Area Forecast Discussion
Issued by NWS St. Louis, MO

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188
FXUS63 KLSX 311935
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
235 PM CDT TUE MAY 31 2016

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

(Tonight)

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.

(Wednesday)

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.

Gosselin

.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.

Byrd
&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1230 PM CDT Tue May 31 2016

Main concern over the next 24 hours will be on convective trends
across the area and its possible impacts at the terminals. Outside
of thunderstorms...conditions are expected to be VFR. Believe best
chance of showers/storms will begin this evening and last into the
overnight period across portions of central and northeastern
Missouri. As a result...have a prevailing group for shra vcts and
added a tempo for low MVFR visbys in TSRA at both KCOU and KUIN
tonight. IFR visbys will also be possible in any heavier
thundershower. For the metro terminals...not quite as high of a
chance for activity as expect area of showers/storms to weaken
overnight as it progresses eastward toward the area due to better
forcing further to the north combined with loss of most of the
instability diurnally. Kept a VCSH group in for now but moved up
timing with best chance of seeing showers/weak storms very late
tonight through late Wednesday morning.

Initially SE winds this afternoon will become either calm or
light/variable as frontal boundary approaches. Behind the
front...winds will be light out of the west/northwest.

Specifics for KSTL:

Main concern over the next 30 hours will be on convective trends
and its possible impacts at Lambert Field. Outside of
thunderstorms...conditions are expected to be VFR. Believe best
chance of showers/storms will be very late tonight through mid
morning on Wednesday...though higher chances will remain west. Kept
a VCSH group in for now but moved up timing.

Initially SE winds this afternoon will become either calm or
light/variable as frontal boundary approaches. Behind the
front...winds will be light out of the west/northwest.

Gosselin
&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     66  82  64  81 /  50  50  30  10
Quincy          64  82  60  80 /  70  50  10   5
Columbia        64  83  61  79 /  70  30  20  10
Jefferson City  64  83  62  80 /  70  30  20  10
Salem           65  81  64  80 /  40  70  40  10
Farmington      62  81  63  79 /  50  60  40  30

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$
WFO LSX



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