565
FXUS63 KDTX 232249
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
549 PM EST Sat Nov 23 2024

.KEY MESSAGES...

- Dry and seasonable weather with mostly cloudy skies through Sunday.

- Low pressure will bring rain chances and brief shot of milder air
on Monday.

- Below normal temperatures arrive Tuesday and likely persist into
next weekend.

- There is the potential for snow for the upcoming holiday weekend.

&&

.AVIATION...

Per recent ACARS and model soundings, moisture remains trapped under
a deep inversion which will sustain stratus across the Se Mi
terminals. During the night, there is going to be some subtle north
to south differences in the thermal advection patterns across the
inversion. Across the south, weak warming atop the inversion will
lower the cloud bases during the night, increasing the probabilities
for low end MVFR ceilings, especially across the metro Detroit
terminals. Farther north, toward MBS, subtle cooling will lift
inversion bases. This will trend conditions more favorably toward
low end VFR, which is already playing out in current observations.
Late tonight and during the morning on Sunday, there will be some
subtle boundary layer convergence forecast to track into Se Mi from
the southwest. There remain indications in several model solutions
that this added moisture pooling/convergence will support some
drizzle, perhaps even some IFR based clouds. This will be most
probable from KFNT south during the entire morning.

DTW THRESHOLD PROBABILITIES...

*  High in ceilings at or below 5000 ft tonight and Sunday. Low
   Sunday evening.

&&

.PREV DISCUSSION...
Issued at 351 PM EST Sat Nov 23 2024

DISCUSSION...

Rising MSLP field today is the result of subsidence in the wake of
the upper low departing off the coast of New England. This hasn`t
been enough to scour out the stratus layer around 2500 ft AGL but
drizzle production has been shut down leaving a dry and seasonable
but cloudy afternoon and evening. A col in the surface pressure
pattern works in from the west tonight, causing light winds to back
with time. Subsequent moisture pooling may be sufficient to produce
some spotty drizzle overnight given pockets of low-level omega
intersecting the saturated boundary layer. Otherwise, most areas
should stay mainly dry as lows settle into the 30s Sunday morning.
Neutral low-level thermal advection overnight results in another
typical late-November day tomorrow with highs in the 40s. There
should be some breaks in the stratus by late in the day as sfc-900mb
flow flips to the south and cuts off the moisture stream, but the
arrival of high clouds will likely prevent much in the way of
appreciable sunshine.

Monday presents the next chance for light rain as a low pressure
system lifts across the Great Lakes in response to an upper wave
moving in from the Great Plains. Latest guidance keeps us within the
warm sector of this low on Monday, with temps rising into the lower
50s and ensuring an all-rain scenario with bulk of ensemble QPF on
the order of a quarter inch or less. A strong cold front will follow
this system Monday night with temps then tumbling back into the 30s
by Tuesday morning. This will bring the chance for light snow
showers but most of the precip will be on the way out so
accumulations are not anticipated. Additional lake effect showers
will be possible in the Thumb on Tuesday. Otherwise, mainly dry
conditions hold into Wednesday as zonal flow dominates aloft. The
cooler air working in behind the system should hold temperatures
slightly below normal through this period.

For an early look at the Thanksgiving forecast, mean of ensemble
guidance supports longwave troughing developing over eastern North
America which favors a cold and possibly snowy outcome for the Great
Lakes. Relatively high confidence exists in high temps in the 30s
given 90th-10th percentile spread of only about 5 degrees, which is
low for a day 6 forecast. The mean of each ensemble system and the
latest medium range deterministic runs produce a band of deformation
precip somewhere across the southern Great Lakes or Ohio Valley
Wednesday night into Thursday. The 00z and 12z runs of the ENS have
generally favored placing the band near southern lower MI with the
12z run adding more membership on-board for this solution. This would
likely result in accumulating snow for the area. Meanwhile, the GEPS
and GEFS are leaner on snow and precipitation amounts locally with
farther south band placement, but these ensembles are still
supportive of at least a chance of light precip. Something to keep an
eye on for holiday travel concerns.

MARINE...

Northwest winds have subsided substantially today as a result of the
weakening/departing pressure gradient tied to New England low
pressure. Favorable flow across the lake aggregate and the lingering
cold airmass keep scattered lake-enhanced showers going across Lake
Huron tonight until flow sufficiently weakens by Sunday morning. A
quieter marine forecast is in store for Sunday as the Great Lakes
sit under a more diffuse pressure gradient between two low pressure
systems. By Sunday night, flow shifts fully to the southeast ahead
of a low pressure system that will eject out of the Plains. Warm air
on the front end of this system ensures precipitation on Monday is
rain, while also keeping thermal profiles stable enough to prevent
gusts over 20 knots despite the strong low level jet aloft. The
surface low is forecast to track into Lake Huron Monday night,
dragging a cold front through the area. The strength and placement
of this low still differ enough to have significant implications for
the wind field forecast Tuesday-Wednesday, but gales are within the
upper bounds of the guidance.

&&

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

$$

AVIATION.....SC
DISCUSSION...TF
MARINE.......MV


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.