Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 301741

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1141 AM CST Wed Nov 30 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 300 AM CST Wed Nov 30 2016

Focus today and tonight will be cloud cover, which in turn, will
have a large impact on temps.

Large stacked low over nrn Plains into Great Lakes region will
continue to control the weather pattern across the region. Area of
ST continues to move ewd early this morning. The main question
regarding this area of clouds is two fold. First, how far south will
the clouds propagate/develop and second, will the clouds break up
later today.

Based on the latest sat trends, believe much of the operational
guidance is too cloudy. Believe this trend continues thru the day.
The local WRF seems to do a better job currently, but believe it
does not suggest enuf clouds later today. Have therefore attempted
to go with a middle ground between these two solns. For areas
further north, chances of remaining cloudy all day increase
dramatically. However, believe the main cloud deck will remain just
north of the CWA, but uncertainty remains regarding placement.

Given these clouds trends, have trended below the cooler MOS across
the wrn and nrn portions of the CWA. However, given the wly flow and
a secondary area of clouds currently over OK region moving into the
area, have also trended twd the cooler guidance further south and
east, but not below.

As for tonight, with mixing expected to continue thru the night and
with clouds persisting thru much of the night, have trended warm.
That said, going forecast may not be cool enuf for low lying areas
that may decouple tonight. This is especially true for srn portions
of the CWA where the pressure gradient will be more relaxed and
winds lighter.


.LONG TERM...  (Thursday through Tuesday)
Issued at 300 AM CST Wed Nov 30 2016

System over Great Lakes region to finally move away from region, so
will see surface ridge build in over area by Thursday. Despite this,
will remain in west to northwest flow with mostly cloudy conditions
in the far north to mostly sunny far south through Friday. Highs
each day will be near normal, in the low 40s to low 50s.

By the weekend, the next weather system that has been strengthening
over the southwestern US, will begin to to approach region. First in
a series of shortwaves to lift out towards region and try to phase
in with northern stream system. Precipitation chances will be on
the increase especially Saturday night and Sunday morning.
Forecast soundings still indicating mostly rain with snow mixed in
at times with this system. No accumulation expected.

GFS is still the most consistent model and keeps weak ridging in on
Monday before next system slides in from the southwest, phasing with
the next in a series of northern stream shortwaves. Strength, timing
and placement still hard to pin down, so kept chance pops going
Monday night, tapering off Tuesday morning. Precipitation will
mainly be in the form of rain once again, with some snow mixed in a



.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1140 AM CST Wed Nov 30 2016

MVFR CIGs from a cloud shield over UIN and COU and entering the
STL metro area during the past hour is VFR along its edges and VFR
should gradually take over for the MVFR during the afternoon
hours, with the southern edge of this cloud shield sliding
northward towards the I-70 corridor and then north of it tonight,
but currently thinking it will hang in there over UIN but scatter
out for COU and STL metro sites. Otherwise, gusty westerly winds
will diminish this evening and more or less continue at its
current speed with some slight strengthening into Thursday.





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