Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 052201
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
401 PM CST Thu Dec 5 2013
.SHORT TERM: (Through Tonight)
Issued at 356 PM CST Thu Dec 5 2013
Focus continues to be the ongoing winter wx system.
Latest mdl guidance is in fairly good agreement. However, seems to
be on the warm side regarding temps aloft based on latest reports of
sn/ip. Have therefore trended p-type turn over to sn a little faster
than based on progd soundings. Based on reports received within
the last half hour, precip is turning over to sleet, then sn
further S quicker than anticipated. Have therefore increased sn
amounts across sern portions of the CWA this evening. Some
uncertainty exists regarding how far E this heavier sn will make
it as some mdl guidance suggests the precip will weaken as it
Ongoing precip is expected gradually push s and sewd, before pulling
nwd again late tonight into Fri morning.
As for temps, have trended aob coolest MOS guidance.
No changes to headlines are expected based on tonight`s forecast,
but may be needed depending on precip rates this evening.
.LONG TERM: (Saturday through Wednesday)
Issued at 405 AM CST Thu Dec 5 2013
Cold air will settle across the area Saturday as a 1040+ mb high
pushes southeast from the Great Plains. Temperatures will bottom
out in the single digits and low teens across the area. Afternoon
highs will be 20-25 degrees below normal in the low to mid 20s.
This will set the stage for another shot of winter weather late
Saturday night into Sunday. The upper pattern begins to shift
Saturday night with the longwave currently over the western U.S.
moving across the Rockies. Low level warm advection ramps up as
the flow at 850mb turns to the south-southwest. Forecast soundings
indicate primarily snow along and north of the I-70 corridor with
snow perhaps mixing with sleet or maybe even freezing rain in
southern zones. Partial thickness is also agreeable with these
precip types. Model QPF is light, generally 1-2 tenths of an inch,
but is very widespread and not focused in any real discernible
band. Have kept pops nearly identical to previous forecasts with
generally high chance across the entire area.
Another slug of Arctic air will push down from the Northern Plains
into the Mid-Mississippi Valley Sunday night and Monday. The mean
upper level trof is forecast to dig over the eastern 1/2 of North
America Tuesday into Wednesday which will lock this cold airmass
into place. Temperatures will therefore remain as much as 25
degrees below normal into midweek.
.AVIATION: (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1023 AM CST Thu Dec 5 2013
Monitoring latest radar and model trends for snow potential this
afternoon/evening at terminals. It appears that St. Louis metro
sites will be on the northern edge of the snow shield with the
heaviest precipitation falling just south. The next round of snow
is expected to occur late tonight and into Friday. A few inches of
snow is possible. Ceilings and visibility will likely fall to
MVFR, if not IFR category with periods of snow.
Specifics for KSTL:
Light snow should build across the terminal this afternoon and
continue into early this evening. A break in the snow will likely
occur until early Friday morning when another round of light snow
occurs. Light snow accumulation is possible.
.PRELIMINARY POINT TEMPS/POPS:
Saint Louis 20 24 7 21 / 50 80 5 5
Quincy 14 22 3 20 / 10 30 5 5
Columbia 14 22 4 19 / 40 50 5 5
Jefferson City 14 23 4 19 / 50 60 5 5
Salem 23 26 9 20 / 100 90 10 5
Farmington 18 23 4 20 / 100 90 5 5
MO...WINTER WEATHER ADVISORY until 6 PM CST Friday FOR Crawford MO-
Jefferson MO-Washington MO.
WINTER STORM WARNING until 6 PM CST Friday FOR Iron MO-Madison
MO-Reynolds MO-St. Francois MO-Ste. Genevieve MO.
IL...WINTER WEATHER ADVISORY until 6 PM CST Friday FOR Bond IL-
Clinton IL-Fayette IL-Monroe IL-St. Clair IL.
WINTER STORM WARNING until 6 PM CST Friday FOR Marion IL-
Randolph IL-Washington IL.