Area Forecast Discussion
Issued by NWS St. Louis, MO

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854
FXUS63 KLSX 102140
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
340 PM CST WED FEB 10 2016

.SHORT TERM:  (Through Late Tonight)
Issued at 339 PM CST Wed Feb 10 2016

Bands of warm advection snow are moving thou eastern Missouri and
southern Illinois.  Amounts ranging from a little more than a
dusting up to around 1.5 inches have been reported with the bands.
RAP may have been the best model to handle this system today, but
even it wasn`t far enough east with the accumulating precip earlier
today.  Regardless...current thinking is that the western edge of
the accumulating snow will reach the Mississippi River by around 00Z
this evening.  The snow also looks to be deteriorating from the
northwest although there are still a few reports of light snow in
Iowa.  With the RAP, NAM, and GFS continuing to show some pretty
impressive warm advection and low level frontogenesis after 00Z, I
can`t rule out additional (very) light accumulations this evening
along and east of the Mississippi.  Anything more than 1/2 inch
looks very unlikely and probably confined to our southeastern
counties.  Any lingering precipitation should end by midnight.

Carney

.LONG TERM:  (Thursday through Next Wednesday)
Issued at 339 PM CST Wed Feb 10 2016

Dry and continued cold weather on Thursday as a surface ridge drops
southeastward through eastern MO and IL with continued northwesterly
mid-upper level flow.  A northwest flow shortwave will bring some
light snow, mainly to northeast MO and west central IL Thursday
night and Friday morning.  It appears that accumulations will be
light at less than one inch due to the progressive nature of the
shortwave along with limited moisture.  Most areas should just get a
quick dusting of light, powdery snow.  Slightly warmer temperatures
can be expected on Friday, but this will be short lived as another
cold front drops southeastward through our forecast area on Friday
with a strong 1040 mb surface ridge building into the area behind
it. Temperatures may actually begin to fall in northeast MO Friday
afternoon after frontal passage.  Northwesterly winds will
strengthen Friday afternoon and evening after the cold front passes
through due to a tightening surface pressure gradient.  It appears
that this will be a dry frontal passage, but much colder
temperatures can be expected Friday night and Saturday with very
cold wind chillls possible Friday night.  Warm air advection ahead
of a northern stream shortwave may bring some snow to northeast MO
and west central IL Saturday night.  The ECMWF model appears a
little too quick bringing precipitation into the area already by
Saturday afternoon with an initially very dry air boundary layer on
the backside of the strong surface ridge.  Model solutions continue
to vary from the Sunday through Monday period.  The GFS model
spreads snow through the area Sunday and Sunday evening ahead of a
northern stream shortwave.  The ECMWF model is weaker and quicker
with the northern stream shortwave and keeps most of the
precipitation north of our forecast area on Sunday, but then
develops a strong southern stream shortwave and associated surface
low which brings snow to the southern half of the forecast area
Sunday night and Monday morning. With theses model discrepancies,
for now will just include chance pops for the forecast area Sunday
and Sunday night.  Warmer temperatures are expected for Tuesday and
Wednesday as the upper level trough shifts east of the region with
upper level heights rising and surface winds becoming southerly. The
ECMWF model is not as warm for Wednesday compared to the GFS as it
brings another cold front southeastward through our area as an upper
level trough moves through the Great Lakes region.  The GFS solution
does not have either the upper level trough or the cold front.  For
now will keep with the warming trend for Monday through Wednesday.

GKS

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1129 AM CST Wed Feb 10 2016

IFR flight conditions associated with a band of snow will move
east out of central Missouri into eastern Missouri and southwest
Illinois through the afternoon. Current expectations are that the
heaviest snow won`t make it much further east than the Mississippi
River, so south central Illinois counties will likely only see
very light snow with MVFR or VFR conditions. Snow should be ending
by around 06Z. Some low MVFR ceilings expected over the Ozarks
tonight which should be gone by mid-late Thursday morning.

Specifics for KSTL:

Band of snow is moving toward the terminal at this time. 19Z start
time of precipitation in the TAF may be a little late...probably
more like 1830Z based on current radar. Once snow begins, expect
the visibility to drop to IFR category...although ceiling looks to
stay MVFR based on upstream observations. Current guidance is
hinting that the heaviest snow will be this afternoon, and
becoming much lighter this evening and finally ending around
05-06Z. Wouldn`t be surprised to see some flurries linger a little
longer than that, but should have little impact on airport
operations.

Carney

&&

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

$$

WFO LSX



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