Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 212337

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
737 PM EDT Fri Jul 21 2017


Steady increase in mid level cloud through the first half of the
night, aided by the downstream propagation of a steadily weakening
area of convective showers now crossing Lake Michigan.  These trends
suggest simply a very limited opportunity for a few high based
showers to survive into the southeast Michigan airspace overnight.
Main focus now on convective trends with activity lifting across
southern WI/northwest IL this evening.  The main instability axis
still resides to the south, favoring greater expansion and
propagation of any thunderstorm complex into Indiana.  There is
still however a good chance for a region of showers with some
embedded thunderstorms to develop north of the main convective
complex, impacting portions of Se Mi late tonight into Sat morning.

For DTW...Best window for TSRA associated with any convective
complex centered on Saturday morning /09z-14z/.


* Medium for thunderstorms late tonight (after 09Z) through Saturday

* Medium for cigs aob 5000 feet late tonight and Saturday.


Issued at 321 PM EDT Fri Jul 21 2017


Upper level ridge center over/near Oklahoma this afternoon with the
top of the ridge flattening out over Northern Plains with the jet
energy tracking through, as upper level wave/low over southern
Alberta is on track to move through Lake Superior on Sunday, leading
to a cool down for early next week.

Very warm day over southeast Michigan, as temperatures are pushing
toward 90 degrees, but fortunately dew pts are under 70 degrees.

Broken line of convection extending from the Upper Mississippi River
Valley southeast into Western Ohio Valley through much of the day
has kept the good Midwest moisture bottled up west, and there is now
a clear consensus the deep moisture will be tracking through Chicago
area this evening and riding along and south of the Michigan border
late Tonight, with MCS complex propagating toward the max instability
over the Ohio Valley, supported by Corfidi vectors as low level jet
veers around to the west/northwest. Bulk of heavy rain will likely
fall along and just south of the Border, and with the failure of good
low level moisture transport and destabilization (12z nam keeps
1000-850 mb cape under 1000 J/KG) the prospects for severe storms is
very low/almost nil (exception being right near southern Michigan
Border). This includes during the day on Saturday as well, as
southeast Michigan resides in the subsidence wake of the departing
MCS and flow is out of the northwest, with continuing lack of
instability and what looks to be strong mid level cap in place (700
mb temps around -12 C per 12Z EURO). The 12z Euro also maintains
1000-850 MB Capes under 1000 J/kg for the most part, but surface low
is bit deeper (1006-1007 MB) Tonight, placing Lenawee county is a
concerning triple point position around 12z Saturday, with 50 knots
at 850 MB, and corresponding 38 knots of 0-1 KM bulk shear. Still,
based off current trends, good chance this boundary will end up being
a bit farther south.

Previous mentioned upper wave/trough tracking through northern Great
Lakes on Sunday will bring cold front through southeast Michigan
during the day, but moisture looks to be lacking to support much
more than scattered coverage, with 0-6 KM bulk shear around 40 knots
drawing some concern for isolated severe storms, but mid level lapse
rates look marginal and majority of solutions still indicating
1000-850 mb capes under 1500 J/kg.

Some lingering showers will be possible early on Monday as low
pressure departs the region. High pressure will then build into the
region through the day as a thermal trough swinging through keeps
Monday`s highs in the mid to upper 70s. High pressure will remain in
place through Tuesday bringing pleasant and dry conditions with
highs topping out near 80 and lows in the mid 50s to near 60. The
next chance for thunderstorms returns during the midweek period as a
weak cold front drops through the region. Slightly milder, more
humid air will advect ahead of the front on Wednesday allowing highs
to increase into the mid 80s.


Light and variable winds will transition toward south to
southeasterly on Lake Huron Saturday morning as a frontal boundary
extends across the southern Great Lakes. Wind gusts will remain
below 20 knots, while waves will undergo a slight uptick during the
afternoon. Low pressure will expand across Lower Mi on Sunday, while
high pressure expands across Quebec. This will lead to an increase
in southeast winds on Lake Huron Sat night into Sunday, especially
the northern half of the lake. Winds will then back to the north
Sunday night into Monday as low pressure exits to the east and high
pressure builds in from the west.


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



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