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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 241912
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
312 PM EDT Wed Apr 24 2024

.KEY MESSAGES...

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- A Freeze Warning is in effect for all of southeast MI tonight
through early Thursday morning as temperatures dip into the mid to
upper 20s.

- Dry conditions with a warming trend bring high temperatures to the
50s on Thursday and 60s on Friday.

- Showers are likely Friday night with windy and warm conditions
this weekend. There is low confidence in shower and thunderstorm
potential latter half of Saturday and Sunday.
-- End Changed Discussion --

&&

.DISCUSSION...

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Mid-level height recovery is well underway today with the departure
of the trough axis toward the mid-Atlantic as surface high pressure
builds in from northwestern Ontario. Strengthening subsidence
combined with significant dry air advection (dewpoints falling to
around 20F) has supported rapid north to south clearing trends since
late this morning. Southern areas still beneath the lingering
stratus/stratocu will see clearer skies by this evening. Very
favorable radiative cooling set up tonight with surface high
pressure keeping winds light and variable in addition to the drier
airmass being firmly in place with model PWATs advertised near daily
climo mins of ~0.10". All of southern lower MI remains under a
Freeze Warning tonight as a result as lows, outside of Detroit
proper and the immediate lakeshores, drop into the mid to upper 20s
(~25-28F).

Temperature moderation is muted Thursday as upper level/thermal
troughing lingers over the central Great Lakes holding 925mb temps
in the low single digits (C) supporting continued below average
highs in the mid 50s (lower 50s more likely downwind of the lakes).
That said, with surface high pressure still in place overhead, dry
airmass and weak gradient results in a sunny day with lighter
southeasterly wind. Pattern shift occurs going into Friday as upper
ridging over the Plains shunts thermal troughing east setting up
southerly lower level return flow. 850mb temps climb by 8-10C from
Thursday evening to Friday evening allowing highs to climb back into
the 60s.

WAA is further strengthened by late Friday evening as the elevated
portion of a surface warm front lifting out of the Ohio Valley
reaches southern lower MI. Front marks the lead edge of the warm
conveyor originating out of the western Gulf tied to broad low
pressure over the central Plains. ~50kt LLJ accompanies this frontal
boundary resulting in impressive moisture advection into southern
lower MI as PW values quickly rise from <0.25" Friday afternoon to
>1" by late Friday night-early Saturday morning. Confidence remains
high on widespread showers overnight Friday into the first half of
the day Saturday as the surface front works north through the area.
Latest 12Z model guidance has hinted more at weak elevated
instability (<500J/kg) being able to creep north into SE MI late
Friday night with lapse rates steepening to between 6-6.5C/km
Saturday morning. While thermodynamic ingredients are not
particularly robust, the addition of respectable lift along the
frontal boundary lends a bit more confidence in the chance for a few
embedded thunderstorms during this timeframe. Any that manage to
develop are not expected to be severe at this time given their
likely elevated nature and very marginal mid-level lapse rates.

Second half of the day Saturday looking to have a good shot at being
mostly if not entirely dry once the surface front clears to the
north, entrenching the area within the system`s warm sector as mid-
level nudges in from the Tennessee/Ohio valleys. This sector holds
over the region through Sunday as a secondary low develops along the
first system`s cold front over the Plains briefly stalling this
frontal boundary`s translation east. With this persistent WAA into
SE MI, 850mb temps climb into the mid teens (C) supporting highs
well into the 70s if not cracking 80 in the southern half of the CWA
on Sunday, especially if mid-level capping holds preventing
convection from cropping up. Secondary low is progged to lift into
the northern Great Lakes Monday easing the cold front through the
state over the course of Monday afternoon into early Monday night
with widespread showers/storms in advance.
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&&

.MARINE...

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High pressure will settle in over the Great Lakes tonight through
tomorrow, which will gradually reduce winds speeds, bringing light
winds through Friday morning. High pressure will then settle across
New England on Friday with return flow from the high supporting
southeast flow across the Great Lakes through the day. Wind speeds
are expected to increase Friday and Saturday morning as a result of
the pressure gradient strengthening in response to a low pressure
system filling in across the Midwest. Gusts just below gales will be
possible across portions of Lake Huron during this time frame,
however, extremely stable over-lake conditions should help prevent
sustained mixing of the stronger winds aloft. Showers and
thunderstorms will also be possible late Friday into Saturday, along
a warm front.
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&&

.PREV DISCUSSION...
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Issued at 103 PM EDT Wed Apr 24 2024

AVIATION...

High pressure inbound from northern Ontario brings cool and dry air
to Lower Mi this afternoon. North wind gusting around 20 knots lifts
remain MVFR ceiling into low end VFR across SE MI by mid afternoon
while also clearing from north to south late in the day. Clear sky
and light wind follow the high pressure center across the Great
Lakes tonight and Thursday. Clouds are limited to thin cirrus while
light east wind sets up with some lake breeze augmentation Thursday
afternoon.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less through mid afternoon.
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&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning from midnight tonight to 8 AM EDT Thursday for
     MIZ047>049-053>055-060>063-068>070-075-076-082-083.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422-
     441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

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

$$

DISCUSSION...KDK
MARINE.......AM
AVIATION.....BT


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