Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 171713
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1113 AM CST Wed Dec 17 2014

.UPDATE:
Issued at 1023 AM CST Wed Dec 17 2014

Updated forecast to account for less cloud cover this afternoon
across a good majority of the CWA. Boosted temperatures a few
degrees as well. Otherwise, forecast remains on track for later
this evening, tonight and Thursday morning with a quick hitting
shot of accumulating snow.

CVKING

&&

.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 18z TAFs through 18z Thursday Afternoon)
Issued at 1109 AM CST Wed Dec 17 2014

The stratus continues to scatter across Illinois this morning with
much of the area seeing clear skies across the southeast portion
of Missouri ahead of the next weather system. Snow still expected
to spread from KS and western MO into central MO near or just
after midnight, with flight conditions lowering to IFR several
hours after the onset. Snow should spread into the St. Louis area
in the 10-11z time frame. The snow will taper off to flurries or
drizzle Thursday afternoon. Minor if any accumulation will occur
on runways thanks to relatively warm surface (road) temperatures.

Specifics for KSTL:

VFR conditions and light winds expected into the evening hours as
high pressure dominates the area. Snow is expected to spread
northeast from central and southern MO into the terminal around
10-11z, with flight conditions lowering to IFR by 15z Thursday.
Improving visibility is expected after 17Z with IFR ceilings
continuing in the wake of the storm.

CVKING

&&

.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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