Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 180334

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1134 PM EDT WED AUG 17 2016


Lingering clouds will largely be east of the terminals by 06Z.
Current sfc temp/dewpoint spreads indicate adequate boundary layer
moisture for some fog development under decent radiational cooling
conditions. A little better moisture pooling across the Saginaw
Valley may support some IFR or lower visbilities in fog toward
daybreak at MBS.

For DTW... The evening rainfall and overnight radiational cooling
will support MVFR type visibilities in fog toward daybreak.

//DTW Threshold Probabilities...

* none.


Issued at 734 PM EDT Wed AUG 17 2016


For the most part, conditions have cleared generally along and
south of the I-69 corridor. Convection has however been
redeveloping across the Saginaw Valley and thumb region. The
regional water vapor loop indicates the center of a mid level wave
now rotating into the tri cities/I-69 corridor regions, with
some mid level deformation ongoing across the thumb. This wave
will slowly depart east of the forecast area by 06Z. The forcing
and weak instability will sustain at least some convection across
the northern half of the forecast area through a good portion of
the evening while it slowly drifts south. So some locations
farther south into the thumb and Port Huron region still stand the
chance for some late evening convection. The forecast has been
updated to reflect these latest precip trends.

Issued at 301 PM EDT Wed AUG 17 2016


Narrow band of thunderstorms following expectations this afternoon.
Well-mixed boundary layer is contributing to gusts around 40mph with
the stronger convection while mode remains disorganized. Instability
axis containing the existing convection will exit to the east by
around 00z this evening. Second batch of showers directly beneath
the PV anomaly has sprung up over Northern Lower this afternoon and
may rotate through the Saginaw Valley and northern thumb before
before dissipating with the loss of heating this evening.

Height rises in the wake of this afternoon`s shortwave will favor
some northward building of high pressure presently over the Ohio
Valley. Anticyclonic flow and mid-level subsidence will scour the
sky of low and mid-level cloud debris. Dewpoints will fall into the
low to mid 60s as surface winds turn WNW with the exception of the
Thumb where flow off the water will keep temps and dewpoints
elevated due to marine modification.

Bumped up temperatures into the mid/upper 80s on Thursday as
forecast soundings look very dry. Weak push of mid-level moisture
around expansive high centered to the SE will coincide with a low
amplitude convectively enhanced ripple in the flow Thurs afternoon.
All indications at this point is that little more than some enhanced
cu-up ought to be expected as moisture quality and forcing will be
very limited. Included low chc pops Thursday night as mid-level
moisture push becomes more robust. Given the nocturnal timing,
difficult to to envision anything more than a short-lived/poorly
organized line of showers along the theta-e gradient. Lack of
forcing will be problematic on Friday as well as instability
gradient and better LLJ pass north. However, subtle height falls will
yield a slightly weaker cap compared to Thurs worthy of just a low
end chc pop for isolated pulse convection. Enhanced nocturnal wind
field in advance of approaching trough and the potential for
increasing sfc Td to yieldUMEROUS SHOWERS AND THUNDERSTORMS...
THEN  SB instability of several hundred j/kg
through the night warrants increase in pops to chc category Friday

SATURDAY THROUGH THURSDAY...Rain chances increase for the weekend as
an upper trough and surface cold front gradually work into the area.
Near normal temperatures Saturday will give way to a drier/cooler
trend with below-normal temperatures possible Sunday through mid-
week next week.


Generally weak gradient flow through the latter half of the week
will sustain a period of modest wind and wave conditions across all
marine areas.  Scattered showers and thunderstorms will affect
mainly areas from southern Lake Huron south to western Lake Erie
into early this evening as a surface trough cross the area.
This activity will dissipate with the loss of daytime heating.


Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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