499
FXUS63 KDTX 061653
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1253 PM EDT Thu Jun 6 2024

.KEY MESSAGES...

- Cooler today with highs in the mid 70s. Even cooler on Friday with
highs in the upper 60s.

- Periodic rain chances continue Friday and into the weekend.

&&

.AVIATION...

A broad area of low pressure is locked in across northern Ontario
and will be in control of conditions across Lower Mi today through
Friday. West wind is the highlight for this afternoon as gusts in
the 20-30 knot range carry in cooler and less humid air. The low
pressure influence contributes to increasing VFR cumulus across SE
Mi with greater coverage toward MBS where a stray light shower is
also possible late afternoon through this evening. Mid level clouds
linger after midnight and again with greater coverage toward MBS
where ceiling approaches MVFR by sunrise Friday morning.

For DTW/D21 Convection...Thunderstorms are not expected this
afternoon through Friday.

 DTW THRESHOLD PROBABILITIES...

* Low for exceeding crosswind threshold this afternoon.

&&

.PREV DISCUSSION...
Issued at 350 AM EDT Thu Jun 6 2024

DISCUSSION...

A pattern shift is underway today, evident via local mid-level
height falls of 5.0-7.0 dam over the past 12 hours owing to the
expansion of a deep upper low that is centered over Manitoba. As
this low expands overhead, several shortwaves will ripple through
the longer wavelength trough between today and Friday. The first of
these waves has caught up to a low level theta-e axis, which is
driving a cluster of showers and a few rumbles of thunder across
much of SE Michigan this morning. Best coverage throughout the
morning will be favored toward the Tri Cities and Thumb in closer
proximity to the height fall center, while areas near the Ohio
border may see little to no rain at all.

Overwhelming consensus among the guidance is to push the wave into
Ontario by mid-morning, before boundary layer destabilization can
occur. Considering a strong backdrop of Dcva and dry advection in
the low levels, conditions dry out for all of SE Michigan. Healthy
coverage of diurnal cumulus is then expected to develop by
afternoon, although should not have too strong of an impact on deep
boundary layer mixing. Breezy conditions thus are able to develop
this afternoon with gusts of generally 25 to 30 mph. The depth of
the mixed layer squeezes out high temperatures in the mid 70s, even
with the onslaught of cold advection.

By this evening, the upper low will have made significant
southeastward progress into northern lower Michigan. This will wrap
a more cohesive stream of moisture into the Tri Cities and Thumb,
leading to isolated to scattered shower development as MUCAPE
rebounds to a few hundred J/kg. Equilibrium levels at best reach -10
C, limiting thunder chances both tonight and Friday. A showery day
is in store for Friday as cold advection ramps up. H8 temperatures
of +3 C to +5 C moving across warm Lake Michigan waters (+16 C) will
trigger a lake response to support scattered showers and stratocu
that will stream into SE Michigan. This will be the coolest day of
the forecast period, with daytime highs sticking in the mid to upper
60s.

Expansive troughing patterns holds in place over Canada for several
days, with dual upper lows developing by the weekend. This maintains
an active jet across the northern part of CONUS, including lower
Michigan, which will direct additional shortwaves into SE Michigan
through the weekend. This is likely to result in dry periods and
unsettled periods throughout the weekend. Daytime highs will fall a
few degrees short of normal, in the low to mid 70s for Saturday and
Sunday. Ensemble mean 500mb heights do not show a breakdown in the
troughing pattern until middle of next week, so additional
precipitation chances are likely to evolve through then.

MARINE...

The ongoing passage of a cold front will bring a line of showers and
thunderstorms across the Great Lakes through the afternoon and
evening. Some isolated development ahead of this main line is
possible. There will be a marginal risk for severe weather across
all of the eastern Great Lakes given the building instability, where
wind gusts in excess of 30 knots and hail to an inch will the most
likely hazards with the strongest storms. While much less likely, an
isolated waterspout cannot be ruled out with the thunderstorms.

Passage of the front will veer wind direction from the southeast to
the southwest. A cooler air mass will then gradually setup over the
Great Lakes into the end of the week. The enhanced mixing depths
will bring some breezy conditions, particularly for the nearshore
zones. A Small Craft Advisory has been issued for the Saginaw Bay
tomorrow as a smaller window for southwest fetch will enhance wind
gusts potential to around 25 knots, which would produce wave heights
to or in excess of three feet. Wind speed and gust potential will
then reduce in magnitude overnight.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ441>443.

     Small Craft Advisory until 10 PM EDT this evening for LHZ421-422.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.

&&

$$

AVIATION.....BT
DISCUSSION...MV
MARINE.......AM


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