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Area forecast discussion...updated aviation 
National Weather Service St Louis MO
531 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.


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 Continental U.S.. 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 County Warning Area 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

(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.



Aviation: (for the 00z tafs through 00z Friday evening)
issued at 524 PM CST Thu Dec 25 2014

VFR conditions expected through at least 18z Friday. High clouds
will thicken this evening, with high-end MVFR cloud deck moving in
by around 18z. Earlier gusty surface winds will diminish
overnight at kcou and should remain at or below 14 knots there.
Elsewhere southerly surface winds should remain at 10-12 knots
through this taf period.

Specifics for kstl: VFR conditions with only high clouds expected
through 18z, when cloud deck near 2500 feet will move in from the
south. After that time, ceilings in that range should continue
through this taf period. Southerly winds will continue at around
12 knots.



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