Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 121711
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
111 PM EDT Sat Aug 12 2017


.AVIATION...

The passage of a low level trough in combination with continued
moist cyclonic flow will sustain a high coverage of VFR
stratocumulus through the afternoon period.  Greater concentration
of associated shower activity will generally reside north of PTK,
potentially resulting in a temporary reduction of ceiling into MVFR.
Modest northwest flow gradually veering to northerly this evening
with the trough passage.  Loss of daytime heating will promote a
general clearing trend during the evening period, leaving a mostly
clear sky overnight.  Winds becoming light/variable overnight, with
a residually moist near surface environment possibily resulting in
some shallow fog development near daybreak.

For DTW...Higher coverage of stratocumulus will persist through the
latter half of the day, before exiting as heating wanes this
evening.  Some vsby restrictions in light fog becomes possible
toward daybreak.

//DTW THRESHOLD PROBABILITIES...

* High for ceiling below 5000 feet through the afternoon.

&&

.PREV DISCUSSION...
Issued at 307 AM EDT Sat Aug 12 2017

DISCUSSION...

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.

MARINE...

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.

&&

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

$$

AVIATION.....MR
DISCUSSION...SC
MARINE.......DRK


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