Winter Storm Warning 1, NWS St. Louis, MO

002 
WWUS43 KLSX 081823
WSWLSX

URGENT - WINTER WEATHER MESSAGE
National Weather Service St Louis MO
1223 PM CST Mon Jan 8 2024

MOZ034-035-090930-
/O.UPG.KLSX.WW.Y.0001.240108T2100Z-240110T0600Z/
/O.EXA.KLSX.WS.W.0001.240108T2100Z-240110T0600Z/
Monroe MO-Ralls MO-
1223 PM CST Mon Jan 8 2024

...WINTER STORM WARNING IN EFFECT UNTIL MIDNIGHT CST TUESDAY NIGHT...

* WHAT...Heavy snow expected. Total snow accumulations between 3 and 
  6 inches. Winds gusting as high as 40 mph.

* WHERE...Monroe MO and Ralls MO Counties.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Monday evening and Tuesday morning 
  commutes. Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The rapid accumulation of snow will make travel extremely difficult, 
if not impossible. If travel is necessary, be sure to exercise 
extreme caution. If you must travel, keep an extra flashlight, food 
and water in your vehicle in case of an emergency. The latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

ILZ095-096-MOZ018-019-026-027-090930-
/O.CON.KLSX.WS.W.0001.240108T2100Z-240110T0600Z/
Adams IL-Brown IL-Knox MO-Lewis MO-Shelby MO-Marion MO-
Including the cities of Hannibal, Quincy, and Mount Sterling
1223 PM CST Mon Jan 8 2024

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CST TUESDAY 
NIGHT...

* WHAT...Heavy snow expected. Total snow accumulations between 6 and 
  10 inches. Winds gusting as high as 40 mph.

* WHERE...Portions of west central Illinois and northeast Missouri.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Travel could be very difficult. The hazardous conditions 
  could impact the Monday evening and Tuesday morning commutes. 
  Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The rapid accumulation of snow will make travel extremely difficult, 
if not impossible. If travel is necessary, be sure to exercise 
extreme caution. If you must travel, keep an extra flashlight, food 
and water in your vehicle in case of an emergency. In Illinois, the 
latest road conditions can be obtained at 
www.gettingaroundillinois.com. In Missouri, the latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

ILZ058-098-099-MOZ049-051-052-090930-
/O.EXA.KLSX.WW.Y.0001.240108T2100Z-240110T0600Z/
Greene IL-Calhoun IL-Jersey IL-Osage MO-Montgomery MO-Lincoln MO-
1223 PM CST Mon Jan 8 2024

...WINTER WEATHER ADVISORY IN EFFECT UNTIL MIDNIGHT CST TUESDAY 
NIGHT...

* WHAT...Snow expected. Total snow accumulations between 1 and 3 
  inches. Winds gusting as high as 40 mph.

* WHERE...Portions of southwest Illinois and central and east 
  central Missouri.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Monday evening and Tuesday morning 
  commutes. Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Illinois, the latest 
road conditions can be obtained at www.gettingaroundillinois.com. In 
Missouri, the latest road conditions can be obtained at 
traveler.modot.org/map or by calling 1-888-275-6636.

&&

$$

ILZ097-MOZ036-041-042-047-048-050-090930-
/O.CON.KLSX.WW.Y.0001.240108T2100Z-240110T0600Z/
Pike IL-Pike MO-Boone MO-Audrain MO-Moniteau MO-Cole MO-Callaway
MO-
Including the cities of Mexico, Fulton, Bowling Green,
Pittsfield, Jefferson City, and Columbia
1223 PM CST Mon Jan 8 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT CST 
TUESDAY NIGHT...

* WHAT...Snow expected. Total snow accumulations between 2 and 4 
  inches. Winds gusting as high as 40 mph.

* WHERE...Portions of west central Illinois and central and 
  northeast Missouri.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Monday evening and Tuesday morning 
  commutes. Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Illinois, the latest 
road conditions can be obtained at www.gettingaroundillinois.com. In 
Missouri, the latest road conditions can be obtained at 
traveler.modot.org/map or by calling 1-888-275-6636.

