Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 212142

342 PM CST SAT NOV 21 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 258 PM CST Sat Nov 21 2015

Surface low over northwestern OH will continue moving northeastward
as a surface ridge over the central and southern Plains builds
eastward into MO and IL. The clouds will clear out aross southeast
MO and southwest IL early this evening as the surface low pulls
further northeast of the area. The surface wind will weaken as
well as the surface pressure gradient relaxes. A northwest flow
shortwave will bring some mid-high level cloudiness southeastward
into our area later tonight. These clouds will be the only
limiting factor for an unseasonably cold night as the models drop
the -10 degree 850 mb isotherm southward to near STL by 06Z
Sunday. The lows tonight should be at least 10 degrees below
normal for late November. The coldest lows will likely be over
the extreme northern portion of the forecast area where a little
leftover snow cover which does not melt this afternoon will
enhance the radiational cooling.


.LONG TERM:  (Sunday through Next Saturday)
Issued at 258 PM CST Sat Nov 21 2015

Cold and dry conditions will continue for the rest of the weekend
with a warmup for the start of the upcoming work week as upper
level heights rise as the upper level trough shifts well east of
the region, and as southerly surface/low level flow begins to
strengthen on Tuesday as the surface ridge shifts well east of
our area and surface troughing develops in the lee of the Rockies.
The models begin to generate some very light QPF over our area as
early as Tuesday night. This may be more of a reflection of
increasing low level moisture and cloudiness over the area, rather
than actual measureable precipitation. More significant
precipitation will likely hold off until Thanksgiving or Thursday
night as a deep upper level trough approaches with an associated
strong cold front. The GFS model is a little quicker with this
storm system and its associated precipitation compared to the
ECMWF model. Even if the slower solution of the ECMWF model is
more correct, most of the precipitation should shift east of our
forecast area by Friday night as colder air advects into the
region behind the cold front. With precipitation likely ending by
Friday evening it appears that the precipitation type will all be
in the form of liquid rain.



.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1150 AM CST Sat Nov 21 2015

Rapidly moving low pressure system has moved to Indiana taking the
precipitaton with it. Clouds will quickly scatter and clear this
afternoon. Northwest wind will also calm down going light and
variable tonight. High pressure moves east of the area Sunday
bringig a light south wind.

Specifics for KSTL: MVFR clouds looks to scatter and clear around
22z. Clear overnight with wind becoming light and variable after
06z as high pressure moves in. The high quickly moves east Sunday
bringing a light south to southwest wind. An upper level
distubance will bring in some mid clouds overnight.





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