Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 260448
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1148 PM CDT Sun Oct 25 2020

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Monday)
Issued at 324 PM CDT Sun Oct 25 2020

Northern stream upper wave continues to deepen southward towards the
four corners region while a secondary cutoff low is beginning to
enter the southern CA coast. Broad quasi-zonal westerly flow ahead
of the wave has aided in persistent low level moisture and weak
ascent as the stratus deck lowers through the afternoon and evening.
Light drizzle has been observed over north central and portions of
east central Kansas thus far and would expect the light precip to
linger before the system arrives tonight. If temps fall near or
below freezing, this may result in a light glaze on elevated
surfaces.

The first of two disturbances rounds the Four Corner basin this
evening while the cutoff low ejects into the southern plains by
morning. Widespread frontogenetical forcing in the h85-h7 layer
dropping southward into north central Kansas aft 00Z will be the
driver in precipitation rapidly developing and expanding eastward
into most of the CWA by 09z. Latest model trends are a bit faster
with the colder, freezing temps, and given our western areas have
not warmed and are hovering near freezing already, the wintry precip
transition to all snow should be brief overnight. Impact to morning
commute is likely as wintry precip should be ongoing with the
exception for areas south of I-35.

Model solutions begin to differ Monday afternoon as the mid level
vort max associated with the cut off low develops another band of
higher QPF in the southeast KS to central MO vicinity. Temperature
profiles vary by a few degrees towards east central KS which may
result in freezing rain or sleet mixing in with the snow. While this
will cut down on snowfall totals, a light glaze of ice may add to
the additional impact of travel for tomorrow. It is also worthy to
note the RAP forecast soundings were showing elevated instability
mid to late morning across the area - indicative of banding snow and
locally higher amounts across east central Kansas so cannot rule
out the potential for locally higher snowfall totals.

Current snowfall forecast is generally 1 to 4 inches this evening
through Tuesday evening with locally higher amounts possible if any
banded snowfall or convection were to occur. Headlines included
expanding the Winter Weather Advisory further east to encompass the
entire area as well as extending the time through 06Z Tuesday to
account for lingering light snow and light freezing drizzle. Plan to
also mention the freezing temps as forecast lows tonight will be in
the 20s to low 30s.

.LONG TERM...(Monday night through Sunday)
Issued at 324 PM CDT Sun Oct 25 2020

A second killing freeze is likely Tuesday morning with lows in
the upper teens to low 20s, effectively ending the growing season.

Multiple rounds of precipitation, including wintry precipitation,
remains possible Tuesday through Thursday as the upper low occludes
as it shifts across the southern plains. Precip on Tuesday is mostly
confined to areas south of Interstate 70 where light snow mixes with
sleet and rain through the daytime. Confidence remains low on how
far north the wintry mix impacts the area, and the amounts so
evaluation of extending the winter weather advisory will be made in
later forecasts. Rain appears most likely Wednesday and Thursday as
the warmer air raises temps back into the 40s for highs. Models exit
the upper low by Thursday evening with drier, and more mild
temperatures next weekend as highs peak in the low 60s and overnight

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1145 PM CDT Sun Oct 25 2020

MVFR CIGS will persist through much/all of the TAF period. Patchy
-FZDZ should transition to -SN in the 08-09Z timeframe with VSBY
 dropping to MVFR/IFR through mid-morning. VSBY and CIGS should
 gradually improve through the day. Precipitation may transition
 back to a wintry mix of -FZDZ and -SN tomorrow afternoon,
 especially at the Topeka sites. Northerly winds will remain near
 15 kts through the period.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 4 AM Monday to 1 AM CDT Tuesday for
KSZ012-024-026-039-040-055-056-058-059.

Winter Weather Advisory until 7 PM CDT Monday for KSZ008-009-020-
021-034-035.

Winter Weather Advisory until 1 AM CDT Tuesday for KSZ010-011-
022-023-036>038-054.

&&

$$

SHORT TERM...22
LONG TERM...22
AVIATION...Baerg



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