Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 252151
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
351 PM CST Thu Dec 25 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 349 PM CST Thu Dec 25 2014

Return flow on the backside of a sfc high centered across the Deep
South and in advance of the next cold front currently extending
across the nthrn Plains scheduled for Saturday will keep sthrly
winds going tonight. This will aid in a warm night with lows in the
mid 30s to near 40 which is 15-20 degrees above normal. Due to the
warm conditions expected tonight and the known cool bias MOS has in
this set up, generally went above the warmest guidance. Otherwise
expect a quiet night with mostly clear to partly cloudy skies.

Miller

.LONG TERM:  (Friday through Next Thursday)
Issued at 349 PM CST Thu Dec 25 2014

(Friday through Sunday)

Have not changed much from the going forecast in that temperatures
will be above normal until a front moves through the area on
Saturday.  This same front will bring a chance of rain with it
Friday Night into Saturday.  Models were in relatively good
agreement and generally followed.

It still appears that a shortwave trough will eject out of the
longwave trough currently over the western CONUS.  This first
shortwave will round the base of the longwave tonight and reach the
upper Midwest by Saturday morning.  This will cause the front
currently over the Great Plains to move through Missouri during the
day on Saturday.  Still expect rain to develop over the area on
Friday night as some low level moisture convergence increases ahead
of the shortwave trough.  The rain will continue into Saturday, with
likely PoPs over southeast Missouri into southern Illinois where the
GFS depicts strong moisture convergence coupled with relatively
strong mid-level ascent associated with the shortwave trough.   Some
rain chances will linger over the southeastern part of the CWA into
Saturday evening as the front exits the area before drier air and
subsidence moves in.

Still looks like there may be some snow mixing with the rain over
parts of central and northeast Missouri as well as west central
Illinois on Saturday as temperatures cool behind the front.
Generally followed NAM and GFS MOS temps which are in good agreement
and have temperatures falling behind the front during the day on
Saturday.

(Monday through next Thursday)

Global models are in relatively good agreement that upper flow will
be  mainly zonal during this period with little storminess.  These
scenarios are not usually high confidence forecasts.  For now went
mainly dry with close to normal temperatures.

Britt

&&

.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1132 AM CST Thu Dec 25 2014

Quiet conditions with a VFR fcst thru tonight with high pressure
dominating the area. Return flow on the backside of the high will
allow for potential LLWS tonight. The set up looks marginal attm
with sfc winds around 10kts increasing to 30kts around 1kft to
40-50kts near 2kft. Will let later shifts determine the need to
include it in the fcst. MVFR CIGs are expected to move into the
terminals late Friday mrng as better moisture works back into the
area.

Specifics for KSTL:

VFR fcst thru tomorrow mrng with high pressure in control before
MVFR CIGS move into the terminal around 18Z. There is the
potential for marginal LLWS tonight but will late later shifts
address the need to include it in the fcst.

2%

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





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