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000
FXUS63 KLSX 010001
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
601 PM CST Sat Nov 30 2013

.SHORT TERM:  (Through Late Tonight)
Issued at 322 PM CST Sat Nov 30 2013

A weak cold front extending from nwrn WI sw through cntrl KS will
move sewd to around COU and STL by 12z Sunday.  Low level cloudiness
is expected to develop and advect into at least sern MO and swrn IL
late tgt ahead of this front.  The NAM and GFS models were depicting
very light qpf over portions of sern MO late tgt.  Although I could
not rule out a little patchy drizzle in this area late tgt, this
very light qpf from the models is likely more of an indication of
stratus clouds and possibly also fog as the sfc/boundary layer
moistens, along with the light surface wind expected.  Low
temperatures tgt will be slightly warmer across sern MO and swrn IL
ahead of the cold front due to continued low level waa and increased
cloud cover.

GKS

.LONG TERM:  (Sunday through Next Saturday)
Issued at 322 PM CST Sat Nov 30 2013

(Sunday - Wednesday)

NW upper level flow will begin this period with a shortwave slated
to pass thru late Sunday night and Monday morning.  At the surface,
a cold front will pass thru Sunday and then stall over southern MO
and IL Sunday night and into Monday.  What is left of the front will
then re-advance thru our region as a warm front on Tuesday.  The
flow will then shift to out of the SW by mid-week with S surface
flow.

Lo level moisture will attempt to ride up into our area by Sunday
morning, likely resulting in a stratus cloud deck mainly S of I-70
corridor with these clouds persisting thru the day on Sunday and to
some extent, into Monday, given how we are now in that time of year
where clouds have a hard time going away once they dig in.

Cold front on Sunday is expected to go thru pcpn-free, but when it
stalls over southern MO by late afternoon, its lo level convergence
that it provides interacting with the lo cloud deck expected to
already be in place should result in some patchy drizzle toward
sundown.  This patchy drizzle probably will then continue into
Sunday night with the stalled front, giving way to more conventional
light rain with the upper level shortwave on Monday.

Temps should remain above normal thru much of this period:  a bit
cooler and closer to average with the front Sunday, continuing into
Monday, with what looks like the return of 60 degrees for Tuesday
and Wednesday.

(Thursday - Next Saturday)

SW upper level flow will dominate this period, with a powerful
Pacific storm system digging in and remaining a fixture up to our
N.  There is some decent model disagreement on where this PAC storm
ends up, and how far S and E it propagates.  The GFS is the outlier
in taking it S and E, with the EC and GEM more conservative.  Where
this storm ends up will have a lot to say about two key things:
when a strong surface arctic cold front moves thru and how long does
the precipitation linger into late week.

The GFS being the outlier has been discounted for now, but its
solution is more or less the same as the others, just a day moved
up.  Instead, the EC and GEM take the surface cold front thru
Wednesday night with cold air building in Thursday with falling
temps.  The SW upper level flow will result in an overrunning pcpn
event which will also be much slower to cool than at the surface.
Putting it all together, the initial pcpn-type will be rain, but
with the shallow cold air building in on Thursday thru Friday, will
eventually progress thru the plethora of mixed winter pcpn-types of
FZRA, PL, and finally snow before pulling out.  Fortunately, at this
time, it does not appear to be that FZRA or PL will occur for very
long until it reaches snow, but either way, it looks ugly and
something all interested parties need to keep a close eye on.

Of greater confidence is another arctic air intrusion for late week
and next weekend, where max temps may struggle to get out of the 20s
in many areas, especially if there is any fresh snowpack, with mins
potentially dipping into the single digits.

TES

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 541 PM CST Sat Nov 30 2013

Weak frontal boundary extending from northwest Wisconsin through
east-central Kansas continues to move eastward. High Pressure
extends along the eastern seaboard Light south to southwest flow
continues east the weak frontal boundary while light northwest
winds are located behind the front. Weak frontal boundary expected
to move through UIN and COU between 1000-1200 UTC and over STL
region around 1400 UTC.

Specifics for KSTL: Light south to southwest winds expected over
STL through 0900 UTC. Scattered clouds 040 kft will move
northeastward with STL as the northern edge of the cloud layer.
Scattered to broken clouds around 030 kft possible between 1100 and
1400 UTC. No visibility restrictions over STL. Possible 5 SM in
light fog for KSUS between 1000 - 1400 UTC. Scattered clouds 040
kft after 1400-1500 UTC period as weak frontal boundary continues
to move southeast.

Przybylinski


&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX