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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 211943
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
343 PM EDT Sun Apr 21 2024

.KEY MESSAGES...

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- A Frost Advisory is in effect tonight for all of Southeast
Michigan.

- Warming trend continues Monday with dry and sunny conditions.

- Showers and possibly a thunderstorm arrive Tuesday with gustier
winds.

- Dry and cooler conditions return Wednesday.
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&&

.DISCUSSION...

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Cooler resident thermal profile still entrenched to finish the
weekend period. Weak surface ridging arrives overnight as deep layer
stability strengthens under broader anticyclonic mid level flow as
upper heights slowly build. Emerging corridor of warm air advection
upstream unlikely to arrive nocturnally with low level flow still
veered, affording a reasonable window of solid radiational cooling
under the mostly open sky, a very dry mid level profile and
diminishing overall gradient flow. A targeted low temperature range
of 31 to 35 degrees on track, highlighting some potential for
patchy/areas of frost. Frost advisory now in effect overnight after
collaboration with surrounding offices.

Modest warming trend Monday as weak warm air advection solidifies
under low level southwest flow and capitalizes on a high degree of
isolation potential within transient shortwave upper ridging. High
temperatures arriving invof average - lower 60s. Strengthening upper
level jet streak emerging along the south flank of a mid level
system ejecting out of southwest Canada will direct a plume of higher
moisture eastward toward the region. Associated uptick in mid level
moist isentropic ascent will bring a good chance for light rain
development late Monday night into early Tuesday. Exit pace of this
initial period of supportive upward vertical motion will dictate
duration window, if any, for dry conditions to exist into Tuesday
afternoon, before attention turns to the inbound mid level wave set
to arrive Tuesday night. Some improvement in mixing depth with time
translates into gusty southwest conditions for the afternoon.
Combination of dcva and frontal forcing acting on steep mid level
lapse rates then yields a higher probability for convective shower
development from northwest to southeast Tuesday evening into early
Tuesday night. General reduction in column stability above 700 mb
affords an isolated t-storm opportunity, but too limited in
magnitude or depth to bring concern for greater organization.

Remainder of the mid week period marked by dry and stable conditions
as expansive high pressure settles in beneath weakly confluent
mid level northwest flow. Sustained period of cold air advection
results in well below average temperatures Wednesday. Magnitude of
this cold air intrusion brings renewed frost/freeze considerations
for Wednesday night as the surface high centers over the local area.
Benign weather lasting through at least Thursday as dry low level
easterly flow maintains control within lingering ridging. Modest
warming trend as geopotential heights build with time, but with temps
still on the cooler side of average Thursday.

Prototypical corridor of warm/moist air advection emerges upstream
late next week, responding to increasing magnitude and depth of
southwest flow ahead of a mid level wave ejecting out of the
southwest conus. This pattern offers increasing likelihood for rain
to manifest within the broader zone of isentropic ascent along an
advancing elevated warm frontal boundary. This will establish a
period of wet conditions sometime late Friday into Friday night.
Less defined forecast heading into next weekend, with the detail
reliant on behavior of the governing wave as it continues northeast
into the upper miss valley and any corresponding response downstream
within the warm sector.
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&&

.MARINE...

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Breezy conditions are in place today with northwest flow over Lake
Huron leading to improved fetch through the northern half of the
basin. This offers peak winds near 30 knots through this evening as
a trough/frontal axis clips the northern waterways. Elsewhere, high
pressure builds into the region resulting in a relaxed pressure
gradient late tonight and into Monday morning. A Small Craft
Advisory will expire over Saginaw Bay this evening as waves respond
to decreasing wind speeds, attributed to the influence of high
pressure. The composite ridge gets displaced toward the east Monday
afternoon as a closed low over Saskatchewan opens up and phases with
a jet streak as the merged upper-level wave crosses into the High
Plains. This backs winds southerly by Monday afternoon with enhanced
flow across Lake Huron, including some diurnally drive gusts to
around 30 knots for a few hours. The low then crosses central
Ontario on Tuesday bringing a period of showers, a few
thunderstorms, and stronger southwesterly winds to the Great Lakes.
Brisk northerly flow ensues Wednesday with some low-end potential
for gales.
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&&

.PREV DISCUSSION...
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Issued at 110 PM EDT Sun Apr 21 2024

AVIATION...

VFR conditions hold through the forecast period as the region
resides below Midwestern high pressure. Diurnal 5-6kft cu field has
steadily expanded southward from northern lower MI over the course
of the morning and is expected to work into SE MI this afternoon,
though at generally FEW-SCT coverage. Deeper layer mixing will also
continue to support west/west-northwest wind gusts in the 20-25kt
range through early evening. Loss of diurnal heating/mixing allows
winds to drop significantly overnight to more light and variable
conditions as well as allow for clear or mostly clear skies.

DTW THRESHOLD PROBABILITIES...

* Low in ceilings aob 5000 feet through Monday morning.
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&&

.DTX WATCHES/WARNINGS/ADVISORIES...
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MI...Frost Advisory from midnight tonight to 8 AM EDT Monday 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.

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

$$

DISCUSSION...MR
MARINE.......KGK
AVIATION.....KDK

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