Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 271951
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
251 PM CDT Mon Mar 27 2017

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 251 PM CDT Mon Mar 27 2017

Surface low over south central MO will continue to track to the east
northeast through the evening hours. So the wrap around showers,
mainly over northern portions of forecast area, will taper off from
west to east. Otherwise, could still see some isolated/scattered
showers and a few thunderstorms pop up south of surface low,
affecting areas along and south of I-44 through the early evening
hours.

Beyond this evening, will see lingering wrap around cloud cover as
system exits and mild temps in the 40s tonight. On Tuesday, dry
conditions to linger, but with cloudy skies and light north to
northeast winds, highs will only be in the upper 50s to mid 60s.

Byrd

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 243 PM CDT Mon Mar 27 2017

It still appears that the closed lows train will continue with the
potential for strong to severe storms and some widespread rain in
the next 7 days.

GFS/ECMWF/Canadian are in good acquirement that upper low that
will be near the Four Corners on Tuesday morning will move east
across the Plains into Missouri by Thursday evening. In the
meantime, the chance for showers will increase late on Tuesday
night from west to east as a low level jet increases moisture
transport into the area. The showers will become widespread on
Wednesday and Wednesday night as this low level forcing combines
with increasing mid-upper ascent from the approaching upper low.
There will also be a chance of thunderstorms as various models are
showing some MUCAPE spreading northward into the area,
particularly late in the night when the GFS/ECMWF show the warm
front moving north into the area. Will need to continue to watch
this time period for the potential for a few severe thunderstorms
given the instability and shear parameters. Both the GFS/ECMWF
show the surface low moving across the central part of the CWA
during the day on Thursday, though with slight timing differences.
There will be questions about the amount of instability
availability given the time of day and extent of showers, however
there will be ample shear so will still have the potential for a
few strong storms.

Rain will exit from west to east on Friday as an upper low exits
into the Ohio Valley.  Saturday looks dry at this point as an upper
ridge moves across Missouri and Illinois.  Then the GFS/ECMWF/
Canadian all showed another upper low dropping into the southern
Rockies by Friday that will move into the central CONUS by early
next week. While there is currently some disagreement on the exact
timing and movement of this system, it does appear that there
will be the chance for showers and thunderstorms as soon as
Sunday that will continue into next Monday.

GEFS mean MOS continues to favor above normal temperatures over the
next week.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1243 PM CDT Mon Mar 27 2017

Surface low currently over south central MO, will continue to
track to the east northeast this afternoon. So will see scattered
showers with some isolated thunderstorms possible, but mainly
south of taf sites. Did keep VCTS mention in STL metro area tafs.
Otherwise, showers to taper off between 22z Monday and 02z
Tuesday.

As for cigs, to remain MVFR/IFR through most of forecast period.
Winds to remain north to northeast as well.

SPECIFICS FOR KSTL:
Surface low currently over south central MO, will continue to
track to the east northeast this afternoon. So will see scattered
showers with some isolated thunderstorms possible, so did keep
VCTS mention in STL metro area tafs. Otherwise, showers to taper
off by 01z Tuesday.

As for cigs, to remain MVFR/IFR through most of forecast period.
Winds to remain north to northeast as well.

Byrd

&&

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

$$

WFO LSX



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