Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 192030
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
330 PM CDT Tue Aug 19 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 309 PM CDT Tue Aug 19 2014

Morning and early afternoon convection associated with a mid/upper
level shortwave has moved east of the CWA. Cold front approaching
from the northwest is sparking a few thunderstorms across extreme
northeast Missouri. Will watch this convection over the next hour
and decide how far south to forecast thunderstorms this evening
with the front.

Front is expected to settle into a northwest to southeast
orientation overnight from near Kansas City area to southern
Illinois. Model guidance is not as enthusiastic with convection
developing overnight - but with front in vicinity and low level
jet can`t rule out elevated convection. Have maintained chance
POPs for now and will let evening shift determine need to increase
or decrease by NOWCast.

CVKING

.LONG TERM:  (Wednesday through Next Tuesday)
Issued at 309 PM CDT Tue Aug 19 2014

Story will be the HEAT and HUMIDITY. It`s finally going to feel
like summer with the first real heat wave beginning tomorrow. Have
decided to hoist an Excessive Heat Warning for the urban zones of
the Greater St. Louis Metropolitan Area. Temperatures will be in
the middle 90s tomorrow and rise into the upper 90s through at
least Sunday. The long duration of afternoon/early evening heat
index values around 105 degrees will cause life threatening
conditions for those that do not have access to air conditioning.

Outside of the urban areas, the heat will increase, but not reach
advisory levels until Friday. Will let later shifts access the
need for additional heat headlines.

There is still a chance, albiet slight, for thunderstorms to
develop on Wednesday as the warm front lifts through the area.
After that, I`m not sure we will see any rain until next week when
a front moves south and stalls somewhere across the Midwest. If
the front does not make it far enough south - the heat headlines
will likely have to be extended into the next work week.

CVKING

&&

.AVIATION:  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1241 PM CDT Tue Aug 19 2014

Showers and thunderstorms have moved east of taf sites, but could
still see some redevelopment as front moves through. Confidence is
low on coverage and timing, so kept tafs dry for now. Otherwise,
south to southwest winds to become westerly behind boundary. Then
winds to become light and variable this evening, before picking
back up from the southwest on Wednesday. Some models indicating
activity firing north of frontal boundary as it lifts back north
through region later tonight. But once again confidence on timing
and coverage hard to pin down, so kept tafs dry.

Specifics for KSTL:
Showers and thunderstorms have moved east of metro area, but could
still see some redevelopment as front moves through. Confidence is
low on coverage and timing, so kept taf dry for now. Otherwise,
south to southwest winds to become westerly behind boundary after
20z Tuesday. Then winds to become light and variable by 01z Wednesday,
before picking back up from the southwest 17z Wednesday. Some models
indicating activity firing north of frontal boundary as it lifts
back north through region later tonight. But once again confidence
on timing and coverage hard to pin down, so kept taf dry.

Byrd

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...EXCESSIVE HEAT WARNING from 1 PM Wednesday to 7 PM CDT Sunday
     FOR St. Louis City MO-St. Louis MO.

IL...EXCESSIVE HEAT WARNING from 1 PM Wednesday to 7 PM CDT Sunday
     FOR Madison IL-St. Clair IL.

&&

$$

WFO LSX




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