Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251649
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1149 AM EST Sun Feb 25 2018


.AVIATION...

Low clouds (2500-3500 feet) will continue to mix out early this afternoon
with skies becoming clear by sunset. Clear/mostly clear skies then
persisting this evening through the end of the taf period. The
exception may be across MBS, as modestly cold westerly flow off Lake
Michigan may support a high MVFR deck over northern Lower Michigan
late tonight into tomorrow morning, which may extend far enough south
to impact MBS.

The strong southwest winds this morning around 20 knots sustained
and gusts of 30-40 knots will diminish this afternoon, with
sustained winds lowering to around 10 knots this evening with gusts
ending. Winds then mostly below 10 knots late tonight into tomorrow
morning.


/DTW THRESHOLD PROBABILITIES...

* Medium for cigs below 5 kft until 19z.

&&

.PREV DISCUSSION...
Issued at 1107 AM EST Sun Feb 25 2018

UPDATE...

The wind headlines remain in effect with expiration times looking
good. Peak gusts will settle below 45 mph a little sooner than 2 PM
near the Ohio border up to the Detroit metro area while the Saginaw
Valley and northern Thumb will likely continue through the 5 PM
expiration.

Morning observations match up well with DTX and model soundings that
indicate the gust trend following boundary layer growth through late
morning. This will be the primary driver of conditions going forward
now that the immediate post front kinematic surge has run the
course. There is also a diminishing gradient wind trend from south to
north across the area that will work in tandem with boundary layer
growth to keep conditions marginal near the Ohio border. A 2 PM
update is anticipated to trim the headline there at expiration.
Conditions will also need to be evaluated again by that time to check
the I-69 corridor for possible extension.

PREV DISCUSSION...
Issued at 300 AM EST Sun Feb 25 2018

DISCUSSION...

Dynamic mid level system rapidly ejecting northeast early this
morning, the associated robust height falls driving a period of
strong surface cyclogenesis. Surface low on track to drop roughly 15
millibars as it lifts north up the western spine of lake Michigan
and settles over central Lake Superior this morning. Sizable low-mid
level kinematic response underway as this process unfolds,
effectively driving a high magnitude wind field eastward coincident
with the pronounced trailing frontal circulation. This front on
track to sweep across southeast Michigan during the mid morning
period /11z-13z/. Upstream observations certainly lend confidence in
witnessing a solid wind gust response immediately along the cold
frontal interface, with some peak gusts noted reaching in excess of
50 mph over eastern IL/western IN. The ensuing cold air advection
and growth to the mixed layer post-daybreak will then subsequently
sustain gusty conditions throughout the day. Strongest gusts during
the first half of the day, with recent probability guidance
indicating a high likelihood for gusts to frequently achieve 30 to
35 knots. Peak gust potential occasionally reaching 40 kts at times
certainly attainable within the post-frontal environment,
particularly across the Saginaw valley and thumb region. Wind
advisory now in place to capture both the wind pop along the front
this morning and the period of trailing gusts of 35 mph and greater
expected to linger well into the day. Winds will ease in gust
magnitude and then frequency from south to north during the latter
half of the day. Mixing will help offset the advective process,
maintaining a rather steady diurnal temperature curve during the
day. Highs again in the 40s.

Any lingering diurnal stratocu quickly fades this evening as
nocturnal stability takes hold under strengthening mid level
subsidence. Surface ridging then becomes a predominant feature
through Monday as high pressure drifts across the Ohio Valley.
Neutral thermal advection under this pattern, retaining a modestly
mild resident airmass for late February standards. This in
combination with nearly full insolation will ease temperatures back
into the 45 to 50 degree range, or ballpark 10 degree above average.

Increasing depth to emerging low level southwest flow in the wake of
this ridging will establish weak warm air advection for Tuesday.
Mixed signal yet on the degree of low level warming, as upper
heights don`t rise significantly and the response may struggle until
late in the day or even Tuesday night. Regardless, some moderation
of an already seasonably mild thermal profile means highs of lower
and middle 50s will be attainable. Similar conditions into
Wednesday, albeit potentially more unsettled as weak shortwave
energy lifting across the Ohio valley leads to an increase in cloud
cover and the possibility for a lower coverage of rain shower
activity.

MARINE...

Rapidly deepening low pressure tracking northwest of the region will
lead to a tight pressure gradient and southwesterly gale force winds
today and into early tonight across Lake Huron, especially across
central Lake Huron and the Straits where high-end gales are likely.
A few sporadic gusts to storm force cannot be ruled out across
central Lake Huron as well, but duration will be too short to
warrant an upgrade to the ongoing Gale Warning. High pressure
building in behind the departing low pressure system will lead to
winds rapidly diminishing late tonight and into Monday. Light
southwesterly flow will continue to prevail into Tuesday with high
pressure passing by to the south.

HYDROLOGY...

Flood Warnings continue to remain in effect for several area rivers,
with moderate flooding continuing along the Saginaw River at
Saginaw and Huron River at Hamburg. River levels will continue to
slowly recede across the region over the next few days. Light rain
this morning accompanying a low pressure system tracking northwest
of the region will have negligible effects with less than a quarter
of an inch expected. A period of dry weather will then begin this
afternoon and continue through at least Tuesday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 2 PM EST this afternoon for MIZ060>063-068>070-
     075-076-082-083.

     Wind Advisory until 5 PM EST this afternoon for MIZ047>049-053>055.

Lake Huron...Gale Warning until 10 PM EST this evening for LHZ361>363-421-422-
     441>443-462>464.

Lake St Clair...Gale Warning until 4 PM EST this afternoon for LCZ460.

Michigan waters of Lake Erie...Gale Warning until 4 PM EST this afternoon for LEZ444.

&&

$$

AVIATION.....SF
UPDATE.......BT
DISCUSSION...MR
MARINE.......IRL
HYDROLOGY....IRL


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



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