Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 012337

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
737 PM EDT Sat Oct 1 2022


A secondary area of surface high pressure is building aggressively
southward through much of northern Ontario this evening. Models show
an enhanced pressure gradient at the edge of this secondary high
pressure which is now positioned over the northern Great Lakes. This
enhanced pressure gradient is forecasted to release southward
through Southeast Michigan late tonight taking on the form of a weak
cold front. Model soundings show a good amount of shallow cold air
advection centered between 1.5 and 3.0 kft agl after 06Z tonight
from north to south. This caa may be good enough to result in
saturation and development of stratus/stratocu. The inherited tafs
were aggressive with this cloud and will continue the mention for
BKN MVFR north of the Detroit taf sites. Northwest wind direction
theoretically enhances the potential for additional Lake moisture to
duct into the area. The parent air mass remains dry and will favor
very clear skies then once daytime heating occurs Sunday.


* Low for cigs aob 5000 feet tonight and Sunday morning. Low to
  Moderate potential late Sunday morning or early afternoon.


Issued at 304 PM EDT Sat Oct 1 2022


There will be a persistence of light northeast low level winds
tonight as the region lies between strong high pressure across nrn
Ontario and the now extratropical remnants of Ian lifting into
Virginia. The result will be some shallow cold air advection through
the night. Model soundings suggest this will result in a deepening
low level inversion. Both RAP and the 3km NAM indicate the moisture
flux off Lake Huron will result in some low stratus ducting off the
lake under this inversion, supporting the likelihood of an inland
expansion of stratus overnight into early Sun morning. This and the
lingering gradient flow will limit nocturnal cooling, supporting
nighttime mins in the mid 40s to lower 50s.

The blocking pattern over the upper Midwest/Great Lakes will persist
into early next week. Mid level ridging will actually amplify across
the Great Lakes Sunday into Monday, enhancing low to mid level
anticyclonic flow. There will be an initial surge of low level dry
air from the northeast on Sunday, clearing any lingering status
during the afternoon. Deep layer dry air and sfc high pressure will
then influence Se Mi thru Tuesday night. Light winds with ample
clear sky will result. Model soundings and ensemble guidance suggest
mainly seasonal highs in the 60s to low 70s. Conditions will however
be favorable for good radiational cooling which will support some
cool nights. Some nighttime fog, especially considering the lingering
light easterly flow off the lakes, will be the only potential
weather concern for the next few days.

A highly amplified northern stream wave is then forecast to break
down the blocking pattern, driving a potent fall cold front across
the Great Lakes. There is not only strong model agreement in this
long wave pattern shift, ensemble members do not show too much
spread in timing the system into Lower Mi despite this being around
day 5 (Thursday). The approach of this upper wave/sfc front will
bring the next chance for rain on Thursday. 850mb temps are forecast
to drop into the negative single digits behind this wave, resulting
in a period of respectable early October cold air during the end of
the forecast period.


Northeast winds continue to strengthen this evening as the region
remains in between the remnants of Ian and strong high pressure over
northern Ontario. Strongest winds still anticipated late
evening/early tonight over central Lake Huron and the Saginaw Bay
where gusts top out in the 25-30kt range. There still appears to be
a brief window where gusts could approach entry-level gales over the
central open waters of Huron late this evening however strength and
duration not expected to warrant any headlines. Small craft
advisories continue for all nearshore waters into Sunday before
winds and waves gradually begin to relax as the Ontario high sags
south into the Great Lakes. This weakening high drifts south across
the region through the first part of the next work week bringing a
return to favorable marine conditions.


Lake Huron...Small Craft Advisory until 4 AM EDT Monday for LHZ421-441>443.

     Small Craft Advisory until 10 PM EDT Sunday for LHZ422.

Lake St Clair...Small Craft Advisory until 10 AM EDT Sunday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EDT Sunday for LEZ444.




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