833 
FXUS63 KLSX 020937
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
337 AM CST Sat Jan 2 2021

.SHORT TERM...  (Through Late Tonight)
Issued at 337 AM CST Sat Jan 2 2021

Primary concern for today and tonight is the potential for more 
wintry weather.  The short wave currently over the Great Plains will 
move east today and close off as it enters Missouri and Arkansas 
this afternoon.  Light precipitation is expected to develop over 
southern Missouri and spread to the northeast through the afternoon 
as the low deepens.  Thermal profiles on the latest short range 
guidance are not a straight forward as on earlier runs, and there is 
the potential for light drizzle/freezing drizzle mixed in with light 
snow at times.  Storm total QPF of less than .10 inch is 
expected...and temperatures will likely be within a degree or two 
one way or another of freezing, so some of that drizzle will likely 
not freeze.  Therefore, confidence in any impacts from this mix of 
precipitation is low...and will not issue any winter weather 
headlines at this time.

Expect that much of the drizzle will transition to light snow by 
early evening as the low continues to deepen and temperatures within 
the core of the system drop.  Snow accumulations from a dusting up 
to about 1 inch are possible, with the higher end of those amounts 
from east central Missouri into south central Illinois along the low 
track.  The precipitation will end from southwest to northeast 
overnight.

Carney

.LONG TERM...  (Sunday through Friday)
Issued at 337 AM CST Sat Jan 2 2021

Sunday through Tuesday continues to look dry with relatively mild 
temperatures.  Deterministic guidance shows two short waves moving 
across the Mid Mississippi Valley, one on Sunday evening and another 
late Monday night.  However, these waves won't have much moisture to 
work with in order to produce precipitation since the Gulf will be 
closed off in the wake of Saturday and today's storm systems.  They 
should move through with little more than some mid and high clouds 
to mark their passage.

The next chance for significant precipitation will come Wednesday 
and potentially linger into Thursday and Thursday night. 
Deterministic GFS and ECMWF show a high amplitude upper level 
trough moving across the Rockies Tuesday night into Wednesday 
morning.  The models are in good agreement in fracturing that trough 
developing a closed low over the eastern Plains by Wednesday 
night/Thursday evening.  The resulting stacked low pressure system 
then moves from the eastern Plains across the Mississippi Valley 
into the Tennessee Valley Wednesday night through early Friday 
morning.  GEFS has been solidly in the mid and high chance range for 
PoPs for Wednesday through Thursday afternoon for several runs. Will 
therefore bump up PoPs over NBM, but won't go too high just yet as 
there's still a lot of time to watch this system evolve.  Current 
thinking is that temperatures will be warm enough for any precip 
that falls Wednesday through Thursday should be liquid.

Carney

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1030 PM CST Fri Jan 1 2021

Ceilings have popped around between IFR and LIFR flight categories
over the evening, but conditions are expected to deteriorate to 
LIFR conditions at all TAF sites over the next couple of hours. 
With significant low level moisture and patchy fog, LIFR ceilings
and reduced visibilities are expected to persist overnight and 
into the day tomorrow ahead of the next approaching winter weather
system.

The purely snow system will move eastward through the TAF sites 
tomorrow afternoon into evening, with the best chance for snow
occurring during the evening at the St. Louis metro terminals, 
including KSTL.

Northerly winds around 10 kts will become light and variable
overnight into tomorrow morning.

MRM

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     34  29  39  29 /  40  60   0   0 
Quincy          31  23  33  26 /  20  30   0   0 
Columbia        31  23  40  28 /  40  40   0   0 
Jefferson City  32  24  42  28 /  50  40   0   0 
Salem           36  30  40  28 /  20  70   0   0 
Farmington      34  26  44  26 /  30  50   0   0 

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX