Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 120954

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
554 AM EDT Sat Aug 12 2017


Combination of advective clouds wrapping around the low over
southern Ontario, and radiative clouds forming overhead is making
for a tricky early morning cloud field. CIGS as of 10Z range from
400-6000ft. Expect a solid MVFR stratus deck to fill in across the
board this morning, with maybe a few stray IFR obs. CIGs should lift
slowly through the morning before making better progress toward VFR
as better mixing kicks in this afternoon. There remains a chance of
some scattered showers today but coverage should low enough to leave
out of the tafs. Best activity should be over the Thumb. High
pressure should scour out all the clouds later tonight, opening the
door for some fog to set up by morning.

For DTW...MVFR ceiling is expected develop and persist into early
afternoon before lifting into VFR below 5000 ft through early


* High for ceiling below 5000 feet toward sunrise through afternoon.


Issued at 307 AM EDT Sat Aug 12 2017


A mid level trough axis now extending from nrn Quebec to Lower Mi
will slowly slide east of the state late this evening into the
overnight. The associated sfc low, already east of Georgian Bay,
will continue on an easterly track during the course of the day. A
sfc trough extending from this low stretches across northern Lake
Huron as of 06Z. This trough will advance south into Se Mi this
afternoon and will sustain low level cyclonic flow across the area.
The regional satellite data has been showing an expanding region of
stratus within a low level thermal trough over nrn and cntl Lower
Mi. This stratus will overspread much if not all of the forecast
area this morning with the advancing low level trough. Diurnal
heating will lift the clouds into a strato cu field this afternoon.
Despite limited instability, model soundings suggest convective
cloud depths within the moist low level cyclonic flow will be
supportive of some light showers today. The coverage and intensity
of which will be a little greater across the thumb region due to
added convergence from the aforementioned sfc trough and moisture
off Lake Huron and Saginaw Bay. The degree of cloud cover through
much of the day will limit afternoon mixing depths. This along with
850mb temps around +10C will support highs in the 70s.

High pressure will expand into the region from the west tonight
within mid level confluent flow in the wake of the departing trough
axis. This along with the low level moist axis pushing east of the
region will lead to clearing skies during the evening. Residual near
sfc moisture due to the limited degree of daytime mixing will
support some fog overnight as clearing skies and a weakening
gradient supports good decoupling in the boundary layer.

High pressure overhead and mainly sunny skies will result in better
daytime mixing depths on Sunday, supporting highs near 80. A mid
level short wave impulse now evident on the water vapor image over
northeast Montana is forecast to undergo some amplification as it
crosses the nrn Plains and upper Midwest this weekend, before
tracking across the Great Lakes region Monday and Mon night. Ample
dry low level air will warrant a continued dry forecast with this
feature. The upper wave and entrance region jet forcing will however
generate some degree of mid and high level clouds. Rebounding mid
level heights through mid week will support a modest warming trend.
The next chance for convection will be during the end of the work
week (Thursday per bulk of 00Z guidance) as a mid level wave is
forecast to rapidly lift into the region from the central Rockies.


A weak low pressure system over Ontario will lift into Quebec today.
A trailing trough will drop down through the eastern lakes this
morning causing winds to become north-northwesterly. A cooler, more
unstable flow should cause gusts to increase closer to 25 knots
across the Huron basin. Waves along the shoreline will rise to 2 to
4 feet, remaining just below small craft criteria. Tonight and
Sunday will see a high pressure system settle over the lakes for a
light wind regime which will persist into the new work week.


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



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