Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 210820
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
420 AM EDT Tue Mar 21 2017

.DISCUSSION...
For the rest of this morning main issue will be widespread fog from
about the I69 corridor on south as plenty of low level moisture
resides within a weak surface ridge gradient.  Visibilities vary
with most widespread denser fog from the Detroit Metro area south
with pockets as low as a quarter mile.  Fog should mix out
within a few hours after sunrise.

For today, a strong arctic cold front will be blowing through the
area reaching the Saginaw Valley near noon then through the Detroit
Metro area around 4pm.  Very moisture starved front so its passage
will only be marked by some clouds and an increase in northwest
winds with gusts to around 25 mph.  Highs today will reach the mid
40s north late this morning just prior to frontal passage to the mid
50s along the Ohio border.  Very cold air will continue to funnel
into the region through Thursday as the large arctic high slides out
of central Canada and settles over Michigan Wednesday then slowly
slides to the east Thursday.  Mostly clear skies and cold temps
through this period with lows both Wednesday and Thursday mornings
reaching the teens and even single digits. Only concern precip wise
will be lake effect snow band brushing the eastern shoreline of the
Thumb tonight. At this point mixing depth and moisture in this band
does not look too deep or high so expecting little if any
accumulatlons if it brushes on shore.

Large trough off the Pacific coast will work eastward inducing lee
cyclogensis over eastern Colorado Wednesday. This system will close
off quickly then drift over lower Michigan for the weekend. In the
meantime a surface warm front will begin developing and strengthening
over lower Michigan Thursday night then lift slightly north before
stalling across central lower late Friday. This will bring rain
showers to the area late Thursday night possibly mix with snow at the
onset. Showers activity will likely last throughout the weekend with
mild temperatures as highs Friday behind the warm front could push
into the low 60s and 50s for the weekend.

&&

.MARINE...

Persistent weak troughing over portions of Ontario north of the Lake
Huron and Lake Superior has kept the arctic air bottled up north of
the region this morning. Weak winds are expected during the next 6
hours or so. This will change very rapidly by midday when an arctic
cold front will push steadily southward through lower Michigan. The
arctic air mass is forecasted to flood into the northern Lake Huron
basin by 18Z. Cold, unstable conditions then leads to high
confidence in gale force winds across the Lake Huron basin. Fairly
high confidence exists that gale force will not impact Saginaw Bay.
Aggressive nature of cold advection tonight necessitates a small
craft advisory for Lake St Clair and the Michigan waters of Lake
Erie from 20z this afternoon through 14Z Wednesday. Much quieter
marine weather is forecasted for both Wednesday and the beginning of
Thursday with sprawling arctic high pressure parked overhead.

&&

.PREV DISCUSSION...
Issued at 1152 PM EDT Mon Mar 20 2017

AVIATION...

Despite ample mid and high clouds overhead, remnant low level
moisture has result in widespread fog across metro Detroit. Dry air
will contiue to nudge into the region from the north during the
early morning. This will result in an erosion of the fog during the
pre dawn hours or shortly after. Arctic air will advance into the
region Tues afternoon. The increased gradient and deepening mixed
layer will support increasing west-northwest winds mid to late Tues
afternoon.

For DTW...With some thinning of the high clouds overnight, dense fog
has become more probable at metro. The expections are for the drier
air from the north to lift the fog by 12Z. The timing of which does
however carry some degree of uncertainty.

//DTW THRESHOLD PROBABILITIES...

*  Moderate in ceilings and/or visibilities dropping below 200 ft/
   one half ile this morning.

*  Low in crosswind thresholds being exceeded Tuesday afternoon and
   evening.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning from 4 PM this afternoon to 4 AM EDT Wednesday for
     LHZ362-363-441-462>464.

     Small Craft Advisory from 4 PM this afternoon to 10 AM EDT
     Wednesday for LHZ421.

     Gale Warning from 8 PM this evening to 8 AM EDT Wednesday for
     LHZ442-443.

     Gale Warning from 4 PM this afternoon to 10 PM EDT this evening for
     LHZ361.

Lake St Clair...Small Craft Advisory from 4 PM this afternoon to 10 AM EDT
     Wednesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 4 PM this afternoon to 10 AM EDT
     Wednesday for LEZ444.

&&

$$

DISCUSSION...DRC
MARINE.......CB
AVIATION.....SC


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



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