Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 200442
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1142 PM EST Sun Nov 19 2017


.AVIATION...

Low level warm and dry air advection should lift the strato cu field
northeast of the terminals by 06z, leaving just higher based clouds
through the morning. Wind speeds have dropped with some boundary
layer decoupling. An increasing southwest gradient during the course
of the morning will lead to a slow increase in the wind speeds
toward daybreak, with peak daytime heating supporting some gusts
over 20 knots Mon afternoon.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 333 PM EST Sun Nov 19 2017

DISCUSSION...

The embedded wave within northwest flow impacting the Great Lakes
today will lift to the east along with the main upper trough as it
moves into the northeastern US tonight. Replacing it will be the
north side of a high pressure building across the southern US. The
loss of synoptic forcing and winds backing to a more westerly
direction will help bring an end to the lake effect snow showers
later today. Clouds will begin to slowly across parts of the area as
dry air begins to take over throughout the night. With a few less
clouds and cold air in place, temperatures will sink a little lower
into the mid to upper 20s by tomorrow morning.

Tomorrow will see some warm air advection with mostly clear skies as
high pressure brings a dry start to the work week. Zonal flow at mid
levels with more southwest flow at lower levels will push the cold
air aloft to the east. Temperatures at 850mb will increase by around
14-15 C from this afternoon to tomorrow afternoon resulting in high
temperatures in the mid to upper 40s. Pressure gradient will increase
slightly ahead of the next low pressure system to affect the Great
Lakes region. This will lead to an increase in winds during the
afternoon with a few gusts during the day to around 20-25 mph.

Height falls will begin to spread across the region as the low
pressure system digs across the western Great Lakes Monday night
into Tuesday morning. Southwest winds will stay elevated through
this time as the center of the surface low moves through southern
Ontario. The upper trough gains amplitude into Tuesday across the
central Great Lakes as associated cold front sweeps through Michigan.
Slight chance of rain will be possible ahead of the front with good
synoptic forcing and an increase in moisture, albeit still low.
Rain/snow mix could be possible on the back edge of precipitation as
temperatures drop towards the evening. Winds will remain elevated
until lighter post frontal winds arrive in the evening.

High pressure will build into the region on Wednesday and remain in
control through Friday. This will bring a period of dry, calm
conditions with highs in the mid to upper 30s for the Thanksgiving
holiday. Weak ridging will move across the region on Friday ahead of
a low pressure system tracking eastward through southern Canada.
Increased southerly flow on Friday will help boost temperatures into
the 40s before the next chance of precipitation arrives Friday
night. With model solutions all showing the low tracking through
Ontario, the better forcing for precipitation looks to stay mainly
north of SE Michigan with higher chance for rain across the Tri
Cities and Thumb. Warm advection Friday night should be enough to
keep precipitation all liquid before a cold front pushing through
the region early Saturday brings a return to northwest flow and cold
advection across the region next weekend.

MARINE...

Northwest winds will gradually decrease this evening into tonight
and back to a more westerly direction. That said, gusts to near 30
knots will be possible into early evening over northern parts of
Lake Huron. Small Craft Advisories along the nearshore waters, other
than near the tip of the Thumb, will expire with this issuance, and
for these final two zones by mid evening after waves and remaining
wind gusts subside.

A Gale Watch remains in effect Monday night into Tuesday as winds
back further to the southwest and increase as low pressure tracks
across northern Ontario and leads to an strong pressure gradient as
the trailing cold front approaches on Tuesday. Wind funneling up
Saginaw Bay looks as if it may be enough to bring gale force gusts
to the bay as well, so the watch has been extended for this area.
Northwest flow behind the aforementioned cold front may very well
lead to a period of gales into Tuesday night, at least over far
northern portions of Lake Huron.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Watch from Monday evening through Tuesday afternoon for LHZ362-
     363-421-422-462>464.

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

$$

AVIATION.....SC
DISCUSSION...AA/JD
MARINE.......DG


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