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000
FXUS63 KSGF 050021
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
621 PM CST Wed Dec 4 2013

.UPDATE...
Issued at 615 PM CST WED DEC 4 2013

We have inserted a mention of drizzle early this evening across
portions of southwestern and central Missouri. Northwesterly winds
up the northern slope of the Ozark Plateau has been enough to
squeeze out some drizzle. We are not expected the drizzle to
persist for more than three hours or so...which is a good thing as
temperatures will approach the freezing mark around midnight. One
other tweak was to bump up cloud cover for the remainder of
tonight.

&&

.SHORT TERM...(Through This Evening)
Issued at 138 PM CST WED DEC 4 2013

A cold front was in the process of making its way east across the
region this afternoon. Temperatures ahead of the front were in the
lower 60s. Behind the front, temperatures had fallen to around 40
degrees. The cold air will filter into the region through this
evening, bringing an abrupt end to the mild weather the region has
seen over the past few days.

As the front pushes east, the rapid drop in temperatures was
allowing for the development of advection fog. Visibilities along
and just behind the front were dropping to less than a mile. The
thickest fog will remain closely associated with the front, with
visibilities improving behind the front. Some light fog and low
clouds will remain over the region after the front moves through
with winds turning to the northwest and temperatures falling
through the evening and overnight.

.LONG TERM...(Thursday through Wednesday)
Issued at 138 PM CST WED DEC 4 2013

Cold air will continue to build into the area during the overnight
hours tonight, with temperatures dropping below freezing in most
locations during the predawn hours.  By 12z tomorrow morning, expect
all but the far southeastern corner of the CWA to be below freezing,
with areas along and north of I-44 well into the mid to low 20s.

Precipitation should begin to develop during the morning hours on
Thursday, with a steady increase in both coverage and intensity from
mid morning through mid afternoon as the upper level jet intensifies
over the Midwest, with the Ozarks well within its right entrance
region.  Onset of precip appears to be a little slower, with the
heaviest activity afternoon tomorrow. With some dry air to be
overcome, especially the further north and west that one goes in
the CWA, it may take a bit for precip to reach the ground,
especially along the I-44 corridor. Once it does however, given
cold ground temps, would expect to see rapid increases on area
roadways.

Initial precipitation type remains most likely to be a mix of snow,
sleet, and perhaps a little freezing rain along the I-44 corridor,
with a mix of sleet, rain, and freezing rain across far south
central Missouri, before enough cold air builds in for a change over
the freezing rain and sleet, and then sleet and snow, and eventually
all snow by tomorrow evening.  Guidance continues to trend colder
aloft, and thus believe the vast majority of freezing rain
accumulations will remain south of the CWA.  Will continue to
advertise a glaze to tenth of an inch of freezing rain along and
southeast of an Anderson to Marshfield to Salem line.  Along with
the ice accumulations, snow/sleet accumulations should be fairly
minor during the daytime hours tomorrow, with a quarter inch to one
inch of combined snow and sleet by late afternoon.  Again, however,
it`s important to note that with cold temps in place before the
onset of precipitation, immediate accumulations and impacts are
expected tomorrow during the daytime hours.

By tomorrow evening, enough cold air should be in place to change
precipitation over to all snow for all but the extreme southeastern
portion of the forecast area.  That area should finally change over
to all snow between midnight and 3 AM.  After a relative lull in
activity during the evening hours, another wave of snow should
overspread the area as the upper jet increases in intensity and
another shortwave arrives from the Southern Plains.  Will need to
watch the Thursday night/Friday morning snow carefully for the
potential for higher accumulations that what is currently forecast,
given the potential for much higher than usual snow to liquid ratios
due to the very cold temperatures.  For this forecast, generally
used a 13:1-17:1 ratio, depending in temperature. In addition to
SLR issues, cross sections indicate the potential for some lower
static stability and possible development of slantwise convection,
especially if an axis of mid level frontogenesis develops far enough
north to tap into the CSI.  Snow should end during the day Friday as
the mid level wave swings through.

Once all is said and done Friday evening, storm total snow
accumulations should range from 1-3 inches north of I-44, 2-5 along
the greater I-44 corridor, and 4-6 inches across southern and south
central Missouri.  A glaze to tenth of an inch of freezing rain will
also be possible Thursday across south central Missouri.

With heavier accumulations and more substantial mixed precipitation
across southern/south central Missouri, will go ahead and upgrade
the Winter Storm Watch area to a Winter Storm Warning.  North of the
Warning, a Winter Weather Advisory will be issued as far north as
roughly U.S. 54. The main impact for this event will likely be to
roadways/travel, especially considering what should be almost
immediate accumulations once precipitation begins on Thursday.

Friday night and Saturday look to be dry across the region, as very
cold and dry air builds into the area.  Temperatures Friday night
will fall into the single digits, especially with fresh snow cover
in place.  Highs Saturday will only warm into the low to perhaps mid
20s.

Another wave of precipitation will overspread the area Saturday
night into Sunday, most likely in the form of snow.  A few
additional inches of snowfall will be possible with this system. The
majority of this activity looks to end by Monday morning.

After relative "warmth" in the upper 20s on Sunday, the coldest air
in nearly two and a half years will overspread the area for Monday
and Tuesday.  For now, highs both days look to be in low 20s, with
low temperatures in the single digits, approaching zero.  It is
worth noting that some guidance does bring in even colder readings,
with the possibility of later forecasts taking low temperatures
below zero Monday and Tuesday mornings in some spots.  Much will
depend on snow cover both here and to our north, so this will
certainly be something to keep an eye on over the next few days.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 542 PM CST WED DEC 4 2013

A band of IFR ceilings and light fog will push east across
southern Missouri early this evening behind a passing cold front.
Flight conditions are then expected to improve later this evening
with surface winds increasing out of the northwest. A storm system
will then bring deteriorating conditions to southern Missouri on
Thursday. A band of mixed wintry precipitation will develop across
the region. At this time, the most widespread precipitation is
expected around Branson, where a mixture of freezing rain and
sleet will transition to sleet and snow from Thursday morning into
Thursday afternoon. Springfield will be on the northern edge of
this precipitation with a sleet and snow mixture changing to all
snow from late morning into the afternoon. IFR visibilities can be
expected with snow. At this time, it appears that most of the
precipitation will remain just south of Joplin. We have therefore
elected to only carry a TEMPO group for light snow.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WARNING from 9 AM Thursday to 6 PM CST Friday FOR
     MOZ095>098-101>106.

     WINTER WEATHER ADVISORY from 9 AM Thursday to 6 PM CST Friday
     FOR MOZ057-058-069>071-077>083-088>094.

KS...WINTER WEATHER ADVISORY from 9 AM Thursday to 6 PM CST Friday
     FOR KSZ097-101.

&&

$$

UPDATE...Schaumann
SHORT TERM...Hatch
LONG TERM...Boxell
AVIATION...Schaumann