Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 230343

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1043 PM CDT SUN MAY 22 2016

.SHORT TERM... (Through Monday Afternoon)
Issued at 315 PM CDT Sun May 22 2016

Surface ridge centered over eastern Missouri will drift east tonight
and Monday allowing the wind to turn to the south across the area by
Monday morning.  Expect another relatively cool night due to light
wind and clear sky providing good radiational cooling conditions.
Don`t expect dewpoint temperatures to really begin rising until
after 12Z Monday so think lows will drop to near dewpoint
temperatures in the low to mid 50s across most of the area.

Southerly flow on the western periphery of the ridge on Monday will
begin moistening up the boundary well as begin warm
advection over the region in earnest.  With 850mb temps approaching
the mid teens MOS highs in the mid 80s look very reasonable.  Still
some question whether or not there`s a chance for storms in central
MO.  Latest run of the NCEP 4km WRF model has a broken line of
storms approaching the area (tho not quite) into our CWFA) by 00Z.
NSSL WRF also has a broken line of convection which is weakening as
it approaches the western fringes of our CWFA late Monday afternoon.
The The latest NAM has backed precip chances further west...and the
GFS has been pretty consistently dry over our area for Monday
afternoon.  Given how close it looks like thunderstorms might get, I
think I`ll keep a low chance/slight chance area going late Monday
afternoon in central and northeast Missouri


.LONG TERM... (Monday Night through Next Sunday)
Issued at 315 PM CDT Sun May 22 2016

Southwest flow aloft beginning Monday night will usher in deep, rich
moisture into our region along with the instability that nearly
always seems to comes with it.  This pattern, coupled with southerly
flow at the surface, will persist thru the end of the week.  Throw
in a stream of upper level disturbances to get things going, and you
end up with a near continuous chance for thunderstorms during this
timeframe with dry periods very hard to come by.  Went with PoPs
each 12-hour period that were above climo (~30%).

Monday night`s thunderstorm threat is a continuation of what begins
late Monday afternoon with what initially forms to our west edging
our forecast area in northeast and central MO.  With the sun setting,
this activity should struggle to move much more to the east into more
stable air.

The days with the highest levels of instability are expected to be
Tuesday for areas mainly west and north of STL metro and much of
the forecast area Wednesday and Thursday.  It will be these days
that will have an elevated threat for severe thunderstorms.

The pattern begins to shift a bit by late next weekend where a
period of dry wx may finally work its way in.

Above average temps can be expected each day, with maxes mainly in
the 80s and mins in the 60s.



.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1035 PM CDT Sun May 22 2016

VFR and dry thru at least Mon afternoon. Sfc ridge continues to
build ewd out of the region allowing sely to sly winds to return
to the area. Chances for TSRA increase Mon evening, mainly for
KCOU and KUIN. With slightly better chances at KUIN, will mention
VCTS for now late in the period.





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