Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 192307

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
707 PM EDT Sat Aug 19 2017


High pressure will bring VFR conditions throughout the forecast
period even as it splits off to the east during the day Sunday.
Light/variable winds will become southwest under 10 knots on the
backside of this high by mid/late morning with just a few diurnal
cumulus possible within a rather dry airmass.


* None.


Issued at 251 PM EDT Sat Aug 19 2017


Upper level trough axis/cold pool (-15 C at 500 MB per APX sounding)
pushing east of the Central Great Lakes this afternoon. Modest
pocket of moisture in and around Saginaw Bay could trigger isolated
activity, but loss of daytime heating and increasing upper level
northwest confluent flow/warming mid levels should end activity
around 00z if anything does in fact go up. Large surface high center
to track near the southern Michigan border tonight and into the
eastern Ohio Valley tomorrow. Surface dew pts have slipped into the
55 to 60 degree range this afternoon, which looks to be a good target
for mins overnight across most locations, which is probably cool
enough for patchy fog around inland lakes with calm winds.

Southwest return flow around the high tomorrow to allow temps to
push into the mid 80s based off 850 MB temps reaching around 16 C.
Even warmer airmass in place for Monday ahead of a weak cold front,
as 850 MB temps progged to climb to around 19 C, suggesting maxes
approaching 90 degrees. None-the-less, increasing moisture and clouds
expected, along with the eclipse during peak heating, anticipating
maxes more in the 85 to 88 degree range. In fact, main moisture surge
(per 850- 700 MB Theta-E fields) look to be occuring during the
morning hours, with moisture axis (PW values around 1.75 inches) in
place by 00z Tuesday. It`s possible there may be enough instability
to trigger a few showers or thunderstorms, but warm layer in 5-10 KFT
layer may just enough to cap activity with no clear cut low level
convergence/trigger, as 500 mb heights are also around 588 DAM. Much
better chance Monday night with increasing height falls, as deepening
low pressure pushes into the Western Great Lakes.

A cold front pushing northwest to southeast will provide additional
rain and thunderstorms chances through Tuesday morning, with
confidence regarding precipitation further enhanced as an amplified
upper-level trough with a strong embedded upper-level disturbance
pushes over the area aloft. Likely rain and thunderstorm chances
will diminish throughout Tuesday afternoon as winds veer from the
southwest to the northwest following the cold front, allowing dry,
stable air to enter Michigan. This cold front will have a
significant impact on temperature and humidity. Daytime highs
forecasted in the upper 70s to lower 80s on Tuesday are expected to
drop into the lower 70s for a high on both Wednesday and Thursday.
Likewise, dew points in the upper 60s on Tuesday morning and
afternoon are expected to diminish into the low to mid 50s both
Wednesday and Thursday. Temperatures will gradually climb back into
the mid to upper 70s by the weekend. Otherwise, a broad surface high
pressure and ridging aloft will look to keep conditions dry heading
into the weekend.


Modest northwesterly flow will back to southwesterly by early
Sunday. Speeds will remain moderate - with sustained winds in the 10-
15kt range. The offshore nature will preclude waves from becoming
much of an issue. The next significant weather maker will arrive
Monday night and persist through Tuesday. Moderate northwest flow
with higher waves will set up behind the cold front by Tuesday night.


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



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