789
FXUS63 KDTX 181659
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1259 PM EDT Wed Sep 18 2024

.KEY MESSAGES...

- Warm and dry weather prevails through the end of the week and
likely through the weekend.

- A weak cold front has a slight chance of reaching Lower MI with
spotty light rain possible late Friday into Saturday.

&&

.AVIATION...

Daytime heating has resulted in a scattered cumulus field early this
afternoon while the light easterly flow supplies the low level
moisture boost. Skies are expected to remain VFR, but cloud bases
will settle right around 3-4 kft and an occasional BKN observation
is possible. A return to mostly clear skies and light winds tonight
will bring another round of patchy to locally dense fog development.
Have tempo groups for MVFR VSBYs, but it will be possible to see
lower VSBY restrictions before lifting around 13-14Z. Winds remain
east-southeast and below 10 knots tomorrow with another round of
diurnal cumulus with the lake moisture boost.

For DTW/D21 Convection...No thunderstorms are forecast through this
week.

 DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 346 AM EDT Wed Sep 18 2024

DISCUSSION...

Deep layer ridging over the Great Lakes is responsible for continued
dry, stable, and warm conditions today through the end of the week.
Remnants of a tropical system and the parent cut off upper low will
remain stalled across the Carolinas today with the bulk of its
moisture holding well to our south. The main impact will be more
boundary layer cumulus that develops today as a tongue of sub-800mb
moisture spreads in from the southeast. Otherwise mostly sunny skies
will send high temps back to the lower 80s this afternoon. Mainly
clear skies follow for tonight, setting us up for another night of
favorable radiating conditions and patchy fog around daybreak
Thursday.

A pseudo omega block sets up Thursday into Friday as the cut off low
and a second deep upper low over the northern Plains maintain an
amplified 500mb shortwave ridge directly over the Great Lakes. This
favors a persistence forecast with little prospect for air mass
advection in this setup. Highs in the lower to mid 80s and lows in
the mid 50s to lower 60s will continue to be the norm. Mostly sunny
skies likely Thursday but Friday shows signal for higher cloud cover
as the northern Plains low sends an elevated front over the region.
This will be largely detached from the surface front that will lag
behind until Friday night or into Saturday morning. The parent low
will be far displaced over Hudson Bay so the front will be steadily
weakening as it moves in and encounters the resident ridge and dry
air mass. Still, this front presents our next opportunity for a few
light showers Friday night into Saturday.

A pattern shift is looking possible by early to mid next week with
the past few runs of medium range guidance advertising the ridge
giving way to a 4 Corners low and/or a Pacific trough. Still plenty
of details to work out regarding the interaction of these systems
but the pattern does support our first appreciable chances for rain
in over two weeks. Not surprising at this stage that there is a good
amount of spread in temperatures among ensemble members, but the
general trend does suggest a trend toward more seasonable temps will
be possible.

MARINE...

Persistent surface high pressure situated beneath a split-flow
configuration aloft maintains benign marine conditions across the
central Great Lakes through Friday, if not Saturday. Light east-
southeast winds (generally AOB 10 knots) veer more easterly today as
the surface ridge recenters over southern Ontario. Upstream surface
low pressure then tracks northeast across central Canada and into
Hudson Bay by Friday as its cold front extends well south of the
circulation offering low-end potential for showers/storms. Current
thinking favors dissipation of activity before anything reaches the
local waterways as the boundary is forecast to quickly wash out. The
next system emerges over the High Plains Saturday and translates
eastward through Monday offering an opportunity for slightly more
energetic winds and a non-zero chance for precipitation to close out
the weekend. Regardless, no marine headlines are expected through
the next seven days.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....AA
DISCUSSION...TF
MARINE.......KGK


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