241
FXUS63 KDTX 291953
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
353 PM EDT Wed May 29 2024

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms continue along and
  south of I94 until around sunset.

- Clear sky and light north wind result in chilly low temperatures
  tonight and Thursday morning. Lows near 40 will be common outside
  of metro Detroit.

- Dry weather and a gradual warming trend unfold Thursday and Friday.

- The next chance of rain is late Saturday and Saturday night.

&&

.DISCUSSION...

Another uncapped/low CAPE density convective setup developed this
afternoon only with a much smaller geographic footprint compared to
yesterday, mainly south of I96/696, and which is already winding
down and exiting southward at issuance time. Mid afternoon hourly
mesoanalyses and RAP model projections indicate surface based CAPE
holding around 1000 J/kg south of I94 as Td lingers in the mid 50s
to fuel convection for a couple more hours. Also like yesterday,
model soundings indicate freezing level still hovering around a
relatively low 8000 ft which makes mainly pea size hail possible in
a few stronger updrafts when combined with the skinny CAPE density
shown in model soundings. A few precip loaded sub 40 mph wind gusts
are also possible until activity weakens while exiting south of the
border by sunset.

Elsewhere and otherwise, cool and dry boundary layer advection is on
full display to the north across the rest of Lower Mi this
afternoon. The inbound dry air already has clear sky in place north
of I69 across the Tri Cities and northern Thumb, and this will
spread southward across the rest of SE Mi this evening. Clear sky
across the area after midnight then combines with a lingering light
north wind for a chilly temperature pattern into Thursday morning.
The wind disrupts full radiational cooling potential but the
forecast still leans toward the lower end of the guidance range for
lows near 40 outside of metro Detroit. This is a solid 10-15 degrees
below normal while still well above record lows that are all in the
lower to mid 30s for May 30th.

High pressure then takes firm control of conditions across the Great
Lakes for the late week period. Temperatures rebound quickly from
the chilly morning start with the benefit of full morning sun and
just scattered/shallow afternoon fair weather cumulus and some
cirrus streamers. The long wave mid level flow is amplifying during
this time leading to ridge building across the Midwest which
fortifies downstream subsidence into the central Great Lakes.
Effective larger scale subsident forcing is reflected in very dry
model mean RH to maintain mostly clear sky and rule out
precipitation Thursday night and Friday. The low level thermal
trough is projected to our east even tonight and Thursday and shifts
even farther east by Friday which allows a larger temperature
rebound back into the mid and upper 70s.

The weekend becomes more active in terms of rain potential but is
not a washout by any stretch. Consensus of extended range model
solutions brings a short wave into the upper Midwest and the next
chance of rain to Lower Mi late Saturday and mainly Saturday night,
however it is a progressive system with a weak front, both of which
are east of the area by Sunday. The weak front and trailing modest
high pressure keep temperatures hovering around 80 each day.

&&

.MARINE...

High pressure becomes fully established tonight with the departure
of surface troughing. This supports weakening winds (and subsequent
waves) through the evening as lighter flow (at or below 15kts) takes
hold by early Thursday. While northerly flow persists for Thursday,
weaker winds are expected to hold waves sub small craft criteria
around the Thumb. Surface high drifts directly over the central
Great Lakes through the remainder of the week maintaining dry
conditions and light southerly winds.

&&

.PREV DISCUSSION...
Issued at 149 PM EDT Wed May 29 2024

AVIATION...

Axis of narrow showers, including some isolated lightning strikes,
continues to work south across the southern terminals early this
afternoon. Instability profiles are marginal (up to 500 J/kg of
MUCAPE) with limited effective shear (less than 15 knots), thus
pulse-type convective mode should persist a bit longer. Further
north, a SCT-BKN MVFR cumulus deck has thinned a bit while the main
clearing line is currently positioned near I-69 (and moving
southward). Expect VFR conditions across all TAF sites by 19Z with
clearing skies into the evening and overnight hours. SKC in-place
Thursday morning as surface high pressure centered over the WI/MI
border builds across the Great Lakes with lighter northwest flow
through the end of the TAF period.

For DTW/D21 Convection...Narrowed the window for additional
convection from the 1614Z amendment to end the TEMPO at 19Z as
storms remain sub-severe and exhibit a weakening trend with north-
south storm motions of 15-20 knots.

DTW THRESHOLD PROBABILITIES...

* Medium in ceiling at or below 5000 feet during convection through
  19Z today.

* Medium for additional thunderstorms through 19Z today.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422-
     441>443.

Lake St Clair...None.

Michigan waters of Lake Erie...None.

&&

$$

DISCUSSION...BT
MARINE.......KDK
AVIATION.....KGK


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