Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 172038
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
238 PM CST Wed Dec 17 2014

.SHORT TERM: (Through Thursday Night)
Issued at 231 PM CST Wed Dec 17 2014

Lift ahead of an approaching shortwave will bring light snow to
the area tonight and tomorrow morning. The LSX CWA will be
positioned beneath favorable upper level divergence (LER of an
upper jet), and models also show frontogenesis developing between
900-850 hPa across central and southeastern MO. Forecast snowfall
amounts are less than 2 inches across the CWA, and some locations
may not receive very much snow at all due to the initially dry
levels between approximately 900-600 hPa (per KSGF/KILX 12z
RAOBs) which must be overcome before precipitation can reach the
ground. Surface temperatures are comparatively warm, and even
minor accumulations may be limited to grassy/elevated surfaces.
Any lingering snow should taper off after noon on Thursday,
perhaps transitioning to drizzle due to the loss of ice crystals
aloft.

Other than the novelty of seeing snowflakes, few impacts are
expected. The Winter Weather Advisory will be maintained for
collaboration purposes.

Kanofsky

.LONG TERM: (Friday through Next Wednesday)
Issued at 231 PM CST Wed Dec 17 2014

Our area may be too far north to receive much precipitation from
the next system to move across the southern part of the US. The
upper trough is forecast to move through MO/AR/LA on Friday night,
but the associated surface low will be hugging the Gulf Coast.
Trended a bit lower and farther south with PoPs for Friday night.

NWP guidance points to additional systems which could bring rain
or snow to the area on Sunday (passage of an upper trough), Sunday
night into Monday (strengthening upstream vort max), and/or the
middle of next week (closed low migrating into northern MO or
southern IA), but there is too much variability attm for much more
than broad-brushed PoPs AOB 40% with RA/SN.

Kanofsky

&&

.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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