Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 211130

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


Aggressive push from surface ridging has allowed northerly winds to
develop over the northern Detroit metro area this morning. This has
resulted in improving surface visibility trends. VLIIFR fog that was
in place at KFNT and KPTK between 07-09Z has improved to MVFR-IFR
before 11Z while some modest improvements area also ongoing at KDTW
and KYIP. Given the trends, will continue to see improvements the
next hour or two and have reasonable confidence low cloud will
erode. Otherwise, high cloud with low opacity will stream west to
east across the region today. Compact pressure gradient and
increased mixing due to cold air advection will allow northwest
winds to increase today after 19Z, then lingering well into the
overnight. High confidence in wind gusts today ranging between 20
and 25 knots.

For DTW...Fog will rapidly erode the first hour or two of the
forecast. High confidence in NW winds developing after 19Z of 20 to
25 knots. Moderate probability of crosswind thresholds being met by
early this evening.


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


Issued at 420 AM EDT Tue Mar 21 2017

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.


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.


MI...Dense Fog Advisory until 9 AM EDT this morning for MIZ075-076-082-

Lake Huron...Gale Warning from 4 PM this afternoon to 4 AM EDT Wednesday for

     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

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

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.




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