Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 291133
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
533 AM CST Tue Nov 29 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 332 AM CST Tue Nov 29 2016

Focus thru this period will be temps.

Stacked low continues to slowly move ewd over the nrn Plains this
morning. A secondary sfc wave is developing over srn KS/nrn OK along
the cdfnt. This low will pull newd today, keeping the CWA under
rather strong WAA thru the afternoon.

While the going forecast contains a substantial amount of cloud
cover thru the day, those clouds will be mid to high clouds with
breaks expected. This shud allow some insolation. In addition,
forecast soundings suggest the region will mix to around 900 mb.
Have therefore trended twd the warmest guidance for today.

For tonight, with the cdfnt moving thru the region, have generally
trended cooler. However, with continued mixing expected overnight
and some cloud cover, generally used a consensus.

As for precip chances, some mdl solns are suggesting light precip is
possible across the ern portions of the CWA this afternoon. There is
some enhanced low level moisture convergence associated with a s/w
ejecting ahead of the approaching cdfnt. However, guidance suggests
this wud be falling from a mid deck with rather dry levels below.
Have therefore kept the forecast dry for now, but will need to
monitor for including sprinkles in future updates.

Tilly

.LONG TERM...  (Wednesday through Monday)
Issued at 332 AM CST Tue Nov 29 2016

Forecast area to remain in cyclonic flow as system over Great Lakes
slowly slides to the east. So will see gusty west winds on Wednesday
with wrap around clouds on the increase. Highs will be near normal
in the 40s.

By Thursday, weak surface ridge builds into the region with partly
to mostly sunny skies. Weak CAA, so temps will not dip too much for
the last part of the work week, as highs will remain in the 40s each
day.

In the meantime, system over the southwestern US will continue to
strengthen. Extended models still have timing and placement
differences on how to handle this system. Leaning more towards GFS
solution as it has been the most consistent. First in a series of
shortwaves to lift east northeastward towards region by Saturday
night and remaining just south of forecast area, trying to phase
with a northern stream shortwave. So precipitation will be on the
light side, but with temperatures dipping below freezing Saturday
night and Sunday night, will see rain during the day, then a
rain/snow mix, possibly changing to mostly light snow for brief
periods each night. By Monday entire system begins to lift northeast
out of southwestern US, as a stronger northern stream system
approaches forecast area. Will have another round of precipitation
moving in by late in the day on Monday.

Byrd

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 524 AM CST Tue Nov 29 2016

Area of IFR cigs currently over SE MO and srn IL is expected to
move newd and shud remain just east of KCPS. However, these IFR
cigs will need to be monitored as some guidance does suggest they
will move more nwd than newd. If so, these cigs shud impact
KSTL/KCPS and perhaps as far west as KSUS.

Otherwise, expect VFR and dry conditions thru the TAF period. Cigs
shud lower to around 12 kft late this morning into the afternoon.
Winds will become wly behind an approaching cdfnt.

Tilly

&&

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

$$

WFO LSX



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