866
FXUS63 KDTX 030750
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
350 AM EDT Mon Jun 3 2024

.KEY MESSAGES...

- Temperatures warm up Monday and Tuesday with highs returning to
the 80s. Chance for showers or storms Tuesday night.

- Showers and some thunderstorms likely Wednesday as a major weather
pattern shift begins. After Wednesday, below normal temperatures are
likely through at least the end of the week.

&&

.DISCUSSION...

Low amplitude mid-upper level ridging is supporting an area of weak
(1016mb) high pressure over Lower Michigan this morning. Calm to
very weak easterly flow with little to no airmass turnover has
caused a formation of shallow ground based br/hz over virtually all
of the region. There have been a few holdouts, namely inside of the
urban heat island of Detroit. Based on trends with a bouncing of
surface observation, expecting fog through daybreak but then burning
off fairly quickly or rising into a lower low coverage stratus.
Forecast soundings are not that supportive of a strong ground based
inversion.  A long day with powerful solar intensity will result in
the growth of the PBL. Highs today are expected to climb above 80
degrees with sunshine this afternoon.

Flow trajectories are expected to remain largely anticyclonic
Tuesday particularly in the 850-600mb layer. Background forcing will
support large wavelength ridging albeit with increases in warm
advection by the evening. Models have shown upstream convective
activity over Wisconsin approaching the northern cwa sometime Monday
night and early Tuesday. The blended guidance has had a tough time
with the setup and has been broadbrushing Pops. Did go ahead and
removed some chance PoPs in this period. Some differences remain on
the timing of the richer thetae content but there is a signal that
enhanced convective augmented moisture will arrive from the Mid
Mississippi River Valley after 00Z Wednesday. The most notable
aspect of the Tuesday is the warmth and mugginess with daytime highs
reaching the upper 80s and dewpoints well into the middle 60s.

Shower and thunderstorm chances begin increasing Tuesday night in
response to a larger scale, upright warm front lifting northward
Lower Michigan. Uncertainty does remain for Tuesday night as
downstream ridge amplification will continue immediately ahead of
the unseasonably strong Potential Vorticity anomaly over the
northern Plains. Disagreement exists between the NAM and ECMWF when
precipitation arrives with confidence increasing for the daytime
Wednesday. If thundestorms were to develop Tuesday night no strong
thunderstorm activity is expected with relatively high stability in
the lowest 5.0 kft agl. The particulars are rather interesting for
Wednesday as a very strong potential vorticity trough is forecasted
to turning to a strongly negative tilt over Southeast Michigan at
midday. The issue is that opaque cloud in place during the morning
with a low level pressure circulation embedded back into the warm
sector is expected to significantly compromise the insolation.
Current model data is marginal with convective available potential
energy at just under 1000 J/kg SBCAPE for the early afternoon hours.
0-6km bulk shear is generally in the 25 to 30 knot range. The latest
Swody3 has a General Thunderstorm designation for Southeast Michigan
Wednesday.

A closed upper level low pressure system is then forecasted to
impact Southeast Michigan with a very long duration of northwest
flow from Thursday through next Monday. Periodic rain chances will
exist but will remain virtually impossible to time. High
temperatures during the period are expected to be in the upper 60s
to 70s with lows in the 50s.

&&

.MARINE...

Upper level shortwave ridge brings a brief period of high pressure
into the area today. Light northerly winds provide chances for
patchy fog this morning, with any pockets that do develop
dissipating by sunrise. Approaching warm front brings some chances
for some light showers to develop Tuesday followed by a cold front
on Wednesday, seeing chances for storms in the latter. Low-level
flow up to 30 knots on Wednesday is expected 1000 feet above the
surface, meaning that a stray strong gust mixing to the ground is a
distinct possibility. Small Craft Advisories are not currently
expected for Wednesday, but could remain a possibility if an upward
wind gust trend develops in the models.

&&

.PREV DISCUSSION...
Issued at 1214 AM EDT Mon Jun 3 2024

AVIATION...

The combination of high surface moisture, light northerly winds, and
clearing skies brings a high probability for fog developing tonight.
There have already been scattered observations early this morning of
MVFR visibility restrictions. Expect more widespread IFR to LIFR
restrictions to develop early in this TAF period. Visibilities and
ceilings will gradually lift in the typical post sunrise warm up with
VFR conditions becoming more likely by mid/late morning into the
early afternoon. Scattered cumulus lingers around 4 kft during the
early afternoon before high clouds prevail during the evening hours.
Light and variable winds tonight will become southeasterly as fog
lifts and holds from this direction into tonight.

For DTW/D21 Convection...Thunderstorms are not expected through this
forecast period.

DTW THRESHOLD PROBABILITIES...

* Moderate for cigs/vsby falling below 200 ft and/or 1/2 SM to
  around sunrise this morning.

* Low for ceiling at or below 5,000 feet this afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

DISCUSSION...CB
MARINE.......BC
AVIATION.....AA


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