Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 130928
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
328 AM CST Sat Jan 13 2018

.SHORT TERM...  (Through Late Tonight)
Issued at 328 AM CST Sat Jan 13 2018

A strong surface ridge, cold air mass centered over eastern ND will
continue to build southeastward into our area today.  Continued low
level cold air advection will lead to unseasonably cold temperatures
today and tonight.  Highs today will be 15 to 20 degrees below
normal.  Mid level cloudiness across northwestern MO ahead of a
northwest flow shortwave will advect southeastward into our forecast
area this morning.  Much of this cloud cover will shift southeast of
our forecast area by late afternoon.  Very low surface dew points
and light surface winds tonight will lead to very cold lows in the
single digits.

GKS

.LONG TERM...  (Sunday through Friday)
Issued at 328 AM CST Sat Jan 13 2018

Not much change in the overall pattern with NW flow aloft expected
thru Wed. Models continue to be fairly good agreement, although
timing differences exist with precip on Sun and Mon. Differences
also appear late in the forecast period with the approaching system
on Thurs.

A quick moving s/w is still expected to pass just west of the CWA on
Sun. This track is once again shifted slightly west than prev
cycles. However, have still kept some low PoPs as this weak trof
moves thru the area. There may still be enuf moisture available for
flurries or light snow with some WAA across the area while the main
s/w is expected to pass south of the CWA.

Mdls continue to be in good agreement with an upper trof digging
into the region with an associated cdfnt dropping thru the area.
However, there are some timing differences with the arrival of this
front. Still expecting much of the area to see around one inch of
new snow, with some areas seeing up to 2 inches possible. However,
confidence is low as to where those higher bands may be at this
time.

With a large, cold dry airmass building into the region behind this
front, the remainder of the forecast period remains dry. This sfc
ridge focuses on the next impact to the area, namely the dangerously
cold temps and wind chill expected.

With the sfc ridge currently in place moving east out of the area on
Sun, have trended cool again with clouds spilling into the area with
the initial s/w mentioned above. However, with winds becoming sly,
Sun shud be slightly warmer compared to today. With the strong sfc
ridge building into the area behind the front on Sun night and Mon
and anticipated new snowfall, have trended aob the colder guidance
for Mon thru Wed night. The cold temps coupled with stronger winds
behind the front, dangerously cold wind chill values are expected
Mon thru Tues night. Wind chill values of -15F or lower is expected
across much of the area Mon night. These low values may linger into
Tues night as well, although winds are expected to be much lower.

The upper trof and sfc ridge eventually move east out of the area
allowing swly winds to return to the region. Differences among mdls
regarding the upper approaching the region on Thurs still exist,
although less so compared to yesterday. Still, late next week shud
see a warm-up, but low confidence regarding how warm temps will be
due to differences.


Tilly

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1133 PM CST Fri Jan 12 2018

MVFR stratus has been clearing to the south across eastern MO and
southwest IL this evening and should clear both KSUS and KCPS by
06Z. VFR flight conditions are expected at all of the terminals
through the forecast period with increasing high-mid clouds
overnight and into Saturday morning. Northerly winds have begun
diminishing and this trend will continue overnight, then winds
will veer and become light on Saturday night.


SPECIFICS FOR KSTL:

VFR flight conditions are expected through the forecast period
with increasing high-mid clouds overnight and into Saturday
morning. Northerly winds have begun diminishing and this trend
will continue overnight, then winds will veer and become light on
Saturday night.

Glass

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     24   8  26  23 /   0   0  10  20
Quincy          17   3  25  17 /   0   0  30  60
Columbia        21   7  27  22 /   5  10  20  60
Jefferson City  21   8  29  23 /   5  10  20  40
Salem           22   5  24  21 /   0   0   5  20
Farmington      23   7  25  22 /   5   0  10   5

&&

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

$$

WFO LSX



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