Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 142138
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
338 PM CST Sat Jan 14 2017

.SHORT TERM...(This evening through Monday)
Issued at 331 PM CST Sat Jan 14 2017

Current satellite shows holes in the cloud cover that have caused
temperatures to warm into the mid 30s. Slight isentropic downglide
has contributed to this drying, but has kept the dew points much
lower. The only exception would be far eastern KS where the moisture
is deeper and closer to the ground. An area of showers and rain is
moving towards the area from the southwest. It should arrive in the
forecast area late this afternoon and evening. Wet bulbing due to
evaporation should cool the temperatures into the 20s and lower
30s therefore resulting in freezing rain once the column saturates.
Some of the high res models are struggling with this batch of
precipitation by either eroding it away or tracking it south of the
forecast area. They are also underestimating the precipitation
coverage. There is a chance that once freezing rain begins it might
not stick to objects or pavement until conditions cool this evening
and wet bulbing is finished. Also, temperatures are forecasted to
cool a few degrees in general due to the loss of daytime heating.
Most of the area stays below freezing before sunrise tomorrow
morning.

Larger scale models bring a continuous stream of precipitation in
the form of freezing rain tonight for areas mainly along and south
of I-70. This is when these areas could receive significant icing.
While more isolated to scattered freezing rain showers are possible
north of I-70. By late tomorrow morning the freezing rain may still
be ongoing for most of the area. Temperatures will begin to warm to
near freezing starting in east central KS, and that trend will
gradually move northward into the afternoon. This will be the tricky
part of the forecast since a few degrees separates freezing rain vs
rain. The models are now hinting that the majority of the
precipitation tomorrow late morning and onward will fall along and
north of I-70. This is when these areas could receive significant
icing. Light precipitation is still possible elsewhere during this
time frame. There could be a lull Sunday evening and overnight
before the main upper level low pressure lifts out over the plains.
By this time a majority of the area may be above freezing. Although
there is a chance that portions of north central KS could stay in
the freezing rain. This would cause higher amounts in these areas by
Monday morning. Generally ice amounts will be between 0.25" and
0.75" with locally higher amounts possible.

A closer look of at the 12z GFS ensembles show that the operational
GFS has some of the warmest temperatures by a few degrees out of all
of the members. Also, the 18Z NAM keeps wet bulb temperatures below
freezing for a majority of the area through tomorrow evening. The
operational GFS has the some of the lowest total QPF compared to all
of the ensemble members for northeast KS through tomorrow night. The
orientation of the 850 mb low level jet would suggest strong
moisture convergence to support this widespread precipitation
through tomorrow. Neutral advection at the surface under light
northeast winds would suggest steady temperatures. Not sure how much
mixing of the warm nose down to the surface will actually take
place. All of these factors would lead me to believe that widespread
significant ice accumulations as still possible.

.LONG TERM...(Monday night through Saturday)
Issued at 331 PM CST Sat Jan 14 2017

On Monday night the upper level low will move overhead and off to
the northeast. There is some potential for moisture to wrap around
the low, interact with an incoming weak vort max from the
northwest, and possibly support a last shot of a light wintery
mix of precipitation. Chances for anything to accumulate are low
and additional impacts are unlikely but will continue to monitor
this period in case deep moisture and lift are a bit stronger or
if the upper low moves out a bit slower.

Temperatures warm markedly for the rest of the forecast period.
Several negatively tilted upper level short wave troughs will
cross the Plains between Thursday and next weekend, but moisture
return will be limited prior to the weekend. For now have only
very small pops for the system on Friday, which looks to have warm
temperatures to support rain if precip develops. The late weekend
storm system looks potentially more interesting but the current
storm track looks to have the local area on the warm side of
things.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1127 AM CST Sat Jan 14 2017

TAFs start out VFR with most ceilings in the area around 4000
feet. A large area of freezing rain will move toward TAF sites,
likely arriving in the 04-08Z time frame. When this arrives,
conditions will rapidly decrease to IFR and possibly LIFR with
occasional freezing rain continuing through the remainder of the
TAF period. Freezing rain is very likely to accumulate on all
surfaces at all TAF sites.


&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Ice Storm Warning from 6 PM this evening to midnight CST Sunday
night for KSZ024.

Ice Storm Warning until midnight CST Sunday night for KSZ026-
035>040-054-055.

Ice Storm Warning from 6 PM this evening to noon CST Monday for
KSZ008>012-020>023-034.

Ice Storm Warning until noon CST Sunday for KSZ056-058-059.

&&

$$

SHORT TERM...Sanders
LONG TERM...Barjenbruch
AVIATION...Barjenbruch


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