Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
539
FXUS63 KLSX 132343
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
543 PM CST SAT FEB 13 2016

.SHORT TERM: (Through Sunday)
Issued at 304 PM CST Sat Feb 13 2016

Shortwave now over MT will drop southeastward into southwest IA
by 12Z Sunday. Low-mid level warm air advection will be increasing
over our area ahead of this feature. A strengthening southwesterly
low level jet over southwest MO will bring increasing low level
moisture into our area overnight. A band of snow is expected to
develop and extend into northeast MO and west central IL this
evening, then light snow will break out across the rest of the
forecast area late tonight. The greatest snow accumulation of up
to 1 inch should occur across northeast MO and west central IL
with a dusting elsewhere late tonight. The greatest snowfall
intensity and accumulation should occur Sunday morning as the
shortwave, vort max moves eastward through the MO IA border. Most
of the accumulating snowfall should shift east into IL and
southeast MO Sunday afternoon with most of the precipitation
ending across central MO. Total snow accumulations should range
from near 4 inches in Quincy and Mt. Sterling IL to around 2
inches in the St Louis metro area to around 1 inch in COU. The
forecast soundings were depicting an elevated warm layer in the
FAM area on Sunday which could lead to some sleet across parts of
southeast into central MO. As the moisture profile becomes more
shallow and the lift weakens there may also be some patchy
freezing drizzle late Sunday morning and afternoon across parts of
central and southeast MO. With forecast snow amounts increasing
slightly from the previous forecast, plus the inclusion of sleet
and freezing drizzle across parts of the area have expanded the
winter weather advisory to our entire forecast area for late
tonight and Sunday.

GKS

.LONG TERM: (Sunday Night through Next Saturday)
Issued at 304 PM CST Sat Feb 13 2016

The precipitation should shift east and southeast of our forecast
area Sunday night. Another shortwave will dive southeastward out
of the Plains and carve out an upper level trough over the
central US Monday. It appears that any measurable precipitation
will remain south-southeast of our forecast area. Temperatures
will be warmer on Monday allowing much of the snow to melt. A
northwest flow shortwave and associated weak surface low will drop
southeastward through the region late Monday night and Tuesday.
The NAM and GFS model move this feature through northern MO or
southern IA and central IL, while the ECMWF model is further
southwest with the track moving it southeastward through our
forecast area. There will be some potential for accumulating snow
across northeast MO and west central IL near and left of the track
of the upper level/surface low with mainly rain elsewhere with
warmer temperatures Monday night and Tuesday. Still looking
unseasonably warm for the end of the work week with upper level
ridging over the central US on Thursday along with strong south-
southwesterly low level flow.

GKS

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 542 PM CST Sat Feb 13 2016

Ceilings will slowly lower this evening as snow moves into
northeast MO and west central IL including KUIN by late evening,
and then KUIN and the St. Louis area terminals overnight. There
will be a 6-8 hour of MVFR and IFR visibilities in snow with
accumulations between 1-3 inches. The snow will begin to end by
late morning or early afternoon, with a possible transition to
freezing drizzle at KCOU and the St. Louis area terminals which
could produce a light glazing before it ends.

Specifics for KSTL: Snow is expected to move into the terminal
around 09Z with visibilities fall to MVFR initially and then IFR
by 12Z. Currently expect snowfall accumulations to be around 2
inches by the time the snow transitions to freezing drizzle around
18Z. There may be a light glazing of ice tomorrow afternoon before
the precipitation ends.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...Winter Weather Advisory from midnight tonight to 6 PM CST Sunday
     FOR Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO-
     Franklin MO-Gasconade MO-Iron MO-Jefferson MO-Lincoln MO-
     Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
     Osage MO-Pike MO-Ralls MO-Reynolds MO-Shelby MO-St. Charles
     MO-St. Francois MO-St. Louis City MO-St. Louis MO-Ste.
     Genevieve MO-Warren MO-Washington MO.

     Winter Weather Advisory from 9 PM this evening to 6 PM CST
     Sunday FOR Knox MO-Lewis MO.

IL...Winter Weather Advisory from midnight tonight to 6 PM CST Sunday
     FOR Bond IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-
     Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-
     Montgomery IL-Randolph IL-St. Clair IL-Washington IL.

     Winter Weather Advisory from 9 PM this evening to 6 PM CST
     Sunday FOR Adams IL-Brown IL-Pike IL.

&&

$$

WFO LSX



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.