Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 260902

Area Forecast Discussion
National Weather Service Saint Louis MO
402 AM CDT TUE JUL 26 2016

.SHORT TERM...  (Through Late This Afternoon)
Issued at 309 AM CDT Tue Jul 26 2016

A few storms were across southwest IL, northeast of STL early this
morning. This activity appeared to be associated with a surface
dewpoint gradient and along the 850 mb front. A surface ridge
centered over eastern Nebraska and Iowa was bringing slightly
cooler air and lower humidities to northeast MO and west central
IL along with a clear sky. The chance of showers and storms will
continue today, mainly across southeast MO and southwest IL,
south of STL near a weakening cold front and where low-mid level
moisture and instability will be maximized.


.LONG TERM...  (Tonight through Monday)
Issued at 309 AM CDT Tue Jul 26 2016

The threat for convection should be mainly confined to southeast
MO and southwest IL tonight into Wednesday, then across most of
the forecast area by Wednesday night and Thursday as the weak
front lifts back northward as a warm front and the surface ridge
shifts east of the area allowing low level moisture and
instability to spread northward. Shortwave energy will also be
carving out an upper level trough over the central US by Thursday
leading to more cloud cover and possibly slightly cooler high
temperatures. This upper level trough should bring another cold
front slowly southeastward through our area by Thursday night.
This may eventually shunt much of the convection south of our
forecast area by Friday night with surface ridging moving slowly
eastward through the Great Lakes region, or at least to parts of
southeast MO and southwest IL. Temperatures Friday and Saturday
may be slightly below normal, but then return to near normal
values by Sunday as southerly surface/low level flow returns.



.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1136 PM CDT Mon Jul 25 2016

While isolated showers/thunderstorms are possible for mainly KCPS
tonight...main concern continues to be on fog/stratus potential.
Did not make too many changes to previous set of TAFs. Did move up
timing of MVFR ceilings a couple of hours at KCPS and hit fog a
bit harder at KSUS as T/Td spread is almost nil already. Cannot
rule out fog and stratus at KCOU and KUIN but better chances for
the metro terminals. Best chances of showers/storms late tonight
and during the day on Tuesday continue to look to be just to the
SE of the terminals...but could be close for the metro TAFs. Winds
will remain largely light/variable tonight and early on Tuesday
before becoming light out of the northeast by Tuesday afternoon.

Specifics for KSTL:

Some MVFR ceilings and possibly visbys with fog still appear
likely later on tonight. Conditions should improve by mid morning.
Winds will remain light/variable tonight and early on Tuesday but
become more northeasterly by afternoon. Chances of showers/storms
continue to look too low attm to mention in TAF but are possible
throughout the 30-hr forecast.





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