Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 170959
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
359 AM CST Wed Dec 17 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 354 AM CST Wed Dec 17 2014

Surface ridge overhead today. SC deck to finally scatter out over
most of forecast area this morning. However, mid and high clouds
beginning to stream in ahead of next weather system. Winds will be
lighter today with highs in the 30s.

Byrd

.LONG TERM:  (Tonight through Tuesday)
Issued at 354 AM CST Wed Dec 17 2014

Upper level shortwave to slide northeast towards forecast area
tonight. So will see warm advection increase tonight with light snow
developing over southwestern Missouri and spread northeast into
forecast area. However, there is a lot of dry air to overcome and it
will take some time for snow to make progress to the northeast. It
should move into central and southern MO by 06z Thursday, towards
12z Thursday for STL metro area and by midmorning for areas to the
north and east. So it will be a rather quick shot of snow with
highest amounts, between 1 and 2 inches, along and south of a Columbia
to Farmington line, with lesser amounts to the north. Fortunately air
temperatures will be near freezing and ground temps are still
relatively warm, so most of the accumulations will be on grassy
surfaces and elevated objects. Could still cause some messy road
conditions in central and southern Missouri, so will issue a
winter weather advisory for this area from 06z Thursday to 16z
Thursday. By Thursday afternoon, upper levels dry out, losing ice
crystals, so could see some light drizzle as system exits.
Temperatures over far northern portions of forecast area could be
near freezing, so some light freezing drizzle possible.

Surface ridge builds back in Thursday night with dry weather
returning to the region. However, another system to slide through
region Friday night with main energy well south of forecast area. We
will remain on the cold side of system with overrunning
precipitation developing which could reach as far north as I-70
corridor. Could see a brief mix of light rain and snow over southern
portions of forecast area Friday evening before changing over all
snow. System exits region rather quickly as upper trof lifts it
northeast towards great lakes region. Precipitation tapering off by
Saturday morning.

Beyond that, surface ridge moves off to the east by Sunday allowing
southerly winds to return to the region once again. Temperatures to
moderate through the first part of next week with highs in the 40s.
Another system to move in by Monday, but with temps above freezing
should be in the form of rain through Tuesday.

Byrd
&&

.AVIATION:  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1128 PM CST Tue Dec 16 2014

MVFR ceilings will soon clear out of KCOU, but will likely remain
in KUIN and the St. Louis metro TAF sites through 12-14Z based on
the latest satellite trends. There is still some possibility that
additional MVFR ceilings will move south in KCOU between 06-12Z
and will monitor over the next few hours. Otherwise expect mainly
dry and VFR conditions from mid morning Wednesday through at
least 00Z. Then another storm system will approach the area from
the southwest and bring a chance of snow to KCOU before
06Z...though uncertainty is too high at this point to include in
the TAF at this time. Accumulations before 06Z at KCOU are
expected to be light.

Specifics for KSTL: MVFR ceilings will likely hold through 12-14Z
based on latest satellite trends. Then dry and VFR conditions are
expected with winds becoming light and variable as high pressure
moves across the area. Then a storm system will approach the area
late in the period with light snow developing at the terminal
after 06Z, with MVFR or IFR conditions possible after 12Z.

Britt
&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...WINTER WEATHER ADVISORY from Midnight tonight to 10 AM CST
     Thursday FOR Boone MO-Callaway MO-Cole MO-Crawford MO-
     Gasconade MO-Iron MO-Madison MO-Moniteau MO-Osage MO-
     Reynolds MO-St. Francois MO-Washington MO.

IL...NONE.
&&

$$
WFO LSX






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