&&

$$

Gosselin

736 
WWUS43 KLSX 082030
WSWLSX

URGENT - WINTER WEATHER MESSAGE
National Weather Service St Louis MO
230 PM CST Mon Jan 8 2024

ILZ095-096-MOZ018-019-026-027-034-035-091130-
/O.CON.KLSX.WS.W.0001.240108T2100Z-240110T0600Z/
Adams IL-Brown IL-Knox MO-Lewis MO-Shelby MO-Marion MO-Monroe MO-
Ralls MO-
Including the cities of Hannibal, Quincy, and Mount Sterling
230 PM CST Mon Jan 8 2024

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CST TUESDAY 
NIGHT...

* WHAT...Heavy snow expected. Total snow accumulations between 4 and 
  9 inches. Winds gusting as high as 40 mph.

* WHERE...Portions of west central Illinois and northeast Missouri.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Travel could be very difficult. The hazardous conditions 
  could impact the Monday evening and Tuesday morning commutes.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The rapid accumulation of snow will make travel extremely difficult, 
if not impossible. If travel is necessary, be sure to exercise 
extreme caution. If you must travel, keep an extra flashlight, food 
and water in your vehicle in case of an emergency. In Illinois, the 
latest road conditions can be obtained at 
www.gettingaroundillinois.com. In Missouri, the latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

MOZ059-060-091130-
/O.EXA.KLSX.WW.Y.0001.240108T2100Z-240110T0600Z/
Gasconade MO-Warren MO-
230 PM CST Mon Jan 8 2024

...WINTER WEATHER ADVISORY IN EFFECT UNTIL MIDNIGHT CST TUESDAY 
NIGHT...

* WHAT...Snow expected. Total snow accumulations between 1 and 3 
  inches. Winds gusting as high as 40 mph.

* WHERE...Gasconade MO and Warren MO Counties.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Monday evening and Tuesday morning 
  commutes. Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

ILZ058-097>099-MOZ036-041-042-047>052-091130-
/O.CON.KLSX.WW.Y.0001.240108T2100Z-240110T0600Z/
Greene IL-Pike IL-Calhoun IL-Jersey IL-Pike MO-Boone MO-Audrain
MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-Lincoln
MO-
Including the cities of Mexico, Fulton, Bowling Green,
Pittsfield, Jefferson City, and Columbia
230 PM CST Mon Jan 8 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT CST 
TUESDAY NIGHT...

* WHAT...Snow expected. Total snow accumulations between 2 and 4 
  inches. Winds gusting as high as 40 mph.

* WHERE...Portions of southwest and west central Illinois and 
  central, east central, and northeast Missouri.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Monday evening and Tuesday morning 
  commutes. Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Illinois, the latest 
road conditions can be obtained at www.gettingaroundillinois.com. In 
Missouri, the latest road conditions can be obtained at 
traveler.modot.org/map or by calling 1-888-275-6636.

&&

$$

Gosselin

661 
WWUS43 KLSX 090021
WSWLSX

URGENT - WINTER WEATHER MESSAGE
National Weather Service St Louis MO
621 PM CST Mon Jan 8 2024

ILZ095-096-MOZ018-019-026-027-034-035-091530-
/O.CON.KLSX.WS.W.0001.000000T0000Z-240110T0600Z/
Adams IL-Brown IL-Knox MO-Lewis MO-Shelby MO-Marion MO-Monroe MO-
Ralls MO-
Including the cities of Hannibal, Mount Sterling, and Quincy
621 PM CST Mon Jan 8 2024

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CST TUESDAY 
NIGHT...

* WHAT...Heavy snow. Additional snow accumulations between 3 and 8 
  inches. Winds gusting as high as 40 mph.

* WHERE...Portions of west central Illinois and northeast Missouri.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Travel could be very difficult. The hazardous conditions 
  could impact the Monday evening and Tuesday morning commutes.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The rapid accumulation of snow will make travel extremely difficult, 
if not impossible. If travel is necessary, be sure to exercise 
extreme caution. If you must travel, keep an extra flashlight, food 
and water in your vehicle in case of an emergency. In Illinois, the 
latest road conditions can be obtained at 
www.gettingaroundillinois.com. In Missouri, the latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

MOZ061-062-072-091530-
/O.EXA.KLSX.WW.Y.0001.000000T0000Z-240110T0600Z/
Saint Charles MO-Franklin MO-Crawford MO-
Including the cities of Washington, Union, Sullivan, and Saint
Charles
621 PM CST Mon Jan 8 2024

...WINTER WEATHER ADVISORY IN EFFECT UNTIL MIDNIGHT CST TUESDAY 
NIGHT...

