Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 290543

1143 PM CST SAT NOV 28 2015

Issued at 930 PM CST Sat Nov 28 2015

Somewhat nebulous precip threat over the CWA this evening as AMS
certainly remains saturated, but lifting mechanisms are weak and
rather ill-defined. There does appear to be two potential areas of
somewhat stronger ascent...the first is over southern sections of
the CWA, where several minor shortwaves appear to be embedded in
the strong westerlies. The second area is currently over nw MO,
where weak WAA into 850 baroclinic zone appears to be aiding
precip. In between, rain threat will likely be limited to some
drizzle or very light rain/sprinkles.

Just getting a look at some of the new 00z data, and it
would appear that the aforementioned WAA over nw MO will be
working into northern sections of our CWA by tomorrow morning.
Therefore, have allowed some low chance pops associated with this
lift to work into northern sections of the CWA after midnight
tonight, and have maintained this threat into the morning hours.

Temps in our far northwest counties would suggest a threat of
frozen precip during the predawn hours if the precip does reach
this area. Don`t think this would be a big deal given warm ground
temps and what should be a rather brief period of time temps will
be below 32, but will certainly continue to monitor.



.SHORT TERM:  (Through Late Tonight)
Issued at 255 PM CST Sat Nov 28 2015

Although the cold front has pushed well south-southeast of
our forecast area, extending from southern AR northeast into
southern OH, will continue to get waves of mainly light rain moving
through at least parts of southeast MO and southwest IL tonight as
weak west-southwest flow shortwaves continue to move through the
region ahead of the upper level low over the Rockies. The models
were depicting upper level divergence over our region well ahead of
the upper level trough or low.  There may also be some patchy
drizzle across our area tonight from the persistent low level
stratus cloud deck.  Temperatures should be warm enough that the
precipitation will fall as liquid rain, although could not rule out
a little light freezing rain or drizzle across parts of northeast MO
late tonight.  May be a little erosion of the low level cloud deck
across parts of northeast MO and west central IL due to drier air
advecting in from the north on the southern periphery of the surface
ridge moving eastward through the northern Plains. There should
still be mid-high level cloudiness across this area. With continued
cloud cover the model MOS low temperatures tonight look a little too
cool and went just above guidance for minimum temperatures for most


.LONG TERM:  (Sunday through Next Saturday)
Issued at 255 PM CST Sat Nov 28 2015

(Sunday - Monday)

As the wound-up western CONUS storm begins to stir eastward, the
pattern over our region remains status quo thru Sunday night, with an
active southwest flow aloft and additional disturbances tracking
thru, overrunning moisture well to the north of the old surface
boundary at times in a light pcpn "flare-up".

One of these such "flare-ups" will be later in the day on Sunday and
into Sunday night.  The models are showing the initial outbreak of
rain to be in central MO by early afternoon with it then expanding
mainly to the north from there but the atmosphere and synoptic setup
is such that it will be hard to go completely dry in other areas.
Bumped PoPs to likely for areas north and west of STL metro, with
low chances elsewhere.  QPF looks to be light for areas that do get
pcpn, with up to one-quarter inch liquid equivalent possible.

The influence of the main storm system center itself will be felt on
Monday and Monday night as an upper level disturbance rotates around
the southern periphery of what should still be a closed LOW as it
tracks to our north.  This will combine with what will initially be
an occluded front passing thru, with a cold front shortly after.

A more widespread rain event should result on Monday and perhaps
into Monday evening, but the best rainfall amounts will once again
be found over areas north and west of STL metro where the better
upper level support will reside.  Up to a third of an inch of
liquid equivalent will be possible from this event.

P-types throughout this period should be entirely rain with vertical
temp profiles strongly supportive of liquid falling, and surface
temps should remain above freezing when any pcpn is falling.  Too
early in the season to worry about cold surfaces influencing things.

With extensive cloud cover anticipated, favored daytime max temps at
or below the coldest MOS; conversely preferred nighttime min temps
at or above the warmest MOS.

(Tuesday - Next Saturday)

Models in better agreement throughout this period than they were
yesterday, with major items worked out.  Wound-up storm begins the
period to the north and pulling away, with NW flow aloft thru
Thursday and an ill-defined and weak shortwave that passes thru a
moisture-starved column on Thursday, showing preference for the EC
solution from yesterday.  Ridging aloft then takes hold for late
week.  No signs of any significant cold air intrusions thru this
period, with seasonable to above average temps preferred by mid-late

This will all combine with westerly surface flow thru Thursday,
becoming southerly Friday and Saturday.  With strong influence from
high pressure throughout, this will favor a dry forecast for a

One interesting item of note, depending on how fast the cooler air
builds in on Tuesday, could see temps reach the mid 50s in spots
thanks to anticipated deep mixing from WSW flow.  After a brief
cooldown from there Wednesday and Thursday, could very well see
temps make a run on 60F by week`s end.



.AVIATION:  (For the 06z TAFs through 06z Sunday Night)
Issued at 1129 PM CST Sat Nov 28 2015

IFR/low MVFR ceilings will continue to prevail along and south of
the I-70 corridor for the rest of the night. The three TAFs in the
STL Metro area look to remain right on the edge all night, but
current thinking is that ceilings below 1000 FT will creep back
north before sunrise. An area of light rain will affect parts of
the region on Sunday...not sure exactly where it will end up, but
best chances still look over central and northeast MO as well as
west central and parts of southwest IL. Ceilings will be highly
dependent on areal coverage and intensity of rain...tho generally
speaking I expect higher ceilings (VFR/MVFR) over central/west
central IL, with lower ceilings across central through southeast
MO and southern IL.

Specifics for KSTL:

Ceilings around 1000 ft will prevail at Lambert for the rest of
the night into Sunday morning. Think it likely that the ceiling
will dip into IFR territory at some point before sunrise, though
I`m uncertain as to exactly when. There is a chance for some rain
by mid to late morning, tho I did not mention it in the TAF
because current thinking is that most of the rain will stay
west/northwest of the terminal. Ceilings should improve during the
late morning/early afternoon, but I think it unlikely the ceilings
will get above 2000 ft until later in the period.





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