Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 171124

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
524 AM CST Wed Jan 17 2018

.SHORT TERM...  (Through Late Tonight)
Issued at 319 AM CST Wed Jan 17 2018

The sfc ridge currently centered over ern OK will build SE today
allowing winds to slowly back to become sely thru tonight. WAA will
not be overly strong today and despite expecting ample sun today,
have trended twd the cooler guidance given the snow cover. That
said, there is some question regarding cloud cover this morning
across nrn portions of the CWA. Small patches of clouds continue to
develop and dissipate across sern IA this morning. Mdls support enuf
moisture across nrn portions of the CWA that patches of clouds may
develop thru the morning hours. However, this is expected to only
delay warming slightly as any clouds shud move east thru the morning
given the wly flow.

As for tonight, winds are expected to continue to back to become
swly as well as increase. While the clear sky and what snow cover
remains will help to cool temps, the WAA over the region shud
increase thru tonight. Still, with MOS being too warm recently,
possibly due to climo, have trended twd the cooler guidance.


.LONG TERM...  (Thursday through Tuesday)
Issued at 319 AM CST Wed Jan 17 2018

A warming trend will continue Thursday into the weekend with a
prolonged period of south-southwesterly surface winds.  Full daytime
solar insolation both Thursday and Friday with only a little high
level cloudiness will help lead to warmer high temperatures as well.
Highs on Friday should be 10 to 15 degrees above normal which will
feel quite warm due to the recent stretch of very cold weather we
have been in.  Higher surface dew points moving into our forecast
area Friday night and Saturday over the cold ground may lead to some
advection fog.  Low to mid level warm air advection and increasing
low level moisture may also lead to patchy drizzle Saturday and
Saturday night with weak upward vertical motion and shallow low
level moisture.  Unseasonably warm temperatures should peak at
around 20 degrees above normal Saturday night and Sunday.  An
approaching upper level low and associated deepening surface low and
trailing cold front will bring more significant showers and possibly
a few storms Sunday and Sunday evening as low level moisture
continues to increase and deepen. The models have trended slower
with this storm system, with the ECMWF model still slower than the
operational GFS.  Deformation type rain or snow may continue across
northeast MO and west central IL on Monday in the wrap around
moisture on the backside of the surface low as colder air advects
into the region late Sunday night and Monday after passage of the
surface low and trailing cold front.  Although temperatures will be
colder beginning late Sunday night and Monday they should still be
at or slightly above normal.



.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 522 AM CST Wed Jan 17 2018

VFR and dry thru the period. Winds will increase late this morning
and gradually back to become swly by late this afternoon. Winds
will remain swly around 8 to 10 kts overnight tonight under a
clear sky.



Saint Louis     26  17  42  26 /   0   0   0   0
Quincy          23  15  37  24 /   0   0   0   0
Columbia        26  15  41  25 /   0   0   0   0
Jefferson City  26  16  43  25 /   0   0   0   0
Salem           22  14  38  23 /   0   0   0   0
Farmington      25  15  41  24 /   0   0   0   0




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