Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 201700

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
Issued by National Weather Service Kansas City/Pleasant Hill MO
1200 PM CDT Thu Oct 20 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 350 AM CDT Thu Oct 20 2016

Post frontal band of showers and storms continue to move
through southeast MO and southwest IL early this morning, just
southeast of STL.  This band of convection will continue to
gradually shift southeastward this morning with most of this
precipitation southeast of our forecast area by noon as the surface
ridge over the northern Plains builds southeastward into our area.
Although the low levels will be drying out today the light rain over
northwest MO early this morning associated with the upper level
trough may move into portions of northeast and central MO late this
morning and early this afternoon before completely dissipating. This
light precipitation shifting into parts of our area by early
afternoon is evident on the latest HRRR model runs. Much cooler
temperatures are expected today and tonight with low level cold air
advection behind the cold front leading to only a small diurnal rise
in temperatures. The 850 mb temperature will drop down to around 3
degrees C in the STL area tonight.  Good radiational cooling can be
expected tonight as the surface ridge axis shifts southeastward into
northwest MO by 12Z Friday leading to a clearing sky, diminishing
northwest winds, and surface dew points dropping into the 30s. Lows
tonight will only be about 5 degrees below normal for late October,
but it will feel colder after the past stretch of unseasonably warm
weather.  There may be some light patchy frost in northeast MO late


.LONG TERM...  (Friday through Wednesday)
Issued at 350 AM CDT Thu Oct 20 2016

A nice stretch of quiet wx is expected into early next week thanks
to NW flow aloft, an absence of upper level disturbances, and a dry
column.  A cold front will drop down late Sunday and into Sunday
night, but due to the lack of any moisture in the column expected
thanks to a blocking surface RIDGE in place across the southeastern
CONUS, dry wx is forecast.

A more substantial increase in moisture is anticipated on Tuesday as
the Gulf of Mexico begins to open up, with rain chances returning to
our region by Wednesday as an upper level disturbance and a surface
frontal system move thru.

After the second below average temperature day in a row on Friday,
where daytime temps will struggle to get out of the 50s, temps will
return to above average values on Saturday and continue well into
next week.  However, daytime maxes are not expected to be nearly as
warm as they were earlier this week, with forecast values in the



.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1141 AM CDT Thu Oct 20 2016

MVFR conditions currently moving through the area will be short-
lived as drier air begins moving into the area this afternoon.
Meanwhile...a passing shower or two will be possible at COU this
afternoon as an upper-level shortwave moves through the region.
The other main story in the near term will be breezy north winds
with gusts of 20-25 kts possible at times before winds weaken
this evening. VFR conditions expected through the overnight as
northwest winds of 5-10 kts continue under clearing skies aloft.

SPECIFICS FOR KSTL: High-end MVFR cigs should begin to rise
shortly after 18z with BKN-OVC at flight level 070 prevailing
through the afternoon hrs. SCT clouds between 025-030 expected
this afternoon...with sustained NNW winds of 10-15 kts with gusts
to 25 kts possible. Clearing skies expected through the overnight
with NNW winds of 5-10 kts likely.





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