458
FXUS63 KDTX 220004
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
804 PM EDT Fri Mar 21 2025

.KEY MESSAGES...

* Breezy SW wind continues this evening while a cold front remains
  on schedule to sweep through Lower Michigan late tonight into
  early Saturday morning.

* The front brings a light mix of rain changing to snow as
  temperatures fall rapidly into the mid 20s to lower 30s.

* Colder but dry weather holds through Saturday.

* The next low pressure system brings increasing coverage rain and
  snow showers Sunday afternoon through Sunday night. Minor
  accumulation is possible, mainly north of I-69.

* Unsettled weather continues into Monday as a large low pressure
  system lingers across the Great Lakes.

&&

.AVIATION...

VFR conditions will last through this evening while southwest winds
remain gusty within the 25 to 30 knot range. A strong low level jet
with 50 knots winds will reside at 2 to 3 kft AGL during the 00Z to
06Z time frame bringing some LLWS concerns. Soundings point towards
surface winds remaining gusty, so will continue to preclude mention
at this time and will monitor surface wind trends for any needed
amendment. A strong cold front will be tracking through southeast
Michigan after 06Z and will bring a northwest wind, a chance of
light rain/snow, and MVFR ceilings across all terminals. Timing
across the area for this activity is between 09Z and 13Z and have a
TEMPO for light rain/snow all terminals. Southern metro terminals
carry a little more uncertainty in coverage. Early to mid morning
MVFR ceilings become VFR by late morning and afternoon.

For DTW...Frontal passage is expected between 09z and 13z tomorrow
morning, with a wind shift to 330 degrees and a chance of light rain
and snow. No accumulation is anticipated.

.DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 ft tomorrow morning.

* Low for precip type as snow tomorrow morning.

&&

.PREV DISCUSSION...
Issued at 411 PM EDT Fri Mar 21 2025

DISCUSSION...

Gusty SW wind is helping temperatures rebound from a frosty start
this morning into the lower 50s as of mid afternoon. This is a
typical quick warming trend in stronger gradient flow ahead of the
next Midwest cold front that is on schedule to move through Lower Mi
late tonight. The front is tied to northern Ontario low pressure
that has quickly followed the system that swept Gulf moisture from
the entire country east of the Rockies during the mid week period.
Broad surface high pressure along the Gulf coast is now preventing
all but the most slightly modified cP air from returning into the
Great Lakes frontal zone tonight. This lack of Gulf moisture will be
somewhat compensated for by strong short wave forcing that wrings
out what mid level Pacific moisture is available. Model depictions of
near 0 C 850 mb LI and 700-500 mb lapse rate near 8 C/km indicate a
component of elevated instability to help with pockets of briefly
higher precip rate. The front itself covers the rest of entry level
categorical rain shower coverage as it enters SE Mi after midnight.
Rain showers mix with and change to snow showers as low level cold
air surges in post front and along the west flank of the system
moisture axis. Blended model temperature projections take readings
down into the upper 20s by sunrise everywhere except closer to the
Canadian and Ohio borders. These are optimistically warm numbers
given single digit readings observed upstream across northern
Ontario this afternoon, but which ensure at least a short period of
all snow and possibly a slushy coating of accumulation on unpaved
surfaces, before the moisture axis exits eastward by mid morning.

Flurries linger for the rest of Saturday morning followed by a
decreasing cloud trend in the afternoon. Surface high pressure
builds aggressively eastward with a mid level short wave ridge from
the Plains and Midwest to a position over Lower Mi Saturday night.
Low temperatures in the 20s are the weather highlight promoted by
clear sky and light wind into Sunday morning.

Rapid progression of mid level systems continues Sunday and lines up
the Great Lakes for the next round of precipitation in the afternoon
through Sunday evening. Classic cyclogenesis in the lee of the
Rockies occurs across the northern Plains which by then has access
to a much better Gulf moisture supply. SE Mi is still on the "cold"
side of the system with an easterly component to the low level wind
field that favors deterministic models with lower surface
temperatures by Sunday afternoon. There is also substantial wet bulb
cooling potential in model soundings as the leading band of
precipitation reaches the Great Lakes. These elements battle the
strength of mid March daytime heating for dominant influence on
precipitation type. As it stands in today`s data, the best chance of
rain/snow mix to all snow is north of I-69 across the Thumb Sunday
afternoon into Sunday evening. The system then fully occludes and
stalls over the Great Lakes to start off next week with cool and
unsettled conditions.

MARINE...

Moderate to strong southwest winds persist through much of this
evening in response to an approaching arctic cold front. Strongest
winds over the Saginaw Bay/central Lake Huron peak around 30kts as
warmer air maintains sufficient stability to limit/outright prevent
gusts reaching 34kts. A slight weakening trend occurs after sunset
as diurnal mixing ends though gusts between 20-25kts can be expected
across most of the waters. Said cold front drops through the central
Great Lakes at/after midnight tonight ushering in renewed cold
northwest flow. Gusts along/immediately following the front will be
able to reach around entry-level gales (local probabilities still
suggest 40-50% to reach 34kts). The window for occurrence is
relatively narrow, only 2-4hrs, as surface high pressure is fairly
quick to start building in behind the front early Saturday. With the
marginal setup for both duration and wind strength, have continued
to hold off on any gale headlines with the forecast update. Small
craft advisories however will be needed for all nearshore waters due
to the combination of stronger winds and subsequent larger waves.
High pressure drifts over the region Saturday through the first half
of Sunday supporting lighter flow and dry conditions. Another low is
set to move into the northern Great Lakes late Sunday lifting a warm
front into the central lakes bringing widespread rain-snow showers
and moderate SW/WSW flow.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT Saturday for LHZ421.

     Small Craft Advisory until 4 PM EDT Saturday for LHZ422.

     Small Craft Advisory from 2 AM to 10 PM EDT Saturday for LHZ441-442.

     Small Craft Advisory from 8 AM to 10 PM EDT Saturday for LHZ443.

Lake St Clair...Small Craft Advisory from 8 AM to 4 PM EDT Saturday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 8 AM to 4 PM EDT Saturday for LEZ444.

&&

$$

AVIATION.....AA
DISCUSSION...BT
MARINE.......KDK


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