Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 290425
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1125 PM CDT SUN AUG 28 2016

.UPDATE...
Issued at 900 PM CDT Sun Aug 28 2016

The few showers and storms that were in our forecast area have
dissipated this evening. It appears that the convection around us
from the Kansas City area, to southeast IA to southeast IL will
remain outside of our forecast area tonight. There is an outside
chance that a few showers/storms could clip northeast MO and west
central IL late tonight. Warm and muggy conditions can be expected
again tonight with high dew points. Lows will be similar to the
previous night, and around 5 degrees above normal for late August.

GKS

&&

.SHORT TERM...  (Through Late Tonight)
Issued at 248 PM CDT Sun Aug 28 2016

Storms fired up a bit earlier today along an area of moisture
convergence. Storms continue to develop back to the southwest of
original activity over central and northeast Missouri, mainly due to
outflow boundaries. Will see isolated/scattered activity through the
evening hours before diminishing. With slow movement and PWs near 2
inches, storms that do develop will drop quite a bit of rain in a
short amount of time.  Otherwise, another mild night in store with
lows in the mid 60s to low 70s.

Byrd

.LONG TERM...  (Monday through Next Sunday)
Issued at 248 PM CDT Sun Aug 28 2016

The synoptic pattern at the start of the long term period will
feature generally weak flow aloft across much of the CONUS as mean
ridging prevails.  However, a strong trough/associated PV anomaly
will dig into the Northwest early this week while another PV anomaly
dives out of central Canada, each acting to knock down the ridge
over the region by the middle of next week.

Scattered mainly diurnally driven convection will persist into the
day on Monday.  Still not much synoptically to focus the convection,
so will continue with generally broad-brushed 20-40 pops, with the
highest coverage expected across north-central MO where capping will
be slightly weaker given greater displacement from the upper-level
ridge.  Given temperatures overachieving the past couple of days,
will continue to go above most guidance for highs Monday.

Convective coverage may increase a bit Tuesday into Wednesday as a
cold front approaches from the north.  This front will be double-
barreled, with a wind shift/weak convergence to focus convection on
Tuesday mainly across northern MO/western IL and another wind shift
and actual airmass change late Wednesday as Canadian high pressure
builds into the region.  The Wednesday front will also have some
upper-level support as a weak PV anomaly passes through and knocks
down the ridge. Given a surface focus and the upper-level forcing
for ascent, went ahead and upped pops on Wednesday.

Behind Wednesday`s front, a pleasant airmass will push into east-
central MO and western IL.  Some guidance is advertising widespread
mid/upper 70s Thursday into Friday.  However, given overachieving
temperatures as of late and the cool bias noticed in guidance with
the last fropa, will keep temps in the upper 70s/low 80s.

Conditions will slowly warm through the weekend as surface ridging
shifts east of the region and southerly flow commences.  However,
the region should continue to remain mostly dry as isentropic ascent
ahead of the next system should remain focused just to the west of
the region.

KD

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1117 PM CDT Sun Aug 28 2016

Although could not rule out an isolated shower/storm late tonight,
it appears that the taf sites should be dry with mainly just some
high level clouds. A light surface wind can be expected late
tonight, then mainly an easterly wind on Monday with a surface
ridge extending from the Great Lakes region southwest into
northeast MO. There may be some fog in SUS and CPS late
tonight/early Monday morning. Scattered diurnal cumulus clouds
will develop again late Monday morning and afternoon along with
isolated to scattered showers/storms during the afternoon and
evening.

SPECIFICS FOR KSTL: Although could not rule out an isolated
shower/storm late tonight, it appears that STL should be dry with
mainly just some high level clouds. A light surface wind can be
expected late tonight, then mainly an easterly wind on Monday with
a surface ridge extending from the Great Lakes region southwest
into northeast MO. Scattered diurnal cumulus clouds will develop
again late Monday morning and afternoon along with isolated to
scattered showers/storms during the afternoon and evening.

GKS

&&

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

$$

WFO LSX



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