Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 211754

1154 AM CST SAT NOV 21 2015

.SHORT TERM: (Through Tonight)
Issued at 255 AM CST Sat Nov 21 2015

Ongoing precipitation will continue through early afternoon,
eventually tapering off from west to east due to strong
subsidence behind a cold front. A few snowflakes could mix in
with the rain at times almost anywhere across the CWA, especially
just as the rain is ending because that is when the colder air
will also be arriving. However, only the far northern CWA appears
to stay cold enough for long enough to see any accumulation, and
likely only a dusting at best.

Strong CAA behind the aforementioned cold front will produce
falling temperatures during the day across most of the area. The
exception may be across the far eastern CWA where temperatures
could remain steady or perhaps rise by a degree or two before the
front arrives.

Very windy conditions are expected today, especially for the
first few hours after fropa. A tight pressure gradient will lead
to sustained winds of 15-25 mph, and stronger winds aloft will mix
down and produce gusts of 30-40 mph. These values are consistent
with upstream METARs early this morning. BUFKIT soundings from
the RAP and the NAM do suggest that the wind gusts could even be
a bit higher than currently forecast, which would approach
criteria for a wind advisory. However, it does not appear that
wind gusts of that magnitude will be widespread enough to warrant
issuing a wind advisory, therefore no wind headlines are planned
attm. The next shift may revisit the need for wind headlines based
on observational trends. Winds should diminish quickly this

The coldest temperatures of the season so far are expected
tonight and early tomorrow morning. Overnight lows will likely
drop into the upper teens to lower 20s across the area. Overnight
temperatures would be even lower if it weren`t for the expected
mid/high clouds ahead of a secondary vort max dropping through the
upper trough tonight. These clouds will interfere with radiational
cooling processes.


.LONG TERM: (Sunday through Friday)
Issued at 255 AM CST Sat Nov 21 2015

A surface high pressure center will be located south of the area
this weekend, keeping winds from the west or west-southwest until
the surface ridge moves farther eastward during the early or
middle part of the week. At that point, winds will likely become
southerly ahead of a developing low pressure system, bringing
warmer air back into the region. Unlike the 00z runs on the last
two days, the current ECMWF/GFS/GEM 00z model runs are in
remarkably good agreement on large scale atmospheric features
through 00z Wed. The primary features of interest are a large,
complex low pressure system over NV/UT and broad southwesterly
flow aloft over MO/IL. Model solutions quickly diverge thereafter,
and confidence in the forecast beyond Tuesday is low.



.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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