Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 312017

Area Forecast Discussion
National Weather Service Saint Louis MO
317 PM CDT WED AUG 31 2016

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 315 PM CDT Wed Aug 31 2016

Band of showers and thunderstorms will continue to move southeast
late this afternoon and will be south of the CWA by early this
evening as low level winds begin to advect cooler and drier air into
the area.  Mid and high level clouds will begin to clear out of the
area by late this evening and overnight and north winds will be
light allowing for decent radiational cooling.  Even though the
northerly flow will be advecting in some drier air, recent rains as
of late have added to wet soils as well as warm river temperatures
should allow for some patchy fog late tonight and early tomorrow
morning. Any fog on Thursday morning will dissipate as skies will be
mainly sunny in the the morning.  Some diurnal cumulus is expect to
develop over the northeast half of the CWA by afternoon as a weak
mid level trough passes through the area.

Lows tonight will fall at or below MOS guidance in most areas as
drier air moves into the area.  Expect highs tomorrow to be closer
to warmer NAM MOS guidance which has values closer to 80 degrees in
most areas.


.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 315 PM CDT Wed Aug 31 2016

High pressure remains in control of the weather through the weekend.
The ridge will stay locked in over the region at least through
Sunday now due to a highly amplified blocking pattern with a deep
trof over the western CONUS and another amplified trof with
tropical influence over the eastern CONUS. Friday and Saturday
temperatures should be well below normal with highs the mid 70s to
near 80 and lows in the mid 50s to low 60s Sunday will probably be
warmer than Friday or Saturday due to airmass modification and
progressively more southerly flow on the western side of the
ridge...although temperatures will only climb to near normal in
the low 80s. Humidity will begin returning too, though current
indications are that dew points will only rebound into the low to
mid 60s.

Should see more summer-like temperatures and humidity for Monday
through Wedenesday as deep southwest flow returns to the Mississippi
Valley.  Could see some warm advection showers and storms as early
as 06-12Z Monday morning...primarily over northern Missouri with
some potential lingering into the daytime hours of Monday.  The rest
of the forecast for Tuesday and Wednesday looks warm and humid with
only slight chances for any precipitation.  A strong upper level
ridge will develop over the deep south and the Mid Mississippi
Valley will be on the northern periphery.  There also won`t be
any synoptic boundaries in the area to focus convection.  With these
two factors in play, any convection will have to rely on orographic
effects or mesoscale boundaries to develop.  Temperatures look to
jump back above normal in the mid and upper 80s.



.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1247 PM CDT Wed Aug 31 2016

Showers will move out of KCOU shortly.  Scattered showers and
thunderstorms will affect the St. Louis area terminals early this
afternoon. Have included VCTS through 20Z in the TAF for now. MVFR
ceilings are still affecting KCPS and KSUS early this afternoon
and have included these low ceilings through 20Z. Then went with
dry and VFR conditions through most of the evening, though think
there will be some fog redevelopment  overnight that could affect

SPECIFICS FOR KSTL: Scattered showers and thunderstorms are
developing north of the terminal currently, so included VCTS
through 20Z. Otherwise expect dry and VFR conditions through the
rest of the period. Current westerly winds will turn
northerly later this afternoon.





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