030
FXUS63 KDTX 042303
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 PM EDT Sat May 4 2024

.KEY MESSAGES...

- Scattered showers and possible non-severe thunderstorms this
evening through Sunday morning.

- High pressure builds in latter half of Sunday through Monday
bringing drier conditions and closer to average temperatures.

- Developing low pressure over the Midwest brings widespread shower
and thunderstorm chances Tuesday into Wednesday.

&&

.AVIATION...

Late afternoon and early evening peak instability is just enough for
a blossoming of showers as southerly cloud layer flow reinforced
moisture across the area. Within and outside of the showers,
borderline MVFR/VFR ceiling is widespread across SE Mi along with a
notable area of clear sky or scattered clouds over western Lower Mi.
A brief clearing trend along the SE Mi terminal corridor adds
complexity to the forecast as open sky could lead to fog and/or low
cloud development post sunset but with low predictability. Lower
ceiling and visibility are supported by boundary layer moisture
continuing to pool ahead of the expansive Midwest cold front. The
issuance time position of the front extends from Lake Superior
through the mid MS valley and into the southern Plains while
supporting a broken line of thunderstorms along its length. The
front maintains integrity while moving into Lower Mi after midnight
while the storms weaken with the loss of daytime instability. The
front then moves through SE Mi with some lingering showers while
maintaining IFR ceiling late tonight and early Sunday. A standard
daytime ceiling improvement occurs as cooler north wind gains
traction Sunday afternoon.

For DTW/D21 Convection... Thunderstorms south of TOL at issuance
time are slow moving and dependent on daytime instability. These
stay south of DTW while a pop-up shower or storm remains possible
over or near the terminal until sunset. Instability continues
decreasing this evening as a cold front and line of storms enter
western Lower Mi. These storms also weaken to a few stray showers as
the front moves through the DTW area around sunrise Sunday.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms tonight.

* High for ceiling 5000 feet or less tonight and Sunday.

&&

.PREV DISCUSSION...
Issued at 241 PM EDT Sat May 4 2024

DISCUSSION...

Southeasterly lower level flow has developed this afternoon in
response to a weak cold front gradually sagging into the western
Great Lakes. This wind shift supports modest moisture advection from
Ohio, where dewpoints are holding in the mid 60s, nudging local Td`s
into the low 60s late this afternoon-evening. Even with this extra
moisture, both SB/MLCAPEs are expected to stay fairly meager,
holding closer to 500 J/kg. Forecast soundings advertise an uncapped
environment with weak column winds (<20kts thru 500mb) which
supports scattered pop-up showers and perhaps a thunderstorm into
early tonight as height falls move in from the west and a diffuse PV
anomaly lifts NE over far northwestern Ohio. Surface cold front
crosses the area Sunday morning offering another window for
scattered showers, particularly along/north of I-69 owing to closer
proximity to parent shortwave which offers slightly better upper
support/forcing compared to locales further south.

Marginally cooler airmass fallows the frontal passage as 850mb temps
drop to around 4-5C keeping highs Monday in the upper 60s to around
70 for most areas. Easterly flow beneath the surface high that will
be centered over northern lower MI by this point keeps areas
downwind of the lakes like Monroe and especially the Thumb cooler-
upper 50s to lower 60s favored.

Upper ridging and associated surface high are shunted east by early
Tuesday as a potent mid-upper wave ejects out of the Rockies into
the northern Plains. A secondary surface low is progged to develop
over the upper Midwest along the original, now stacked, low`s triple
point. This system lifts a warm front into southern lower MI over
the course of Tuesday bringing the area`s next appreciable chances
for showers and thunderstorms. The attendant cold front quickly
follows Tuesday night generating additional widespread showers and
storms. Worth noting that longer range solutions suggest a ~40kt LLJ
could work into the area from west MI setting up a higher shear
environment with severe potential dependent on how much
destabilization occurs once the warm sector fully expands of the
area. SE MI resides on the edge of SPC`s Day 4 15% severe weather
outlook so will be something to keep on eye on as we get closer.

MARINE...

An elongated area of low pressure over Wisconsin/Illinois this
afternoon tracks east into the central Great Lakes tonight, pulling
a warm front north ahead of it. This will result in an increasing
coverage of showers as well as modest southeasterly winds tonight.
There will be a slight chance of thunderstorms but severe weather is
not expected. A cold front follows on Sunday morning with continued
shower/t-storm chances and a shift to northwest wind of around 15 to
20 knots as conditions dry out for the afternoon. High pressure then
builds in to bring quiet marine conditions for Monday and much of
Tuesday. The next round of likely precip arrives late Tuesday as a
warm front moves into the area. This marks the beginning of a more
active period through the rest of the week with several disturbances
working through.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.

&&

$$

AVIATION.....BT
DISCUSSION...KDK
MARINE.......TF


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