Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 250211

911 PM CDT Sun Aug 24 2014

Issued at 859 PM CDT Sun Aug 24 2014

A quiet night is on tap across the area, with a mostly clear sky
and mild, humid conditions. Overnight lows in the 70s area-wide
including upper 70s in the St. Louis metro area still look on
target this evening. Thus, no changes have been made to the going
forecast aside from minor adjustments to account for near-term



.SHORT TERM:  (Through Late Tonight)
Issued at 336 PM CDT Sun Aug 24 2014

Thunderstorms have once again developed this afternoon across the
eastern Ozarks in response to heating and potentially some orographics.
These pulse storms should dissipate near or shortly after sunset
and have a mention for early this evening. Also added some low
pops across the far eastern CWA where the combo of heating and dew
points in the mid-upper 70s has pushed SBCAPE to over 5500 j/kg
and CIN is quite weak. While convergence looks pretty weak, there
is a cu field in that region and convective temperatures could be
reached over the next few hours. After the early evening hours,
any precipitation threat should be well removed and north of the
CWA. Another mild-warm and humid night will be the rule.


.LONG TERM:  (Monday through Next Sunday)
Issued at 336 PM CDT Sun Aug 24 2014

The dominant upper ridge will expand over the next 48-60H and
maintain the current heat wave across the region. The current
combination of heat advisories and excessive heat warnings through
Tuesday appear right on the mark. There may be some subtle day to
day differences in dew points and ambient temperatures, with
temperatures near or a deg or so cooler over the next few days but
on the same hand the dew points look to once again increase
westward with the highest values across Illinois. Low level
moisture depth is improved both Monday and Tuesday. I see no
reason given the trends of the past 3 days not to include a threat
of isolated diurnal thunderstorms across the eastern Ozarks on
Monday. The threat of diurnal pulse storms will expand to most of
the CWA on Tuesday as low level moisture becomes better stratified
and mid level temperatures cool slightly. The lack of an organized
focus however should keep overall coverage more isolated.

A short wave trof moving across the northern tier and into the
Great Lakes will begin to break down the amplitude of the upper
ridge some Tuesday night into Wednesday, and allow for an east-
west oriented back door front to sink into the region. This will
be accompanied by cooler temperatures and a greater threat of
showers and thunderstorms.

The jury is still out on the extended period from Thursday into the
weekend with higher than normal uncertainty. Overall the pattern
will change as the rige aloft continues to break down and is
replaced by an upper trof moving into the central U.S. The details
of this evolution and the surface pattern are messy however. The
back door front may ooze southward through late Thursday then
retreat back northward before another cold fropa late in the
weekend. While the extreme heat appears to come to an end by Wed,
highs in the upper 80s to lower 90s could linger into the weekend.



.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 609 PM CDT Sun Aug 24 2014

Expect VFR flight conditions and light east-southeast flow to
prevail tonight. There may be patches of fog again between 10Z and
13Z. It was surprising to see how low KUIN and KCPS fell this
morning. Can`t entirely rule out IFR conditions again since not
much has changed with the weather pattern, but this is definitely
outside the norm for this time of year. Any fog that does form
should dissipate quickly after sunrise. Wind will turn once again
to the southwest Monday morning. Expect VFR flight conditions and
southwest flow to prevail.

Specifics for KSTL:

Expect VFR flight conditions and southeast flow to prevail at
Lambert tonight. While I cannot rule out a brief period of MVFR
visibility again, temperatures this evening are marginally warmer
than yesterday which should help to keep fog from forming early
Monday. If any fog does form, expect it will be light and brief.
VFR flight conditions and southwest flow to prevail Monday.



MO...HEAT ADVISORY until 8 PM CDT Tuesday FOR Audrain MO-Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Knox MO-Lewis MO-Madison MO-Marion MO-Moniteau MO-
     Monroe MO-Montgomery MO-Osage MO-Ralls MO-Reynolds MO-
     Shelby MO-St. Francois MO-Ste. Genevieve MO-Warren MO-
     Washington MO.

     EXCESSIVE HEAT WARNING until 8 PM CDT Tuesday FOR Jefferson MO-
     Lincoln MO-Pike MO-St. Charles MO-St. Louis City MO-St.
     Louis MO.

IL...HEAT ADVISORY until 8 PM CDT Tuesday FOR Adams IL-Brown IL.

     Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey IL-
     Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
     Pike IL-Randolph IL-St. Clair IL-Washington IL.



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