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000
FXUS63 KTOP 010527
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1127 PM CST Sat Feb 28 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Sunday)
Issued at 348 PM CST SAT FEB 28 2015

Late this afternoon water vapor satellite showed a minor short-wave
upper level trough moving east across central KS. Isentropic lift at
the 280mb through 300mb level continues across northeast and east
central KS. Most areas across the CWA have received 1 to 3 inches of
snowfall. There may be an additional half to one inch across
northeast and east central KS the remainder of this afternoon.
Moderate to heavy snowfall could provide portions of Coffey and
Anderson counties with closer to 2 more inches of snow this
afternoon into the early evening hours.

As the first H5 trough moves east into MO, the snow should become
light and may stop in some areas for several hours through about 300
AM Sunday.

A stronger upper level trough across eastern MT and southern Canada
will dig southeast across the northern and central plains Tonight.
Most models show the frontogenetical forcing increasing ahead of the
digging H5 trough across eastern KS. Though models all differ quite
a bit in timing and and intensity of the forcing at mid levels. The
ARW shows a rather intense band of snow developing along the I-70
corridor after 12Z Sunday and lasting into the late morning hours of
Sunday. This could give areas of east central KS about 2 to 4 inches
of snow on Sunday morning. The 18Z NAM develops the frontogenesis at
mid levels between 9z and 14Z across northeast KS into northern MO,
which would cause a band of 1 to 2 inches of snow to develop after
9z and shift east into MO by 14Z with just a dusting farther south
across east central KS. I`ll probably trend more towards a
NMM/GFS/ECMWF solution which shows a band of light to moderate snow
developing around 12Z SUN and moving east of the area during the
late morning hours. Total additional snow accumulations across north
central KS Tonight and Sunday morning will be a half inch or less.
Additional snowfall across northeast and east central KS will be 1
to 2 inches. Most of the snow will shift east in MO by Noon on
Sunday.

I`ll keep the winter weather advisory going through the afternoon
hours. The next shift will probably have to cancel the advisory for
north central KS.

Lows Tonight will only drop off into the upper teens and lower 20s.
Highs tomorrow will reach the lower to mid 30s, with upper 30s if we
see some late afternoon insolation.

.LONG TERM...(Sunday Night through Saturday)
Issued at 348 PM CST SAT FEB 28 2015

Dry conditions are expected by Sunday night as the mid-level trough
axis progresses northeast of the area and surface high pressure
advances into the Central Plains behind the exiting system. Much of
the area should be dry through the day on Monday, however models
still show a few weak embedded shortwaves developing within the
mid-level flow over western and possibly central Kansas, with some
light precipitation possibly clipping far north central Kansas.
However, due to the low confidence in this occurring, only have a
mention of slight chance PoPs. Depending upon the timing of any
light precipitation that occurs, it may be in the form of light
rain, freezing drizzle, or snow.  Some model soundings are
suggesting the potential for some areas of drizzle to develop
throughout the day on Monday as some isentropic lift will be
present, but there may not be enough saturation present so have not
included a mention of it at this time but it`s worth monitoring in
future forecast updates. As winds shift to the southeast, Monday
high temperatures should reach into the upper 30s to around 40
degrees.

Precipitation chances increase once again Monday night through
Tuesday as another mid-level trough deepens across the Rockies and
tracks eastward into the central U.S. through mid-week. This
advancing trough will help to push an area of surface low pressure
over the Rockies eastward across Kansas on Tuesday. Expect winds to
veer to the southwest and increase in speed Monday night into
Tuesday morning, resulting in warm air advection and rising
temperatures through the overnight period. Temperatures near the
Nebraska/Kansas border Monday night may be near freezing, so any
initial precipitation that develops may potentially be in the form
of rain or freezing rain. But with temperatures quickly rising,
precipitation type should transition to all rain by mid/late evening
as this precipitation becomes more widespread across the area. This
system will be accompanied by a strong cold front, which should move
into north central Kansas Tuesday morning and track eastward across
the forecast area through mid afternoon. In general, models seem to
be a bit faster with the timing of this frontal passage. As cold air
comes surging into the area behind the front, expect temperatures to
quickly plummet through the afternoon hours. There should be a
decent temperature gradient over the area, but with there still
being some model uncertainty in the exact timing of this frontal
passage it`s still difficult to fine-tune this gradient. At this
time, have high temperatures ranging from the low 40s to low 50s
(from northwest to southeast), with falling temperatures during the
afternoon. Precipitation should remain in the form of rain Tuesday
morning and have kept the mention of isolated thunder for far east
central Kansas as the GFS continues to hint at some weak elevated
instability. Otherwise expect rain to transition to snow as the
temperatures fall below freezing. There is still some uncertainty
with how quickly the dry air will move in behind this system, with
some soundings showing maybe only flurries lingering over the area
Tuesday night as we lose saturation in the dendritic growth zone. As a
result, have continued to lower PoPs for Tuesday night into
Wednesday morning but most of the forecast area should be dry by
early Wednesday morning. With the steady cold air advection, low
temperatures should drop into the teens Tuesday night with highs
only in the 20s for Wednesday.

Surface high pressure will advance into the region by mid week with
dry conditions expected through Saturday. As this high shifts to the
east and winds veer to the southwest again, temperatures should
gradually moderate for the latter part of the week with highs into
the 50s by Friday and Saturday.

&&

.AVIATION...(For the 06Z TAFs through 06Z Sunday Night)
Issued at 1125 PM CST SAT FEB 28 2015

WILL SCATTER OUT THE 2KFT DECK AT THIS TIME AS PREVALING CIG
HEIGHT IS GENERALLY BETWEEN 3-4KFT. WILL KEEP PREVAILING SNOW FOR
LIGHT BAND MOVING OVER TAF SITES BUT HAVE IMPROVED VISBY TO 4SM.
STILL HOLD LOWER CLOUDS TILL AROUND THE NOON HOUR BEFORE STARTING
TO LIFT AND CLEAR OUT LATER IN THE PERIOD.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until Noon CST Sunday FOR KSZ021>024-026-
034>040-054>056-058-059.

&&

$$

SHORT TERM...Gargan
LONG TERM...Hennecke
AVIATION...67