Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 200827

327 AM CDT Wed Aug 20 2014

.SHORT TERM:  (Through Tonight)
Issued at 240 AM CDT Wed Aug 20 2014

Main focus thru the period will be PoPs, which will influence
temps today and therefore, also headlines.

There is still some uncertainty regarding heat headlines thru the
weekend, but will go ahead and issue a Heat Advisory for portions
of central and ern MO and SW IL. This expansion is due to expected
heat index values of 100+ for at least 4 days. However, values of
105+ degrees may be possible across the adv area, especially Thurs
and Fri. This adv may need to be expanded to include counties not
currently in the adv. However, since criteria is not expected to
be reached today, will handle that area tomorrow.

Dewpoints are the main question as portions of central and SE MO
have been mixing out well the past few days. These are the areas
that have seen the least rainfall lately and generally mix out
well during the day. Have therefore kept the ern Ozarks out of the
adv for now.

As for PoPs...the HRRR, local 4km WRF and the 4km NSSL WRF seem
to be handling the current convection fairly well. Have therefore
tailored PoPs for the remainder of today and into tonight twd
those solns. In general, ongoing storms over IA and far NE MO shud
move sewd impacting mainly the nrn portions of the CWA this
morning. Mdls suggest storms developing this afternoon over the
ern Ozarks or along the MS Rvr, but these shud remain isod. For
tonight, storms shud remain focused along the fnt and where 850mb
convergence is greatest. Believe the best chances will remain NE
of the CWA, but have kept slight chance PoPs along the nern
counties due to uncertainty.

A lot of questions remain regarding temps today due to possible
convection. However, have trended above the cooler MOS, but stayed
below the warmer MOS. Overall, this verified fairly well
yesterday. Temps for tonight are a little more complex as mixing
shud be greater across central MO. However, have trended above the
warmer MOS due to swly winds thru the night.

.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.



.AVIATION:  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1110 PM CDT Tue Aug 19 2014

A weak cold front was draped from central IL thru northern MO late
this evening and was producing very little in the way of clouds
and only one cell just to the east of UIN. This front is expected
to move thru our region uneventfully for the next few hours and early
overnight, before stalling out and eventually retreating to the
north as a warm front late. When this does happen, scattered
convection is expected to break out along the front as it pushes
thru the TAF sites thru mid Wednesday morning. Have upgraded to
VCTS mention, but southern extent looking a bit more iffy if front
does not work its way far enough south as originally expected. Some
fog is also expected, especially at SUS and CPS, but will be in a
narrower window than last night due to the expected clouds and
convection firing along the warm front. VFR conditions are then
expected for the remainder of the TAF period from late Wednesday
morning on as the entire area moves into a warm sector setup.
Surface winds will become S-SW as the warm front moves thru.

Specifics for KSTL: VFR conditions outside of rain are expected
thru the period. A small window early Wednesday morning for rain
is anticipated as a warm front moves thru. An outside chance for
some VSBY reductions in mist late tonight as well, but small
enough to preclude mention in the TAF at this time.



Saint Louis     95  75  96  77 /  30  10   5  10
Quincy          89  71  93  73 /  60  20  10  10
Columbia        95  73  96  74 /  20  10   5  10
Jefferson City  96  73  97  74 /  10  10   5  10
Salem           90  72  92  73 /  20  20  10  10
Farmington      94  70  95  72 /  20  10   5   5


MO...HEAT ADVISORY from 1 PM this afternoon to 7 PM CDT Sunday FOR
     Audrain MO-Boone MO-Callaway MO-Cole MO-Franklin MO-
     Gasconade MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO-
     Montgomery MO-Osage MO-St. Charles MO-St. Francois MO-Ste.
     Genevieve MO-Warren MO.

     EXCESSIVE HEAT WARNING from 1 PM this afternoon to 7 PM CDT
     Sunday FOR St. Louis City MO-St. Louis MO.

IL...HEAT ADVISORY from 1 PM this afternoon to 7 PM CDT Sunday FOR
     Bond IL-Calhoun IL-Clinton IL-Greene IL-Jersey IL-Macoupin
     IL-Marion IL-Monroe IL-Randolph IL-Washington IL.

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



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