Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 272310
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
710 PM EDT Thu Apr 27 2017

.AVIATION...

Cooler air will continue to spread over Lower Michigan during the
evening and carry in MVFR stratocu that extends all the way south
into Indiana and west through Iowa and the Midwest. There is some
sign in observations of an upward mixing trend during the late
afternoon but not nearly as optimistic as near term guidance,
especially with radar indications of sprinkles/drizzle over western
Lower. The observational evidence supports carrying MVFR ceiling
through the evening with some improvement to low end VFR overnight
as the cooler air deepens over the region and then a clearing trend
late. The wind gust component of the strong westerly flow will only
diminish slowly after sunset as the pressure gradient remains
elevated and the boundary layer remains well mixed until closer to
sunrise. Backing low level flow during Friday morning will direct
any remaining low clouds into the northern Great Lakes and leave
behind generous coverage of higher clouds moving in ahead of the
next low pressure system, however rain is expected to hold off until
Friday evening.

//DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less tonight.

&&

.PREV DISCUSSION...
Issued at 323 PM EDT Thu Apr 27 2017

DISCUSSION...

The surface low tracked due north through Lake Michigan, preventing
some of the stronger winds from extending east into southeast
Michigan, but peak gusts still topped out around 40 MPH, with Flint
hitting 43 mph and Saginaw 42 mph.

Thunderstorm threat looks to be over as mid level dry slot has arrived.

The upper level circulation/500 MB low near Arrowhead of Minnesota
lifting north into Ontario Tonight, leaving a rather sharp south to
north low level temperature gradient/baroclinic zone over lower
Michigan. Cold airmass, as 850 mb temps will be below zero north of
I-69, likely able to sustain low clouds overnight. A few sprinkles
also can`t be totally ruled out over northern third of the CWA with
the steep low level lapse rates.

Energetic/upper level wave train tracking through the Great Basin
to Four Corners region and through the southern Plains.

Warm advection begins to kick in around 12z Friday, as next wave
already coming out of the southern Plains lifts northeast. 925 mb
temps in the lower teens during the afternoon projects to highs in
the mid 60s, right around normal values. Moisture advection right
through the day, but the heart of the moisture axis (PW values
around 1.75 inches) will fold over along the Ohio River by Friday
evening Friday Night. Still, sufficient moisture (850 mb dew pts up
around 10 C) coupled with weakening surface wave/reflection coming
out of Missouri and rolling through southern Lower Michigan Friday
night should be sufficient to generate showers by Friday evening,
especially south of M-59. Granted, did note the 12z Euro solution,
which is mainly dry over southeast Michigan, as moisture gradient is
farther south. However, with local probabilistic SREF weighted guidance
being very aggressive, would lean toward much of southeast Michigan
seeing some rain. Heavier rain likely by Saturday night with strong
warm front and abundant moisture lifting into the southern Great
Lakes as 850 MB dew pts of 12+ C arrive, as strong low pressure
system lifts into Missouri.

An active weather pattern continues through next week, as several
waves low pressure develop over Texas and push northward into the
Ohio River Valley. On Sunday, as low pressure continues moving out
of the southern plains; the associated warm frontal boundary will
lift northward across Lower Michigan. Expect another surge of warm
moist Gulf air to raise temperatures into the upper 60`s for
Sunday/Monday, with a few 70 degree readings possible in counties
nearest the Ohio Border. Rain and thunderstorms will also persist;
on Sunday with the warm front and again for Monday as the cold front
pushes through. A cooler air mass filters into the region behind the
cold front for early next week with highs returning to the mid 50s
to low 60s. The next system is expected to push out of Texas
Wednesday afternoon and reach southern lower Michigan sometime on
Thursday.

MARINE...

Gusty southwest winds will persist into the first part of the
evening as a cold front progresses east of the area. A Small Craft
Advisory will remain in effect for the Lake Huron nearshore waters.
This front will also sweep any remaining showers and thunderstorms
east out of the area.ginaw Bay and the lake Huron nearshore waters.
Winds and waves will diminish later this evening as high pressure
builds into the region. Lower southwest winds speeds are expected
Friday as this high sustains a weaker gradient.

HYDROLOGY...

Rain chances will increase from Friday night into Saturday and
Saturday night as moisture is pulled north into the region in
advance of developing low pressure over the southern and central
plains. Through Saturday night, rainfall amounts are forecast to
range from about a third of an inch over the Thumb to nearly one
inch near the Michigan and Ohio state line. While no flooding is
expected by that time frame, additional rainfall on Sunday and
Monday may begin to lead to some flooding concerns. However, this
will be highly dependent on the track of this low as it lifts into
the upper midwest and western Great Lakes early next week.

&&

.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.

&&

$$

AVIATION.....BT
DISCUSSION...SF/DE
MARINE.......SF
HYDROLOGY....SF


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