Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 202350
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
550 PM CST Fri Jan 20 2017

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 316 PM CST Fri Jan 20 2017

Main issue will be fog potential tonight.

Clearing line continues to slowly advance newd this afternoon. With
nrn portions of the CWA clearing late this evening or after
Midnight, expect at least some light fog to develop overnight.
However, if mixing persists longer, fog may not develop. Regardless,
it does not currently appear that visbys will drop into the dense
fog category.

Focus then turns to temps on Sat. Have conflicting guidance with the
GFS suggesting warmer temps with deeper mixing while the NAM limits
mixing to around 1200 ft. Upstream obs show temps have topped out in
the upper 60s with a few 70s. Do expect some clouds, perhaps
becoming broken, during the day. While these are expected to be mid
and high clouds, this shud limit heating a bit. Going forecast
appeared close and made only minor modifications.

A s/w will be passing thru the region ahead of the approaching
system during the afternoon on Sat. There is some difference among
mdl guidance, but believe there will be a lack of moisture to expect
precip.

Tilly

.LONG TERM...  (Saturday Night through Next Friday)
Issued at 316 PM CST Fri Jan 20 2017

A powerful storm system that will come onshore to southern
California this evening will enter a pattern of a longwave TROF that
dominates much of the western CONUS.  This storm is then expected to
track across the southern CONUS and pass to our south on Saturday
night and Sunday.  Normally this time of year, a track such as this
would raise eyebrows on potential for a significant winter storm
somewhere in our CWA, but there is no cold air anywhere to be found
or tap with this system.  The EC is showing a bit better northward
extent to its pcpn shield than the other models, but either way, the
pcpn-types should be all rain.

After a brief interlude of a weak RIDGE thru our region late Monday
into early Tuesday, another strong Pacific storm system will
approach late Tuesday.  The brunt of the lift with this system will
pass to our north Tuesday night, but several models are showing
additional and weaker upper level disturbances sliding down into our
region from the resultant northwest flow aloft for much of the
period from Wednesday into Friday.  However, the column gets
progressively drier and confidence decreases on any one event with
time, and so have tapered off PoPs as a result.  Pcpn-types will be
more questionable late Tuesday into Wednesday, especially in
northern MO and central IL, and have a rain-snow mix at times for
these areas.

Temperatures are expected to remain above average until the middle
of next week, with a more favorable pattern for cold air attempting
to setup afterwards.

TES
&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 540 PM CST Fri Jan 20 2017

As warm front lifts northward through forecast area, clearing
skies slowly lifting northward as well. KCOU has already cleared
out and will remain VFR through forecast period. As for metro area
tafs, MVFR cigs to lift and scatter out by 02z Saturday. In KUIN,
MVFR cigs/vsbys to persist through about 05z Saturday, before
becoming VFR. Otherwise, main issue tonight will be LLWS mainly
between 07z and 14z Saturday. Beyond that VFR conditions and south
to southwest winds for rest of forecast period.

SPECIFICS FOR KSTL:
As warm front lifts northward through metro area, clearing skies
slowly lifting northward as well. MVFR cigs to lift and scatter
out by 02z Saturday. Otherwise, main issue tonight will be LLWS
mainly between 08z and 14z Saturday. Beyond that VFR conditions
and south winds for rest of forecast period.

Byrd
&&

.CLIMATE...
Issued at 1253 AM CST Fri Jan 20 2017

January 21st Record High Information

St. Louis, Missouri  STL  75  (1986)
Columbia, Missouri   COU  73  (1957)
Quincy, Illinois     UIN  69  (1957)


&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     47  68  46  54 /  10   5  30  30
Quincy          44  60  39  48 /  10   5  10   5
Columbia        44  63  42  50 /  10   5  20  10
Jefferson City  45  65  42  52 /  10   5  20  20
Salem           50  66  48  58 /  10   5  30  30
Farmington      47  65  47  56 /  10  10  40  50

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$
WFO LSX


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