000
FXUS63 KSGF 130552 AAA
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1152 PM CST Thu Dec 12 2013

...Update to Aviation Section...

.UPDATE...
Issued at 947 PM CST THU DEC 12 2013

Near term forecast updated to account for rather wild fluctuations
in hourly temperatures. Snow cover, wind and incoming clouds will
continue to play havoc with temperatures the rest of tonight.

Concerning the forecast for tomorrow, incoming NAM and latest
RUC/HRRR suggest that precipitation onset may be delayed a few
hours Friday morning as compared to the going forecast. The very
dry 00 UTC raobs from KSGF/KLZK/KSHV/KOUN do lend credence to a
slightly slower onset. The NAM and RUC continue to be more
aggressive with the warm nose with this system versus its global
model (GFS/Euro/GEM) counterparts. With such a dry airmass in
place will come rather substantial wet bulbing potential, thus am
not buying off on the strength of the warm nose in the NAM/RUC.
Thus, other than a slight delay in onset, precipitation type
expectations have not changed. Snow, sleet and rain/freezing rain
(dependent upon surface temperatures) are all plausible Friday
and Friday night. Surface temperatures will remain very, very
tricky tomorrow. Again, wet bulbing will have a big affect on
readings through at least the morning hours. Most locations will
be a few degrees either side of the freezing mark, with localized
cooler spots in the area terrain. Full forecast update will be
provided when GFS/Euro/GEM are available for investigation.

&&

.SHORT TERM...(This Evening through Saturday)
Issued at 245 PM CST THU DEC 12 2013

A complex forecast the next 48 hours as a storm system tracks
across the region bringing a wintry mix.

A shortwave trough now over the Baja California region will track
northeast toward the Ozarks Friday. Clouds will be on the increase
later tonight as the associated moisture plume streams
northeastward.

A jet streak and accompanying lead disturbance will impact the
region beginning Friday morning. The Ozarks will become favorably
positioned within a coupled jet structure to promote strengthening
synoptic scale lift. This will result in a rapid development and
expansion of precipitation as early as day break and more so
during the morning hours Friday.

Progged low level thermal profiles suggest that precipitation
will begin as a wintry mix in the form of freezing rain and sleet.
Existing cold surfaces and potential of moderate precipitation
rates will likely lead to rapid deterioration of road conditions
Friday morning.

Temperatures will slowly rise Friday with readings rising above
the freezing mark from southwest to northeast. Most locations west
of Highway 65 will rise above freezing by midday while freezing
temperatures and wintry mix linger into at least early afternoon
east of Highway 65 into the eastern Ozarks. Just how long
temperatures remain below freezing will have to monitored closely.

The uncertainty on the exact precipitation type and duration lead
to questions on the exact amount of ice accumulation. At this time
generally expect a few hundredths to near one tenth of an inch ice
accretion.

The shortwave trough will push across the region Friday night
bringing a continuation and even an increase in precipitation
Friday evening. Meanwhile temperatures will slowly settle back
down toward freezing. Expect a wintry mix to expand across the
eastern Ozarks and also spread south across the remainder of the
area. Expect precipitation to transition to a mix of snow and sleet
before diminishing later Friday night. Light snow accumulations are
expected Friday night mainly across central Missouri and the
eastern Ozarks where an inch or two of snow accumulation is
expected.

Areas and perhaps widespread freezing drizzle is expected to develop
late Friday night into Saturday morning. This could result
hazardous travel conditions through Saturday morning.

Temperatures will rise little Saturday with all precipitation
ending during the afternoon.

With the expectation of winter precipitation a Winter Weather
Advisory will be issued from Friday morning into Friday night for
most of the Missouri Ozarks generally east of Interstate 49. The
most impacted area from this event will be along and east of the
Highway 65 corridor. Exact ice and snow accumulations remain
somewhat uncertain and the latest weather information should be
monitored.

.LONG TERM...(Saturday Night through Thursday)
Issued at 230 PM CST THU DEC 12 2013

A Canadian surface high pressure will move in for Saturday night
into early Sunday morning. Temperatures will be coldest with lows
down into the middle to upper teens especially over the higher
terrain of the Ozark Plateau and if any snow cover still remains
on the ground by that time.

Southerly to southwesterly winds will begin on Sunday on the
backside of the surface high. Sunday will remain chilly and below
average but sunny. Temperatures will rebound nicely by the early
part of next week back to more seasonable weather. The upper level
flow will try to flatten somewhat for the middle of next week.

Another weak and dry front will pass through early on Tuesday but
no real temperatures differences expected on either side of the
boundary. A dry and seasonable weather looks to stay around for
the early and middle portion of next week with possibly some
significant weather changes just beyond the 7 days toward the end
of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1152 PM CST THU DEC 12 2013

Very messy and complex forecast for the next 24 to 36 hours.
Please refer to the short range discussion aloft for the explicit
details regarding the dynamics of this system and the temperature
profiles that will dictate a variety of precipitation types. The
forecast bottom line is that conditions will remain quiet through
tonight. Precipitation will move in from the southwest during the
daylight hours of Friday morning and continue in an on again/off
again fashion through Friday night. All precipitation types are
possible Friday...starting at a mix of freezing rain/sleet/snow
changing to rain/sleet/snow as surface temperatures rise above
freezing by a few degrees. Any flight restrictions will initially
be tied to visibility (MVFR). As the afternoon progresses,
ceilings will lower to low end MVFR. As the core of the system
passes over the region Friday night, a swath of snow will develop
over a portion of the region, with better chances of affecting
SGF/BBG. Widespread IFR visibility and ceilings are expected (LIFR
is plausible). A transition to freezing drizzle is expected just
beyond the end of the TAF cycle with IFR continuing.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY from 6 AM Friday to 6 AM CST Saturday
     FOR MOZ055>058-066>071-077>083-089>092-094>098-102>106.

KS...NONE.
&&

$$

UPDATE...Gagan
SHORT TERM...Foster
LONG TERM...Griffin
AVIATION...Gagan