Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KLSX 271803

103 PM CDT Wed Aug 27 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 1148 AM CDT Wed Aug 27 2014

Going forecast trends still look reasonable. Ongoing activity
over northern Missouri should continue to drift east and
weaken with time as additional storms develop and become focused
along the southward pushing outflow boundary (approximately near a
KJEF-KUIN line attm) and along ill-defined remnants of synoptic
surface front, roughly from northern Ozarks, through the STL
metro, into central IL. Since there has been very little change in
the warm, humid airmass, expect that the storms that form along
the outflow and/or frontal boundary will pose a pulse-type severe
storm threat (gusty winds and some hail)...much like what occurred


.LONG TERM: (Thursday through Tuesday)
Issued at 237 AM CDT Wed Aug 27 2014

Boundary will be slow to lift back north on Thursday and may become
orientated more northwest to southeast across the CWA...paralleling
the Mississippi River. Once again, afternoon convection will be
possible in the vicinity of this front.

The boundary should finally lift north as a warm front Thursday
night with dry and seasonably warm weather expected on Friday
ahead of the shortwave/cold front that approaches from the west.

Have tried to focus likely POPs Friday night and Saturday with this
next system as blended guidance seems to give too long of a period
of POPs when compared to reality. So, after a wet and cooler
beginning to the Labor Day Weekend, it appears chances of
precipitation will decrease for Sunday and Monday (Labor Day), with
temperatures beginning to inch back up above normal in the wake
of this storm system.



.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1245 PM CDT Wed Aug 27 2014

Have gone with the idea that storms over north central MO will be
weakening this afternoon and will not impact UIN as low level jet
(finally) loses it`s punch. Meanwhile, scattered convection is
epected to develop along outflow boundary and/or the very ill-
defined remnants of synoptic frontal boundary, and the latest
surface data and hi-res output suggests this activity will be east
of COU and primarily impact STL metro sites. For now have stayed
with VCTS in the STL area TAFs, and will update if/when convective
trends become more clear. Much like yesterday, these storms will
be capable of very localized, microburst winds, and will be
monitoring radar trends for this threat as well. Have allowed the
afternoon thunderstorm threat to end by 01z, with generally
tranquil conditions during the late evening and overnight hours.
Heading towards daybreak have maintained some MVFR vsbys in fog
along the I-70 corridor in the warm humid AMS, and reintroduced
VCTS at UIN as leading edge of complex that forms to our NW
overnight should be threatening northern parts of the CWA by that

Specifics for KSTL: Aviation concerns can expect scattered
TSRA to form over the Bi-State area this afternoon, but some doubt
about whether the storms will actually impact within 10nmi of the
STL aerodrome. Aviation interests should also be aware that these
storms will be capable of producing micro-burst wind, much like
affected parts of STL county yesterday afternoon. Have allowed
this threat to diminish early this evening, with generally
tranquil conditions overnight. Area has been experienced MVFR
vsbys in fog the past several mornings, and without a change in
airmass have included this in the 08-12z time frame. More ams-type
TSRA are possible again on Thursday, but have not included in TAF
attm due to the large uncertainty of where the axis of
development will be.



MO...HEAT ADVISORY until 8 PM CDT this evening FOR Audrain MO-Boone
     MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Madison MO-Moniteau MO-Montgomery MO-Osage MO-
     Reynolds MO-St. Francois MO-Ste. Genevieve MO-Warren MO-
     Washington MO.

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

IL...EXCESSIVE HEAT WARNING until 8 PM CDT this evening FOR Bond IL-
     Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey IL-
     Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
     Randolph IL-St. Clair IL-Washington IL.



WFO LSX is the U.S. government's official web portal to all federal, state and local government web resources and services.