Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 181659

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1259 PM EDT THU AUG 18 2016


Scattered diurnal cumulus will fade with loss of daytime heating
this evening. With light winds and partly cloudy skies, low level
moisture should be sufficient for at least patchy fog (and perhaps
stratus). It should be noted that an area of dense fog and LIFR
stratus formed over Thumb region early this morning (but missed the
terminals). Slight SSW gradient flow on backside of high pressure
tonight should limit a repeat performance of that magnitude.

For DTW...Scattered cumulus will lift above 5kft between 18z-22z and
dissipate this evening. Patchy fog should develop late tonight, but
not very confident in degree of VSBY reductions or whether low CIGS
accompany for a time. Will maintain MVFR VSBYS for this forecast.

//DTW Threshold Probabilities...

* None.


Issued at 344 AM EDT Thu AUG 18 2016


Brief break in the widespread active weather across the region today
and into Friday as northerly flow really dried out the column
Wednesday. Cannot rule out some isolated showers or thunderstorms
today near the state line, but should be a dry one for most
locations. Chances remain low Friday but a mid level wave should
produce a few showers or thunderstorms. Higher confidence forecast
this weekend as a strong, dynamic trough sweeps across the Great
Lakes. After a few rounds of thunderstorms this weekend, this system
will bring a much cooler airmass for the start of next week where
temps will top out in the 70s.

As mentioned above, today should be a dry one across the area.
Moisture in the column has been scoured out with PWATs only around 1
inch and models soundings show a cap around 7000ft which should help
keep little more than a cu field around. The one caveat will be
around the state line where a lingering frontal boundary will have
some activity along it most of the day. Had to rule out a
shower/storm or two trickling north into Lenawee and Monroe
Counties so put in a slight chance there.

Not alot of confidence with the Friday precip forecast. The strong
weekend trough will be edging into the northwestern Great Lakes
while draping southwest into the plains. A shortwave is advertised
to track up along this trough roughly just west of Lake MI. A weak
warm front will usher a high theta e plume into southern MI early
Friday morning and could see a narrow line of showers on the lead
edge of the gradient lift through. Then Friday afternoon a weak cold
front associated with the shortwave will sweep through which could
again result in some showers/thunderstorms. There will be some
instability built up with CAPE averaging 1500 j/kg throughout the
model suite (as temps rise into the mid/upper 80s and dewpoints rise
to 70) but the NAM is showing a formidable cap from 850-700mb. Still
enough evidence to keep at least a chance mention going.

By Saturday the trough has become well established throughout the
plains and Midwest. A jet streak nearing 100 kts entering the base
of the trough will help strengthen the developing surface low around
Iowa. This low will then lift NE through the straits Saturday night
and into northern Quebec by Sunday. Will likely see a couple rounds
of storms move through the area as a prefrontal trough moves through
Saturday afternoon and the cold front follows overnight. The system
will be very dynamic with early model output showing around 30 knots
of bulk shear so cannot rule out some organization to cells that go

After the system starts to lift out Sunday, a much cooler airmass
will surge into the region. 850mb temps will drop from 17-18C on
Saturday down to 5-8C by Monday morning. This will drop highs from
the mid/upper 80s Friday and Saturday, down to mid 70s Sunday and
Monday. Ridge will start building back into the region Tuesday which
will bring temperatures back to near normal (low 80s) by Wednesday.


Generally weak gradient flow will maintain a period of modest wind
and wave conditions through the end of the week.  Limited potential
for showers and thunderstorms through this time.  There will be an
increasing chance of thunderstorms this weekend.


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



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