Area Forecast Discussion
Issued by NWS St. Louis, MO

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582
FXUS63 KLSX 280403
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1103 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 06z TAFs through 06z Tuesday Night)
Issued at 1043 PM CDT Mon Mar 27 2017

Surface low and trailing cold front have passed well southeast of
the taf sites this evening. A surface ridge over the northern
Plains and Great Lakes region will build southward into our area.
The stratus cloud deck will remain over the area late tonight and
Tuesday morning with the cloud ceiling likely dropping down to
around 500 feet late tonight. There will also be patchy light
drizzle and fog. Will see a gradual rise in the cloud ceiling
height late Tuesday morning and afternoon, possibly into the VFR
catagory by late afternoon. North-northwesterly surface winds will
veer around to a northeasterly direction by Tuesday morning.

SPECIFICS FOR KSTL: Surface low and trailing cold front have
passed southeast of the STL area this evening. A surface ridge
over the northern Plains and Great Lakes region will build
southward into our area. The stratus cloud deck will remain over
the area late tonight and Tuesday morning with the cloud ceiling
likely dropping down to around 500 feet late tonight. There will
also be patchy light drizzle and fog. Will see a gradual rise in
the cloud ceiling height late Tuesday morning and afternoon,
possibly into the VFR catagory by late afternoon. Northwesterly
surface winds will veer around to a northeasterly direction by
Tuesday morning.

GKS

&&

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

$$

WFO LSX



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