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000
FXUS63 KDTX 201154
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
754 AM EDT Sat Apr 20 2024

.KEY MESSAGES...

- Brisk and mostly cloudy today followed by more sun and a
temperature rebound on Sunday. Frost is possible tonight and Sunday
night.

- Next chance of showers and thunderstorms arrives Tuesday.

&&

.AVIATION...

Substantial midlevel cold advection within deep troughing will
support VFR stratus/altostratus over much of Lower Michigan today.
Diurnal heating will also promote additional boundary layer
stratocumulus development after 17Z. West to northwest winds of 15
to 25 knots is expected in deepening boundary layer mixing. Strongly
anticyclonic flow trajectories tonight will help clear skies after
dark.

DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 355 AM EDT Sat Apr 20 2024

DISCUSSION...

Mid-level height falls are evident in regional water vapor imagery
this morning as a lobe of PV is driven across the Great Lakes by a
deepening closed low over Hudson Bay. This is sending a cold front
across the region but with minimal moisture advection into the 0.30
inch PWAT environment sampled by the 00z DTX RAOB, the front is
passing over largely precip-free save for some light flurries in the
Thumb. It will however usher in just enough post-frontal boundary
layer moisture to maintain a healthy stratocumulus field through
much of the day. 850mb temps settle to near -8 C this afternoon
which is below the 10th percentile per SPC sounding climatology,
keeping high temps seasonably cool in the mid 40s to around 50.
Meanwhile, a stout pressure gradient holds over the region between
the Canadian low and high pressure building into the Ohio and
Tennessee Valleys, producing a breezy west wind at 20 to 25 mph. The
end result will be a brisk and mostly cloudy April day with a wind
chill in the lower to mid 40s.

The cold and dry air mass will stick around through tonight before a
slight temperature rebound on Sunday. With our growing season off to
an early start, frost/freeze concerns come into play with low temps
likely to fall to the lower to mid 30s. Lots of clouds noted in
upstream satellite imagery and plenty of variance among model
solutions brings uncertainty in the degree of clearing that will
occur tonight. Weak gradient wind will also be a factor that will
likely prevent temps from completely cratering. Did consider a Frost
Advisory with this package but ultimately decided to defer to the
next shift when trends in clouds, winds, and low temps should become
more apparent.

Another dry mid-level trough passes overhead Sunday morning,
ushering out the coolest air and inducing a deep layer subsidence
response through the rest of the day. This warms the column while
maintaining mostly sunny skies to provide a boost in surface
heating. This nets a meaningful temperature rebound to the mid to
upper 50s. The breezy west wind will remain pervasive over the
region for another day. This leads into another chilly period Sunday
night with lows again flirting with the freezing mark. On Monday, an
amplified 850mb ridge crests overhead, keeping conditions dry and
opening the door for more meaningful warm advection to trend high temps
up a few more degrees into the lower 60s.

Tuesday remains the target for our next round of showers and
potential thunderstorms as there continues to be good agreement in
model solutions showing a closed low over Manitoba ejecting ESE as
an open shortwave. Developing southwest flow provides a steady
moisture stream ahead of the attendant cold front, with LREF mean
showing PWATs increasing to around 0.75 inches. This supports the 60-
70% PoPs provided by the NBM. The GEFS suite continues to advertise
a stronger cold advective response behind this wave, driven by a
seemingly over amplified Hudson Bay PV anomaly not represented in
the ENS and GEPS ensembles. The mid-week temperature forecast
continues to carry a good amount of uncertainty at this stage, but
potential is there for sub freezing temperatures if the colder
solution does play out.

MARINE...

Upper level trough holds over the central Great Lakes this weekend
maintaining the cooler than normal airmass already in place.
Westerly winds shift northwesterly today as a wave embedded within
the trough swings through the region though little to no precip
anticipated with this system outside a couple light rain-snow
showers over far northern Lake Huron. Gradient weakens latter half
of today allowing for a modest reduction in winds (falling below
20kts) going into the overnight period. Stronger west turning
northwest flow redevelops daytime Sunday as low pressure tracks over
eastern Ontario/Quebec re-tightening the local gradient. Strongest
winds expected over the central and northern portions of Lake Huron
where peak gusts reach 25-30kts. Small craft advisories likely will
need to be reissued for the Saginaw Bay and potentially portions of
the Thumb nearshore waters as a result. Gusts closer to 20kts
favored over the southern portions of the region.

&&

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

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

$$

AVIATION.....CB
DISCUSSION...TF
MARINE.......KDK


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