* WHAT...Snow. Additional snow accumulations of 1 to 2 inches. Winds 
  gusting as high as 40 mph.

* WHERE...Crawford MO, Franklin MO, and Saint Charles MO Counties.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Monday evening and Tuesday morning 
  commutes. Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

ILZ058-097>099-MOZ036-041-042-047>052-059-060-091530-
/O.CON.KLSX.WW.Y.0001.000000T0000Z-240110T0600Z/
Greene IL-Pike IL-Calhoun IL-Jersey IL-Pike MO-Boone MO-Audrain
MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-Lincoln
MO-Gasconade MO-Warren MO-
Including the cities of Jefferson City, Fulton, Bowling Green,
Columbia, Mexico, and Pittsfield
621 PM CST Mon Jan 8 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT CST 
TUESDAY NIGHT...

* WHAT...Snow. Additional snow accumulations between 1 and 3 inches. 
  Winds gusting as high as 40 mph.

* WHERE...Portions of southwest and west central Illinois and 
  central, east central, and northeast Missouri.

* WHEN...Until midnight CST Tuesday Night.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Monday evening and Tuesday morning 
  commutes. Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Illinois, the latest 
road conditions can be obtained at www.gettingaroundillinois.com. In 
Missouri, the latest road conditions can be obtained at 
traveler.modot.org/map or by calling 1-888-275-6636.

&&

$$

Pfahler

166 
WWUS43 KLSX 090857
WSWLSX

URGENT - WINTER WEATHER MESSAGE
National Weather Service St Louis MO
257 AM CST Tue Jan 9 2024

ILZ095-096-MOZ018-019-026-027-034-035-100000-
/O.CON.KLSX.WS.W.0001.000000T0000Z-240110T0600Z/
Adams IL-Brown IL-Knox MO-Lewis MO-Shelby MO-Marion MO-Monroe MO-
Ralls MO-
Including the cities of Hannibal, Mount Sterling, and Quincy
257 AM CST Tue Jan 9 2024

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CST 
TONIGHT...

* WHAT...Heavy snow. Additional snow accumulations between 3 and 8 
  inches. Winds gusting as high as 45 mph.

* WHERE...Portions of west central Illinois and northeast Missouri.

* WHEN...Until midnight CST tonight.

* IMPACTS...Travel could be very difficult. The hazardous conditions 
  could impact the Tuesday morning and evening commutes. Gusty winds 
  could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The rapid accumulation of snow will make travel extremely difficult, 
if not impossible. If travel is necessary, be sure to exercise 
extreme caution. If you must travel, keep an extra flashlight, food 
and water in your vehicle in case of an emergency. In Illinois, the 
latest road conditions can be obtained at 
www.gettingaroundillinois.com. In Missouri, the latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

ILZ058-097>099-MOZ036-041-042-047>052-059>062-072-100000-
/O.CON.KLSX.WW.Y.0001.000000T0000Z-240110T0600Z/
Greene IL-Pike IL-Calhoun IL-Jersey IL-Pike MO-Boone MO-Audrain
MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-Lincoln
MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO-Crawford
MO-
Including the cities of Mexico, Washington, Pittsfield, Fulton,
Jefferson City, Union, Columbia, Bowling Green, Sullivan, and
Saint Charles
257 AM CST Tue Jan 9 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT CST 
TONIGHT...

* WHAT...Snow. Additional snow accumulations between 1 and 3 inches. 
  Winds gusting as high as 45 mph.

* WHERE...Portions of southwest and west central Illinois and 
  central, east central, and northeast Missouri.

* WHEN...Until midnight CST tonight.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Tuesday morning and evening commutes. 
  Gusty winds could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Illinois, the latest 
road conditions can be obtained at www.gettingaroundillinois.com. In 
Missouri, the latest road conditions can be obtained at 
traveler.modot.org/map or by calling 1-888-275-6636.

&&

$$

Elmore

721 
WWUS43 KLSX 091926
WSWLSX

URGENT - WINTER WEATHER MESSAGE
National Weather Service St Louis MO
126 PM CST Tue Jan 9 2024

ILZ095-096-MOZ018-019-026-027-034-035-100600-
/O.CON.KLSX.WS.W.0001.000000T0000Z-240110T0600Z/
Adams IL-Brown IL-Knox MO-Lewis MO-Shelby MO-Marion MO-Monroe MO-
Ralls MO-
Including the cities of Mount Sterling, Hannibal, and Quincy
126 PM CST Tue Jan 9 2024

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CST 
TONIGHT...

