Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 221933
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
333 PM EDT SAT OCT 22 2016
Low level cyclonic flow associated with the deep low pressure system
over New England is finally loosening its grip across Se Mi. A
surface ridge axis now sliding across wrn Lower Mi is forcing the
low level flow across Se Mi toward more anti cyclonic. This and the
very shallow nature of the cloud cover today has resulted in a rapid
clearing trend. There are however some mid clouds now over Lake
Michigan. These have developed within a narrow ribbon of mid level
warm air advection. This axis of warm air advection/isentropic
ascent will track across the forecast area this evening and during
the first half of the overnight, providing some degree of mid clouds
tonight. The gradient will be much weaker tonight and there will be
at least some periods of clear skies. This will support min temps
down into the mid 30s to low 40s.
A low amplitude mid level trough axis over the Montana/Canadian
border this afternoon will move into upper Mi on Sunday, then
advance into the eastern Great Lakes/upstate New York Sun night. The
associated mid level height falls will force weak sfc low pressure
and an associated cold front from Wisconsin to srn Lower Mi Sun
afternoon. The 12Z model suite all indicate a plume of mid level
moisture advecting into Lower Mi Sun afternoon ahead of the upper
wave. Strengthening frontogenesis in the 925-850mb layer will
interact with this moisture plume to provide a chance of showers,
mainly Sun evening. The expected brevity of the forcing and lack of
appreciable depth to the moisture suggest low chance pops and
minimal QPF with any showers. Low level warming ahead of the sfc
wave is expected to push 925mb temps up to +10 to +13C, which will
support afternoon highs into the 60s over much of the area (outside
the thumb) on Sunday.
A broadening of an upper low over ern Canada and an amplification
of a long wave ridge over central North America on Monday will
lead to fairly strong mid level confluent flow across the region
during the first half of the week. As a result, sfc high pressure
will expand across the wrn Great Lakes, forcing low level
northwesterly flow across the region. This will bring cooler air
back into Se Mi Sunday night into Monday, where it will persist
into mid week. Lake aggregate troughing should become firmly
established across the region within this airmass and will likely
support a fair amount of cloud cover, especially on Monday.
High pressure building into the area on Tuesday will keep us dry as
we see a mixture of clouds and sunshine throughout the day. The next
chance for precipitation will come Wednesday afternoon into Thursday
as low pressure from the Central Plains pushes ENE, settling over
Michgan on Thursday. With unimpressive instability parametes, rain
showers will be the main concern with the low, along with slightly
breezy conditions. Additional chances for precipitation will be
possible Friday into the weekend as a second low pushes east across
Gusty fresh northwest wind will diminish late tonight which will
allow waves to subside and for expiry of Small Craft Advisories.
Marine weather will then remain on the quiet side through most of
Sunday before a passing clipper brings renewed surge in northwest
wind causing widespread gusts to near-gales Sunday night into Monday
night. Small Craft Advisories will once again be needed for
nearshore zones during this time.
Issued at 1154 AM EDT Sat OCT 22 2016
Inversion above 3kft on 12z DTX sounding supports lake enhanced
diurnal cu field remaining VFR through the period, particularly
given shallow nature of moisture. Clouds will dimnish late in the
day as moisture mixes out and gusty winds will subside by early
evening with the loss of heating. Winds back to the SW tonight as
mid-level cloud band over eastern WI moves across thea rea.
For DTW...Visible satellite trends suggest broken ceiling by
forecast issuance time. Stout nature of this morning`s inversion
will likely keep cigs below 5kft. Expect to see a trend of
thinning/dissipating cloud cover as early as 20z. Wind gusts pushing
25kt from the NW and therefore potentially causing crosswind issues
will be short-lived as winds within the boundary layer weaken
through the day.
//DTW Threshold Probabilities...
* Medium for cigs aob 5kft this afternoon. Low tonight after 06z.
* Low for brief/marginal crosswind 300/25kt during the first 1
or 2 hours of the forecast.
Lake Huron...Small Craft Advisory until 4 AM EDT Sunday FOR LHZ421-441>443.
Small Craft Advisory until 10 PM EDT this evening FOR LHZ422.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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