Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 300846
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
346 AM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sat Aug 30 2014

Regional radar is showing a number of areas of showers and
thunderstorms across Missouri and western Illinois early this
morning. These are generally within a weak warm advection regime
ahead of a upper trof moving through the MS Valley and in advance
of the attendant cold front. While all the current activity should
continue moving east northeast this morning, the overall consensus
amongst the guidance and convection allowing models is that there
should be a general increase in the scattered activity currently
over southwest Missouri as the morning progresses and it moves
northeast. Additional development is also expected during the
later part of the morning into the afternoon in a broad southwest
to northeast zone ahead of the slowly advancing cold front and centered
through the southeast half of the CWA. Given the current temperatures
in the 70s, low-mid 80s looks reasonable for highs today.

Glass

.LONG TERM:  (Tonight through Friday)
Issued at 330 AM CDT Sat Aug 30 2014

Convective trends are not completely clear cut tonight. The main
upper trof axis should have passed to the east by early this
evening, but there is a weak lingering vort max still to pass and
the front appears to wash out across northeast Missouri and west
central Illinois. Sans the NAM, the model consensus keeps a chance
of showers and thunderstorms centered though the southeast half of
the CWA during the evening. Sunday looks largely dry and warmer
with possibly some isolated diurnal storms across southeast MO and
southwest Illinois. The threat of organized covection should
slowly spread into northeast Missouri late Sunday night with the
approach of a progressive long wave trof and attendant cold front and
intensifying southwesterly LLJ. Thunderstorms appear likely on
Labor Day and Monday night as the cold front moves slowly southward
into a moist unstable air mass, and as a southwesterly LLJ and the
upper trof contribute to lift and cap removal. This system will be
accompanied by deep layer shear of 30-40+ knots resulting in the
potential for organized severe storms. Showers and thunderstorms
could persist across the southern CWA Tuesday and maybe even into
Tuesday night and Wednesday in the vicinity of the front and then
as it retreats back northward late Wednesday.

Late in the week ahead the upper ridge is forecast to restablish
itself over the southeast half of the Nation, bringing a return of
more summer like weather/heat.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1042 PM CDT Fri Aug 29 2014

There were two areas of showers and storms this evening. The first
was across southeast MO and will likely remain southeast of the
taf sites late tonight, although they could get close to CPS.
There were scattered showers/storms across northwest MO ahead of
an approaching upper level disturbance which may impact the UIN
area late tonight. May include VCTS in the UIN taf. It appears
that there will be enough cloud cover and strong enough surface
winds to deter fog formation, although could not rule out light
fog late tonight/early Saturday morning in SUS and CPS where the
surface wind will be a little lighter and in areas which had
significant rainfall this evening. Should be at least scattered
showers/storms in the St Louis metro area Saturday afternoon along
and ahead of weakening cold front/surface trough dropping
southeastward through the area. Sly surface winds will become
more swly late tonight and Saturday morning.

Specifics for KSTL: Current shower/storm activity on radar will
likely miss STL late tonight, although could not rule out a
passing sprinkle. Will likely leave STL taf dry late tonight and
Saturday morning due to uncertainty in coverage and timing of
additional convection. Will include VCTS in the taf Saturday
afternoon with at least scattered showers/storms expected at this
time due to diurnal destabilization along and ahead of a weak
surface trough/cold front. Prevailing s-swly surface winds through
the period.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     86  72  90  74 /  60  30  20  10
Quincy          84  67  88  71 /  30  10   5  50
Columbia        86  68  91  72 /  40  20  10  40
Jefferson City  86  69  91  72 /  50  20  10  30
Salem           85  70  86  72 /  60  50  20  10
Farmington      84  69  87  72 /  60  50  20  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





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