Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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253
FXUS63 KDTX 270720
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
320 AM EDT TUE SEP 27 2016

.DISCUSSION...

Expansive upper level low to plague the region right through the
weekend, with the wild card being the amount of Atlantic moisture
wrapping back into the Great Lakes Region during the end of the work
week.

00z model trends certainly support what yesterday`s 00z Euro
advertised, a stronger and more symmetric system, taking longer to
be dislodged from the area.

Dry air/850-700 mb theta-e minimum in place this morning over
southern Lower Michigan will slowly be sinking south during the day.
The key word, slowly, and at the very least, areas south of I-69
should remain dry today. The 00z GRB Raob indicated 3 C at 850 MB
which will make inroads into the State, but there does look to be a
northwest (3 C at 850 MB) to southeast (6 C) temp gradient setting
up, as max height falls take place back across the Midwest.
Subsequently, expecting low clouds having difficult time sinking
southeast of the Irish Hills during much of the daytime hours, and
temperatures should rise into the upper 60s across Detroit and
points south, with low to mid 60s north.

Model consensus indicates Sfc-850 mb circulation progged to sink
south along the eastern Lake Michigan shoreline Tonight into
Wednesday, a bit farther west than indicated yesterday. Have
trimmed back pops some tonight. Tomorrow, southeast michigan will
reside on the milder and modestly unstable side, with MLcapes of
250-500 J/kg, which should be sufficient to touch off high
scattered-numerous shower activity, as spoke of energy also
rotates up from western Ohio. Isolated thunderstorms remain
possible as nam soundings show EQL climbing above -20 c isotherm,
but the positive area is sliver thin that high. Any thunderstorm
that materializes could contain small hail with low freezing
levels in place.

Upper level center/500 mb low digging down into Kentucky with Warm
Conveyor belt arching back into southeast Michigan Thursday-Friday,
and there is now solid agreement in a good Atlantic Moisture (10
C dew point at 850 MB) connection reaching southeast Michigan.
With the moisture advection, cyclonic flow, and multiple upper
waves/pv centers rotating around the large circulation, it appears
likely showers will be around. Very low risk of an embedded
thunderstorm as showalter index oscillates around zero per 00z
Euro.

The system finally looks to slowly unravel over the weekend as
some upper level energy over BAJA California tracks northeast into
the plains, weakening the upper level ridge and allowing for slow
Eastward advancement.

&&

.MARINE...

Small craft advisories remain in effect through today for all marine
areas of southeastern Michigan. Wave action will begin to diminish
today but remain in the 5 to 7 foot range over the open waters of
central Lake Huron. Low pressure will then stall south of the Great
Lakes for the remainder of the week, setting up several days of
moderate to occasionally fresh easterly winds. There is expected to
be an extended time period from Wednesday through Friday when small
craft advisories will be needed on Lake Huron.

&&

.PREV DISCUSSION...
Issued at 1155 PM EDT Mon SEP 26 2016

AVIATION...

The upper short wave feature which generated some showers across the
Saginaw Valley and thumb this evening will depart to the east early
this morning, leaving a period of large scale subsidence in its wake
this morning. Recent observations suggest just some mid level clouds
will impact the region this morning, mainly north of metro Detroit.
The onset of daytime heating late in the morning will support the
expansion of a VFR based cu field and an increase in southwest winds.

For DTW... Winds will increase in the 15 to 17Z time frame on
Tuesday as daytime heating increases the boundary layer depth. The
gradient on Tuesday will support a more southwesterly direction.

//DTW Threshold Probabilities...

* Low in ceilings at or below 5000 ft tonight and Tuesday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening FOR LHZ421-422-
     441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening FOR LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening FOR LEZ444.

&&

$$

DISCUSSION...SF
MARINE.......CB
AVIATION.....SC


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at www.weather.gov/detroit.



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