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Area Forecast Discussion (AFD)

Issued by Kansas City/Pleasant Hill, MO (EAX)

                            
000
FXUS63 KEAX 190519
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1119 PM CST Mon Feb 18 2019

.Discussion...
Issued at 329 PM CST MON FEB 18 2019

Next round of winter weather is well on its way as a deep upper
trough, currently evident in WV imagery over western AZ, pushes 
east and then ejects out into the Plains Tuesday. The upper trough
will guide developing surface low pressure out of the Gulf and 
into the ArkLaTex region, but as the trough becomes increasingly
negatively tilted and pulls northward, moisture and a developing
secondary surface low lift into the forecast area Tuesday eve. As
is common, high-res models are beginning to show an earlier onset
to precipitation than the broader resolution GFS/NAM/EC, and while
saturation of the midlevels may take a bit and these initial
lower PoPs in high-res guidance may be elevated precipitation, the
potential for snow to begin during the evening commute is an 
increasing possibility. Precipitation type may be a brief light
snow/sleet mix as the atmosphere saturates, then will switch over
to snow as the deeper moisture arrives.

Highest snowfall rates are expected during the evening and early
overnight hours on the nose of the PV anomaly and in the deepest
moisture, then drier air begins to work in aloft, beginning to
eliminate cloud ice gradually early Wednesday morning. Since the
mechanism for freezing precipitation is a loss of cloud ice and
not a strong warm nose under deeper moisture, freezing drizzle 
should be fairly light and ice accumulations should not total more
than a tenth of an inch even over the extended period it will be 
possible across central-northeast MO, and near the KC area, the
more noticeable result will be a quick drop off in snow rates as
snow quickly lightens and begins to mix with freezing drizzle.
Farther to the northeast, moisture should stay deep enough to
support snow, although amounts will also drop off behind the
initial wave of better forcing. Current snow totals are likely
broader than the end result will be, since greater than 6" of
total snow accumulation is possible in areas that see little
to no loss of cloud ice, then a quick drop off will occur where
a full changeover to freezing drizzle is expected. The KC Metro
unfortunately remains right near the expected gradient, but should
receive at the very least 2-3 inches of quick accumulation at the
onset of snow, and areas with a longer duration (likely the NW
side) receiving 4-5 in total.

Winter weather headlines will change within the next 12 hours,
with the winter storm watch essentially a placeholder for the
location that could go either advisory or warning depending on
where models continue to indicate the band of highest totals. A
recent trend has been to bring the highest QPF a bit further to 
the northwest especially in the 12z NAM, which was discounted by 
WPC for its anomalous strength and placement of the surface low,
so will need another look at these trends before deciding either
way. The earlier onset of precipitation further to the south has
prompted the issuance of the advisory with this forecast package,
especially since snow could begin to impact the end of the evening
commute.

Precipitation will come to an end from southwest to northeast on
Wednesday, likely tapering to a light freezing drizzle/freezing
mist before ending altogether. Temperatures Wednesday night will
be chilly as the system departs; however, moderating temperatures
are still anticipated for Thursday and beyond as southwest flow
redevelops. Precipitation remains possible this weekend as has
trended back to a much warmer track/solution than yesterday, so
suffice to say models are still flip/flopping beyond the current
system and will not buy into any one p-type at this time.

&&

.Aviation...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1108 PM CST MON FEB 18 2019

Mid-level clouds will continue to drift overhead through the
overnight while winds remain light as a surface ridge approaches 
from the north. The next winter storm system will overspread the 
area late Tuesday afternoon and into the evening hours. Will 
initially see MVFR ceilings develop around 21Z, followed by a 
quick onset of light snow by 23Z to 00Z. IFR ceilings are then
expected to develop as the evening progresses. Snow, moderate at 
times, will then transition to a wintry mix Tuesday night and 
finally, freezing drizzle, before activity pushes eastward 
Wednesday morning.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Winter Weather Advisory from 4 PM Tuesday to 9 AM CST Wednesday 
     for KSZ025-057-060-103>105.

     Winter Storm Watch from Tuesday evening through Wednesday 
     morning for KSZ102.

MO...Winter Weather Advisory from 4 PM Tuesday to 9 AM CST Wednesday 
     for MOZ028>033-037>040-043>046-053-054.

     Winter Storm Watch from Tuesday evening through Wednesday 
     morning for MOZ001>006-011-012.

     Winter Weather Advisory from 6 PM Tuesday to 9 AM CST Wednesday 
     for MOZ007-008-013>017-020>025.

&&

$$

Discussion...Laflin
Aviation...Welsh