Area Forecast Discussion
Issued by NWS St. Louis, MO

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318
FXUS63 KLSX 141201
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
601 AM CST SUN FEB 14 2016

.SHORT TERM:  (Through Late This Afternoon)
Issued at 417 AM CST Sun Feb 14 2016

Focus will be precip today.

Overall, not a lot has changed with the forecast for today. What has
changed is increased amount of IP expected across the srn portions
of the CWA. Expect precip to begin as IP across srn portions of the
CWA, with cooling expected later in the morning as the trof arrives.
Area of precip over ern KS is expected to reach cntl MO around
sunrise and also expected to begin as IP. However, as it moves ewd,
the area of precip shud expand nwd, but be largely SN further N.
This transition from IP to SN is expected to occur along the CWA
boarder.

Elsewhere, SN is expected to overspread the region this morning and
quickly move ewd. Latest indications are that the bulk of the SN
will fall in a window of only a 3 or 4 hours, but will have high
snowfall rates for at least a couple of those hours.

Precip shud be exiting the ern portions of the CWA early this
afternoon. Expect areas of FZDZ to develop as the SN comes to an end
this afternoon. Exactly how expansive this area of FZDZ will be is
difficult to determine, but expect most of the region to see a light
glaze of ice.

To add to the complexity of this forecast, temps are expected to
warm to just above the freezing mark across portions of central MO
this afternoon as the clipper moves thru the region. These warm
temps will be short lived as temps are expected to drop quickly with
nightfall.

Tilly

.LONG TERM:  (Tonight through Saturday)
Issued at 417 AM CST Sun Feb 14 2016

A longwave TROF will continue to prevail over eastern North America
until the middle of this week.  This will continue the train of
disturbances, about one every 24 hours or so.

First off is tonight, with the setup for drizzle almost identical
from this afternoon lingering into the evening, with a fairly thick
deck of low stratus and weak low level convergence.  Surface temps
again look to be sufficiently cold for the drizzle to be freezing
drizzle.  This should exit by midnight

The next disturbance is currently just coming ashore over British
Columbia province and should be sampled fairly well with the next
set of raob launches in a few hours.  A good model consensus has
developed with this system, with the GFS the first to latch on to
this possibility a day or two ago, and the rest have since fallen in
line...tracking it thru northern AR and the mid-South during the
daytime Monday, placing the lift associated with it thru the entire
forecast area at some point during that day. Now the lift will not
be as strong as what we should see with the system today, but it
should still be sufficient enough to now justify adding mentionable
PoPs into the forecast.  Pcpn-types will increasingly favor liquid
over frozen types heading thru the day on Monday, but if this system
arrives early in the morning like it currently is expected, it
should still be cold enough to begin as snow.  Some very light
additional snow accums will be possible for areas in northeast and
central MO.

Temps on Monday will be tough with the track of this next clipper-
like system to effectively separate areas that warm very well (into
the lower 50s) to the right of the track of its surface reflection,
from areas that will warm very poorly to its left and likely never
get out of the 30s.  Have a large temp gradient across the forecast
area as a result, but with decent bust potential in place as well.

Another disturbance is still progged for late Monday night into
Tuesday as well, but the details associated with this continue to
shift with timing and track, and thus remains low confidence.  The
latest model consensus now tracks this more northeastward thru
southern IA and central IL and will leave much of the forecast area
in its warm sector (with temps rising well into the 40s or lower
50s) and likely dry.  The system itself is still over the Pacific
ocean and will not get sampled well until tomorrow.  Where this
system does track, it should still be sufficiently cold for mostly
snow given the more favorable diurnal timing, and should lead to
additional small snow accums for where it does track.

The models are trying to develop another (and final) weak clipper
system on Wednesday daytime, but details and confidence on this are
even more sketchy and have maintained a dry forecast for most areas
with this package.

Otherwise, look for a mainly dry forecast from Wednesday on, with
above average temps into next weekend, with what could be a very
warm day on Friday.

TES

&&

.AVIATION:  (For the 12z TAFs through 12z Monday Morning)
Issued at 527 AM CST Sun Feb 14 2016

Area of IP has developed over wrn and swrn MO and continues to
move ewd. As it does, expect cooling to occur and gradually change
to SN as it impacts COU. Any TS is expected to remain S of the
terminal this morning. SN is expected to begin at UIN by mid
morning. Both will see a brief period of SN with accumulations of
1 to 2 inches. As the SN ends this morning, expect precip to
change to FZDZ before ending by this eve.

Specifics for KSTL/KSUS/KCPS: Expect precip to begin as SN by mid
morning. SN shud fall in a brief window of only a couple of hours
before ending as FZDZ. Will need to monitor trends, but there is
some indication that FG or low stratus may develop tonight over
gradual improvement.

Tilly

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...Winter Weather Advisory until 6 PM CST this evening FOR Audrain
     MO-Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-
     Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln
     MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
     Osage MO-Pike MO-Ralls MO-Reynolds MO-Shelby MO-St. Charles
     MO-St. Francois MO-St. Louis City MO-St. Louis MO-Ste.
     Genevieve MO-Warren MO-Washington MO.

IL...Winter Weather Advisory until 6 PM CST this evening FOR Adams IL-
     Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-
     Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-
     Montgomery IL-Pike IL-Randolph IL-St. Clair IL-Washington
     IL.

&&

$$

WFO LSX



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