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000
FXUS63 KLSX 150438
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1138 PM CDT Fri Mar 14 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 359 PM CDT Fri Mar 14 2014

Mid-high level cloud cover should clear out of our forecast area
later this evening as a shortwave shifts east of the Great Lakes
region and weak cold front progresses southeast of our area.  With a
mostly clear sky and diminishing surface winds the low temperatures
tonight will be cooler than the previous night, although still at
or just above normal for mid March.

GKS

.LONG TERM:  (Saturday through Next Friday)
Issued at 359 PM CDT Fri Mar 14 2014

Rain should begin to spread northeastward into our forecast area
late Saturday afternoon and evening as the southern stream shortwave
now over southern AZ moves through the southern Plains, and the
northern stream shortwave now over WA drops southeastward and moves
through the central Plains Saturday night on the heels of the
southern shortwave.  A southerly low level jet will bring increasing
low level moisture into our area ahead of the 850 mb low.  Upper
level divergence will also be increasing Saturday night ahead of the
approaching upper level trough. It appears that the highest qpf will
occur over the southern half of our forecast area Saturday night
and Sunday, just north of the track of the 850mb/surface low which
will track through AR. The latest models are bringing in the
colder air southeastward into our area faster than the previous
model runs leading to colder temperatures for Saturday night. The
rain should change over to snow across northeast MO and west
central IL late Saturday night, with a brief period of sleet
possible looking at the partial thickness forecasts and forecast
soundings which do indicate an elevated warm layer. Temperatures
on Sunday should be nearly steady or actually fall leading to the
rain across central and southeast MO and southwest IL gradually
changing over to snow with most of the precipitation along and
south of I-70. The precipitation should eventually shift southeast
of our forecast area by late Sunday night as the upper level
trough shifts east of our area and the surface low shifts well
southeast of the region. Still a lot of uncertainty with regards
to where the heaviest precipitation will fall along with the
temperature profile, but it currently appears that the highest
snow accumulation will occur along and just south of I-70,
potentially through COU and the St Louis metro area. For now will
go with 1-2 inches of accumulation, but these amounts may change.
Accumulation amounts will also depend a lot on the surface
temperatures on Sunday, especially due to the warm ground and
road temperatures. Surface air temperatures will need to be at or
below 32 degrees along with snowfall of moderate to heavy
intensity for good accumulation of snow on Sunday. Low
temperatures will be well below normal for Sunday night. A warming
trend will begin Monday afternoon as the surface winds become
southerly as the surface ridge shifts east of the region. The
ECMWF model brings in more precipitation on Tuesday night and
Wednesday as an upper level trough and associated cold front moves
through the region, while the GFS model keeps all the
precipitation north of our area. For now will just include chance
pops on Tuesday night.

GKS

&&

.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1134 PM CDT Fri Mar 14 2014

VFR conditions expected through 06Z Saturday Night. Southeast wind
will become northeast and increase during the evening with mid
level clouds on the increase ahead of the next storm system. Rain
should hold off until after 06Z.

Specifics for KSTL:

VFR conditions expected through 06Z Saturday Night. After 06Z rain
will begin to overspread the terminal with ceilings lowering to
MVFR and northeast winds increasing to near 20KT with gusts to
30KT. Falling temperatures will likely lead to a brief period of
freezing rain around 12Z Sunday Morning before the precipitation
transitions to sleet and/or snow on Sunday. Some ice and snow
accumulation is possible on Sunday.

CVKING

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX