597
FXUS63 KDTX 282340
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
740 PM EDT Tue May 28 2024

.KEY MESSAGES...

- Numerous showers and thunderstorms through tonight bring a few
  strong storms capable of small hail, locally heavy rainfall, and
  gusty winds.

- Dry weather builds in during Wednesday which continues through
late week.

- Temperatures drop below average throughout the mid week period
before warming up again into the weekend.

&&

.AVIATION...

Numerous coverage of convective showers, with a few thunderstorms,
will continue to percolate across southeast Michigan through the
late evening period. Gradual decline noted in the overall coverage
of lightning as daytime heating fades and rain cooled/outflow driven
environment takes an increasing hold currently precludes a defined
tsra mention and will continue to monitor near trends. Pockets of
heavier rainfall will offer brief reduction of visibility at times.
VFR conditions will prevail outside this activity early tonight.
Lingering high based cloud for the overnight hours. Despite the
recent rainfall, sufficient gradient flow from the northwest limits
fog potential for the early morning period. A general increase in
diurnal cu on Wednesday as moisture associated with a low pressure
system to south slowly vacates the region. This may trigger a low
coverage of showers/t-storms of limited duration across mainly the
Detroit corridor Wednesday afternoon.  Winds prevailing from the
north Wednesday, with some intermittent gusts to 20 knots possible.

For DTW/D21 Convection...There remains a low probability for a
thunderstorm to move through DTW late this evening. A secondary,
brief window for isolated thunderstorm development will exist
Wednesday afternoon.

DTW THRESHOLD PROBABILITIES...

* Low in ceilings aob 5000 feet through tonight. Medium Wednesday.

* Low for thunderstorms this evening and again Wednesday afternoon.

&&

.PREV DISCUSSION...
Issued at 403 PM EDT Tue May 28 2024

DISCUSSION...

Convection flared up on schedule early in the diurnal heating cycle
this afternoon in favored locations off the higher terrain of
northern Lower Mi and within the lingering early morning altocu
south of I-69. Consolidating and converging outflows favor new
development filling in along the M-59 to I-69 corridors while
ongoing activity plays out through late afternoon and evening. Mid
afternoon hourly mesoanalysis measures 0-1 km MLCAPE below 1000 J/kg
which is the more likely convective response due to the uncapped
profile vs 1000-1500 J/kg surface based CAPE. At least one report of
pea size hail came in from a brief reflectivity hotspot and this
will be the primary storm mode through peak instability as freezing
level holds at a relatively low 8 kft level. Slow-moving shower and
thunderstorm clusters also present a localized heavy rainfall threat
as the profile is uncapped and also moisture rich with PW hovering
around 1 inch. Predictability on location or duration remain low
given the random nature of outflow driven redevelopment expected
through the event.

The component of surface based convection fades by midnight north of
I-69 while transitioning into a band of showers and a rumble of
thunder associated with the upstream mid level circulation. The
system over the upper Midwest this afternoon dives into IN/OH while
keeping showers churned across the southern border region late
tonight into Wednesday morning. Upstream satellite presentation this
afternoon offers confidence in model strength and track projections
as leading deformation matures into the primary source of forcing.
The mid level circulation and surface reflection track far enough
south of the Michigan border for a setup of the 850-700 mb moisture
axis/theta-e ridge along/south of I-96 from which the consensus
model QPF axis holds south of I-94, and even south of the Michigan
border in many solutions.

Some residual showers linger near the southern border through
Wednesday morning while clouds hold across the rest of Lower Mi into
the afternoon. Today`s models are bullish on a broad region of cool
surface high pressure gaining dominance under lingering cyclonic
flow aloft. This maintains a greater cloud component until Wednesday
night when deep layer subsidence take hold to bring a clearing
trend. Below normal temperatures then become the weather focus for
the late week period, mainly at night, and despite nearly full sun
through Thursday. A few of the more sheltered and typically colder
locations could touch 40 for low temperatures Wednesday night into
Thursday morning before readings rebound to finish the week.

MARINE...

Scattered showers and thunderstorms will continue to develop through
the afternoon-evening, particularly along and south of Saginaw Bay.
Isolated gusts in these storms may exceed 35 knots alongside
frequent lightning, heavy downpours, and small hail as they track
southeast across the marine zones. Showers and thunderstorms
continue through Wednesday morning before the upper trough axis
moves through mid-day. On the broader scale, waves and gusts subside
as the pressure gradient relaxes briefly tonight. High pressure then
gains influence through the day Wednesday, veering flow to the north
with modest increase in winds/waves toward Small Craft Advisory
thresholds again by Wednesday morning. Given headline expirations
this afternoon will defer additional issuances to the evening
update, noting that Small Craft Advisories will likely be needed
beginning Wednesday morning for Saginaw Bay and portions of the Lake
Huron nearshore. High pressure holds overhead through the rest of
the week with quieter conditions anticipated.

HYDROLOGY...

Clusters of showers and thunderstorms will be active this afternoon
and this evening with locally heavy rainfall. Spotty totals near a
half inch are possible while basin average totals remain light to
moderate, generally in the one quarter to one third inch range from
this afternoon through sunrise Wednesday. Minor flooding in prone
areas or ponding of water on roadways can be expected mainly late
this afternoon and early this evening.

&&

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

$$

AVIATION.....MR
DISCUSSION...BT
MARINE.......MV
HYDROLOGY....BT

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at www.weather.gov/detroit.