* WHAT...Snow, heavy at times. Additional snow accumulations up to 
  two inches. Winds gusting as high as 45 mph.

* WHERE...Portions of west central Illinois and northeast Missouri.

* WHEN...Until midnight CST tonight.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Tuesday evening commute. Gusty winds 
  could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The rapid accumulation of snow will make travel extremely difficult, 
if not impossible. If travel is necessary, be sure to exercise 
extreme caution. If you must travel, keep an extra flashlight, food 
and water in your vehicle in case of an emergency. In Illinois, the 
latest road conditions can be obtained at 
www.gettingaroundillinois.com. In Missouri, the latest road 
conditions can be obtained at traveler.modot.org/map or by calling 
1-888-275-6636.

&&

$$

ILZ059-100>102-MOZ063>065-073-100600-
/O.EXA.KLSX.WW.Y.0001.000000T0000Z-240110T0600Z/
Macoupin IL-Madison IL-Saint Clair IL-Monroe IL-Saint Louis MO-
Saint Louis City MO-Jefferson MO-Washington MO-
Including the cities of Belleville, Cahokia, Edwardsville, Saint
Louis, and Alton
126 PM CST Tue Jan 9 2024

...WINTER WEATHER ADVISORY IN EFFECT UNTIL MIDNIGHT CST TONIGHT...

* WHAT...Snow. Snow accumulations up to one inch. Winds gusting as 
  high as 40 mph.

* WHERE...Portions of southwest Illinois and east central Missouri.

* WHEN...Until midnight CST tonight.

* IMPACTS...Plan on reduced visibility and slippery road conditions. 
  The hazardous conditions will impact the Tuesday evening commute.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Illinois, the latest 
road conditions can be obtained at www.gettingaroundillinois.com. In 
Missouri, the latest road conditions can be obtained at 
traveler.modot.org/map or by calling 1-888-275-6636.

&&

$$

ILZ058-097>099-MOZ036-041-042-047>052-059>062-072-100600-
/O.CON.KLSX.WW.Y.0001.000000T0000Z-240110T0600Z/
Greene IL-Pike IL-Calhoun IL-Jersey IL-Pike MO-Boone MO-Audrain
MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-Lincoln
MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO-Crawford
MO-
Including the cities of Mexico, Columbia, Union, Washington,
Sullivan, Bowling Green, Saint Charles, Pittsfield, Fulton, and
Jefferson City
126 PM CST Tue Jan 9 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT CST 
TONIGHT...

* WHAT...Snow. Additional snow accumulations up to two inches. Winds 
  gusting as high as 45 mph.

* WHERE...Portions of southwest and west central Illinois and 
  central, east central, and northeast Missouri.

* WHEN...Until midnight CST tonight.

* IMPACTS...Plan on slippery road conditions. The hazardous 
  conditions could impact the Tuesday evening commute. Gusty winds 
  could bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. In Illinois, the latest 
road conditions can be obtained at www.gettingaroundillinois.com. In 
Missouri, the latest road conditions can be obtained at 
traveler.modot.org/map or by calling 1-888-275-6636.

&&

$$

Glass

790 
WWUS43 KLSX 100104
WSWLSX

URGENT - WINTER WEATHER MESSAGE
National Weather Service St Louis MO
704 PM CST Tue Jan 9 2024

ILZ095-096-MOZ018-019-026-027-034-035-100215-
/O.CAN.KLSX.WS.W.0001.000000T0000Z-240110T0600Z/
Adams IL-Brown IL-Knox MO-Lewis MO-Shelby MO-Marion MO-Monroe MO-
Ralls MO-
Including the cities of Quincy, Mount Sterling, and Hannibal
704 PM CST Tue Jan 9 2024

...WINTER STORM WARNING IS CANCELLED...

