Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 230918

Area Forecast Discussion
National Weather Service Saint Louis MO
418 AM CDT SAT JUL 23 2016

.SHORT TERM... (Through Sunday)
Issued at 346 AM CDT Sat Jul 23 2016

After a brief respite from the heat yesterday due to a nocturnal
thunderstorm complex which lasted much longer than expected,
hot/humid conditions are expected across the region again today
and tomorrow. Highs should reach the mid to upper 90s, and
overnight lows will be in the mid to upper 70s. The upper air
pattern remains largely unchanged from the last few days. An upper
ridge remains in place across the central US, although heights
will rise slightly over the northern plains today in response to
an approaching shortwave which was over MT early this morning.

700 mb temps of +14 didn`t pose a problem for convection
maintenance ydy morning, therefore there is no reason why
slightly cooler H7 temps today would pose much of an impediment
to iso-sct SHRA/TSRA today.


.LONG TERM...  (Tonight through Friday)
Issued at 346 AM CDT Sat Jul 23 2016

The aforementioned shortwave will break down the ridge and end
the heat wave for the LSX CWA by sending a cold front into MO/IL
tomorrow night. The front is forecast to approach northern MO on
Sunday night, and precip chances begin to increase with its
approach. A southerly LLJ is also fcst to develop across OK/KS by
06z Mon, interacting with the front to produce an area of pcpn
overnight. The front then continues moving into the CWA on Monday
before stalling somewhere across the region. Instability increases
ahead of the front on Monday aftn, and thunderstorms should
develop across at least the southern half of the CWA depending on
where the front is located.

There is some question regarding how far south the front will
reach before it stalls. Some models show the front moving all the
way through the CWA, but there is doubt about this scenario given
that there will be limited forcing after the shortwave zips off to
the east and that the front will be nearly parallel to the flow
aloft. Regardless of where the front stalls, it will serve as a
focus for TSRA dvlpt through the middle of next week. Several weak
disturbances are expected to move through the quasizonal to weakly
NW flow aloft, providing occasional large-scale ascent for pcpn.



.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1148 PM CDT Fri Jul 22 2016

VFR conditions and light surface winds will prevail at the TAF
sites thru much of the valid period. Only two concerns remain at
this time. First is possibility of VSBY reductions in mist, and
with thick CI cloud shield moving off to the east, this
possibility is looking better. The other concern is rain chances
from various sources and locations generally to our north. There
is some isolated storms forming over central IL. This activity
should remain to our northeast but will need to be monitored for
backbuilding to the southwest. Another area of storm development
over northwest MO should try to take advantage of westerly flow
aloft and advect eastward, but as of now, not much of a push yet
and its movement has been very slow. Will keep TAFs dry at this
point, but if either of these areas of convection approaches, will
need to get at least a VC added in.



MO...Excessive Heat Warning until 8 PM CDT Sunday for Audrain MO-
     Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-
     Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln
     MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
     Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint Charles MO-
     Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
     Genevieve MO-Shelby MO-Warren MO-Washington MO.

IL...Excessive Heat Warning until 8 PM CDT Sunday for Adams IL-Bond
     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-Saint Clair IL-Washington



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