Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 271910

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
310 PM EDT Thu Jul 27 2017


Diurnal destabilization is allowing some convective redevelopment
across the area. As of 18Z, most of this is occuring along a remnant
mid level moist axis across the I-69 corridor. The mid level moist
axis will slowly sink south across the area late this afternoon and
evening, suggesting convective chances will decrease from north to
the south. Mid level lapse rates across the region are not terribly
steep. This and ongoing weak low level dry air advection will limit
the strength of any late day convection. High pressure anchored to
the northwest of the Great Lakes tonight will sustain northeast winds
across Se Mi. The rate of low level dry air advection will remain
weak. Model soundings suggest there will be enough remnant low level
moisture to actually support some late night stratus development over
portions of the area. Some lingering fog/low stratus over srn Lake
Huron is lending support to this idea.

The northeasterly gradient will strengthen across the ern Great
Lakes on Friday as high pressure builds in from the northwest and
sfc troughing holds across Lower Mi. The deepening daytime mixed
layer will lead to breezy conditions, especially downwind of Lake
Huron and Saginaw Bay. There is strong support from the 12Z model
suite in showing amplification of the mid level short wave impulse
now over nrn Minnesota into a compact upper low as it tracks across
Se Mi (15-21Z) on Friday. Although there will be ongoing dry air
advection, model soundings suggest there will be enough moisture to
generate weak to moderate instability as the mid level cold pool
(and associated steep mid level lapse rates) traverses Se Mi. These
factors will support a chance of showers/thunderstorms, with the
exception of the northern thumb which looks to remain displaced from
the colder mid level temps. Assuming instability will be able to
achieve deep convection, the degree of mid level dry air suggests
gusty winds and hail would be possible with the strongest storms.
Subsidence in the wake of this feature and building mid level
heights across the northern Great Lakes will allow the sfc high to
expand across Lower Mi on Saturday, with dry and relatively cool
conditions to start the weekend.

High pressure will remain stationary over the Great Lakes region for
the beginning of next week allowing for dry weather and clear skies.
A cold front will then pass through the area during the middle of
the week, bringing the next chance for showers and thunderstorms.
High temperatures will be in the low to mid-80s and low
temperatures in the 60s.



Moderate northeast flow will become fresh Friday into Friday night
as high pressure builds into the area. Persistent onshore fetch will
build significant wave heights up to five feet and maximum wave
heights near seven feet. Small craft advisories are in effect for
the duration of Friday. Saturday through the remainder of the
forecast period will feature moderate winds gradually backing and
diminishing as high pressure settles overhead.


Issued at 109 PM EDT Thu Jul 27 2017


Locations north of PTK experiencing IFR have improved to MVFR under
increasingly dry northeast flow. Cigs will continue to rise and
scatter under this dry flow and diurnal heating. Clearing line is
already noted in the tip of the Thumb. This will gradually work
south through today. Lack of morning overcast has yielded a more
typical summertime outcome in the Detroit area with diurnal cu
around 4kft increasing in coverage. Outflow from morning activity is
evident on visible satellite near KYIP/KDTW extending west. Any
diurnal showers will likely be focused along or south of this line,
which is forecast to gradually sag south of DTW in the next hour or
two. East flow will bring at least a low chance of MVFR stratus by
early Friday morning.

For DTW...Wind out of the northeast will favor NE operations through
the forecast period.


* High for cigs aob 5kft today. Low after 09z Friday morning.

* Low in thunderstorms this afternoon.


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



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