000
FXUS63 KEAX 052339
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
539 PM CST Thu Dec 5 2013

.SHORT TERM...(This Evening through Saturday Night)
Issued at 332 PM CST THU DEC 5 2013

The deep freeze is now firmly entrenched across the CWA, with
afternoon temperatures ranging from the mid teens to the lower 20s
and wind chills in the 5-10 degree range. Meanwhile, a deepening
southern stream trough located over the southern Rockies was
funneling a long plume of Pacific moisture across the Southern Plains
into the mid Mississippi Valley region. A broad band of wintry
precipitation had already developed along and south of I-44, and is
just the start of a snow and ice storm that will impact a large
portion of Oklahoma, southern Missouri, northern Arkansas and points
east through the day tomorrow.

Locally, the big question is moisture content and the approaching
trough pivots late tonight, possibly allowing deeper moisture to
retrograde northwest into the southern CWA. Currently, very dry air
persists below 10Kft, aided by strong northerly ageostrophic flow. As
a secondary area of moderate-strong large scale ascent spreads
northeast from Oklahoma by 12Z, models continue to show minor but
impacting difference with respect to the placement of forcing and
moisture depth along the northern fringes of the southern storm. The
12Z and 18Z NAM-WRF continue to trend further north, bringing .10 to
.20" of liquid QPF as far north as Harrisonville to Moberly,
translating to bulky snowfall accumulations tomorrow morning in the
2-4" range over the central MO zones. This model remains an outlier
compared to other solutions, which mute the QPF output in the short
range ensemble output as well. Surrounding WFOs, which have had some
winter weather to date, have noted the NAM`s considerably poor recent
performance with respect to top-down saturation (overdone) and thus
over forecasting of QPF. Given an air mass currently characterized by
dew points in the single digits, it would be tough to argue that the
northern edge of a sharp gradient snow band would penetrate far into
the CWA. Therefore, will keep the NAM advisory type event in the back
pocket for now and stay the course of a trace to around a 1-1.5" snow
event over the southern CWA with the bulk falling between 12-18Z.

Otherwise, bitterly cold temperatures will continue with readings
running some 20-25 degrees below normal. As skies clear tomorrow
night and winds diminish, one syllable low temps are expected (1-6
degrees) with any snow covered areas possibly dipping below zero
tomorrow night.

Very cold conditions will continue Saturday into Saturday Night, with
people "sporting" multiple layers to stay warm. Highs will maybe
reach 20 degrees with lows falling into the upper single digits to
mid teens.

.LONG TERM...(Sunday through Thursday)
Issued at 332 PM CST THU DEC 5 2013

Deep trough over the Rockies will send a weak wave into the area on
Sunday. This system still appears on track to produce a broad swath
of 0.1"-0.2" QPF amounts with the higher amounts north of I-70.
Liquid-to-snow ratios should be around 15:1, similar to what was
seen early Thursday morning, which would result in a broad 1 to 3
inches of light fluffy snow through the day Sunday. Without a
significant source of deep lift or focused mesoscale ascent,
snowfall rates should be quite light, generally under a half inch
per hour. This should keep any impacts from this system on the low
end.

The remainder of the extended looks dry as deep persistent
upper-level troughing over the central U.S. slowly transitions to a
quasi-zonal pattern by the end of the week. This will keep very cold
temps in place early next week with lows as cold as 0 to 5 degrees
Monday morning. First chance to see temperatures finally rise above
the freezing mark doesn`t look to arrive until Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 540 PM CST THU DEC 5 2013

Radar trends through the area indicate that widespread snow is
forming around 8-10 kft. Enough dry air is present below this layer
than the snow is evaporating before reaching the surface.
Observations to the south indicate that while snow is not reaching
the surface it is acting to help gradually saturate the lower
atmosphere. NAM suggests that enough low level saturation will occur
at KMCI and KMKC to warrant a mention of snow reaching the surface
early Friday morning. At this time feeling is that KSTJ will remain
north of the snow, but with it being close to KSTJ will go with a
VCSH mention of early morning vicinity snow showers. Expect a period
of MVFR CIGS as well a a potential for brief periods of MVFR/IFR
VSBY should a heavier band of snow form at or near the terminals.
Gradual improvement back to VFR is expected by 18z.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

SHORT TERM...Bookbinder
LONG TERM...Hawblitzel
AVIATION...Leighton