Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 121909

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


Upper trough axis over the central Great Lakes will shift east this
evening, kicking surface troughing into Canada. Weak cold front
trailing the system will continue to brush across Southeast Michigan
for the next several hours, and will continue to expand current area
of showers further south and sustain precipitation chances through
the early evening. While showers will dominate, a few lightning
strikes will also be possible. Latest SPC analysis shows in excess
of 500 J/kg of ML CAPE extending down through south-central Lower
Michigan, a reflection of steep low-level lapse rates and surface
dewpoints near 60. Severe weather is not expected.

Drier air advecting into the area tonight under northwest flow will
end chances for precipitation and provide a clearing trend to skies.
High pressure expanding in from the west will create favorable
radiational cooling conditions overnight. Residual boundary layer
moisture should be enough per model forecast soundings to allow some
areas of fog to develop late tonight and early Sunday, particularly
in places that receive more rain today. Inherited forecast seems to
cover trends nicely. Cool, almost fall-like, atmosphere tonight will
allow min temps to fall to the low/mid 50s for most of southeast
Michigan, with warmer readings closer to 60 near the Detroit urban
heat island.

The center of high pressure will slide into Michigan tomorrow,
providing a dry and quiet day. More sun and higher mixing heights
should boost temperatures back into the mid 70s to around 80 for max

Upper wave over MT/ND will encounter some shearing as it moves into
the Great Lakes Sunday night and Monday. Latest model runs continue
to support a dry forecast with lack of low-level advection and weak
mid-level forcing.

High pressure centered over the eastern Great Lakes and northeastern
continental U.S., along with an amplified upper-level ridge building
in from the west, will look to keep conditions dry throughout
Tuesday. Rain and thunderstorm chances look to return late Wednesday
into Thursday as low pressure from the Central Plains pushes east-
northeast through Michigan, dragging a warm front through southern
Michigan, allowing daytime highs to peak in the mid-80s. An upper-
level cut-off low across southern Quebec and a upper-level low over
Saskatchewan will then act to flatten the upper-level ridge
throughout Thursday, producing a more zonal-like flow across the
Great Lakes through early next week. The slight chance for on-and-
off rain showers will continue into the weekend as a series of short-
waves moves through Michigan, as zonal flow keeps temperatures
capped in the lower 80s for daytime highs.



Moderate northwest winds will persist through the evening under a
cooler and somewhate unstable environment.  As stability increases
with the loss of heating, winds will ease overnight.  High pressure
building into the region will then bring a period of light winds to
finish the weekend.   The region will remain under the influence of
this high through early next week.


Issued at 111 PM EDT Sat Aug 12 2017


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.


* High for ceiling below 5000 feet through the afternoon.


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



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