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000
FXUS63 KDTX 131917
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
317 PM EDT Sat Apr 13 2024

.KEY MESSAGES...

- There is a chance of thunderstorms late tonight, mainly north of
Interstate 69. Small hail is possible with these thunderstorms.

- Warm conditions expected Sunday.

 - The next chance of rain will be late Tuesday into Wednesday.
There is a chance of thunderstorms on Wednesday.

&&

.DISCUSSION...

A fast moving mid level short wave impulse and upper jet max now
over south central Canada will move across Lake Superior late
tonight into Sunday morning. A strong low level jet (50-60 knots) is
forecast to develop across the western Great Lakes overnight, tied
to the exit region of the upper jet streak. The nose of this
enhanced low level inflow will push across the thumb and Lake Huron.
An elevated mixed layer (EML) will be advected from the central
plains across Lower Mi overnight. Steep mid level lapse rates (700-
500mb) around 8 C/km within a respectable low-mid level moist axis
will contribute to moderate elevated instability (0-3km MU Cape up
to 1500 J/kg) late tonight thru Sun morning. The better chances for
convective initiation will be within the nose of the low level jet
axis (extending from the Saginaw Valley/Thumb regions into Lake
Huron) where forcing will be maximized. A deep stable layer near the
surface will lesson the risk of gusty winds with the storms. However,
the degree of elevated instability does suggest a hail risk with
some of the storms.

Wind speeds will decrease this evening as nocturnal cooling sets in
and a sfc ridge passes overhead. After the last two days of rain,
sfc dewpoints today have dropped nicely (into the 30s). This will
support a rapid drop in temps this evening (into the 40s around
midnight) before mid level clouds and strengthening low level flow
drives warmer air into Se Mi overnight, leading to warming temps
toward daybreak. Sfc low pressure will track across northern Lower
Mi and Lake Huron Sunday, driving a slow moving cold front across Se
MI. This cold front and lake breeze boundaries will establish a
healthy temp gradient across Se Mi, with highs in the 50s in the
thumb to upper 60s to mid 70s inland. Daytime heating will result in
the development of sfc based cape by Sunday afternoon. Despite the
numerous low level boundaries across Se Mi, the strongest forcing
aloft is forecast well southeast of the forecast area. Model
soundings also suggest the EML overhead will maintain a stout
capping inversion. This supports only a slight chance of afternoon
convection at best.

Sfc high pressure will expand across the forecast area Sunday night
into Monday amidst confluent mid level flow, leading to tranquil
conditions across Se Mi. A deep upper low is forecast to emerge from
the lee of the Central Rockies on Tuesday and rotate across the
Great Lakes region on Wednesday. A lead ribbon of elevated frontal
forcing will provide a chance of rain late Tuesday/Tuesday night.
There is reasonable model agreement that the associated occluded sfc
low will track northwest of the forecast area on Wednesday. The main
point of uncertainty is whether the surface instability axis remains
south of the state line or is able to advect into Se Mi. The latter
would result in a greater risk of strong/severe convection given the
shear profiles. This system will be forced northeast of the region
by Thursday as a polar low is forecast to rotate into the Northern
Great Lakes by the end of the work week, supporting a trend toward
cooler temperatures.

&&

.MARINE...

Westerly winds gusting 25 to 30 knots this afternoon across the
Central Great lakes will drop off quickly toward sunset. Will allow
the small craft advisories to expire at 4 PM, although there will
likely be a few leftover gusts around 25 knots for an hour or two
after.

Winds will be light tonight as a surface ridge slides through,
before a weak low tracks through lower Michigan on Sunday. This
system brings chances for additional showers and a few thunderstorms
late tonight into Sunday morning, mainly over Lake St. Clair and
Lake Erie. No wind headlines are expected with this system as wind
gusts generally top out around 20kts. The nearshore waters of Lake
Erie look to be most susceptible to reach wind gusts to 25 knots for
a short period on Sunday, but there is a lot of warm air streaming
in which will lead to stable low level profiles over the water.

Broad surface high pressure in place to start the work week will
provide light winds on Monday, with easterly winds increasing on
Tuesday ahead of the next low pressure system moving into the the
Central Great Lakes on Wednesday. This system will bring widespread
showers and possible thunderstorms.

&&

.PREV DISCUSSION...
Issued at 139 PM EDT Sat Apr 13 2024

AVIATION...

VFR conditions persist under clear skies through the afternoon and
evening before a low pressure system brings mid- and high-level
clouds into the area from the northwest tonight. The core of
stronger winds has moved out and will see westerly winds continue to
taper off and back to the south under 10 knots overnight. MBS and
FNT will stand the best chance to see isolated showers or perhaps a
thunderstorm after midnight but confidence remains too low to
include in the TAF attm. The system tracks over Lake Huron on
Sunday, sending a cold front across the area and veering winds to
the WNW by late in the day. Wind speeds will be generally 15 to 20
knots with gusts near 25 knots. Little to no signal exists for sub-
VFR conditions through the period.

DTW THRESHOLD PROBABILITIES...

*  None.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-422-
     441>443.

     Gale Warning until 4 PM EDT this afternoon for LHZ362-363.

Lake St Clair...Small Craft Advisory until 4 PM EDT this afternoon for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EDT this afternoon for LEZ444.

&&

$$

DISCUSSION...SC
MARINE.......SF
AVIATION.....TF


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