Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 170323

923 PM CST Sun Nov 16 2014

Issued at 923 PM CST Sun Nov 16 2014

Accumulating snow has ended across the area allowing the winter
weather advisory to expire at 9 pm. The band of accumulating snow
continues just south of the CWA which is being forced by strong
frontogenesis that will eventually shift southeast tonight. Some
snow may still occur along and south of a Fredericktown to Salem,
IL line on the northern periphery of this area of snow before
08Z per the HRRR, but any accumulation is expected to be minor.
Temperatures are falling into the teens over northeast Missouri,
and decent cold air advection should allow most of the area to
fall into the teens before sunrise.



.SHORT TERM:  (Through Late Tonight)
Issued at 345 PM CST Sun Nov 16 2014

Snow is clearing from the west to east this afternoon, and latest
short-range guidance shows that it should continue to push east at a
decent clip through early evening.  RAP and HRRR have done a very
good job with this system (as they did with yesterday`s
precipitation) so am following them closely.  The surface cold front
which currently looks to be along a line from near Pittsfield to
near the Lake of the Ozarks, will push slowly eastward tonight.
While accumulating snow should end across most of the area by
00-02Z, some flurries could linger along and east of the Mississippi
from St. Louis southward until the cold front finally pushes through
bringing drier low level air to the area.  An additional 1-2 inches
of snow  with locally higher amounts is still possible until the
snow ends...primarily on elevated surfaces. Based on current obs
and latest radar trends, will be dropping the advisory west and
north of the STL area, while continuing the advisory into the
early evening hours over southeast sections of the CWA.

Guidance appears to have a reasonable handle on overnight lows.
Leading edge of the first round of Arctic air (as defined by
single digits dewpoints) currently entering northwest sections of
the CWA, and this will be followed by a secondary surge of Arctic
air (now working into the mid-Missouri Valley) that will enter the
CWA during the predawn hours. In this situation guidance has a tendency
to be a bit too cool due to mixing and some clouds, but due to the
shear strength of cold air in this situation believe "thinking
cold" is the way to go.


.LONG TERM:  (Monday through Next Sunday)
Issued at 313 PM CST Sun Nov 16 2014


Deep and unseasonably strong UA trof over the eastern half of the
CONUS will mean more unseasonably cold November temperatures in
our area through midweek.  Obviously, temperature specifics are
going to be the main forecast problem in the short term, and going
forecasts appear to have a fairly good handle on the expected

Secondary surge of Arctic air that enters the FA late tonight
will be a much colder airmass than any we`ve experienced during
this early taste of winter, and there is good agreement in the 12z
synoptic runs that 850mb temps of -18 to -20C will be common over
the mid-Mississippi Valley by Monday evening.  Low level RH progs
suggest quite a bit of low level cloudiness overspreading the area
on Monday in the wake of the secondary cold front, and this cloud
cover combined with the very cold airmass will almost certainly
mean highs only in the 20s for most of the CWA.  Perhaps the
biggest question is Monday night. While airmass is extremely cold
for this time of year and there may be snow on the ground in some
locations over the southeast half of the CWA, the center of the
Arctic high is forecast to drop from the Plains into the Arklatex
region. The resultant pressure gradient in our area should mean
that westerly winds will persist throughout much of the night,
with this mixing keeping low temps from reaching record levels.
Normally in this situation would be worried about climo bias
causing guidance to be too warm, but due to the aforementioned
winds and mixing believe it may have a good handle on Monday
night temp trends at this point in time. See climate section for
more info on record lows/record low max temps for the next few

AMS moderation will begin on Tuesday as the center of the Arctic
high works its way in the the se U.S., with additional warming on
Wednesday due to warm advection ahead of next shortwave.

Precipitation threat over the next few days should be limited to a
few flurries with the arrival of the cold air and low clouds


Another shot of cold air will settle into the region in the wake of
Wednesday`s shortwave.   However, this next round of cold air will
not be nearly as strong as the Arctic airmass that invades the region
tomorrow and tomorrow night, and as a result it`s impact on late
week temps will not be nearly as dramatic.

Temperatures will moderate heading into next weekend as trof axis
works east and allows a more zonal flow regime to develop over the
nation`s heartland. Resultant low level warm advection/isentropic
ascent, combined with an approach of an upper level trof in the
southern branch of the westerlies, should mean a chance of
precipitation.   Last several medium range runs, as well as latest
12z guidance, suggests ams will warm enough that the bulk of this
precip will be in liquid form.



.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 544 PM CST Sun Nov 16 2014

Snow has come to an end at KCOU and KUIN, but some lingering light
snow and flurries in STL metro area through 01z. Otherwise, as
cold front moves through cigs to lift to vfr. So KCOU to remain
vfr while KUIN to improve by 01z and metro to lift and improve by
05z. By mid morning on Monday, northwest winds to pickup to around
15kts with gusts to 25kts at times. Will see sc deck develop on
back side of system, so added tempo mention of mvfr cigs for the
afternoon hours.

Specifics for KSTL:
Some lingering light snow and flurries in STL metro area through
01z. Otherwise, as cold front moves through cigs to lift to vfr.
So cigs to lift and improve by 05z. By 16z Monday, northwest winds
to pickup to around 15kts with gusts to 25kts at times. Will see
sc deck develop on back side of system, so added tempo mention of
mvfr cigs for the afternoon hours.




The following are record low maximums and record low minimums for
each of the next 3 days, which corresponds to the expected length
of the current cold spell and record snowfall for St. Louis and
Columbia for Sunday and Monday.

Date:       11/16     11/17     11/18

                         St. Louis

Low High:  29/1997   17/1880   25/1880
     Low:  13/1959    6/1959   14/1932
Snowfall: 0.1/1997  1.0/1951


Low High:  30/1932   23/1959   27/1903
     Low:   8/1959    4/1959    8/1891
Snowfall: 4.8/1932  0.1/1989


Low High:  28/1997   19/1959   24/1903
     Low:   4/1959    3/1959    7/1903




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