Accumulating and impactful snowfall has ended across the region. 
Some patchy blowing snow could linger overnight.

$$

ILZ058-059-097>102-MOZ036-041-042-047>052-059>065-072-073-100215-
/O.CAN.KLSX.WW.Y.0001.000000T0000Z-240110T0600Z/
Greene IL-Macoupin IL-Pike IL-Calhoun IL-Jersey IL-Madison IL-
Saint Clair IL-Monroe IL-Pike MO-Boone MO-Audrain MO-Moniteau MO-
Cole MO-Osage MO-Callaway MO-Montgomery MO-Lincoln MO-Gasconade
MO-Warren MO-Saint Charles MO-Franklin MO-Saint Louis MO-Saint
Louis City MO-Jefferson MO-Crawford MO-Washington MO-
Including the cities of Saint Charles, Sullivan, Mexico, Bowling
Green, Washington, Jefferson City, Edwardsville, Columbia, Alton,
Saint Louis, Union, Cahokia, Pittsfield, Belleville, and Fulton
704 PM CST Tue Jan 9 2024

...WINTER WEATHER ADVISORY IS CANCELLED...

Accumulating and impactful snowfall has ended across the region.

$$

Pfahler

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1110 PM CST Sun Jan 7 2024

.KEY MESSAGES...

- A winter storm will bring snow primarily to northern parts of
  our forecast area beginning Monday afternoon and continuing
  through Tuesday evening. A Winter Storm Watch continues for
  areas expected to be most impacted by this. Snow may spread
  across most of the area Tuesday evening just before it ends.

- Another storm system will track across the central US late this
  week. While there remains considerable uncertainty on the track
  and timing of this system, a consensus is building that our
  area will see at least some impact from this.

- Much colder air will pour into the region behind the late week
  system. Although there is uncertainty on just how cold it will
  be and how quickly it arrives, an extended period of subfreezing
  temperatures is likely (70% or higher).

&&

.SHORT TERM... (Through Late Tuesday Night)
Issued at 235 PM CST Sun Jan 7 2024

(Tonight)

Quiet weather with increasing mid/high level cloudiness is expected
ahead of the approaching winter storm. A surface ridge of high
pressure is forecast to move across the Mississippi River late this
afternoon, and on into the Tennessee Valley early tonight. There
will be increasing southeast winds after the passage of the surface
ridge. These winds combined with the aforementioned mid/high
level clouds increasing across the area are expected to limit the
temperature drop overnight. Because of these factors inhibiting
radiational cooling, leaned close to the 75th percentile of
available model guidance with lows ranging from the upper 20s to
low 30s.

(Monday - Tuesday Night)

Widespread precipitation is expected to move from west to east
during the day on Monday in response to increasing low-level
moisture convergence, strong mid/upper level diffluent flow aloft,
and midlevel positive vorticity advection. Precipitation is forecast
to reach the central Missouri counties around midday. This is
slightly faster than the previous forecast, and it is often very
difficult to start precipitation early enough with strong low-level
warm advection. The earlier onset also matches most of the latest
1200 UTC CAMs, particularly the ARW-WRF and RAP. Precipitation
should then reach the Mississippi River around 2100 UTC, and the far
eastern CWA between 23 UTC Monday and 0000 UTC Tuesday. Models are
in better agreement in the strength of the dry low/mid levels of the
atmosphere ahead of the precipitation shield, but there remains some
slight differences. There is confidence that the combination of
wetbulbing and dynamic cooling in high precipitation rates should
help the precipitation to change over to snow for parts of central
and northeast Missouri as well as west-central Illinois. Uncertainty
increases as you head southeast, with deterministic model soundings
showing surface temperatures just above freezing and a near
isothermal layer straddling 0C above the surface. This of course
is riding the edge and a very fine line between heavy wet
snowflakes and a cold rain. Areas where there are the most
uncertainty include parts of central Missouri (including Jefferson
City/Columbia) east/northeast toward Troy, MO and into south-
central Illinois. While some snow likely will mix in with the rain
a bit further southeast into the St. Louis metro area, there are
more doubts it will fully changeover and come down hard enough
and long enough to produce any accumulations on elevated/grassy
surfaces. Even further southeast, there is high confidence that all
of the precipitation Monday afternoon/night will be a plain cold
rain.

The rain/snow line should move back north/northwest overnight Monday
night due to strong low-level warm air advection ahead of the
approaching 850-hPa low. The vast majority of the area should be
rain after 0600 UTC Tuesday, though parts of northeast Missouri
(particularly Knox/Lewis/Shelby counties) are most likely to remain
snow. How far north/northwest the rain/snow line retreats is a
question mark, but relied most on the GFS/ECMWF which both have
the track of the system closest to the mean of latest model
guidance. The 12Z NAM (~75-100 miles further north/northwest) and
the 12Z CMC (~50 miles south/southeast) appear to be less likely
solutions.

