Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 281902
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
302 PM EDT SAT MAY 28 2016

.DISCUSSION...

Dewpoints are well in the 60s, which will make for another
relatively muggy evening across the fcst area. This afternoon, se Mi
resides along the eastern edge of a plume of deep layer moisture
associated with the upper low over the upper Midwest. This has left
a blanket of mid/high level clouds across the ern portions of the
forecast area. Meanwhile...the western portion of the area
experienced more early day sunshine which allowed for some modest
destabilization. This has supported some convection, enhanced along
a convergent boundary associated with the flow off Lakes St Clair
and Erie. The persistence of weak instability through the afternoon,
0-1 km ML CAPE on the order of 800 to 1200 j/kg and remnant outflow
boundaries will support some additional convection into the evening.
The deep layer moisture plume will traverse the forecast area during
the night as the upper low rotates across the upper Mississippi
Valley. Weak short wave impulses embedded within the deep moist ssw
flow will support isold to sct showers, perhaps an isold
thunderstorm through the night. Mins will only drop down into the
mid/upper 60s given the degree of moisture in the boundary layer and
extent of cloud cover.

The upper low is still forecast to deamplify as it tracks across the
northern Great Lakes on Sunday, but will still lead to some modest
mid level height falls across srn Lower Mi. An associated cold front
is forecast to traverse Se Mi late Sun afternoon. Modest large scale
ascent as a result of these height falls with some upper divergence
within the entrance region of an upper jet max will support a chance
of convection along the cold front or prefrontal trough axis.
Moisture quality looks to be a limiting factor for potential energy
available for convection, which will affect storm intensity and
coverage. The axis of deep layer moisture will exit east of the
forecast area early Sun morning. There is indications in the 12Z
model suite that some influx of higher low level moisture will
precede the sfc cold front or prefrontal trough axis, with sfc
dewpoints in the low to possibly mid 60s. This would support a
narrow ribbon of ML CAPE on the order to 1-2k j/kg with fropa late
Sun afternoon. The degree of mid level dry air does raise some
concerns that daytime mixing will reduce boundary layer moisture to
a greater degree than suggested by model solutions and is one reason
why the forecast area remains in just a marginal risk for severe wx
on Sunday. If boundary layer moisture is sufficient to produce
higher CAPE, the degree of mid level dry air would be supportive of
strong convective downdrafts. Marginal deep layer shear of 20 to 30
knots would also sustain some degree of organization to potential
convection and would be supportive of at least isolated strong to
severe thunderstorms.

Drier and slightly cooler air will filter into the region in the
wake of the sfc cold front. This will lead to rather pleasant
conditions for Memorial Day. The potential for overachievement on
mixing depths will support fcst highs on Memorial day into the low
to mid 80s. Humidity levels will however be much lower.

Tuesday should be a relatively nice day to finish off the month of
May as high pressure overhead keeps skies mostly sunny and dry.
Although temperatures will remain in the 80s over much of SE
Michigan...humidity on Tuesday/Wednesday will drop to more
comfortable levels in north to northeast wind flow around the high.
These conditions look to be short lived though...as broad/moist
southerly wind flow resumes Wednesday night ahead of developing low
over the plains. Low is progged to move into the Great Lakes region
by early Thursday morning. Rain chances bump up Thursday into early
Friday morning as the system pushes through area. Cooler
temperatures behind the front on Friday will return us to a more
seasonally normal range by the weekend...with highs in the lower
70s.

&&

.MARINE...

Some areas of fog remain over Lake Huron this afternoon although
elevated winds have likely minimized the coverage this afternoon.
Winds will subside again tonight allowing fog to increase in
coverage with some areas of dense fog possible. The other concern
will be thunderstorm activity which has begun this afternoon.
Scattered storms will be possible through the evening hours today
before likely tapering off overnight. The best chance will come on
Sunday as a cold front sweeps across the region. Some of these
storms may become strong to severe. In the wake of the cold front,
winds will turn more westerly which will usher drier air into the
region and end the threat of thunderstorms.

&&

.PREV DISCUSSION...
Issued at 128 PM EDT Sat May 28 2016

AVIATION...

Plenty of late morning sun combined with enhanced moisture plume
that lifted into the region this morning has lead to convection
firing before the noon hour. This early round has initiated along a
lake breeze that is being accelerated west by outflow from current
convection. This is really the only focusing mechanism that we will
see today, outside of potential outflow boundaries from future
convection. Guidance has been little help in defining a window of
convection for the taf sites, struggling with plenty of instability
but nothing to focus it on. Should stay VFR through the forecast
except when convection affects the site. With the loss of daytime
heating we should see skies respond favorably this evening with CIGS
rising to 10kft or more. Winds will be around 10 knots with some
gusts nearing 20 knots this afternoon.

For DTW...Lake breeze is the primary focus for thunderstorm activity
currently and is now moving westward further into the state.
Convection has started initiating over Wayne County and will be near
the terminal on and off for the next few hours. Best opportunity for
convection will be from 18Z-21Z. Once convection wanes this evening
with the loss of heating and prior storms using up the instability,
conditions will quickly improve through the rest of the taf cycle.

//DTW Threshold Probabilities...

* Medium for ceiling at or below 5000 FT during the afternoon and
  early evening.

* Medium for thunderstorms affecting DTW/D21 airspace through
  this evening


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

DISCUSSION...SC/DE
MARINE.......DRK
AVIATION.....DRK


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