Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 142028
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
328 PM CDT Mon Apr 14 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 324 PM CDT Mon Apr 14 2014

Main concerns deal with the band of snow currently extending from
near Pittsfield to Rolla as well as the going freeze warning. The
band has been reducing visibilities to as low as 1/2 mile with
some reports of accumulation on grassy surfaces. It is being
caused by mid level frontogenesis ahead of the 500mb trough that
will move through the area tonight. The RAP and HRRR does show the
frotogenesis weakening as it moves acrosss the CWA, but do think
that it will likely maintain itself the next few hours before it
weakens by early evening. Have extrapolated the band through CWA
through early evening, with little or no accumulation of snow
expected given the warm low level and surface temperatures.

The precipitation and clouds will clear out quick as subsidence
moves in behind the passage of the upper trough.  With cold air
advection and dry dewpoints, expect temperatures to drop quickly to
near MOS temperatures.  Going freeze warning looks good and plan no
changes to it.

Britt

.LONG TERM:  (Tuesday through Next Monday)
Issued at 324 PM CDT Mon Apr 14 2014

(Tuesday through Thursday)

Have kept Tuesday into Thursday dry as the area will remain cut off
from any notable moisture from the Gulf and the active storm track
stays north of the area.  While Tuesday night will not be as cold as
tonight, most areas will still be in the lower to mid 30s for
lows.

(Thursday Night-Next Monday)

The ECMWF and GFS are now similar with the amplitude and timing of
the mid level trough and attendant cold front that will move across
the area on Friday. Will continue with the chance of showers on
Thursday night and Friday before subsidence works in behind the
trough keeping Friday night and Saturday dry.  Then confidence
begins to wane late in the weekend as they both develop QPF over the
area.  The GFS is placing more emphasis on an northern stream upper
over the Upper Midwest while ECMWF is placing it`s emphasis on a
shortwave coming out of the southwest CONUS.  Either way, will
continue the chance of showers we have going Saturday night into
Sunday night.  Temperatures during the period look to be near or
slightly below normal.


Britt

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1208 PM CDT Mon Apr 14 2014

Area of SN continues to move ewd. Have made some slight changes to
the prev TAFs based on latest RADAR trends and mdl guidance.
Confidence is higher that precip will be all SN at COU/UIN early
this afternoon. With ample cloud cover across the region, believe
temps will remain cold enuf for all SN at SUS/CPS late this
afternoon. However, with some uncertainty and since main focus
shud be nw of sites, will leave precip as a RA/SN mix for now.
Beyond precip, cigs shud lift quickly and remain VFR thru the
remainder of the TAF period.

Specifics for KSTL: With clouds expected to remain in place,
precip this afternoon has a better chance of being SN. However,
with placement of precip wrt the terminal, precip may remain as a
very light RA or more likely DZ. Beyond precip this afternoon,
cigs shud lift quickly to VFR and remain VFR thru the remainder of
the TAF period.

Tilly

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...FREEZE WARNING from 11 PM this evening to 9 AM CDT Tuesday FOR
     Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO-
     Franklin MO-Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis
     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.

IL...FREEZE WARNING from 11 PM this evening to 9 AM CDT Tuesday FOR
     Adams IL-Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-
     Greene IL-Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe
     IL-Montgomery IL-Pike IL-Randolph IL-St. Clair IL-
     Washington IL.

&&

$$

WFO LSX






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