Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 210503

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1203 AM CDT Mon May 21 2018

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 228 PM CDT Sun May 20 2018

Still a lot of uncertainty on how to handle precip chances over the
next 24 hours. Main system to our southwest to begin lifting north
northeast through forecast area tonight. Will see additional rounds
of showers and storms develop and move through depending on how fast
the atmosphere recovers from this mornings storms. So exact timing
and placement of activity still hard to pin down, so just kept high
chance pops for the area. As for chances of severe storms, again
depends on recovery of atmosphere. As of 19z, CAPE values are back
above 1000 J/kg over southern half of Missouri, but lower and capped
further north.

By midday Monday, main cold front to exit forecast area with some
lingering activity diminishing by 00z Tuesday.

Lows tonight will be mild, in the low to mid 60s with highs on
Monday in the upper 70s to mid 80s.


.LONG TERM...  (Monday Night through Next Sunday)
Issued at 228 PM CDT Sun May 20 2018

By Monday night, system finally exits and will have dry conditions
through at least mid week as surface ridge builds in. Some
differences in timing, strength and placement with next several
systems among the extended models. So kept slight/low chance pops
from time to time through rest of extended period.

As for temperatures, to remain 5 to 10 degrees above normal through
the extended period.



.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1150 PM CDT Sun May 20 2018

Showers will continue pushing northeast through the bi-state
region tonight with embedded thunderstorms. Locally heavy rain is
possible, but thunderstorm intensity will trend downward. Expect
MVFR cigs in the 3k-5k ft range to accompany this activity. Vsby
may briefly drop below 6SM, but will become less common as the
complex weakens.

The main front remains to the west. There may be patchy areas
where cloud break, mainly near KCOU, where cigs could flirt with
IFR. Any opportunity would only last a few hours. The front pushes
east during the day with a few showers possible along the front. A
few thunderstorm could pop during the afternoon, but should be
clear of the TAF sites by the time enough heat builds to result in
afternoon storms.


Showers and thunderstorms will continue through the next couple of
hours before moving northeast by early morning. A few showers may
linger with MVFR cigs improving back to VFR through the early
morning timeframe. The main front will push through during the day
Monday. Showers are possible along the front, especially during
the afternoon. The better chances will line up east of KSTL with
quieter conditions expected through late Monday. VFR conditions
are forecast through the period. MVFR cigs should remain well
north and west of the site, barring any showers directly impact
KSTL Monday afternoon.





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