Scientific Forecaster Discussion
fxus63 kdtx 280349
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1149 PM EDT Sat may 27 2017
Se mi will remain under the influence of departing high pressure
through the morning. This will result in light winds and clear skies
below 6k feet. A subtle influx of moisture late in the morning will
translate to a sct to bkn cu field during the afternoon. The chances
for thunderstorms will increase markedly after 21z with the approach
of a sfc front and upper level short wave feature.
For dtw...the latest guidance is suggesting the most probable timing
period for thunderstorm activity will be between 5 PM and midnight
//Dtw threshold probabilities...
* moderate in ceilings at or below 5000 ft Sunday afternoon and
* Moderate in thunderstorms Sunday evening.
issued at 322 PM EDT Sat may 27 2017
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
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
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.
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.
Lake St Clair...none.
Michigan waters of Lake Erie...none.