Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 051156

656 AM CDT SAT SEP 5 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 322 AM CDT Sat Sep 5 2015

Expect yet another warm day today as high temperatures should climb
once again into the lower-mid 90s under mainly sunny skies.  Mixing
should be above 800mb. Mixing down 850mb temperatures around +20C
support high temperatures in the lower-mid 90s.  Heat index readings
will be close to 100 degrees given that dewpoints will be well into
the 60s if not 70 degrees at times.

Will also stick with a dry forecast as thunderstorms stayed over
eastern Illinois despite the atmosphere being unstable and uncapped
yesterday afternoon.  Conditions will be similar over the area today
with MUCAPES being in the 1000-2000 J/kg range with little CINH and
some of the CAMS showing some convective development by midday.
However, much like yesterday, there will be the mid-level ridge axis
over the region that should suppress thunderstorm development, so
will leave forecast dry for now.


.LONG TERM:  (Tonight through Friday)
Issued at 322 AM CDT Sat Sep 5 2015

(Tonight through Monday)

Will keep forecast dry through late Sunday night as forecast
soundings are showing less instability tomorrow than today as the
ridge axis reorients itself southwest-northeast across the area.
Temperatures and humidity will be similar to today.  Chances of
showers and thunderstorms will begin to increase by late Sunday
night as the upper ridge shifts to the south and low level moisture
convergence increases over central and northeast Missouri.  Chances
will continue to increase over the area Monday and Monday night as
the upper ridge shifts farther south and the faster, upper flow and
eventually the surface cold front moves into northern Missouri and
central Illinois.  Have likely PoPs on Monday night over parts of
central and northeast Missouri as well as west central Illinois.

(Tuesday through Friday)

Cold front will be slow to move through the Missouri and Illinois as
a series of shortwave troughs move through the region during this
period.  First front will move through the area on Tuesday into
Wednesday followed by a secondary front that both the GFS and ECMWF
are showing that will move through late week.  Both the series of
shortwave troughs and the fronts will keep a persistent chance of
showers and thunderstorms in the forecast through next week.

Temperatures will begin to fall back to near normal behind the front
by mid to late next week...particularly with clouds and the chance
of rain.



.AVIATION:  (For the 12z TAFs through 12z Sunday Morning)
Issued at 554 AM CDT Sat Sep 5 2015

Fog at SUS should dissipate by 13-14Z this morning. Little
cloudiness can be expected this forecast period, except few-sct
diurnal cumulus clouds late this morning and this afternoon
around 5000-6000 feet in height. Light suface winds will become
s-sely later this morning with persistent surface ridging just
east of our area.

Specifics for KSTL: Surface wind should pick up to around 7 kts
later this morning into the afternoon, then weaken again tonight.
Just few-sct diurnal cumulus clouds expected late this morning and
this afternoon around 6000 feet in height.





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