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000
FXUS63 KDTX 170412
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1212 AM EDT Wed Apr 17 2024

.KEY MESSAGES...

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

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

- There is a slight chance of severe weather generally south of the
  I-69 corridor mainly this afternoon.

&&

.AVIATION...

VFR conditions will prevail through the early morning hours as
elevated showers spread across southeast Michigan. Showers are
associated with the increasing moisture ahead of the low pressure
moving into the western Great Lakes states. Isolated rumbles of
thunder remain possible through 12Z, but confidence is too low to
include in TAFs. Winds will be out of the east to around 10 knots
before turning more southeasterly around 12Z as warm front lifts
northward. Period of dry weather expected during the mid-morning to
early afternoon period with low level moisture supporting MVFR
ceilings. Then thunderstorms will become possible, mainly within the
19 to 21Z window along a cold front sweeping through Michigan. A few
isolated cells developing ahead of the line will be possible within
the 16Z to 19Z time frame.

For DTW/D21 Convection...A north to south oriented line of
thunderstorms is anticipated to develop and move through between 19Z
and 21Z. Expect reduced visibility from heavy rainfall and strong
winds from stronger thunderstorm. The environment will bring
potential for tornadic thunderstorms as well. Will be monitoring
potential development of discrete cells ahead of the main line in the
16-19Z time frame. Adjustments in timing of the main line also
remain possible with upcoming TAFs.

.DTW THRESHOLD PROBABILITIES...

* Medium for ceiling below 5,000 ft by around 13Z and after.

* Low for thunderstorms through 12Z, then medium during the
  afternoon.

&&

.PREV DISCUSSION...
Issued at 348 PM EDT Tue Apr 16 2024

DISCUSSION...

Plenty of filtered sun today through a veil of high cloud debris
shedding off the approaching low currently over the central Plains.
Easterly flow on the north side of the warm front is helping keep
temps subdued today, holding them in the mid 60s mostly. Cooler in
the shadows of Lakes Huron and Erie. Main issue today is the Red
Flag Warning in effect for a portion of SEMI. Dry airmass and decent
mixing today will help drop RH values toward 25-30 percent. With
some wind gusts to 15-20 knots and plenty of dry fuels pre green up
and coordination with the neighboring offices and MDNR, the warning
was issued through 8 PM.

Attention then turns to the strong Plains low that will lift up into
the Midwest tonight and then across northern lower Wednesday and the
potential for severe weather over SEMI Wednesday afternoon/evening.
Much of the pattern/scenario holds true from the previous few models
cycle with the stacked low over the Midwest starting to phase with
the stronger northern stream trough digging into the northern
Plains. This will cause the mature southern stream wave to start to
occlude and shear out across the Great Lakes Wednesday. Precip
chances begin tonight after 00Z as the initial lobe of vorticity
ejects northeast through lower MI with the low level jet pumping
increasing waves of theta e up the front. With the warm front hung
up across northern IN/OH this will lead to increasing chances of
showers through the night with a non-zero chance of an isolated
elevated thunderstorms.

The occluded front starts working across SW lower early in the day
while the warm front start slowly lifting northward. This while a
shortwave rounding the base of the trough provides a boost eastward
with a westerly 40 knot low level jet. Severe chances will be
dictated by how far north the warm front can reach before the cold
front surges east of the area. Models have been consistent with
taking it up to around I69 which allows a plume of most unstable air
to lift into the region ahead of the cold front. MUCAPE values
around 1000 J/kg can be expected which could get a little extra
boost from daytime heating if clouds can clear out after the morning
showers for a few hours. Regardless, Ample moisture will be around
with dewpoints up to around 60F and PWATs over 1 inch will be in
place with strong shear around 40 knots and the warm front, cold
front, and triple point/meso low passing through the area.
Hodographs have favorable low level profiles with initially
southeasterly flow present so could get some storms to spin. All
this adds up to SPC including us in a Slight Risk area with a 5%
tornado risk. Once the upper level westerly flow helps line out the
storms, main threat would become wind with some large hail as well.
This line could develop to the west over SW lower, leading to more
of a wind threat with a few embedded circs locally, but we`ll see
how that plays out. Main window for storms looks to be from 2PM to
8PM.

Subsidence in the wake of the front with drying throughout the
column will bring the rain to an end early overnight. Thursday
should be dry to start with temps still hanging in the 60s as
westerly flow won`t offer much in the way of cooler air, but the
cold front tied to the northern stream low will then swing through
Thursday evening/night which will bring another round of showers and
cooler air in its wake. Highs Saturday will hold in the lower 50s
with lows Saturday and Sunday nights dropping down into the low 30s.

MARINE...

Low pressure moving into IA this afternoon tracks ENE into the
western Great Lakes tonight, causing easterly winds to strengthen
under the increasing pressure gradient. 35 knot gales are expected
to begin across northern and central Lake Huron shortly after
midnight, continuing through Wednesday with some intermittent gusts
to 40 knots possible. A Gale Warning remains in effect. Farther
south, winds will be easterly at 25 to 30 knots and Small Craft
Advisories remain in effect. Widespread showers and isolated
thunderstorms accompany the system late tonight through Wednesday
night. Some storms may be strong to severe across the south
Wednesday afternoon and evening. The system will be weakening by the
time the center moves through the region Wednesday night with winds
shifting to westerly and decreasing in magnitude on Thursday. A weak
cold front then moves through the region Friday morning with another
round of showers and possible storms. Westerly winds in the wake of
the front reach 20 to 25 knots Friday afternoon and remain moderate
through the weekend.

HYDROLOGY...

A warm front will lift into the region late tonight 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 tonight 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 near a half inch for most locations
with slightly higher amounts north of I69. 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.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning until midnight EDT tonight for LHZ361-362.

     Gale Warning until 11 AM EDT this morning for LHZ363.

     Small Craft Advisory until midnight EDT tonight for LHZ421-422-441.

     Small Craft Advisory from 4 AM early this morning to midnight EDT
     tonight for LHZ442-443.

Lake St Clair...Small Craft Advisory until 11 AM EDT this morning for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EDT early this morning for LEZ444.

&&

$$

AVIATION.....AA
DISCUSSION...DRK
MARINE.......TF
HYDROLOGY....DRK


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