Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 251149

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
649 AM CDT Mon Sep 25 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 359 AM CDT Mon Sep 25 2017

Not a whole lot of change compared to 24 hours ago at the surface
and aloft so expecting similar sensible weather as that of Sunday.
Isolated diurnal convection is forecast to develop by midday and
last through the afternooon hours, mainly focused across the eastern
Ozarks into portions of central Missouri. This activity is expected
to wane and diminish by the mid evening hours.

Temperatures will continue to be 10-15+ degrees above normal with
little to no change in airmass since yesterday. Highs should be in
the upper 80s to low 90s once again and will likely at least
threaten another record high at KSTL (92F in 1900). Lows tonight are
forecast to be in the 60s to low 70s. Did tweak minimums downward a
bit across the eastern Ozarks where very light SE winds will reside
along with at least partial clearing.


.LONG TERM...  (Tuesday through Sunday)
Issued at 359 AM CDT Mon Sep 25 2017

An upper level trough will move through the northern Plains and the
Great Lakes region and send a cold front southeastward through our
forecast area Tuesday and Tuesday night.  It appears that most of
the precipitation will be along and just behind the cold front.
Forecasting no more than low chance pops Tuesday through Wednesday
as the precipitation should be scattered with mainly light amounts
as the better upper level forcing will remain well north of our
area, convergence along the front will be relatively weak, and the
low level moisture will be limited as the Gulf will be cut off.
Temperatures will continue to be unseasonably warm Tuesday and
Tuesday night, especially across southeast MO and southwest IL.  A
pronounced cooling trend will begin on Wednesday with low level cold
air advection after passage of the cold front.  Temperatures will be
close to seasonal normals Wednesday and Wednesday night.  An upper
level trough will deepen over the Great Lakes region Thursday night
and send a reinforcing cold front southeastward through our forecast
area late Thursday night and Friday morning.  This will be a dry
cold frontal passage, but a strong surface ridge will build into the
region from the northern Plains behind the front and lead to below
normal temperatures Friday night and Saturday.  Although the
temperatures should be no more than 5 to 10 degrees below normal it
will feel quite cool in comparison to the recent stretch of
unseasonably warm weather.



.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 635 AM CDT Mon Sep 25 2017

Dry/VFR conditions likely to continue through tonight outside of
any thunderstorms. Isolated storms possible this afternoon, mainly
southwest of metro terminals and southeast of KCOU. KUIN is
expected to remain a bit farther from any convection this
afternoon. Winds will be light out of the south/southeast with
surface high across the Ohio Valley.


Quiet weather likely through Tuesday morning. Isolated showers and
storms should stay southwest of terminal this afternoon. Light
south/southeast winds to continue.





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