Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 242052
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
352 PM CDT Sun Aug 24 2014
.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 18z TAFs through 18z Monday Afternoon)
Issued at 1226 PM CDT Sun Aug 24 2014
VFR through the period with southwest winds backing slightly at
night. Similar to previous nights, there could be brief periods of
light fog between 06-13z.
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-
EXCESSIVE HEAT WARNING until 8 PM CDT Tuesday FOR Jefferson MO-
Lincoln MO-Pike MO-St. Charles MO-St. Louis City MO-St.
IL...HEAT ADVISORY until 8 PM CDT Tuesday FOR Adams IL-Brown IL.
EXCESSIVE HEAT WARNING until 8 PM CDT Tuesday FOR Bond 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.