Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 242340
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
540 PM CST Sat Feb 24 2018

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 253 PM CST Sat Feb 24 2018

Main concerns continue to be flooding and severe weather threats
through the evening.

Latest round of showers with embedded thunderstorms has already
overspread the CWA with additional moderate to heavy rainfall.
This will bring the threat for potential flooding into the evening
hours over the watch area which as already seen significant
rainfall this week. Will also continue to monitor the potential
for few strong to severe thunderstorms across southwest Missouri
into south central Illinois late this afternoon and early this
evening. RAP runs have been consistent today in showing a weak
surface low along the triple point moving northeast from near
Farmington to Effingham. While low level instability is weak, low
level and deep level shear will be more than sufficient to allow
for a few severe thunderstorms. The main threat will be damaging
winds, but cannot rule out a tornado threat.

The front will move east of the area this evening, and there will
be some gusty west to northwest winds behind late evening into
the overnight hours as the pressure gradient will be fairly tight
as the main surface low moves across Missouri into northern
Illinois. The winds will decrease by Sunday morning as this low
exits into the Great Lakes.

Sunday is expected to be dry with sunshine as subsidence sets in as
the upper trough moves off to the east. There is not any notable
cold air moving in behind this system, so temperatures will climb
back above normal on Sunday.

Britt

.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 253 PM CST Sat Feb 24 2018

Dry weather is expected to last into Monday and Tuesday as a
large surface high moves across Missouri and Illinois. The chances
for rain will increase by the middle of next week as the
GFS/ECMWF both show a deep trough moving into the central CONUS
with a surface cold front moving across Missouri and Illinois
Wednesday/Wednesday night. This trough should draw Gulf moisture
northward ahead of it, and have added a chance of thunderstorms
ahead of the the front. Temperatures ahead of the system on
Tuesday and Wednesday should be well above normal, though they are
expected to stay above normal even behind the system late week.

Britt

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 524 PM CST Sat Feb 24 2018

Low ceilings and visibilities will be found over the area through
this evening before conditions improve to VFR everywhere after
06Z. Rain will also move out of the area this evening. Winds will
turn out of west this evening and be gusty before decreasing
early on Sunday.

SPECIFICS FOR KSTL:

Ceilings and visibilities will improve during the evening, and
will turn VFR after 06Z. Scattered showers also may affect the
terminal this evening, but dry weather is also expected after 06z.
Westerly winds will be gusty at times tonight, but will decrease
after 10Z.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch until midnight CST tonight for Crawford MO-Franklin
     MO-Gasconade MO-Iron MO-Jefferson MO-Madison MO-Osage MO-
     Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis
     City MO-Saint Louis MO-Sainte Genevieve MO-Warren MO-
     Washington MO.

IL...Flood Watch until midnight CST tonight for Bond IL-Clinton IL-
     Fayette IL-Madison IL-Marion IL-Monroe IL-Randolph IL-Saint
     Clair IL-Washington IL.

&&

$$

WFO LSX



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