Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 270015
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
815 PM EDT Wed Jul 26 2017


.AVIATION...

Midlevel system relative isentropic ascent combined with deeper
moisture transport to generate nwidespread shower activity across
portions of mid Lower Michigan late this afternoon and early evening.
This activity remains flanked along the northern periphery of
ridging and should persist in some capacity north of the I 69
corridor this evening and overnight. High stability in the 4.0 to
10.0 kft will be a limiting factor towards the south. Hi-resolution
datasets continue to suggests little to no precipitation for the
southern forecast with this event. Will continue a conservative
approach and limit prevailing groups south of MBS. Split cold front
structure will be slow to scour out the airmass tomorrow. Will watch
for moisture pooling ahead of 925mb front to bring some low cloud,
then will watch for possible isolated coverage of cumulus development
possible shower along the 700mb front south of I 69 after 15Z
Thursday.

One last item will be potential for some fog development around
daybreak at KMBS. Covered this with MVFR vsby restriction.

For DTW...Showers and isolated thunderstorms will remain well north
of metro airspace tonight.

//DTW THRESHOLD PROBABILITIES...

* Low in ceilings below 5000 ft Thursday morning and afternoon.

* Low in thunderstorms thursday afternoon.

&&

.PREV DISCUSSION...
Issued at 322 PM EDT Wed Jul 26 2017

DISCUSSION...
Large mid level trough and low centered over Hudson Bay will push a
weak shallow cold front currently across Wisconsin and the U.P.
slowly through lower Michigan tonight. Not much in the way of
dynamics and forcing but decent band of 850mb theta-e along and
ahead of the front is enough to produce the current showers and a
few thunderstorms across central and northern lower. Some of this
activity is moving through the Saginaw Valley and Thumb this
afternoon and is expected to continue into the night as the front
slowly settles southward. Models shunt this higher theta-e more
eastward leaving the southeastern half of the cwa more moisture
starved hence less likelihood for shower and thunderstorm activity,
especially with loss of diurnal component.

The cold front will continue slowly south across lower Michigan
Thursday morning before exiting into Ohio in the afternoon. Higher
850mb theta-e will begin advecting into the area from the southwest
Thursday though giving increase chances for showers or thunderstorms
with best chances along and ahead of the front diminishing further
north of the front. Strong convective activity will likely remain
well south of the border.  Highs Thursday will range from upper 70s
in the Thumb from ne winds off of the lake to low 80s elsewhere.

Thursday night should see a fair amount of clearing across the
northern portions of the forecast area as drier air advects in
however across the south will still see a fair amount of mid and
high level clouds from convection to the south. Lows will remain
mild in the 60s as caa will remains weak.

Friday a deepening mid level wave crashing over the the Midwest
ridge will close off over lower Michigan steepening midlevel lapse
rates enough to produce plenty of clouds and the chance for showers
or thunderstorms.  Breezy northeast winds as large high pressure
builds in from the north will keep highs below average from the low
70s in the Thumb to mid 70s.

Stagnant longwave pattern through the remainder of the forecast
period will have Southeast Michigan positioned immediately upstream
of the mean trough axis. Northwest flow aloft will favor near or
slightly below average temperatures in the mid 70s to 80 degrees
while the occasional shortwave sweeping across the northern tier
will bring a periodic warm up into the mid 80s as warmer mid-level
temps are drawn east. Occasional low t-storm chances not out of the
question during this time, but sensible wx will largely be dominated
by several days of persistent subsidence and surface high pressure.

MARINE...

Southwest winds will decrease during the night as a slow moving
front slides south across Lake Huron. This front will stall over
southern Michigan on Thursday. Post frontal northerly winds will
increase during the course of the day across southern Lake Huron.
Winds will turn northeast into Saginaw Bay. Funneling across the
relatively warm waters of the bay will support an uptick in the
winds, likely gusting over 20 knots. This may support small craft
advisory conditions. Northeast winds will actually increase Thursday
night into Friday as high pressure expands across the northern Great
Lakes while low pressure holds fairly steady across the Ohio Valley.
Small craft advisory conditions are likely over most of the
nearshore waters during this period. The gradient will then relax on
Friday as the high expands into the eastern Great Lakes. This will
allow winds and waves to decrease.

&&

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

$$

AVIATION.....CB
DISCUSSION...DRC
MARINE.......SC


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