Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 262313
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
613 PM CDT FRI AUG 26 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 307 PM CDT Fri Aug 26 2016

The synoptic pattern early this afternoon features a broad
subtropical ridge across the southeastern CONUS with a trough
digging into the northwestern CONUS.  This has placed Missouri and
western IL within broad southwest flow aloft, a regime which will
persist through tonight.

Convection has developed over the last couple of hours across
portions of western IL.  This region received some sunshine earlier
today and has become rather unstable with MLCAPEs around 2500 J/kg.
The better deep layer shear is displaced north of this region, but 0-
6km shear values around 30 knots may be enough for some loose
organization to the multicells as they continue to develop.  Main
threat will be locally strong winds, but the backbuilding nature of
some of the convection in the high PWAT airmass (around 2 inches)
will also lead to some localized flash flooding concerns as well.

Further west across central and east-central MO, expansive low/mid
cloud cover has kept the region more stable.  Therefore, surface-
based convection will be limited in this region with only a few
showers or an isolated storm through the early evening.  Attention
will then turn to the west where convection is expected to develop
near the Kansas City area and spread ENE through the late evening
hours. This activity may attempt to grow upscale into a small MCS
which will likely clip portions of northern MO and west-central IL
(near the Quincy area).  Given the timing, do not expect this
activity to be severe once it reaches the LSX CWA, but a few strong
storms will be possible especially across northern MO.

Deitsch

.LONG TERM...  (Saturday through Next Friday)
Issued at 307 PM CDT Fri Aug 26 2016

Complex that develops over northwestern Missouri tonight to slide
east and diminish Saturday morning. Otherwise, active pattern to
continue through rest of forecast period with weak surface ridge
staying put over region. Will see chance of storms each day as
upper level shortwaves undercut surface ridge. Best chances will
be during peak heating, i.e. afternoon/evening hours.

Highs will be in the 80s Saturday through next Friday, with lows in
the upper 60s to low 70s.

Byrd

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 544 PM CDT Fri Aug 26 2016

Weak frontal boundary extended from near MCI to STL early this
evening. This front will lift back north-northeastward as a weak
warm front late tonight and Saturday as the surface ridge over the
northern Plains and Great Lakes region moves eastward. Light east-
southeasterly surface winds tonight will become mainly southerly
on Saturday. Although outflow boundaries were moving through the
St Louis metro area from convection in IL, the mid level cloud
deck was keeping the atmosphere from getting very unstable and
leading to a lack of convective development with little in the way
of cumulus clouds. Could not rule out an isolated shower or storm
until sunset this evening. Best chance for convection late this
evening and overnight will be in UIN just north of the weak front
and near a modest southwest low level jet. Isolated to scattered
diurnal convection may develop again Saturday afternoon.

SPECIFICS FOR KSTL: Weak frontal boundary extended from near MCI
to STL early this evening. This front will lift back north-
northeastward as a weak warm front late tonight and Saturday as
the surface ridge over the northern Plains and Great Lakes region
moves eastward. Light east-southeasterly surface winds tonight
will become mainly southerly on Saturday. Although outflow
boundaries were moving through the St Louis metro area from
convection in IL, the mid level cloud deck was keeping the
atmosphere from getting very unstable and leading to a lack of
convective development with little in the way of cumulus clouds.
Could not rule out an isolated shower or storm until sunset this
evening. Isolated to scattered diurnal convection may develop
again Saturday afternoon.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     75  88  73  89 /  30  30  30  30
Quincy          70  85  70  86 /  50  50  30  30
Columbia        69  85  70  87 /  20  30  30  30
Jefferson City  70  87  70  88 /  20  30  20  30
Salem           73  87  71  88 /  40  40  20  30
Farmington      71  86  70  88 /  30  30  20  30

&&

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

$$

WFO LSX



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