Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 052021

Area Forecast Discussion
National Weather Service Saint Louis MO
221 PM CST Mon Dec 5 2016

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 217 PM CST Mon Dec 5 2016

Models are pretty close on moving out the closed low over sw Texas
and bringing an open wave across the area. They are also
contining the trend of moving the precipitation futher south and
east. Thus the forecast reflect this trend in the pops. Fog could
be an issue in some places again: Quincy and Columbia. The wind
and quickly advancing clouds may keep that down, but have put
patchy fog in the forecast. Temps pretty close to previous
forecast so have only made minor adjustments.


.LONG TERM...  (Tuesday through Sunday)
Issued at 417 AM CST Mon Dec 5 2016

Surface low pressure should be over Tennessee and Kentucky
Tuesday morning with strong cold advection setting up over the Mid
Mississippi Valley. Lingering precipitation in the deformation
zone in the northwest quadrant of the storm will be moving east
and out of the CWFA by 15-18Z, but guidance still has enough QPF
hanging back during the morning to continue to hang on to chance
PoPs generally along and east of the Mississippi. Doubt there will
be any frozen precip to worry about since the deep cold air won`t
arrive until the afternoon. Wouldn`t be surprised to see steady or
falling temperatures in the afternoon on Tuesday due to the
strength of the cold advection.

High pressure behind the system will be the first true Arctic
airmass to affect our region this season.  The 1050+ mb high with
origins in northwest Canada will build south across the Great Plains
and Midwest through the end of the week.  This will easily be the
coldest weather so of the 2016-2017 winter season so far.
Temperatures will be well below normal through at least
Saturday...with highs not evening climbing out of the 20s Thursday
and Friday and lows in the teens.  Most of the Wednesday through
Sunday period should be dry, but there is a shortwave moving through
Wednesday and Wednesday night which could produce some light snow.
Plenty of frontogenesis out ahead of the wave, but forecast
soundings show a significant low level dry layer to overcome. Not
saying it can`t be done...but think mid-high chance PoPs are still
appropriate rather than likely.

Temperatures should start to moderate on Saturday (although it will
still be below normal) as southerly flow develops in the low levels
and the flow aloft becomes more zonal.  The ECMWF and GFS are in
reasonable synoptic agreement for Sunday with a shortwave and
attendant cold front moving across the Midwest.  GFS spreads warm
advection precip up across the area ahead of the front while the
ECMWF is dry.  Think this may be the GFS`s typical wet bias in
warm/moist advection so dry to only slight chance PoPs across
southeast Missouri look appropriate at this time.



.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 117 PM CST Mon Dec 5 2016

Real mess today. Except for extreme ne mo and wc il the fog and
ifr stratus has lifted. Ceilings remain a mix of vfr and mvfr
although most terminals are not vfr. The next fast moving system
will quickly push mvfr clouds across the area tonight with some
IFR quite possible. Models consistent in continuing to push the
precipitation further south. VCSH will cover it at a couple

SPECIFICS FOR KSTL: STL looked like it might stay mvfr so of
course it broke out. Woill keep a tempo form mvfr going for a
while givern the broken condition just to the se, considering the
light se wind. Next system spreads mvfr clouds back in tonight
with vicinity showers. IFR is possible but will hold off for now.



Saint Louis     37  43  27  38 /  20  10   0  10
Quincy          33  38  22  32 /   5   5   0  20
Columbia        34  40  23  34 /   5   5   0  30
Jefferson City  34  42  25  37 /   5   5   0  30
Salem           39  43  27  39 /  40  30   0   5
Farmington      38  44  26  39 /  40  20   0  10




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