792
FXUS63 KDTX 040357
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Fri May 3 2024

.KEY MESSAGES...

- High pressure fills in Saturday supporting mainly dry conditions
  ahead of the next weak cold front to bring showers and a few
  thunderstorms to SE MI late in the day through Sunday.

- Seasonably warm temperatures expected through early next week with
  high temperatures in the low to mid 70s and lows in the 50s.

&&

.AVIATION...

The late afternoon and evening band of showers collapsed with the
cold front while exiting into Ontario leaving the forecast up to
clouds and fog late tonight through morning. Weak high pressure on
an axis across northern Lake Huron and northern Lower Mi maintains a
flow of cool and moist NE wind into SE Mi augmented by the cold
water of Lake Huron. Just enough pressure gradient remains for wind
speed in the 5 to 10 kt range favoring borderline LIFR/IFR stratus
with a lighter fog component overall. The stratus plume expands
westward from remnants of the cold front mainly affecting PTK, FNT,
and MBS. NE wind direction aligned with the Ontario peninsula guards
the DTW corridor from more than stray coverage. Wind veering SE
directs clouds into western/northern Lower Mi during the morning
while following a standard diurnal trend into a low end broken VFR
ceiling for the afternoon. A stray shower is possible late in the
day and closer to the interior of Lower Mi as Friday`s cold front
stalls in Ohio and then moves back northward as a warm front into
Saturday evening.

For DTW/D21 Convection... Thunderstorms are not expected late
tonight through the morning. Very low potential for a thunderstorm
with limited coverage by late afternoon precludes a mention in the
forecast at this time.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms late afternoon and Saturday evening.

* Moderate for ceiling 5000 ft or less late tonight and high by
  afternoon.

&&

.PREV DISCUSSION...
Issued at 346 PM EDT Fri May 3 2024

DISCUSSION...

Broken line of showers currently extends from roughly Saginaw to
Coldwater, with no observed lightning activity at issuance.
Instability has been the main limiting factor thus far, with MLCAPE
holding aob 250 J/kg and observed temperatures generally in the mid
to upper 60s. Pockets of sunshine ahead of the line may increase
instability enough through the evening to support a few embedded
thunderstorms, but for now storm tops have struggled to even reach
the freezing level. Slow eastward progression of the line (15-20
mph) and waning instability after 00z with loss of diurnal heating
may prevent the line from even getting to easternmost portions of the
cwa.

Post-frontal subsidence introduces a deep layer of static stability
to the column overnight, most prominent near the Tri Cities and
Thumb. In these locations, patchy fog is expected especially as
onshore flow emerges from Lake Huron. Elsewhere, weaker inversion and
poor decoupling signal suggest stratus or more localized fog
development Saturday morning. Otherwise, a drier day is in store
Saturday for SE MI. Upstream, a surface low lifts toward Lake
Superior which effectively draws the theta-e axis back into lower
Michigan by Saturday afternoon which boosts temperatures into the mid
70s. The boost to boundary layer conditions will be enough to build
surface-based instability, but any convective initiation will depend
on localized convergence or lake breezes. So at this point, just a
stray shower or thunderstorm will be possible Saturday afternoon.

Broader convective coverage is expected early Sunday morning as the
surface low sweeps another cold front across the cwa. Persistent
lack of mid-upper level jet support and modest elevated instability
suggest showers and a few thunderstorms to be possible Sunday
morning before clearing out by mid-day. Mid-level ridging then holds
steady through middle of next week ahead of a strong Pacific
disturbance which will be the next opportunity for widespread
precipitation. High temperatures will remain comfortably in the 70s
as an open Gulf and southwest flow keep conditions above average for
early May standards.

MARINE...

A line of showers will continue to work east across the central
Great Lakes this afternoon as a weak cold front pushes through.
Isolated thunderstorms are possible, but severe storms are not
expected. Light northeast wind will occur behind the front tonight
with mainly dry conditions as a localized area of high pressure
builds in. Will monitor observational trends over Lake Huron where
conditions may be favorable for areas of dense marine fog to form
overnight into Saturday morning. Winds then gradually organize out
of the southeast on Saturday as the high departs east. Southerly
winds up to 20 knots develop Saturday night ahead of the next cold
front that will sweep through on Sunday. Scattered showers and
storms will accompany the front with winds turning northwesterly
behind it Sunday afternoon. High pressure then builds in to bring
quiet marine conditions for the early work week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.

Lake Huron...Dense Fog Advisory until noon EDT Saturday for LHZ361>363-421-422-
     441>443-462>464.

Lake St Clair...None.

Michigan waters of Lake Erie...None.

&&

$$

AVIATION.....BT
DISCUSSION...MV
MARINE.......TF


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