Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 271659

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1259 PM EDT FRI MAY 27 2016


The potential for late day thunderstorms once again is the main
aviation concern. The latest regional Radar loop shows some loosely
organized showers/thunderstorms lifting into far SW lower Mi and
south cntl Lake Mi. This area of convection is occurring within a
ribbon of higher low-mid level moisture and will lift northward into
the Saginaw Valley region late this afternoon. There will also be
some added low level convergence associated with a sfc trough draped
across the Saginaw Valley, enhanced by lake breeze convergence. Thus
the terminal with the highest potential for seeing late day
thunderstorms is MBS. Instability will be less farther south. Depth
of mid level dry air is also greater farther south and east of MBS.
So the MBS and possibly FNT TAFs only will carry a chance of late
day thunderstorms. The rest of the terminals may however see a
brief light rain shower late in the day as this mid level moist
plume lifts north. There will be another potential for
thunderstorms overnight, again with the better chances at MBS.
This will be the result of another influx of low to mid level
moisture within a weakly unstable environment. At this time,
chances of overnight thunderstorms appear too low to include in
the terminals.

FOR DTW...The depth of mid level dry air over metro Detroit and weak
daytime instability suggests the better chances for late
afternoon/evening thunderstorms will be well north of metro Airport.

//DTW Threshold Probabilities...

* Low for ceiling at or below 5000 FT this afternoon and evening.

* Low for thunderstorms affecting DTW/D21 airspace this
  afternoon through tonight.


Issued at 1117 AM EDT Fri May 27 2016


The prospects for convection today into tonight appears low. 12z tax
sounding indicated a drier air mass (pw value under 1
inch)...especially in the mid 700 mb dew pt depression
was 30 c. 500 mb trough/modest cold pools working through northern
lower Michigan early this afternoon...with upper level ridge/500
mb heights then building late this afternoon into this
evening...providing negative environment for development.
However...instability will become moderate this
afternoon...mainly across northern third/half of the cwa...where
mlcapes are expected to reach at least 1500 j/kg. if a cell is
able to go up...especially with added low level convergence form
land/marine gradient...can not rule out isolated severe tail of the stronger (35+ knots) 0-6 km shear extends
south past Saginaw bay. No update planned with the zones as the
pops look reasonable, but will update hwo for areas along/north of
I-69 to mention isolated severe possible.

Issued at 310 AM EDT Fri May 27 2016


A warm, and increasingly humid, pattern will persist into Saturday
night/Sunday as an upper ridge over the eastern CONUS amplifies
downstream of an upper level low pressure system as it works from
the southern Rockies into the central plains. This will allow
temperatures to climb into the mid 80s area-wide both today and
Saturday with minimum temperatures holding in the mid/upper 60s as
low level moisture increases and limits radiational cooling to a
greater degree heading into the weekend. Patchy fog will also be
possible early this morning generally along/north of I-69 as the
leading edge of this more humid air mass expands through lower MI.

The chance for showers and thunderstorms will also increase to some
degree as instability edges upward within the increasingly humid air
mass. That said, most forcing will remain well west of the area, so
any activity will be rather disorganized over the next several days.

The aforementioned upper low pressure system then opens and lifts
through the central Great Lakes on Sunday, providing better forcing
for shower and thunderstorm development. With moderately unstable
conditions expected during the passage of this system, suspect that
Sunday will be the best chance of widespread rainfall during the
next week. Even so, the convective nature will most likely leave
some locations dry as the upper system itself passes north of the
area and southern lower Michigan remains in the warm sector.

Conditions cool in the wake of this low pressure system as the upper
pattern evolves into a shallow upper trough over the area early next
week. High temperatures will edge back to around 80 degrees. In the
meantime, with less humid conditions, low temperatures will fall
into the 50s to around 60. A second upper trough will then work into
the area late in the forecast period as upper level low pressure
tracks slowly east across southern Canada. This will bring a renewed
chance of showers and thunderstorms late Wednesday into Thursday
after a quiet start to the week.


High pressure off the east coast and broad low pressure slowly
tracking eastward through the Central Plains and Upper Midwest will
maintain fairly light south to southeast flow through Saturday. A
warm and humid airmass will promote fog development over the cold
waters of Lake Huron today (especially northern portions of the
lake), while also keeping chances for thunderstorms in the forecast.
Thunderstorm coverage through Saturday is expected to remain fairly
low. Low pressure tracking across Ontario will push a weak cold
front across the Central Great Lakes Sunday into Sunday night. This
will bring a better chance for thunderstorms as well as a modest
increase in southerly winds Sunday afternoon and evening.


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



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