Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 172127

Area Forecast Discussion
National Weather Service Saint Louis MO
427 PM CDT Thu May 17 2018

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 308 PM CDT Thu May 17 2018

Focus thru the period will be PoPs. MCV evident in sat image over
wrn MO with another further south into AR will continue to impact
the area thru Fri. With the trof stretching thru the region, these
MCVs will have a Fujiwhara effect with a s/w moving precip back
northwestward into the area late tonight and Fri morning.

Mdls differ exactly where the precip will be in the morning, but
best chances shud be over the ern half of the CWA where the s/w is
tracking nwd. After sunrise, believe a band of TSRA will develop
along the wrn flank of the upper low where insolation is possible.
The 18z NAM just arriving suggests a more ern soln, but will need
to continue to monitor trends. Wherever the lower-res mdls wud
suggest periods of heavy rain possible thru the early morning
hours. If the more wrn soln verifies, going temps for tomorrow are
too high. While I have trended further west slightly, have not
moved PoPs as far west as the NAM soln.

The upper trof will slowly pull newd out of the area Fri afternoon
and evening as the main trof ejects into the Plains. Some precip
shud linger into Fri evening across ern portions of the CWA, but
the threat of precip shud shift east fairly quickly.


.LONG TERM...  (Friday Night through Next Thursday)
Issued at 354 PM CDT Thu May 17 2018

Mdls are in fairly good agreement with a wrmfnt lifting north
through the area Sat morning. With fairly good moisture
convergence associated with this fnt, believe a round of storms is
possible Sat morning across far wrn portions of the CWA. This
threat shud diminish thru the morning, but return across much of
the CWA during the afternoon hours with peak heating. Mdls keep
the warm sector capped, tho differ on placement of the wrmfnt
during the afternoon hours. Have kept some low PoPs during the
afternoon to account for possible isod storms.

Also have slightly higher PoPs for Sun night into Mon as a weak
cdfnt pushes thru the area that shud provide a focus for storm
development. However, mdls disagree with location of best forcing
with this as well.

With 500mb heights in the 582dam range, and a sfc boundary across
the region thru much of the forecast period, have generally
trended warm with numerous period of lower PoPs.



.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1230 PM CDT Thu May 17 2018

TSRA continue along nrn periphery of MCV tracking slowly ewd south
of the area. Believe TSRA will slowly expand/propagate newd this
afternoon. Better chances remain south of KSUS/KCPS, however,
still cannot rule out TSRA impacting these terminals. As upper low
remains over the region tonight and into Fri morning, lower cigs
are expected to move into the area from the east, impacting
KSUS/KCPS early Fri morning. Confidence on the trends for these
lower cigs is somewhat low and therefore kept in going TAF.

SPECIFICS FOR KSTL: Believe bulk of TSRA will remain south of the
terminal, but cannot rule out a stray storm impacting the terminal
this afternoon. Otherwise, MVFR cigs expected to move into the
area early Fri morning. Somewhat low confidence in these cigs and
may need to be adjusted with future updates.



Saint Louis     64  79  64  88 /  40  40  10  20
Quincy          60  76  60  83 /  10  20   5  10
Columbia        59  79  61  85 /  50  30   5  20
Jefferson City  59  80  61  87 /  60  30   5  20
Salem           64  76  62  85 /  50  50  30  20
Farmington      60  75  59  86 /  60  40  10  20




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