Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251721

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
121 PM EDT Mon Sep 25 2017


Quiet aviation conditions will remain as surface high pressure
centered over the eastern Great Lakes continues to persist through
the TAF cycle.  Light southeast winds will continue to maintain some
humidity across the area.  This will allow for scattered cumulus to
form this afternoon along with areas of higher clouds.  VFR
conditions will continue through the overnight hours before light fog
redevelops towards sunrise on Tuesday.


* None.


Issued at 315 AM EDT Mon Sep 25 2017


Record setting upper level ridge (00z DTX sounding revealed a 500 MB
height of 591 DAM) is finally beginning to slowly weaken/break down,
as upper level trough/energy over the Rockies heads off to the
northeast. 500 MB heights progged to fall to 585 DAM on Tuesday, with
what looks to be a dry cold front tracking through Tuesday
evening/night, as there is barely any instability, and mid level
lapse rates are pathetic as upper level support tracks off into

High clouds and increase in moisture coming up from the south today
should help level off the high temperatures around 90 degrees, as
925 mb temps reach 25 C or slightly better. There is even
suggestions by hires models that moisture advection and instability
building up during the day will be sufficient to generate a few
showers and thunderstorms across the north half of the CWA, which is
not totally out of the question with the noted weak surface
trough/convergence. Ultimately, the skinny cape with the dry mid
levels will probably be too much to overcome.

Another reasonable shot at 90 degrees on Tuesday, as light level
southwest flow developing ahead of the cold front should allow for
more uniform highs, with 925 temps still advertised to reach 25 C
and potentially slightly exceed.

Healthy low level cold advection on Wednesday, as 925 mb temps fall
into the mid teens by day`s end, which should hold maxes mostly down
in the 70s. Continued cold advection Wednesday night, with 850 mb
temps also lowering into the 2-5 C range as surface ridge arrives
Thursday morning. Late September insolation should be able to boost
temps into the upper 60s to near 70 degrees, or near normal values.
Temperatures then look to drop below normal as we head into the
weekend with upper level trough sliding through during the Friday-
Saturday time period, with 850 mb temps falling to around zero per
00z Euro.


Record early fall warmth will continue today through Tuesday. The
warm air and light southerly wind will produce ideal marine
conditions during this time. A cold front crossing the central Great
Lakes Tuesday night and Wednesday will then bring temperatures back
down toward normal along with a low chance of showers and
thunderstorms. Winds behind the front will become northwest at light
to moderate speed, although a few gusts near 30 knots will be
possible over the open waters of central Lake Huron. The part of the
forecast to monitor will be the associated higher wave pattern
remaining far enough offshore to avoid the need for small craft
advisories over southern Lake Huron. Another low pressure system and
cold front due Friday will bring a reinforcement of colder air and
unstable marine conditions for the weekend.


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



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