Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 180737
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
337 AM EDT Mon Sep 18 2017

.DISCUSSION...

A cold front continues to slowly work eastward through SE MI through
the early morning hours. The front continues to weaken as the parent
low is well removed over northern Ontario thus shearing out whatever
remains of the frontal forcing. Isolated to scattered showers will
accompany the front during the rest of its passage across the area
through the morning hours. Cold advection with northerly flow behind
the cold front will result in a low stratus deck which should hold
through the afternoon hours before drier air and mixing can scour
out the moisture trapped beneath the subsidence inversion from
building high pressure. Highs should reach into the low/mid 70s
today, but if the stratus holds longer across the north, could very
well see highs only in the 60s.

The high pressure system sliding through the Great Lakes will lead
to dry conditions for Monday once morning showers move east. Tuesday
is the next chance of precipitation as an upper level wave lifts
northeast toward southern MI. There is a slight chance or low chance
of seeing some rain on Tuesday from this system. High pressure will
still reside over the region with the remnant cold front draped just
south of MI. Models show a bit of overrunning as the system
interacts with the front, resulting in some rain over southern MI.
There could be some right entrance region jet forcing over the area
for a short time before it lifts north as well. Not very confident
in this outcome as the ridge could over power the weakening system
and keep the front too far south. Will hold with low pops for now,
but could see a dry forecast for most locations.

Story for the rest of the forecast is sun and warmth as a deep
trough setting up over the west coast resulting in downstream
amplification of the ridge already in place over the eastern conus.
The steering currents around the mid level ridge, building to 590
dam by the end of the week, will keep any shortwaves to our west
through the weekend. Increased southwest flow will eventually push
the thermal ridge into the region where 850mb temps will then hover
in the upper teens (C) for several days. This combined with clear
skies and full sun, will lead to high temperatures in the mid 80s
for the latter half of the week into the weekend. This will be
around 10 degrees F above normal for mid September.

&&

.MARINE...

High pressure will track across the northern Great Lakes today. This
high will drive a secondary cold front into the southern Great Lakes
region later this morning. Modest northerly winds will prevail
through the day in the post frontal environment. Wind gusts over much
of Lake Huron will approach 20 knots today within the post frontal
cool air. Winds will veer toward the northeast tonight into Tuesday
as the high slides into Quebec. A slight uptick in the gradient will
sustain northeast winds generally in the 10 to 20 knot range on
Tuesday. Persistent high pressure is forecast to take hold across
the eastern Great Lakes during the latter half of the weak,
supporting generally light and variable winds across the region.

&&

.PREV DISCUSSION...
Issued at 1153 PM EDT Sun Sep 17 2017

AVIATION...

Another round of showers and isolated thunderstorms is expected
along the cold front moving very slowly through SE Michigan during
the night. This activity will be mainly south and east of FNT down
through the DTW corridor and could last through mid morning as the
front stalls while low pressure ripples along it. Evening
observations over northern Michigan also show mounting coverage of
IFR/MVFR stratus behind the northerly wind shift. This part of the
boundary will bring the best chance of stratus spreading southward
over the region. A clearing trend will then develop during late
morning through afternoon as high pressure builds into the northern
Great Lakes into Monday evening.

For DTW... Timing and coverage of additional showers and isolated
thunderstorms, mainly in the FNT to PTK area, will be such that
short term updates will be the best approach for forecast refinement
at DTW. VFR will then hold until borderline VFR/MVFR develops during
the morning associated with the cold front and northerly wind shift.
Clouds then diminish mid to late afternoon.

//DTW THRESHOLD PROBABILITIES...

* Medium for ceiling 5000 ft or less toward sunrise through mid
  afternoon.

* Low for thunderstorms during the morning.


&&

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

$$

DISCUSSION...DRK
MARINE.......SC
AVIATION.....BT


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



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