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

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FXUS63 KEAX 031117

National Weather Service Kansas City/Pleasant Hill MO
517 AM CST Sat Dec 3 2016

Issued at 327 AM CST SAT DEC 3 2016

Cloud cover will continue to build over the region today from the
southwest ahead of the next storm system, which will begin to impact
the area as early as the late afternoon. A deepening upper low is
sliding southeast across the Baja Peninsula, and will soon cut off
from the upper pattern. Embedded shortwave impulses are emanating
from this feature across the Southern Plains and have triggered
widespread precipitation, now extending as far north as central
Kansas. Also of note is a shortwave trough ejecting out of the
Northern Rockies as depicted on water vapor imagery. The shortwave
impulses to the southwest, along with the shortwave to the northwest
will be the focus of scattered showers, mostly during the overnight
period, as these features cross overhead.

Given the warm thermal profile below 2-3kft, will see all rain
through the evening and overnight hours for most of the area. The
only exception to this scenario is for areas across far north
central to northeastern Missouri, where the cooling thermal profile
may be supportive of a rain/snow mix. Surface wet bulb temperatures
are still expected to remain in the mid-30s, thus although the
potential is present for a wintry mix, precip type should assume
liquid state for most areas. Should greater cooling in the lower
levels occur, any wintry precip will be brief, generally limited to
the early morning hours Sunday. Accumulations, if any, will be
minimal and restricted to grassy areas as surface temperatures will
be too warm to support accumulating snowfall on roadways.

Despite weak warm advection ahead of the storm system, building
cloud cover will bring afternoon temperatures down slightly compared
to Friday. Afternoon highs will range from the lower 40s across
northern Missouri to the mid to upper 40s across areas south of the
Missouri River. Lingering stratus overnight will also maintain warmer
overnight lows in the mid to upper 30s. Will then see a brief break
in the activity through Monday as building southwest flow aloft helps
to push temperatures up slightly Monday, before the more significant
turn in the pattern establishes by the mid-week.

The first chance of activity will occur as the aforementioned cut
off low is brought back in to the main pattern aloft and pushes
through the Mississippi River Valley by Tuesday afternoon. This will
form a surface low well south of the CWA, which could bring a return
of precipitation across areas from central to southeastern Missouri.
The more significant change will occur as an arctic air mass pushes
into the area from the northwest Tuesday morning. Models are pretty
consistent at this point with the arrival of the cold front
occurring Tuesday morning to afternoon. While precipitation is
possible along the cold front, moisture will remain rather limited
and any formation will be brief and as of now appears favored for
areas across northwestern to north central Missouri. This will,
however, translate to the beginning of a sharp cooling trend with
Tuesday highs ranging from the lower 30s to lower 40s, coincident
with the frontal passage. Temperatures for Wednesday through the
latter half of the week continue to trend downward, with afternoon
highs expected to peak in the 20s for a multi-day stretch across
most areas.

Finally, the GFS is becoming better aligned with the ECMWF on
advertising a deepening longwave trough moving through the Central
Plains by the mid-week, though at this time is still producing a
faster solution than the Euro. Dynamics within both of these
solutions do show the potential for accumulating snowfall within a
persistent cold air mass. However, much uncertainty remains in the
extent of these possible scenarios, though it is a potential setup
which will need to be monitored over the coming days. Greater
certainty resides with the much colder multi-day period from the mid
to late work week.


.Aviation...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 502 AM CST SAT DEC 3 2016

Upper level cloud cover will give way to increasing low level clouds
throughout the period ahead of the next storm system. This will
impact all terminal sites, primarily during the overnight hours
Saturday. VFR conditions will persist through much of the morning
and afternoon with light northeasterly winds turning southeasterly
by Sunday morning. Conditions will steadily diminish this evening to
MVFR as low level moisture begins to build across the area. Vicinity
showers will approach the terminals this evening, though better
chances will arrive after 06Z. During this time, low-level moisture
profiles with light winds will result in low-end MVFR ceiling
heights, possibly IFR. Visibility may also degrade during this time
before slowly improving Sunday morning. Precipitation will remain in
the form of rain, with a wintry mix holding further north.




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