Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 280534

1134 PM CST Tue Jan 27 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Wednesday)
Issued at 322 PM CST TUE JAN 27 2015

Water vapor imagery showed a deep, broad mid-level trough stretched
across the eastern half of the U.S. with a mid-level ridge building
along the Rockies. This ridge will continue to slide eastward across
the Central Plains tonight into Wednesday morning before the next
shortwave, which was noted over British Columbia this afternoon,
dives into the Northern and Central Plains Wednesday afternoon. At
the surface, low pressure was situated over the central High Plains,
resulting in a southerly flow across the forecast area today. These
southerly winds combined with sunny skies led to temperatures this
afternoon rising into the 60s and even around 70 degrees in central
Kansas. As the approaching shortwave advances toward the northern
Rockies overnight, it will help to shift the area of surface low
pressure a bit further eastward into the forecast area and cause the
pressure gradient to increase some overnight. As a result, expect
5-10mph south-southwesterly winds to keep temperatures a few degrees
warmer with lows in the mid/upper 30s.

The shortwave will deepen across the northern High Plains and into
the Central Plains through the day on Wednesday, causing the area of
surface low pressure to continue shifting eastward over the area. An
associated cold front is expected to track into north central Kansas
by late morning and move out of the forecast area by early to mid
evening. Model soundings show a very dry atmosphere in place though
with only a few high clouds expected to develop with the frontal
passage so have a dry forecast going for Wednesday. Winds look to be
slow to veer behind the frontal passage with southerly winds
expected to only shift to the west by the afternoon. As a result, do
not anticipate this frontal passage being much of a limiting factor
for how high temperatures will get Wednesday afternoon.  Ahead of
this boundary, models show a decent thermal ridge passing over the
forecast area with 850mb temperatures of at least 12C to 14C. With a
fairly unidirectional wind profile and winds expected to gust
upwards of 20-30mph across northeast and east central Kansas, decent
mixing should occur through the day and have continued to trend
warmer for temperatures with highs in the middle/upper 60s north to
low 70s south. These breezy winds combined with dry conditions will
result in areas of very high fire danger across portions of north
central and east central Kansas.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 322 PM CST TUE JAN 27 2015

Wednesday Night, an upper level trough will dig southeast across the
northern plains into the mid MS river valley and Great Lakes States.
There may be enough ascent ahead of this upper level trough for some
scattered sprinkles across the CWA during the evening hours. A stronger
surface cold front will move through the area early Thursday
morning. Overnight lows will occur between 12Z and 14Z Thursday with
mid to upper 30s.

Thursday through Friday, an upper level trough across the eastern US
will amplify, this will cause a surface ridge to build southward
across the southern plains. Temperatures will be cooler with highs
in the lower to mid 40s and overnight lows in the 20s.

Friday night, An upper level trough across the southwestern US will
begin to phase with a northern stream trough moving east-southeast across the
northern and central high plains. Moisture advection and stronger
ascent ahead of the H5 trough will cause light snow possibly mixed
with rain or freezing rain to shift northeast across the CWA after
midnight. Surface dewpoints will be in the mid to upper 20s, thus
wet bulb cooling should allow temperatures to drop into the upper
20s and lower 30s once the precipitation begins. The ECMWF shows
more of a warm nose between 950mb and 850mb across east central KS,
thus the precip may be in the form of light freezing rain through
the morning hours of Saturday. The vertical temperature profile look
cold enough for snow across north central KS, though amounts look to
be light with under an inch of accumulations.

Saturday, both the GFS and ECMWF show mid 30 degree dewpoints
advecting northward across the CWA. The Boundary layer temperatures
will probably warm into the mid 30s to around 40 degrees thus, most
areas may change over to light rain. North central KS may keep a
rain and snow mix. Given that temperatures are forecasted to reach
the mid 30s to around 40 there should not be much in the way of
travel problems from the late morning hours of Saturday through the
afternoon hours.

Saturday Night, The GFS and ECMWF model solutions begin to diverge.
The ECMWF has a much more amplified upper trough moving east across
the southern and central plains as the northern branch H5 trough
phases with upper low across far west TX. Strong low-level CAA will
bring colder air southward across the CWA during the evening hours
of Saturday changing the rain and rain mixed with snow over to snow.
Stronger frontogenetical forcing will occur ahead of the H5 trough
across much of eastern KS causing for widespread snow. If the ECMWF
were to verify, several inches of snow will be possible. Most areas
could see 2-4 inches of snowfall Saturday night into early Sunday
morning. The GFS solution is less amplified without the phasing
occuring between the northern branch H5 trough and the upper low
over northeast Mexico. The GFS shows much weaker low-level CAA
Saturday night, thus the rain and rain and snow mixture may last
through much of the night before changing over to snow before ending
by 12Z SUN. If the GFS solution were to verify we may see a dusting
up to an inch of snowfall late Saturday night. The GEM model
solution is closer to the GFS solution.

Sunday through Monday, The upper level trough digging east-southeast
across the plains will amplify across the eastern US. Expect colder
weather Sunday and Monday as a surface ridge of high pressure builds
southward across the southern plains. Highs will only reach the mid
20s to lower 30s. overnight lows will be in the teens.

Tuesday, the upper flow will become zonal as the surface ridge
across the southern plains shifts east into the TN valley. Southerly
winds will help to warm highs into the mid to upper 30s.


.AVIATION...(For the 06Z TAFs through 06Z Wednesday Night)
Issued at 1133 PM CST TUE JAN 27 2015

VFR conditions continue to be anticipated. Near-surface winds are
veering quickly to around 3000ft AGL but speeds continue to be a
bit weak and veering too gradual for LLWS. Winds remain to be the
main forecast challenge with direction veering from SE to NW
through the period in response to two cold fronts passing.
Specifics on the more significant shifts is not high and some
adjustments are likely. Could see some stratus near limiting
ranges at the very end of this forecast.




SHORT TERM...Hennecke
LONG TERM...Gargan
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