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000
FXUS63 KSGF 040540
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1140 PM CST Tue Dec 3 2013

.SHORT TERM...(This Evening through Wednesday)
Issued at 101 PM CST TUE DEC 3 2013

Mild temperatures again prevailed across the Ozarks and Osage
Plains Tuesday afternoon under increasing sunshine. Stratus
lingered across portions of eastern Kansas and the eastern Ozarks.

One more relatively mild night is in store as southerly winds
persist ahead of a cold front that will surge southward across the
Plains.

Stratus and fog will again develop tonight as low level warm air
and moisture advection continue and supported by progged hydro
lapse rates. Areas of dense fog will again be possible.

Patchy to perhaps areas of drizzle will likely develop across
south central Missouri late tonight into Wednesday morning where
isentropic upglide will develop on the 295K layer.

The cold front will enter far southwestern Missouri Wednesday
morning and push across the Missouri Ozarks during the day.
Temperatures will be very mild ahead of the front with highs
reaching the lower and even middle 60s across the eastern Ozarks.

Temperatures will fall following the frontal passage with readings
falling into the 30s across southeastern Kansas and far
southwestern Missouri by mid to late afternoon.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 101 PM CST TUE DEC 3 2013

Confidence continues to increase in the potential for accumulating
wintry precipitation Thursday and Friday, with the chance for
another round of light to moderate snow on Sunday also increasing.
The biggest forecast challenge remains precipitation type and
associated accumulations Thursday and Friday.

Arctic air should be spreading south into the region Wednesday
night, with temperatures falling into the 20s by Thursday morning.
Latest model trends have been a bit slower with onset of
precipitation Thursday.  This appears to be due to both a slightly
slower evolution of the overall pattern Thursday morning, as well as
some mid level dry air that will need to be overcome.  Right now, it
appears that ascent will increase considerably during the morning
hours Thursday as a strong jet increases aloft across the region.
By Thursday afternoon, guidance is in good agreement in developing a
subtle coupled jet across the region, with two 140 KT jet maxes at
250 MB, the first located over Iowa and the Great Lakes, and the
second over the Southern Plains.  Thus, the forecast area appears
likely to be within the right entrance and left exit regions of the
two jet streaks, resulting in fairly deep ascent aloft. In
addition, a weak shortwave in the mid levels should move through
the area as well, providing additional lift Thursday and Thursday
evening.

With deep ascent over the region, precipitation will begin fairly
rapidly once the dry air is overcome.  The heaviest axis of
precipitation should be south of I-44, closer to the frontal
boundary and associated mesoscale processes.  Right now, believe the
front will be far enough south for the strongest mesoscale lift
associated with mid level frontogenesis will be just south of the
SGF CWA.  We will need to watch this axis of heavier precipitation
closely however over the next day or two.

Precipitation type Thursday remains a challenge, given the overall
complex scenario and continuing differences among various pieces of
model guidance.  Have strongly trended the forecast toward the
consensus of the GFS, ECMWF and GEM, which all paint a scenario of
mainly snow north of I-44, a mix of snow and sleet along the
greater I-44 corridor (which should then transition to all snow by
early Thursday evening) and a mix of snow, sleet and freezing rain
across southern and south central Missouri. The outlier model
continues to the NAM, which maintains the warm nose much further
north. Given the strength and depth of the arctic air mass moving
south and the lack of strong, focused warm air advection within
the 925-850 MB layer, have a hard time believing that temperatures
aloft will stay so warm so far north. In addition to the
precipitation type issues within the NAM due to the warm nose,
believe the further north frontal position is also responsible for
the much higher QPF amounts, resulting from the strongest axis of
F-gen and some mid level instability remaining north over the
area.

By Thursday night, all precipitation should change over to just
snow as the cold air builds further south and any remaining warm
nose is eroded.  During the overnight hours Thursday night into
early Friday, the upper jet will strengthen, with a 160 KT jet core
stretching from central Missouri into the Great Lakes.  Ascent from
the right entrance region of this jet, along with lift from another
mid level shortwave moving northeast from the Southern Plains, will
result in another round of precipitation--all snow--late Thursday
night into the day Friday.

By the time precipitation ends Friday afternoon, snowfall amounts at
this time look to be in the 2-5 inch range, with a few localized
areas perhaps touching 6 inches.  Some sleet will also be mixed in,
especially along and just south of the I-44 corridor.  A glaze to a
tenth of an inch of freezing rain will be possible on Thursday
across southern Missouri, with 3-5 inches of snow accumulating once
precipitation transitions to all snow Thursday night and especially
on Friday. Total accumulations, especially snow amounts, will be
highly dependent on the exact ratio of mixed precipitation.  A
longer duration of sleet will cut down significantly on snow
amounts, while less or no sleet will result in higher than currently
forecast snowfall.  Given the fact that these differences will be
dependent on a degree or two difference in temperature over a few
tens of miles, accumulation amounts are most certainly subject to
change.

With that said, the main focus at this point should be on the increasing
confidence in accumulating wintry precipitation, not specific
amounts or precipitation types at any one location.  Given the cold
air mass moving into the region and a prolonged period of wintry
precipitation, some impacts to travel are likely Thursday and
Friday.

Skies will clear out Friday evening as the main trough axis finally
swings across the region, and with very cold temperatures aloft and
high pressure at the surface, this will result in excellent
radiational cooling conditions, especially if several inches of fresh
snow cover are in place.  Lows Friday night/Saturday morning look to
drop into the single digits area-wide.  Wind chills Saturday morning
will be in the single digits below zero.

Saturday looks to be a calm but very cold day for the region, with
temperatures remaining in the low to mid 20s.  An additional round
of precipitation, most likely in the form of snow, is expected to
overspread the region late Saturday night and early Sunday, with a
few additional inches of snow possible by Sunday night.

Heading into the next workweek, guidance continues to hint at very
cold temperatures building into the area early in the week and
sticking around for a bit.  Highs Monday and Tuesday look to remain
below freezing, with single digit lows appearing increasingly likely
for Monday and Tuesday nights.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
Issued at 1127 PM CST TUE DEC 3 2013

For the KSGF/KJLN/KBBG tafs...A bit of a mess forecastwise right
now with variable ceilings and visibility over the region. In
general it looks like low clouds/stratus are lifting with mostly
mvfr conditions. However, over se KS and in south central MO and
parts of AR, IFR ceilings and/or visibility are ongoing. Am not
quite as pessimistic as the previous tafs, but will keep some ifr
conditions in toward the 10z-15z time period assuming we see some
stratus build down and advection of lower ceilings from the sse st
some point. A cold front now over the Midwest and central Plains
will surge southeast through the area between 04/18z-24z veering
winds to the nw and bringing in lower post frontal passage
ceilings.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...DENSE FOG ADVISORY until 10 AM CST Wednesday FOR MOZ055-066>068-
     077>083-088>098-101>106.

KS...DENSE FOG ADVISORY until 10 AM CST Wednesday FOR KSZ073-097-101.

&&

$$

UPDATE...DSA
SHORT TERM...Foster
LONG TERM...Boxell
AVIATION...DSA