Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 312302

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
602 PM CDT TUE MAY 31 2016

.SHORT TERM... (Through Wednesday)
Issued at 233 PM CDT Tue May 31 2016


Focus tonight will be on convective trends/PoPs. While isolated to
widely scattered showers/storms are possible across the entire area
late this afternoon into early this evening...believe the better bet
for more widespread activity will be from mid evening into the early
overnight period along a prefrontal trough/sfc convergence zone.
Tied highest PoPs overnight roughly along/ahead of this feature as
it slowly progresses eastward overnight. Have continued the likely
PoPs for most of central and northeastern Missouri as well as west-
central Illinois. Believe activity will weaken slowly overnight as
better forcing aloft translates out of the area and instability
wanes diurnally. As a result...have mid/high chance PoPs across
roughly the southeastern 1/2 of the CWA. Other change made to
tonight`s forecast was to speed up timing of higher PoPs as
aforementioned prefrontal trough looks to be the focus for
thunderstorms through tonight.

Lows tonight will continue to be seasonably warm with most areas in
the mid 60s.


Continued to favor highest PoPs along/ahead of the prefrontal trough
into Wednesday morning. Behind this front...taper PoPs off to the
northwest but did keep at least slight chance PoPs ahead of the
actual cold front which looks to move through the area about 6
hours behind the prefrontal trough.

Temperatures tomorrow look difficult as they will be heavily
dependent on clouds/precipitation. Leaned cool relative to guidance
for the southeastern 1/3 of the CWA which has the highest PoPs and
most clouds into the afternoon hours while northwestern sections I
actually leaned warmer than guidance...even behind the actual cold
front. This is because of a lag in the stronger cold advection at
low levels in addition to decreasing clouds through the afternoon.
As a result...probably will not be much of a difference across the
CWA in terms of high temperatures...most areas should be in the low
to mid 80s.


.LONG TERM... (Wednesday Night through Next Tuesday)
Issued at 233 PM CDT Tue May 31 2016

Frontal boundary to exit forecast area by Wednesday evening,
stalling out just south of Missouri border. So even though most of
area to dry out, southern portions of forecast area will see
lingering showers and thunderstorms due to the stalled front/over
running activity through Friday.

By Friday night, northern stream shortwave to slide southeast into
forecast area. So will see increasing chances of showers and
thunderstorms Friday night and persist through Saturday night before
tapering off on Sunday. Last half of weekend and early next week to
be dry.

Temperatures to remain normal throughout the forecast period, lows
in the upper 50s to mid 60s and highs in the upper 70s to low 80s.



.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 553 PM CDT Tue May 31 2016

VFR conditions expected for the most part for all TAF
sites...however upper level disturbance and late afternoon and
early evening instability will combine to bring a chance for
scattered thunderstorms central MO into west central IL.
Instability will decrease by 06Z with loss of daytime heating so
expect only scattered showers in the KSTL metro TAF sites late
this evening into the morning on Wednesday. Light and variable
winds overnight will become light northwesterly by late morning as
very weak surface high pressure builds in.

Specifics for KSTL: VFR conditions expected through this TAF
period. Scattered showers possible late tonight into the morning
Wednesday ahead of a weak cold front. Light and variable winds
overnight will become light northwestly behind the front by mid
morning on Wednesday.



Saint Louis     67  82  64  81 /  50  50  30  10
Quincy          65  82  60  80 /  60  60  10   5
Columbia        65  81  61  79 /  60  30  20  10
Jefferson City  64  82  62  80 /  60  30  20  10
Salem           66  82  64  80 /  40  70  40  10
Farmington      62  81  63  79 /  50  60  40  30




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