Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 142342
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
542 PM CST Sun Dec 14 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday)
Issued at 310 PM CST SUN DEC 14 2014

Upper low and its strong potential vorticity advection aloft
bringing band of precip with several bouts of thunder steadily
northeast in to central Kansas with clear slot wrapping into
southwestern portions of the state early this afternoon. A few
breaks in the low cloud helping bump some local temps into the
lower 60s.

Short-range models rather similar with this band continuing on
northeast this evening with a few hours of clearing in the dry slot
anticipated. Instability and shear still not very impressive with
this band, but signs of more organized potential remaining for the
late evening and overnight hours as the system comes into the area.
Winds increase and veer aloft in southern areas with cooling aloft
leading to better though still low CAPE. Better forcing at this
point looks to be upstream of the upper low, somewhat removed from
this area however. This will continue to be something to be
monitored tonight with minor severe weather possibilities. Upper low
exits by early Monday afternoon with a few storms still possible
leading it in the morning. Cold air advection ramps up with 850MB
temps dropping several degrees through the day, with falling surface
values common by late morning. Still appears snow potential is
rather low with dry air coming in aloft and only a mention of a mix
justified for north central Kansas. Any accumulations here to be
very minor if any on warm ground and temps still well into the 30s.

.LONG TERM...(Monday Night through Sunday)
Issued at 310 PM CST SUN DEC 14 2014

The storm system should be exiting the area Monday evening with
cold air advecting in from the northwest and the forcing lifting
east and northeast. Have continued with some slight chance POPs
across far north central and northeast KS through the evening as
mid levels are slow to dry out. Also maintained a rain and snow
mention as there is some question in whether temps will cool off
quick enough or whether there will be ice crystals within the
cloud for snow. In any case subsidence gradually increases through
the evening so am not that worried there would be much drizzle to
contend with.

Tuesday and Tuesday night should be quiet with some sunshine
finally breaking out on Tuesday. Unfortunately high pressure
building in with cold air advecting south should keep highs in the
30s with lows dropping into the 20s by Wednesday morning.

There seems to be some consensus between the models for moisture
return on Wednesday and Wednesday night as a lead shortwave
potentially moves from the southern Rockies and into the plains.
Left the daytime hours dry for now, but the moisture return and
forcing could impact parts of the area late in the afternoon.
Nevertheless better chances for precip will be Wednesday night and
Thursday with a low amplitude open shortwave moving across the
area. Highest confidence in a chance for precip is Wednesday night
as the ECMWF and GEM show a similar solution of large scale
forcing affecting the area. Additionally temps look to be cold
enough for the event to be mainly snow. However have kept POPs in
the chance category as the GFS shows to much mid level dry air for
much precip.

By Thursday night and into the weekend, the uncertainty and
inconsistency among model solutions persists. Although the ECMWF
has followed its 00Z run of tracking the main shortwave and
surface low along the gulf coast. Even the GFS ensemble mean
tracks the system further to the southeast than its operational
solution. So the overall thinking is there could be a brief round
of Snow Wednesday night with it ending on Thursday as shortwave
ridging develops. Then the main shortwave trough moves south
leaving much of the area dry heading into Friday. However given
the uncertainty, did not want to make whole sale changes to the
forecast based on a single model run. Therefore have only trended
POPs down for Thursday night through Friday night. Also with the
southern track favored, temps should also be a little cooler with
highs in the lower and middle 30s and lows in the 20s through the
weekend.

&&

.AVIATION...(For the 00Z TAFs through 00Z Monday Evening)
Issued at 530 PM CST SUN DEC 14 2014

Confidence in rain during the first 6 hours of the period remains
high. There is a very small chance there could be an embedded
thunderstorm or two with very small hail. But, generally, after
the first 6 hours we will begin to see very spotty precip
lingering near all terminals with the movement of the moisture
plume ahead of the main low. Uncertainty in the last half of the
TAF period comes with the movement of the main low as it tracks to
the northeast. This area could bring some spotty precip, mostly in
the form of rain, along with it as well. Confidence on the winds
is high with the change to northwesterly flow behind the system
increasing with fairly strong gusts after 17Z.

&&

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

$$

SHORT TERM...65
LONG TERM...Wolters
AVIATION...Drake





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