Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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944
FXUS63 KDTX 271922
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
322 PM EDT Sat May 27 2017

.DISCUSSION...

Main forecast concern over the next few days continues to be timing
and coverage of possible convection on Sunday as weak low pressure
lifts through the area in response to shortwave disturbance pivoting
through the Great Lakes. Models are having difficulty handling this
system (or at least the convection it will help to force). However,
there is general consensus of a slightly slower track, which would
focus best chance of showers and thunderstorms in the 6pm-10pm time
frame. Will not swing that far in the forecast and leave the whole
day dry, but will adjust timing to focus likely precipitation later
in the day, essentially ramping up pops 18z on into this 22z-02z
window.

This even later timing, combined with a fairly consistent idea that
it will remain mostly cloudy much of the day Sunday suggests that
the potential for severe weather will be limited, but not zero.
Rather pedestrian mid level lapse rates won`t be of much assistance
either, especially if daytime heating is stunted by cloud cover and
low level instability is insufficient to overcome the poorer mid
level profiles. While severe storm chances are a bit iffy, scattered
to numerous thunderstorms are still expected with the passage of the
system.

The upper low over south central Canada that this shortwave is
pivoting around will sink south/southeast towards the Great Lakes
late Sunday into Monday, carving out a broad upper  trough over the
area by early next week. This will maintain unsettled conditions on
Monday, namely scattered afternoon showers or storms that develop
under expanding upper level cold pool associated with the upper low.

The upper trough axis does remain west of the region through Monday,
so mild temperatures will continue with afternoon highs once again
climbing into the 70s.

Extended Forecast Tuesday through Saturday: Unsettled weather
pattern continues over the region throughout the extended period.
Models are in disagreement on timing and coverage; however, the
general consensus remains that the quasi-stationary upper level low
over the northern Great Lakes and northern Ontario will allow
several shortwaves to rotate through lower Michigan. This will
generate chances of showers followed by brief dry periods.
Temperatures remain mild with afternoon highs in the upper 60`s to
lower 70`s and over night lows in the 50`s.

&&

.MARINE...

Very light winds to persist into tonight over the Central Great
Lakes, with light southeast winds Tomorrow. However, increasing
chance of showers and thunderstorms during the day, with strong
storms likely late in the day into the early evening hours. Isolated
severe storms are possible as well.  Winds turning southwesterly
behind the cold front Sunday Night, strengthening moderately Monday
through Tuesday as low pressure stalls over Ontario. Winds still
look to reside mainly below 25 knots, with Saginaw Bay the most
likely location reaching around 25 knots.

&&

.PREV DISCUSSION...
Issued at 1243 PM EDT Sat May 27 2017

AVIATION...

Modest 850-700 MB moisture pooling leading to SCT-BKN clouds in the
3-7 kft range this afternoon. This moisture does persist over
southeast Michigan this evening/tonight, but will carry a SCT group
as loss of diurnal component will probably even allow skies to go
mostly clear. Weak wind field to persist through tomorrow, with the
favored direction being out of east-southeast. As such, low chance
of some light fog development late tonight, but left out of the TAFS
as enough high clouds expected by morning to mitigate the fog threat.
Increasing chance of showers and thunderstorms tomorrow, but may be
able to escape most of the daylight hours dry and no mention in TAFs
will be added yet (outside of prob30 at DTW late).

For DTW...Low confidence in sustained ceilings below 5000 feet.
Timing of showers and thunderstorms tomorrow is in question, and
model trends suggest activity may hold off closer to the early
evening hours.

//DTW THRESHOLD PROBABILITIES...

* Low for cigs aob 5000 feet.

* Low for thunderstorms tomorrow.


&&

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

$$

DISCUSSION...DG/DE
MARINE.......DG
AVIATION.....SF


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