Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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729
FXUS63 KDTX 240005
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
705 PM EST Thu Nov 23 2017

.AVIATION...

Dry southwest flow will continue tonight and Friday ahead of low
pressure moving in from central Canada. Conditions will be VFR with
gusty southwest wind the only significant aviation weather
developing by Friday afternoon. Even then, a shallow boundary layer
will limit gusts to the 20-25 knot range. VFR will consist of
stratocu over all the terminals initially except just brushing the
DTW area before exiting eastward during the evening. Mid and high
clouds will then thicken from late morning through Friday afternoon
as the low pressure system moves closer to the northern Great Lakes.

//DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less during the evening.

&&

.PREV DISCUSSION...
Issued at 301 PM EST Thu Nov 23 2017

DISCUSSION...

Skies are clearing this afternoon across southeast Michigan,
allowing temps to climb into the upper 30s to around 40 degrees.
Aggressive warm advection pattern ramping up through tomorrow with
increasing/deepening southwest flow, as strong shortwave trough moves
into Western Great Lakes tomorrow afternoon. Opportunity for winds
to decouple this evening, and with the dry airmass (dew pts in low to
mid 20s), a dip into upper 20s to around 30 degrees appears likely
before midnight, with temps steady or rising slightly overnight.

850 mb temps progged to reach 10+ C by 00z Saturday over southeast
Michigan, with 6 C noted at 925 MB, per 12z NAM, which is supportive
of highs in the mid 50s for Friday, but mixing depths probably
coming up just short of that level and went with temps predominantly
in the lower 50s. 850 MB Theta-E ridge well out ahead of the upper
level support early Friday evening, likely resulting in a mainly dry
cold front passage Friday Evening/Night. Post frontal surge of low
level cold advection and west/northwest flow off Lake Michigan may
provide better chance for sprinkles/light showers, with perhaps
enough cold air (-7 C at 850 MB) to support a few flurries on
Saturday. Regardless, expecting mostly cloudy skies, but mild start
should allow for maxes in the low/mid 40s before the deeper cold air
takes hold late in the day. Clouds slow to clear Saturday evening
and winds staying up much of the night expected to hold mins in the
upper 20s to around 30 degrees Saturday Night.

High pressure will build into the region on Sunday while a shortwave
pivoting southeastward tracks north of Lake Huron. This shortwave
will delay the onset of warm advection with highs in the low 40s on
Sunday. As the expansive region of high pressure becomes established
along the East Coast, southwest gradient flow will increase across
the region ahead of the next low pressure system tracking eastward
across Southern Canada.  This will help boost highs to near 50 on
Monday and well into the 50s on Tuesday.

Upper level ridging will also build across the region early next
week as a strong wave splits into a faster northern and slower
southern wave across the Western US. The northern wave will drive
the Canadian low eastward pulling a cold front through the Great
Lakes late Tuesday. The next chance for rain will accompany this
frontal passage before highs return closer to normal in the low to
mid 40s on Wednesday. Will then need to monitor the evolution of the
southern wave as it could bring another chance of rain/snow to the
region during the middle part of next week.

MARINE...

Area lakes will remain under gusty southwest conditions through
tonight, as return flow strengthens behind surface high pressure
over the eastern U.S. While the gustiest of the southwest winds will
occur out over the open waters of the Lake Huron basin during this
time, wave heights and wind gusts will respond enough in the long
southwest fetch to necessitate a small craft advisory over outer
Saginaw Bay.  The gradient will strengthen Friday in advance of an
approaching cold front. This will bring southwest winds of 25 to 30
knots across lake Huron.  While increasing stability may tend to
limit the overall gust potential, this will allow gusts to reach
gales for a period over the open waters. Winds turn west-northwest
and remain strong as colder air arrives Saturday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

Lake Huron...Gale Warning from noon Friday to midnight EST Friday night for
     LHZ462>464.

     Small Craft Advisory from 7 AM Friday to 4 AM EST Saturday for
     LHZ422-441>443.

     Gale Warning from 7 AM Friday to midnight EST Friday night for
     LHZ362-363.

     Small Craft Advisory until 6 AM EST Saturday for LHZ421.

Lake St Clair...Small Craft Advisory from noon Friday to 4 AM EST Saturday for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from noon Friday to 4 AM EST Saturday for
     LEZ444.

&&

$$

AVIATION.....BT
DISCUSSION...SF/JD
MARINE.......MR


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