Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 251128
AFDDTX

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


.AVIATION...

Rapidly deepening low pressure continues to track northwest of the
region, with occluded front set to cross the region 10z-12z. Light
showers, IFR/MVFR vis will prevail ahead of this feature, along
with curtailed flight conditions (IFR/MVFR visibility and IFR/LIFR
ceilings) in moist boundary layer environment. More notable concern
will be a burst in winds as direction shifts to the southwest and
drier air/enhanced mixing move in accompanying the frontal passage.
Flight conditions will rapidly improve as well, although MVFR
ceilings will linger through roughly 15z. Southwest wind gusts will
generally top out around 35 knots at the TAF sites except at KMBS
where peak gusts could reach 40 knots. Gusty winds continue through
much of the day, 25-35 knots. Rapid entrainment of dry air at all
levels will lead to cloud cover rapidly diminishing late morning and
into the early afternoon as high pressure begins to build across the
region. By 00z, clear skies are expected to prevail along with
rapidly decreasing winds of 10-15 knots as pressure gradient
slackens. Lingering LLWS disappears with strong mixing profile this
morning.

For DTW...Brief period of IFR visibility and IFR/LIFR ceilings early
this morning in moist environment preceding frontal passage 10z-12z.
Main concern will be onset of gusty southwest flow around 35 knots,
likely reach crosswind thresholds. Gusty winds continue through most
of the day, decreasing rapidly towards sunset along with clearing
skies. Lingering LLWS disappears with strong mixing profile this
morning.

/DTW THRESHOLD PROBABILITIES...

* High for cigs below 5 kft through 15z Sunday. Low 15z-18z Sunday.

* High for ptype as rain.

* High for reaching crosswind threshold hold 10-16z Sunday.

&&

.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.....IRL
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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