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

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299
FXUS63 KEAX 211740
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1140 AM CST Wed Feb 21 2018

.Discussion...
Issued at 405 AM CST WED FEB 21 2018

The cold front and associated wintry precipitation from yesterday exited
the region overnight, leaving everyone dry with low temperatures
in the teens and low 20s. The daylight hours today will continue
to be quiet with highs approaching freezing, thanks to the north
wind.

The quiet weather will be short-lived though, as another shortwave
moves across the Central U.S. providing upper-level support for more
precipitation tonight through Thursday. Unfortunately, it will be
another round of wintry precipitation. Above-freezing
temperatures around 850 mb are going to move north across the
forecast area, with ample moisture; while at the surface, the sub-
freezing temperatures are going to remain in place, at least
until Thursday afternoon. The tricky thing about this forecast is
of course the precipitation type. With the warm nose advancing
with the majority of the precipitation, only snow isn`t likely,
at least for areas south of HWY 36. A little snow could mix in
though for areas as far south as the MO River. Right now, it looks
like sleet will be the dominate precipitation type initially, as
the warm nose temperature will be just above freezing with the
introduction of cloud ice. However, the warm nose temperatures
should increase with time, while the introduction of cloud ice
decreases, so we should see a change over to freezing rain. A
freezing rain/sleet mix is likely before we see only freezing rain
though. This scenario is different from what we saw yesterday in
that, this is a longer duration, stratiform event with less QPF
expected, which is actually more ideal for ice accretion. That in
conjunction with an additional 0.10-0.20 of an inch of ice
expected tonight, and not much, if any, melting today has lead to
a Winter Weather Advisory being issued for the entire forecast
area. It is broken into two segments; the first segment starts at
6 PM tonight for counties south of HWY 36 and the second segment
starts at 12 AM Thursday for counties along and north of HWY 36.
The advisory expires for everyone at 12 PM Thursday. Something
that should probably be monitored is trees and power lines,
because if we don`t see much melting today, the additional ice
accumulation could start causing problems.

Thursday afternoon, the precipitation should lighten up and change
over to all liquid as surface temperatures start warming above
freezing thanks to winds shifting to the south. Thursday night,
another shortwave trough will move over the area, increasing
precipitation chances again. Temperatures are expected to dip
below freezing overnight for at least the northwest half of the
forecast area, so a changeover to freezing drizzle since the
the 850 mb warm layer should still be in place. Some ice
accumulation is possible with this round as well.

A couple of more rounds of precipitation are expected Friday and
Saturday as the trough over the western U.S. finally moves east.
Starting Friday, temperatures will trend upward, meaning the
precipitation should be mainly rain, with the exception of some
wintry precipitation possible during the overnight hours when some
of the temperatures dip below freezing.

&&

.Aviation...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1140 AM CST WED FEB 21 2018

VFR conditions expected through the remainder of the afternoon and
into the evening hours. From there, conditions will deteriorate
substantially. Ceilings are expected to become IFR overnight as
the wintry mess of precipitation moves into the area. By mess, it
looks like a mix of snow and sleet initially and then changing to
freezing rain and sleet. This will probably arrive around midnight
or perhaps a little later and persist through the morning hours.
It will not be a good time to travel.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Winter Weather Advisory from 6 PM this evening to noon CST
     Thursday for KSZ025-057-060-103>105.

     Winter Weather Advisory from midnight tonight to noon CST
     Thursday for KSZ102.

MO...Winter Weather Advisory from 6 PM this evening to noon CST
     Thursday for MOZ028>033-037>040-043>046-053-054.

     Winter Weather Advisory from midnight tonight to noon CST
     Thursday for MOZ001>008-011>017-020>025.

&&

$$

Discussion...Grana
Aviation...CDB



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