Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 180951
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
351 AM CST Thu Dec 18 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 323 AM CST Thu Dec 18 2014

Vigorous little shortwave over northern Kansas is producing a broad
area of snow over parts of north central Missouri back toward west
central Missouri.  The going forecast looks pretty good in general;
however current radar and latest short range model guidance suggests
that there will be more precipitation across parts of northeast
Missouri and west central Illinois than previously forecast.  Low to
mid level frontogenesis and isentropic lift will increase through
15Z as the wave passes north of the area.  The shortwave should be
dampening out as it moves into an area of longwave ridging, so
precipitation should be on the decline through the morning, and
there is still a wedge of low level dry air to overcome, but
measurable precip does look likely across most of the area.
Accumulations still look pretty light with most areas receiving an
inch or less except for parts of central and southeast Missouri
where an inch or two of wet snow is likely to accumulate.  With
temperatures hovering right around freezing, expect some slick spots
on any untreated roads this morning, but temperatures should be
rising above freezing in most locations by mid to late morning so
that should alleviate any road issues.  Additionally, expect precip
to be winding down pretty rapidly after 15Z as the shortwave dampens
out and the primary band of frontogenesis and isentropic lift
weakens.  The one place where there may be lingering problems is
northeast Missouri and west central Illinois where temperatures may
struggle to break freezing this afternoon.

Carney

.LONG TERM:  (Tonight through Wednesday)
Issued at 350 AM CST Thu Dec 18 2014

Relatively quiet weather will prevail over the area for the rest of
the week with a large surface ridge extending from southern Canada
through the Upper Midwest and Great Lakes region down into the
Mid-Mississippi Valley.  Another wave will ripple through in the
quasi-zonal flow aloft Friday night.  The lower atmosphere looks too
dry to allow any precip to reach the ground from this wave...all
except for southern portions of the area.  Have kept chance/slight
chance PoPs across southeast Missouri and southwest Illinois with
little or no qpf associated with them.

Saturday and Sunday look warmer with southwest flow deepening ahead
of the next trof with temperatures rising to around normal on
Saturday and above normal on Sunday.  Medium range guidance looks to
be in good agreement that the trof will deepen across the Central
U.S. Monday into Wednesday.  This should bring us another period of
cloudy and occasionally rainy weather with the best probabilities of
precipitation Monday night into Tuesday.  The atmosphere will likely
be too warm for much frozen precipitation until possibly Tuesday or
Tuesday night.  QPF looks pretty light on the GFS and ECMWF by the
time the atmosphere is cold enough to snow, but there may be a few
periods of flurries or light snow Tuesday and Tuesday night.

Carney

&&

.AVIATION:  (For the 06z TAFs through 06z Thursday Night)
Issued at 1137 PM CST Wed Dec 17 2014

Snow will move KCOU in the next 1-2 hours and into the St. Louis
metro area TAFs between 9-12Z. Still appears that conditions will
drop to IFR or low MVFR within 1-3 hours after the onset of the
snow. KUIN will see the onset of snow around 12Z. Accumulations of
snow is still expected to be around 1 inch at KCOU and less at
KUIN and the St. Louis metro TAF sites. The snow will switch over
to drizzle during the afternoon before ending by late in the
afternoon. IFR or low MVFR ceilings are expected through the end
of the period.

Specifics for KSTL: Snow is expected to move into the terminal
after 09Z with VFR conditions initially given dry air in the
atmosphere. IFR conditions and steady snow is expected by 14Z with
an accumulation of less than 1 inch. The snow should switch over
to drizzle by 18Z with IFR ceilings lasting through the rest of
the TAF period.

Britt

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     36  28  37  29 /  80   5   5  10
Quincy          33  25  33  27 /  80   5   5   5
Columbia        36  30  37  30 /  80  10   5  10
Jefferson City  37  29  38  31 /  70  10  10  10
Salem           36  27  37  26 /  40   5   5  20
Farmington      36  28  37  26 /  70  10   5  20

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...WINTER WEATHER ADVISORY until 10 AM CST this morning 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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