Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 270419
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1119 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.
.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.
.AVIATION... (For the 06z TAFs through 06z Saturday Night)
Issued at 1046 PM CDT Fri Aug 26 2016
Weak frontal boundary extended from near MCI to STL this evening.
This front will lift back north-northeastward as a warm front
late tonight and Saturday as the surface ridge over the Great
Lakes region moves eastward. Light east-southeasterly surface
winds late tonight will become mainly southerly on Saturday. Best
chance for convection overnight will be in UIN just north of the
weak front, ahead of an approaching upper level disturbance, and
near a modest southwest low level jet. Isolated to scattered
diurnal convection may develop again over our area Saturday
SPECIFICS FOR KSTL: Weak frontal boundary extended from near
MCI to STL this evening. This front will lift back north-
northeastward as a warm front late tonight and Saturday as the
surface ridge over the Great Lakes region moves eastward. Light
east-southeasterly surface winds late tonight will become mainly
southerly on Saturday. Isolated to scattered diurnal convection
may develop again over our area Saturday afternoon.
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 74 88 73 89 / 30 40 30 30
Quincy 70 85 70 86 / 70 40 30 30
Columbia 69 85 70 87 / 40 30 30 30
Jefferson City 70 87 70 88 / 40 30 20 30
Salem 71 87 71 88 / 40 40 20 30
Farmington 70 86 70 88 / 20 30 20 30