Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 140510

1110 PM CST Sat Dec 13 2014

Issued at 336 PM CST SAT DEC 13 2014

VIS satellite imagery showing low stratus pretty well entrenched over
the lower Missouri Vly this afternoon as low-level moisture continues
to work northward in reestablished return flow. As a result...high
temps are a little lower than previously expected with many locations
across the CWA now residing in the lower to middle 50s. Heading into
tonight...fcst models show little improvement with the low stratus
thanks to strengthening warm air advection that will get underway
ahead of the strong West Coast storm system that brought flooding
rainfalls to California earlier this week. This combined with the
cloud cover should keep temps in the upper 40s to lower 50s for
overnight lows. In terms of sensible wx impacts...see no reason not
to continue a patchy lgt drizzle and fog mention through the
overnight thanks to the very soupy airmass.

Main story heading into tomorrow and tomorrow night will be the long
advertised storm system referenced above. As feature ejects out of the
central and southern Rockies...additional energy will be infused into
the lead shortwave which will allow the consolidated impulse to close
off and take on a negative tilt by Sunday afternoon. Following
this...all models in excellent agreement that feature will work
northeast directly over the area before exiting to our northeast late
Monday afternoon. Rain should begin overspreading the area late
Sunday afternoon/early evening before increasing in coverage during
the overnight period. Heaviest activity likely to exit off to our
northeast late Monday morning with lgt shwr activity then expected to
continue through early Tuesday. Some concerns for winery precip along
the back edge of the feature but latest guidance suggests healthy
drying in the snow growth region Monday night. As a result...have
removed all mention of snow for now while inserting a mention of
patchy freezing drizzle early Tuesday morning as sfc temps cool below
freezing in strengthening cold air advection. Despite this...system
will be leaving our area quite quickly which should negate any
significant icing concerns. Considering feature is a relatively fast
mover...little if any hydro problems expected despite PWAT values
increasing to 2-3 standard deviations above normal. In
general...basin average rainfall totals of 0.50-0.75" can be expected
region-wide from this system.

Following system/s departure...a few dry but cold days can be
expected before unsettled weather returns by the late work week.
Temps both Tue and Wed will remain below normal thanks to high
pressure which will be parked off to our north. Highs both days will
struggle to get out of the middle to upper 30s under continued
northerly low-level flow.

Beyond this...concerns begin to increase for developing winter precip
by late week as yet another southerly stream wave ejects out of the
southern and central Rockies. Out ahead of this feature...a strong
thermal gradient will exist across the ARKLATEX region thanks to
strong high pressure across the upper Miss Rvr Vly and developing
warm air advection along the Gulf Coast. As feature begins to eject
east from the Rockies...models develop precipitation along and north
of the stalled front as early as Wednesday night/early Thursday.
Considering plenty of cold air looks to be in place thanks to the
persistent high to the north...current indications suggest an
increasing likelihood for snow towards the latter stages of the work
week. Quick look at several GFS BUFKIT forecast soundings shows
favorable thermal and moisture profiles for now...but limited large-
scale lift. This makes sense since main upper wave and associated PVA
should slide south and east of our forecast region. Due to the weak
large scale lift...heavy snowfall accumulations are not expected at
this time. Additional looks at the University of St. Louis CIPS
historical analogs suggest lgt...possibly low-end advisory level
snowfalls across southern portions of the fcst area...which may
purely be a result of the system/s expected long duration. That
said...there still remains plenty of time to iron out the details
before getting too excited...especially considering how far out in
the fcst period this system is. Following its departure...dry wx
looks to return by Saturday.


.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1109 PM CST SAT DEC 13 2014

Another night, another challenging aviation forecast. At least for
the initial few hours of the forecast, conditions look to be higher
end MVFR or even VFR. But forecast soundings and guidance all support
a trend to low MVFR and IFR later tonight and into the morning hours
of Sunday. There may be a break in the poor ceilings Sunday
afternoon, but still think at least MVFR will prevail. Ceilings
should once again fall as an area of rain moves into the area late in
the forecast period.




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