By 1200 UTC Tuesday, the consensus location of the 850-hPa low is
most likely to be between St. Louis and Bowling Green, MO. This is
another slight shift to the northwest compared to yesterday, and
looking back 48-72 hours, about 125 miles further to the northwest.
While another shift to the northwest is certainly possible, I
would not expect any additional big shifts to the track. However,
as has been stressed the past few days, even a 10-20 mile
difference will be significant in determining exactly where the
axis of heaviest snowfall ends up and the gradient on the
southeastern side. After the passage of the 850-hPa cyclone, the
rain/snow line will then shift gradually east/southeast as the
system intensifies rapidly and temperatures in the boundary layer
cool into the low 30s. Several more inches of snow are likely in
parts of northeast Missouri and parts of west-central Illinois on
Tuesday, with amounts tapering off the further southeast you go
toward the I-44/I-55 corridors in Missouri and Illinois
respectively.

By the time the snow ends, amounts of 6-8+" are expected in parts
of northeast Missouri and west-central Illinois. This is where
there is the highest confidence in at least a couple of inches of
snow Monday afternoon/night in the warm/moist advection and then
several more inches with the deformation zone on Tuesday. We are
continuing to monitor this storm closely, and decisions to upgrade
the watch will be looked at overnight tonight. Given at least a
chance of another northwest shift, held off on upgrading any part
of the winter storm watch to a warning at this time.

The other issue we remain concerned about is the increasing
northwest winds/gusts late Tuesday into Tuesday evening. Sustained
wind speeds of 20-30 mph and gusts of 30-40 mph could cause some
blowing and drifting of snow in parts of northeast Missouri, but the
wet nature of the snow will at least help initially. However, in
time, the snow field may be able to dry out enough where it can be
blown around a bit in open areas before the stronger winds move out
of the area Tuesday night.

Gosselin

&&

.LONG TERM... (Wednesday through Next Sunday)
Issued at 235 PM CST Sun Jan 7 2024

After our early week storm passes to the east we will see a broad
trough across most of the Continental United States. Shortwave
ridging in the wake of the departing deeper trough will aid in
drying things out and maybe even getting us some sun. The air mass
in the wake of the storm is not that cold, although we do see a drop
in dewpoint indicating at least some colder potential. Temperatures
Wednesday warm into the 40s where the sun comes out and snow cover
is less of a factor (more likely in the south). By Wednesday night
another shortwave trough moves by to our north. The consensus has
been to pull this wave through further to the north limiting the
chances for precipitation (snow) in our area from it. The better
chances exist across Iowa and northern Illinois, although we are
maintaining a very low PoP Wednesday night in our northern counties.

By Thursday a deeper trough will be diving through the Southwestern
US eventually on a track toward our region. Currently this wave is
just a minor feature to the south of the Aleutian Islands, so it's
still a long way away with several turns to make before it gets
here. However, model consensus has been building for this wave to
take a track through the southern US to the south of the track of
the last wave but not so far south that we won't see anything from
it. Compared to the past few days when model solutions were much
more variable, we do have relatively greater confidence now, enough
to say that our area will see at least some impact from this. From
the 00Z ensemble data, greater than 90 percent of members produced
at least measurable precipitation in the southern half of our
forecast area in a 24 hour period centered around Friday. Notably
our forecast PoP is lower than this due to some continued timing
uncertainty that remains evident in the model solutions. The greater
time window to see the core of this wave affect us is from Thursday
night to Friday night, with Friday the most likely time period (and
when our PoP is now above 50 percent).

As far as precipitation type and amounts, there remains considerably
more uncertainty on that as it will depend on how the wave evolves
and how much warm/cold air gets pulled into it. At the moment it
does seem like a primarily rain or snow situation, but we can't
quite rule out other precipitation types just yet. With our area
likely to be on the north side of this wave, we'll be more likely to
see the wintry end of it. From the 00Z ensemble data up to 50
percent of members now show at least 1 inch of snow through the
center of our forecast area, a sign of the confidence that we'll be
on the cold and likely snowy side of the system. On the more extreme
side, worst case scenario, this could be a substantial snowfall
event with several inches falling. There is more cold air in the
vicinity to work with than there is with the prior storm, aiding
both in maintaining snow as the precipitation type as well as
setting up potentially better frontal forcing for precipitation.
Ultimately, though, it's still too early with too much uncertainty
to advertise this in its most extreme form. However, we will begin
messaging the potential for another wintry weather episode at the
end of this week.

