Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 112123
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
323 PM CST Wed Jan 11 2017

.SHORT TERM...(This evening through Thursday)
Issued at 317 PM CST Wed Jan 11 2017

Strong cold front was moving south through northeast Kansas this
afternoon. Temperatures were down into the mid 20s at 3 pm this
afternoon across the northwest part of the forecast area. The front
should continue to move south through the area early this evening.
Strong cold advection as shallow arctic airmass spreads across
northeast Kansas tonight and Thursday. The weather should be dry but
much colder tonight and Thursday with highs only reaching mid 20s to
lower 30s on Thursday which is optimistic given the strength of the
cold advection. The shallow and cold airmass will set the stage for
serious forecast problems this weekend.

.LONG TERM...(Thursday night through Wednesday)
Issued at 317 PM CST Wed Jan 11 2017

Friday through Saturday, the intense upper low will be digging
southeast off the southern CA coast, the upper low will then move
east across northwest Mexico. Moisture at 850mb will begin to be
transported northward from TX across western OK, then northeast
across southeast KS. Increasing isentropic lift will cause freezing
rain or freezing drizzle to develop northward from southern KS into
the extreme southeast counties during the late afternoon hours. Low-
level CAA may keep the northern edge of the freezing drizzle south
of I-70 through the Friday night but I think some patchy light
freezing drizzle may develop north of I-70 after midnight. The light
freezing rain may continue on and off through the day Saturday
southeast of I-35, with patchy freezing drizzle north across the
remainder of the CWA. Ice accumulations of 0.1 to 0.2" may be
possible across the southeast counties of the CWA. Ice accumulations
will only be a trace up to 0.1" across the remainder of the CWA.
Highs on Saturday will be in the 28 to 32 degree range.

Saturday night through Sunday night, the upper low across northern
Mexico will lift northeast into southwest KS. Deep gulf moisture
will advect northward into KS while the shallow cold air remains in
place. Temperatures will only drop off into the mid 20s but heavier
precipitation will develop in the form of freezing rain which will
continue through the day on Sunday. QPF across the CWA will be over
an inch with up to 1.8" in some locations across the western and
central counties. Given 850mb temperatures 5 to 9 deg C, there will
be no sleet and ice accumulations across much of the CWA will range
from 0.25" to 0.5". The GFS tries to warm temperatures into the mid
to upper 30s through the day Sunday but the ECMWF keeps highs in the
mid 20s to lower 30s. Given the northeast winds ahead of the sfc low
in northwest OK, I`m going more with the ECMWF solution. There could
be some major damage across the CWA due to ice accumulations. The
surface low will gradually lift northeast into south central KS.
Surface winds will advect warmer air northward ahead of the surface
low across the eastern half of the CWA, and temperatures may slowly
warm through the 30s and possible to near 40 by 12Z. The western
counties of the CWA will probably remain under northeast and
northerly surface winds which will keep temperatures at or slightly
below freezing. Another 1 to 1.5 inches of QPF could occur across
north central KS which could add 0.25" or 0.5" of ice accumulations.
This will cause major damage to trees and powerlines across north
central KS through Sunday night.

Monday, the heavier precip should shift northeast of the CWA through
the morning hours. Highs may reach to near 60 degrees across the
southeast counties of the CWA during the morning hours, as the
surface low moves northeast up the KS turnpike. The north central
counties may change over to rain as temperatures slowly warm into
the mid 30s. Given the total amount of QPF through the weekend
into Monday, there could be some minor flooding of small stem
streams and rivers.

Monday night into Tuesday morning the upper low will lift northeast
into IA and the wrap around moisture may turn to sleet and snow
across the northern counties of the CWA. Any snow accumulations will
be under 1 inch. Highs on Monday will be in the morning and
temperatures will fall through the 40s into the 30s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1146 AM CST Wed Jan 11 2017

For the 18Z TAFs, winds continue to veer to a northwesterly
component as the cold front moves into the region with mid-clouds
remaining for the afternoon before a low level deck moves in from
the north behind the cold front. There is potential for MVFR
coverage, but have not gone that aggressive at KMHK as some
guidance doesn`t give a very long signal for higher coverage
amounts. Have gone MVFR for the KTOP/KFOE terminals though as the
boundary layer cools tonight. Not as concerned with LLWS as change
in speed and direction seems too small at this time.


&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Johnson
LONG TERM...Gargan
AVIATION...Drake



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