Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 150422

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1122 PM CDT Mon Oct 14 2019

Issued at 937 PM CDT Mon Oct 14 2019

Previously stalled surface frontal boundary just south of I-70 is
beginning to advance northward as a warm front along with the low
level jet also beginning to take shape in western MO. Later
tonight this low level jet and warm front should ignite a few
showers and thunderstorms, probably after 3am, with what looks to
be sporadic development possible through mid-morning Tuesday.

A brief interlude should then result during the late morning hours
before what should be "the main show" gets going around midday
ahead of what will be an advancing cold front for areas near and
south of I-70. More recent model runs have suggested better
coverage of precipitation and have slipped some areas of likely
PoPs in there for portions of southeast MO and southern IL with
the possibility of this expanding further north towards the STL
metro area if this trend continues. Otherwise, precipitation will
end within a couple hours of cold FROPA as cooler/drier air spills
in behind gusty NW winds.



.SHORT TERM...  (Through Late Tuesday Night)
Issued at 243 PM CDT Mon Oct 14 2019

Weak cold front has stalled out just south of St. Louis metro area
today. In the meantime, models still indicating upper level trough
over Northern Plains will continue to deepen as it tracks to the
east towards Great Lakes region. This trough will drag associated
surface cold front towards forecast area with it entering
northwestern MO after 06z Tuesday. Ahead of cold front, stalled
frontal boundary will become a warm front and lift northward
allowing southeast to south winds to return as well as some low
level moisture. Some weak lift on nose of LLJ associated with this
warm front so will see scattered showers and possibly a few storms
develop late tonight, mainly over portions of northeast MO and west
central IL.

After 12z Tuesday, main cold front will begin to slide through
region with increasing chances of showers and storms, especially
Tuesday afternoon through evening from the St. Louis metro area and
points to the south and east. Front will exit region by 06z
Wednesday with surface ridge building in. Winds will pickup from the
northwest behind the frontal boundary with gusts up to 25 mph at

As for temperatures, they will be a bit above normal tonight in the
upper 40s to mid 50s. On Tuesday, another mild day in store with
highs in the mid 60s to mid 70s. Once front moves through Tuesday
night, lows will dip down into the upper 30s to low 40s.


.LONG TERM...  (Wednesday through Next Monday)
Issued at 243 PM CDT Mon Oct 14 2019

With decent northwest flow aloft and surface ridge building into
the region on Wednesday, it will be another cold fall day with highs
only in the 50s, about 10 to 15 degrees below normal.

Wednesday night the surface ridge will begin to slide off to our
east with upper level ridge building in. This will allow southerly
winds to return to the region with warming conditions through the
last part of the work week and into next weekend.

Otherwise, extended models continue to indicate an upper level
trough over the western U.S. will deepen and lift northeastward,
dragging a cold front through forecast area Friday night and
Saturday with slight chances of showers and storms. An even more
robust system is possible for last half of weekend and into early
next week with more rain expected.



.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1122 PM CDT Mon Oct 14 2019

VFR conditions, dry weather, and SE surface winds less than 10kts
will yield to a few SHRA/TSRA developing towards daybreak and an
expanding field of MVFR CIGs around and just after sunrise. A low
level jet around 40kts is taking shape with a base height near
1300ft and should set up over KUIN-KCOU for most of the overnight
period resulting in LLWS there. This low level jet will also aid
in development of isolated SHRA/TSRA late tonight and into early
Tuesday morning but probs are low enough with this currently to
preclude mention in the TAFs. Following dissolution of the low
level jet around daybreak Tuesday, low stratus clouds are expected
to overspread the region and affect all TAF sites. Currently,
these clouds should be MVFR category and linger for most of the
daytime on Tuesday until a few hours after cold FROPA. Speaking
of, a cold front is expected to drive through the TAF sites during
Tuesday afternoon, starting with KCOU around midday and the STL
metro sites around 21/22z. SE surface winds will veer to SW during
Tuesday morning and shift W-NW to NW behind the cold front later
on Tuesday with gustiness developing especially with FROPA.
Another round of SHRA/TSRA expected mainly for STL metro sites
mainly within a few hours of FROPA and have maintained VCSH for





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