Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280251

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
951 PM CDT FRI MAY 27 2016

Issued at 951 PM CDT Fri May 27 2016

One area of showers and isolated thunderstorms have currently moved
into the northern CWA while another small area of showers are
moving into east central Missouri from southeast Missouri. These
areas of rain continue to be generated in pockets of low level
moisture convergence ahead of at shortwave trough currently over
the southern Plains. The latest RAP shows that this trough will
move northeast toward Missouri and Illinois toward morning. Will
keep going chance of showers and thunderstorms through the night
ahead of the upper trough.

Going lows in the mid to upper 60s still look good.



.SHORT TERM...  (Through Late Tonight)
Issued at 305 PM CDT Fri May 27 2016

Showers and thunderstorms were developing and spreading back
northward into our area ahead of the upper level low over eastern
CO and western KS, and northeast of a shortwave approaching from
the southern Plains. These showers/storms should impact most of
the forecast area this evening, possibly continuing into the late
night hours. Mild temperatures can be expected again tonight due
to the cloud cover, relatively high surface dew points, and
southerly winds.


.LONG TERM...  (Saturday through Next Friday)
Issued at 305 PM CDT Fri May 27 2016

The threat for showers/storms will continue on Saturday and
Saturday night as the negatively tilted upper level trough moves
northeastward through the area. Should finally get a dry period
from Sunday into at least early Monday as the upper level trough
shifts northeast of our area with a weak surface ridge moving
eastward through the region after the passage of a weak surface
trough. Convection should return by Monday afternoon or night to
much of the area as a warm and moist southerly flow returns as the
surface ridge shifts east of our area, while weak southwest flow
shortwaves move through the region. The ECMWF and GFS model
solutions diverge after the Memorial Day weekend. The ECMWF model
has a strong upper level trough moving eastward through the
northern Plains which sends a cold front southeastward through our
forecast area late Tuesday night and Wednesday with convection
along and ahead of this front, followed by cooler and drier
weather by Thursday night. The GFS model keeps us in southwest
upper level flow with a slow moving upper level low developing
over the central Plains. The GFS solution would keep the chance of
convection going through the entire extended forecast. The ECMWF
model solution looks more realistic for this time of the year.
For now will reduce pops by Thursday night, but keep slight chance
pops going through the end of the forecast.



.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1238 PM CDT Fri May 27 2016

Difficult forecast regarding precipitation trends for this valid
TAF period. Believe chances for showers and thunderstorms will
increase this afternoon into very early evening ahead of next
shortwave. Could be a lull tonight with another wave late
tonight/early on Saturday possible. Other concern in the near term
is the MVFR ceilings but expect only a short period of these
ceilings before they lift into VFR.

Specifics for KSTL:

MVFR ceilings likely next few hours. Scattered showers and storms
also expected to increase this afternoon ahead of next shortwave
trough. Convective trends become more ambiguous overnight tonight
and into the day on Saturday.





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