Finally the last big story is the upcoming shift toward much colder
temperatures. For much of the winter so far the coldest air has been
on the other side of the polar region across Asian and Europe, but
this has already begun to change. At least a portion of this cold
air mass has crossed the pole and entered western Canada. With each
passing shortwave trough this cold air mass gets pulled further
south deeper into the broader western/central US trough. By
Wednesday it will be crossing the international border into the
Dakotas and Montana. Models vary on how quickly to pull this air
mass southeast and into our area, but the passage of a strong low
near our area late this week would conceptually be a prime
opportunity to do so. NBM interquartile range on temperatures gets
extremely large after Friday, reflecting that uncertainty on when
the core of the cold air moves into our area. The 12Z deterministic
ECMWF only brings a less intense piece through our area initially
before pulling the bulk south and then east early next week. The 12Z
deterministic GFS latches on to the core of the cold air right away,
shoving it through our area this weekend. In either case, though,
the extremity of the cold air mass is notable as 850MB temperatures
15 to 20 degrees (C) below normal exist in the core of the cold air
mass whenever it arrives. That translates roughly to surface
temperatures about 30 degrees (F) below normal.

As for specific temperatures, NBM probabilities of subfreezing high
temperatures increase to 70 percent or higher after Friday as even
the warmer models do at least bring some cold air in this weekend.
So whatever wintry precipitation falls late this week will stick
with us for a while. On the extreme end, probabilities of subzero
low temperatures are now above 50 percent in the northern part of
our area. The overall chance for seeing subzero temperatures at some
point during this air mass is likely higher than that simply due to
the extreme timing uncertainty on when the core of that cold air
mass moves into our area. Getting a clear, calm night would also go
a long way toward achieving some more extreme lows, but at this
range with so many minor shortwave troughs around it's hard to say
when or if that will happen. There is also at least some potential
for additional wintry weather while the cold air is around, but
confidence is very low on any of those specifics yet.

Kimble

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1109 PM CST Sun Jan 7 2024

Since remaining MVFR stratus has cleared earlier this evening, VFR
flight conditions will persist through Monday morning at all
terminals beneath increasing and lowering upper-level clouds.
Additionally, southeasterly winds will strengthen during morning
into afternoon with the start of occasional gusts of 20 to 28 kt.

A storm system will begin arriving Monday afternoon and evening as a
broad wave of precipitation spreads northeastward into the region,
accompanied by deteriorating flight conditions to MVFR and then IFR
as ceilings and visibilities lower. After precipitation onset and
intensity increase, a transition of rain to snow or a rain-snow mix
is expected at KUIN, KCOU, and KJEF. The highest chance of a
transition entirely to snow is at KUIN Monday evening, including
accumulation on runways and most significant impacts of all
terminals, but this transition could also occur at KCOU and KJEF,
albeit with a relatively lower chance. At St. Louis metro terminals,
warmer temperatures will make it more difficult for rain to mix with
snow, let alone accumulate. This main initial wave of precipitation
will begin exiting from southwest to northeast overnight, but IFR
flight conditions and light precipitation will linger.

Pfahler

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Storm Watch from Monday afternoon through Tuesday evening
     for Audrain MO-Knox MO-Lewis MO-Marion MO-Monroe MO-Pike MO-
     Ralls MO-Shelby MO.

IL...Winter Storm Watch from Monday afternoon through Tuesday evening
     for Adams IL-Brown IL-Pike IL.

&&

WFO LSX

Hazardous Weather Outlook
National Weather Service St Louis MO
254 PM CST Sun Jan 7 2024

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-082100-
Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL-
Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL-
Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO-
Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO-
Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-
Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO-
Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO-
Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO-
Madison MO-Reynolds MO-
254 PM CST Sun Jan 7 2024

This Hazardous Weather Outlook is for portions of eastern and
central Missouri as well as west central and southwest Illinois.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Heavy snow is expected over portions of northeastern Missouri and
west-central Illinois Monday night through Tuesday, with lesser
amounts further southeast. See the Winter Storm Watch for additional
information.

Snow is likely somewhere across the area Friday but uncertainty is
high being 5 days out.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Gosselin