Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 191653

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1053 AM CST Thu Jan 19 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 359 AM CST Thu Jan 19 2017

An elongated disturbance over the plains will slowly lift towards
the upper Great Lakes today and tonight, spreading showers and
isolated thunderstorms into MO/IL.


.LONG TERM...  (Friday through Wednesday)
Issued at 359 AM CST Thu Jan 19 2017

The extended forecast features unseasonably warm temperatures and
an active upper air pattern. Startlingly good agreement is noted
between the GFS and ECMWF (through ~150 hrs) for the third day in
a row.

A compact disturbance reaches NM/TX/OK late Thu night, then
intensifies and lifts northeastward through the plains on Fri/Fri
night. Despite a potent upper vort max and favorable H7-H5 lapse
rates across the area on Fri evening, no pcpn is expected attm due
to limited moisture.

Another disturbance reaches the California coast on Friday and
develops into a large low pressure system over TX/OK on Saturday
night. The system begins to occlude and shifts eastward over the
southeastern CONUS on Sun/Sun night. Showers and isolated
thunderstorms associated with this system may affect the LSX CWA
from Saturday night through Sunday night.

Yet another disturbance reaches the west coast on Sunday night
and eventually induces a surface reflection over the plains by
Monday night. After a brief period of upper ridging across MO/IL,
this feature is forecast to lift towards the Great Lakes during
the early and middle part of next week, bringing a chance of rain
to the area.



.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1043 AM CST Thu Jan 19 2017

Persistent upper level system will lead to a series of low
pressure systems moving across the area. The result will be little
change in air mass. A saturated atmosphere and light winds for
most of the period will lead to IFR conditions with occasional drizzle
and fog. Some improvement to MVFR may occur late in the period but
primarily over central MO around COU.

SPECIFICS FOR KSTL: Hard to go against persistence in this case.
Lots of low ceilings, fog and light rain/drizzle will keep
conditions IFR through the night. Soundings are saturated and
models agree with the IFR trend. Improvement to MVFR not likely
until perhaps Friday afternoon as weak high pressure moves in.





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