Area Forecast Discussion
Issued by NWS St. Louis, MO

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992
FXUS63 KLSX 192237
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
537 PM CDT Sat May 19 2018

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 312 PM CDT Sat May 19 2018

Ongoing convection is expected to continue east and may produce
marginally severe hail and/or winds. Behind this area of
convection, airmass has been able to rebound already with 3000
J/kg of MUCAPE already over far SW MO.

The time line is subject to change, but believe ongoing
convection over srn KS/nrn OK will continue ENE along the wrmfnt.
These storms shud reach wrn portions of the CWA around 9 to 10 pm
and will potentially be severe with a hail and wind threat. Expect
more development further north into KS that shud also track into
nrn portions of the CWA. These storms may also be severe either
given the amount of elevated CAPE that shud be available. These
clusters of storms shud quickly move thru the CWA overnight.

The convection this evening increases uncertainty for how things
will evolve late tonight into Sun morning. However, latest
guidance suggests yet another round of storms entering wrn
portions of the CWA around sunrise Sun. The 18z NAM suggests that
the morning convection may be a repeat of today, which is
possible. Unfortunately, with the numerous sfc boundaries that may
be present, confidence is somewhat low and have kept PoPs on the
somewhat low side with questions in timing. With the weak sfc low
traveling across the nrn portions of the CWA, still believe storms
are likely across the nrn half of the CWA during the afternoon and
into the evening. However, going forecast for the morning hours
may be too low. Given the amount of CAPE as well as deep layer
shear available thru the day Sun, any of these storms may be
severe.

Tilly

.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 438 PM CDT Sat May 19 2018

With the cdfnt pushing thru the area on Sun night, have lower
chances of precip on Mon with slightly cooler temps. However, with
500mb heights around 582dam, still expect rather warm temps to
quickly return to the area and persist thru next week.

Mdls are in generally good agreement with the overall pattern
thru the week. That said, no one period looks dry with some
differences in timing/placement. Have kept PoPs going off and on
across the area thru the extd forecast.

That said, have trended warmer late next week with upper ridge
building into the area. Have also trended twd higher PoPs late
next week with good moisture return and an approaching upper trof.

Tilly

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 502 PM CDT Sat May 19 2018

Scattered convection across west central and southwest MO along a
warm front will move into COU this evening and eventually into
the St Louis metro area by late evening and possibly into UIN as
well. A second round of convection may move into COU and the St
Louis metro during the morning hours and into the afternoon ahead
of a surface low and trailing cold front. Conditions should be VFR
outside of the thunderstorms. Surface winds will be somewhat
chaotic due to numerous thunderstorm outflow boundaries across
the area, but generally southeasterly tonight then shifting to a
westerly direction Sunday morning.

SPECIFICS FOR KSTL: Scattered convection across west central and
southwest MO along a warm front will move into STL by late
evening. A second round of convection may move into STL during
the late morning hours and into the afternoon ahead of a surface
low and trailing cold front. Conditions should be VFR outside of
the thunderstorms. Surface winds will be somewhat chaotic due to
numerous thunderstorm outflow boundaries across the area, but
generally southeasterly tonight then shifting to a westerly
direction Sunday morning.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     69  89  67  84 /  40  40  50  20
Quincy          62  81  61  77 /  70  60  50  10
Columbia        64  84  62  79 /  60  30  40  10
Jefferson City  65  86  63  81 /  60  30  40  10
Salem           67  88  65  84 /  40  40  50  30
Farmington      66  87  63  83 /  30  40  40  30

&&

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

$$

WFO LSX



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