199
FXUS63 KDTX 160459
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1159 PM EST Mon Dec 15 2025

.KEY MESSAGES...

- A warmup is forecast for the middle of the week with temperatures
  in the mid to upper 30s Wednesday and 40s on Thursday.

- A strong storm system is forecast to impact the Great Lakes region
  late this week. Much of the precipitation is expected to fall in
  the form of rain on Thursday, transitioning to snow in some areas
  Friday. Gusty winds will accompany this system.

- There is the potential for any moisture on roadways to flash
  freeze Thursday evening/night as arctic air moves back into the
  region.

&&

.AVIATION...

Low clouds under a strong inversion layer have settled down by the
southern Michigan border bringing MVFR ceilings across all terminals.
These MVFR ceilings are expected to hold through the rest of the
night. Potential remains to see isolated flurry activity, but
coverage should be too sparse and light to add any mention of light
snow. Increasing southwest wind will then scatter out this deck from
south to north starting mid morning tomorrow as wind gust potential
reaches around 25 knots during the afternoon hours with some
lingering high clouds.

DTW THRESHOLD PROBABILITIES...

*   High for cigs aob 5000 feet through tonight.

&&

.PREV DISCUSSION...
Issued at 349 PM EST Mon Dec 15 2025

DISCUSSION...

Height rises commencing this evening mark the departure of upper
troughing and a pivot to a zonal flow pattern through mid-week. At
the surface, high pressure will remain relatively steady across the
SE CONUS with southwest return flow targeting the Great Lakes. This
allows for the pervasive arctic air mass to dislodge from the region
and allow for a warming trend through Thursday. Gusty wind this
afternoon will subside heading into tonight while 925-850mb flow
veers to westerly and advects Lake Michigan cloud across the area.
If enough supersaturation is maintained across the state, some
flurries will be possible given the DGZ placement in the boundary
layer. Most guidance is lean with the moisture suggesting mainly
just broken cloud cover. The cloud will dampen the diurnal
temperature response, but resident arctic air still allows for lows
in the lower teens overnight.

Strong warm advection ensues overnight into Tuesday with observed
850mb temperature of -11C this morning trending up to +6 to 7C by
tomorrow evening. This induces a strong stable layer and the warmth
will not be fully realized at the surface, but temps should climb to
around the freezing mark for the first time since last Wednesday.
There is a pool of low-level moisture progged to arrive from the Mid-
Mississippi Valley Tuesday night which may bring some patchy drizzle
or freezing drizzle but chances for this remain below 10% in
probabilistic data. Gusty southwest winds will accompany a
tightening pressure gradient during this period, producing a non-
diurnal temperature response with temps slowly climbing overnight
into the mid 30s by Wednesday morning.

A cold front passes across the area on Wednesday in response to a
low amplitude upper wave arriving from the Midwest. Moisture with
the front will be shallow and the overwhelming model signal is for a
dry fropa. This will send temps back into the 20s Wednesday evening.
Strong elevated warm advection follows from Wednesday night into
Thursday as a deep low emerges over the northern Rockies and tracks
into the Upper Midwest. The mature low will pass across the northern
Great Lakes daytime Thursday placing SE MI well within the warm
conveyor and favoring highs in the mid 40s. A corridor of deep
moisture transport will arrive during the mid to late morning,
favoring widespread rainfall during the day as temps in the lowest 6
kft sit comfortably above freezing. QPF is advertised on the order
of 0.25 to 0.50", which combined with snow melt may bring some
ponding on roads.

Ensemble guidance has come into more agreement for a 50 to 60 kt LLJ
overhead on Thursday which is at the 99th climatological percentile.
Much of this momentum will be locked above a strong inversion
resulting from the warm advection aloft, but still looking at a
period of gusty south winds to around 30 mph during the day. A
stronger pop of wind is possible during the evening as the initial
cold front/dry slot arrives, but by that point much of the momentum
aloft will be directed over the eastern Great Lakes.

The strong westerly flow and cold advection that follow frontal
passage suggest a rapid temperature drop which may result in a flash
freeze scenario with any residual moisture on roadways Thursday
evening. Will need to monitor this potential with regards to the
evening rush hour. As moisture wraps around the system with some
added contribution from Lake Michigan, some light snow showers will
be possible - mainly through early Friday morning but with potential
for additional streamers to arrive daytime Friday. The active
pattern sees another bout of southwesterly warm advection on
Saturday followed by another cold front Sunday tied to a weaker low
north of the Great Lakes.

MARINE...

Several rounds of strong winds will impact the central Great Lakes
through the course of the week. The current small craft conditions
will fade into this evening as a weak surface ridge sweeps by. The
next low pressure system will traverse Ontario, much like the current
one. The surface pressure gradient will be a little tighter,
supporting a stronger southwest flow wind response late Tuesday
afternoon through Tuesday night - especially across Saginaw Bay and
central portions of Lake Huron. Guidance is supporting sustained
winds approaching 30-kts with persistent gales gusts. Once the cold
front moves through early Wednesday, the focus for stronger westerly
winds will be across north-central Lake Huron. However, the
confidence in a meaningful window of gale gusts is not quite as high
Wednesday morning - therefore, will continue the current Gale Watch.
Only a brief respite before an even stronger system moves through the
region Thursday and Friday - with a better shot at gales.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 3 PM Tuesday to noon EST Wednesday for
     LHZ442-443.

     Gale Warning from 2 AM to noon EST Wednesday for LHZ361.

     Gale Warning from 3 PM Tuesday to noon EST Wednesday for LHZ362.

     Gale Warning from 3 PM Tuesday to 6 AM EST Wednesday for LHZ363-421-
     422-441-462.

Lake St Clair...Small Craft Advisory from 3 PM Tuesday to noon EST Wednesday for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 3 PM Tuesday to noon EST Wednesday for
     LEZ444.

&&

$$

AVIATION.....AA
DISCUSSION...TF
MARINE.......GM


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