Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 151153

Area Forecast Discussion
National Weather Service Topeka KS
553 AM CST Sun Jan 15 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 358 AM CST Sun Jan 15 2017

Central Plains remains well downstream of the upper low, now
beginning to rotate northeast into the Southwest states. Modest east
to northeast surface winds remain with high to the northeast, though
pressures were falling, more quickly along the Front Range.
Increasing southerly flow around 850mb leading to best moisture
convergence in southern Kansas where precip has persisted overnight.
Drizzle becoming more prevalent locally in recent hours as the
backing of the winds deeps toward the surface with temps very close
to freezing. Wet bulb temps remain in the mid 20s to near 30 for
freezing precip to be the rule.

Short-range models continue to struggle with the northward push of
measurable precip, but along with synoptic models, do bring the
precip farther northeast today as moisture convergence shifts north.
Still have lower than normal confidence in timing and amounts
however. ECMWF has verified too dry in the lower levels per ceiling
observations, likely contributing to its lower QPF, while the GFS has
some of the lowest QPF of  its ensembles. Deep-layer forcing remains
on track to increase tonight with upper diffluence under rapidly
increasing south to southeast 850mb winds. This also allows for warm
air advection to occur toward the surface and should resulting in wet
bulb values this afternoon through the night for a change to rain to
cross I-335 this afternoon and beyond Interstate 70 late tonight.
Timing of this too is not certain with decent model spreads in
pertinent fields, but given dewpoints in the mid 30s in far southeast
Kansas and the ramping up of winds overnight, am fairly comfortable
ending the Warning as-is over southern and central areas with time.

.LONG TERM...(Monday through Saturday)
Issued at 358 AM CST Sun Jan 15 2017

Upper trough is forecast to move into south central Kansas Monday
morning within the deformation zone across north central and
northeast Kansas. This will lead to efficient rainfall production as
moisture streams around the upper low within the deformation axis.
Models continue to show a warm nose in the soundings across north
central and northeast Kansas during the morning hours on Monday with
max wet bulb temps aloft remaining above zero with surface temps
below freezing. This will lead to an additional 0.10 to 0.20 inch of
ice during the morning hours. In the afternoon temperatures should
warm from south to north above freezing with a transition to all
rain or a rain or freezing rain mix in far north central Kansas.
Therefore the timing of the ice storm warning through 18Z looks
good at this time so will not adjust for now. With the upper low
moving northeast Monday night the precipitation should come to an
end across the area by mid to late evening hours. An upper level
trough will move across the Northern and Central Plains on Tuesday,
but the forecast will remain dry as the moisture will be limited.
Split upper flow on Wednesday transitions to a southwesterly flow on
Thursday with another trough to affect the Plains for Friday into
next weekend. Model differences continue with the track and timing
of the upper low so low confidence for next weekend. Temperatures on
Martin Luther King Day will vary from the mid 30s in north central
Kansas to the lower 50s southeast of I 35. Temperatures remain above
seasonal values for much of the week with highs in the 40s and 50s
and lows in the 30s.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 554 AM CST Sun Jan 15 2017

IFR to LIFR conditions will likely dominate this forecast, but
timing and duration of the lesser restrictions is difficult with
TOP recently high MVFR while FOE was IFR. Continued moistening of
the lower levels should support the greater restrictions with
time. TOP and FOE should get out of freezing precip around 0Z
though again confidence on the timing of this is not high.


Ice Storm Warning until midnight CST tonight for KSZ024-026-

Ice Storm Warning until noon CST Monday for KSZ008>012-020>023-

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



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