central Lake Huron will
see the strongest winds with gusts to gales increasingly likely into
Wednesday and the Gale Watch has been replaced by a Gale Warning
late tonight into Wednesday. Further south, wind gusts are marginal
so will issue Small Craft Advisory for the nearshore waters and
leave the southern open waters without a headline at this point in
time (anticipating gusts more in the 30-32 knot range).

Widespread showers and isolated thunderstorms accompany the system
late tonight through Wednesday night, then taper off Thursday as the
low moves out. Weaker westerly winds follow for Thursday. A weak
cold front then moves through the region Friday with continued
westerly winds in its wake expected to remain light to moderate
through the weekend.

HYDROLOGY...

A warm front will lift into the region late Tuesday night into
Wednesday in advance of a strong low pressure over the midwest.
Showers and a few thunderstorms will be possible along this front
with the greatest coverage occurring overnight Tuesday night into
Wednesday. Additional showers and thunderstorms will impact parts of
the area Wednesday afternoon into early evening as this low tracks
through far northern lower Michigan and forces a cold front through
the area. Total rainfall is forecast to reach one inch in some
locations. While significant flooding is not expected at this time,
expect minor flooding in prone urban and poor drainage areas and
possibly notable rises in area rivers.
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&&

.DTX WATCHES/WARNINGS/ADVISORIES...
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MI...Red Flag Warning until 8 PM EDT this evening for MIZ047-053-054-060-
     061-068.

Lake Huron...Gale Warning from 2 AM Wednesday to midnight EDT Wednesday night
     for LHZ361-362.

     Gale Warning from 2 AM to 11 AM EDT Wednesday for LHZ363.

     Small Craft Advisory from 11 PM this evening to midnight EDT
     Wednesday night for LHZ421-422-441.

     Small Craft Advisory from 4 AM Wednesday to midnight EDT Wednesday
     night for LHZ442-443.

Lake St Clair...Small Craft Advisory from 11 PM this evening to 11 AM EDT Wednesday
     for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EDT Wednesday for LEZ444.
-- End Changed Discussion --

&&

$$

AVIATION.....KGK
UPDATE.......DRK
DISCUSSION...DG
MARINE.......TF/DG
HYDROLOGY....DG


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