Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 012025

Area Forecast Discussion
National Weather Service Saint Louis MO
325 PM CDT SUN MAY 1 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 324 PM CDT Sun May 1 2016

Clouds will continue to move southeast and will overspread the area
by mid evening as upper trough back over eastern Nebraska drops
southeast into Missouri and Illinois.  Isolated afternoon showers
and thunderstorms should diminish by early this evening with the
loss of daytime heating.  Some isolated showers may begin to develop
toward morning underneath the upper trough over central and
northeast Missouri.  Lows tonight will fall into the middle 40s to
around 50s.


.LONG TERM...  (Monday through Next Sunday)
Issued at 324 PM CDT Sun May 1 2016

(Monday through Wednesday)

GFS/ECMWF are in relatively good agreement that upper trough will
move across the area tomorrow with relatively deep layer moisture.
Will carry chance PoPs for much of the area for this reason.  Drier
air will begin to move into the area by Monday night, so will go
with mainly dry conditions.  A second trough moves across the area
on Tuesday which begins the switchover in the upper pattern to
northwesterly flow.  GFS/ECMWF are still showing a third upper
trough moving across the Great Lakes and the Midwest on Wednesday
that will bring an attendant cold front across Missouri and Illinois.
Models indicate that best low level moisture and forcing will
still limit rain chances to the eastern part of the CWA.

Monday still looks quite cool with clouds, showers, and cold air
advection. Tuesday will be slightly warmer with less clouds and
winds turning out of the west.  Wednesday will see near steady
temperatures during the afternoon behind the front.

(Thursday through Sunday)

CONUS will be in highly amplified upper flow late week into next
weekend because of an omega block that will set up over North
America. It still looks like we will be dry through at least
Saturday as we will lie under northwesterly flow aloft and a large
surface high will be moving across Missouri and Illinois.  By next
weekend, the GFS and ECMWF show the upper ridge moving over us and
the low level flow becoming southwesterly across the Midwest.  This
may allow for some return of Gulf moisture into our area by late in
the weekend.  Have added a chance of thunderstorms on Sunday as both
the GFS and ECMWF are hinting at a frontal boundary moving back into
the area.  This will also cause temperatures to climb from below
normal on Thursday with 850mb temperatures around 5C to above normal
temperatures over the weekend with southwesterly surface flow and
850mb temperatures around 15C.



.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 106 PM CDT Sun May 1 2016

Specifics for KCOU: KCOU is far enough west that VFR conditions
should prevail for the first 0-6 hours of the valid TAF pd.
Thereafter, MVFR cigs are expected for most of the night. Ceilings
may fall to IFR late tonight, but confidence was too low to
include in the TAF attm.

Specifics for KUIN: IFR conditions are expected for at least the
next few hours. Minor improvement is possible during the late
afternoon, but cigs should fall back to IFR this evening.
Scattered rain showers are possible after 20z.

Specifics for KSTL, KSUS, KCPS: IFR and MVFR cigs extended farther
south late this morning than the models had previously predicted,
and IFR/MVFR cigs are expected to remain in place through the
afternoon based on upstream satellite imagery and METARs. Cigs
are expected to fall to IFR again tonight, likely after 06z based
on RAP and local WRF soundings in BUFKIT. Light fog is also
possible overnight. Rain showers are possible after 12z, but the
St. Louis metro area should be on the northern fringe of the rain





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