997
FXUS63 KDTX 040707
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
307 AM EDT Sat May 4 2024

.KEY MESSAGES...

- Morning fog and low clouds give way to a warm Saturday with highs
in the low to mid 70s.

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

&&

.DISCUSSION...

Despite the showers and clouds yesterday, high temperatures were
able to sneak into the lower 70s across most areas. Extremely dry
airmass noted with the 00z APX raob, and some of the mid level dry
air has/will make inroads into southeast Michigan. However, cool
northeast flow off Lake Huron and lingering low level moisture looks
sufficient to saturate the low levels, and deep enough moisture (5+
kft layer) to potentially trigger stray light rain showers,
especially toward the southern Michigan border, as some of the
deeper moisture over Ohio attempts to work back north late in the
day, ahead of a weak cold front moving through from the western
Great Lakes tonight. With surface capes under 1000 J/kg today and
the mid level dry slot, do not see EQL levels getting high enough to
generate thunderstorms during the daytime, but a slight chance of
non-severe storms appears warranted this evening/tonight with the
modest height falls and the slightly negative showalter values
tracking through. Stability will be on the increase 15-17Z Sunday as
the front clears the State.

Despite a fair amount of clouds today and the early morning fog,
will allow high temperatures to reach into the mid 70s across most
locations, based on the forecasted 925 MB temps of 17 C.

Westerly confluent upper level flow Sunday night preceding an upper
level ridge axis arriving early next week, supporting dry weather on
Monday and likely during the daylight hours of Tuesday before a warm
front brings widespread showers and possible thunderstorms Tuesday
evening/night.

&&

.MARINE...

An area of high pressure centered over the region this morning is
resulting in a weak gradient with light winds and waves across the
region. Elevated dew points within the stable environment have
resulted in areas of dense fog across Lake Huron and a Dense Fog
Advisory is in effect until noon today. The gradient increases this
afternoon as the high departs east, with wind organizing out of the
southeast late today into tonight. A stalled front lifts north as a
warm front tonight as a weak low moves from the upper Mississippi
Valley into the northern Great Lakes. The system then sends a cold
front through early on Sunday with a chance of showers and
thunderstorms. Wind shifts to northwesterly behind the front Sunday
afternoon, peaking at around 15 to 20 knots. High pressure then
builds in to bring quiet marine conditions for Monday and much of
Tuesday. The next warm front moves into the area late on Tuesday
with stronger easterly flow developing ahead of it.

&&

.PREV DISCUSSION...
Issued at 1157 PM EDT Fri May 3 2024

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.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Dense Fog Advisory until noon EDT today for LHZ361>363-421-422-
     441>443-462>464.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

DISCUSSION...SF
MARINE.......TF
AVIATION.....BT


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at www.weather.gov/detroit.