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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

                            
000
FXUS63 KTOP 181137
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
537 AM CST Fri Jan 18 2019

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 355 AM CST Fri Jan 18 2019

For the near-term forecast, a winter storm system is on track to 
impact the area starting today and lasting into the early portions 
of Saturday morning.  

Currently, GOES-16/17 satellite loops feature and eastern trough 
along the East Coast region with a broad low amplitude dirty ridge 
with a strong low level inversion in place keeping stratus 
entrenched over the forecast area and much of the center portions of 
the CONUS.  Meanwhile, split flow pattern is in place with a 
southern stream broad shortwave working over the Intermountain West. 
 As this feature continues to advance east, lee surface troughing 
will continue to deepen and lee side cyclogenesis will continue to 
evolve into the morning hours and strengthen into the this 
afternoon.  

As upper level dynamics interact with the developing surface low 
over southeastern Colorado, isentropic ascent on the 295-300K 
surface will be encouraged over the central Plains region through 
the forecast area.  Southeastern low level flow as been increasing 
over the past several hours with moisture advection and higher 
theta-e air on the rise into the area. Some areas of light mist 
are being reported. As northern stream energy and associated 
shortwave dig into the northern plains, some phasing will take 
place with the southern storm system developing over the area. PVA
will increase through the day and into the overnight period. 
Ultimately, the progression of p-types today will be from mist to 
drizzle to then rain and eventually snow across the entire area. A
warm nose extending up into the northern counties along the KS/NE
border gives some concern for freezing drizzle through about the 
noon time frame with low level cold air in place and temperatures 
below freezing with the northern extent of the warmer temperatures
along and south of I-70 generally. There is still a spread in 
guidance about how far north warmer low level temperatures push 
into the area, which mean the difference between freezing precip 
or not. But, concern is still high enough to warrant mention of 
the period of possible freezing precip. 

Into the afternoon and evening, low to mid level frontogenesis and 
CAA increase.  Divergence aloft increases and encourages further 
baroclinicity to develop at the surface.  This dynamic cooling and 
wet-bulb effect in the mid levels should help to erode the warm nose 
over the area quickly into the afternoon and allow for a brief 
period of mixed rain/snow before changing to all snow across the 
area from north to south.  Right now, a light glaze of ice remains 
to impact areas along the Hwy 36 corridor, due to possible freezing 
precip previously discussed.  A consistent trend in recent model 
runs has been to speed the system up overall once the midlevel 
trough advances east of the Rockies.  The result of this has been 
temper overall snow totals and the main focus for highest amounts is 
still over far northeast KS into portions of east central KS.  Could 
still see around 4 inches over far northeastern zones -- some 
locally higher amounts -- and a healthy 1 to 3 inches elsewhere. The 
system should move east of the area by 12Z Saturday with snow having 
come to an end over the area.  Have decided to end the winter 
weather advisory by the 12Z time due to the impacts being low with 
winds calming down.  This should allow for blowing snow to become 
less common across the area.  

Although not as cold as originally forecast, the cold push from a 
modified arctic high pressure system will still be felt after the 
system exits the area.  Thus, high temps on Saturday struggle to 
reach 20.  

.LONG TERM...(Saturday through Thursday)
Issued at 355 AM CST Fri Jan 18 2019

Saturday night a 1032 mb surface high is forecast to be over eastern 
Kansas departing to the east into Missouri by 12Z Sunday. Winds will 
shift around to the southwest and south on Sunday as warm air 
advection kicks in through the day. Morning lows Sunday morning are 
forecast to range from the single digits to the teens with the 
colder readings over the northeast. Morning wind chills are expected 
to range from zero to 8 below. Highs on Sunday are forecast to warm 
into the upper 20s northeast to the upper 30s toward central Kansas.

Northwesterly flow aloft will shift to the east as a mid and upper 
level ridge build across the southern and Central Plains. This 
occurs in response to an upstream trough moving across the western 
states. Moderate warm advection is expected across the central 
Plains on Monday where some of the warmest temperatures in a couple 
of weeks will be possible as highs warm into the 40s most areas. 

A positive tilt upper trough is then forecast to progress 
eastward across the Plains Monday night and Tuesday bringing the 
next chance of winter weather to the area. Model thermal fields 
would suggest it will be cold enough for snow although some areas in 
east central Kansas could see a rain/snow mix Tuesday afternoon. 
Depending on the track of the surface and mid level synoptic 
features there could be a dusting to as much as a few inches of snow 
for parts of north central and northeast Kansas. With a cold front 
expected to move through Monday night, high temperatures Tuesday are 
forecast to cool back into the 20s and 30s. Lows Wednesday morning 
are expected to drop into the teens. 

A mid level wave is forecast to move southeast across the Plains on 
Thursday bringing another cold front southward through the CWA 
during the day. Limited moisture precludes inclusion of 
precipitation at this time.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 533 AM CST Fri Jan 18 2019

TAFs remain fairly consistent with low stratus and low VIS
restrictions common throughout the period. Drizzle will develop
later this morning and transition to light rain with snow by this
evening. Progression of the system is slightly faster, so this
should allow for LIFR/IFR restrictions to improve to MVFR around
the midnight time frame or shortly after.  

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 9 AM this morning to 6 AM CST 
Saturday for KSZ011-012-023-024.

Winter Weather Advisory from 6 PM this evening to 6 AM CST 
Saturday for KSZ026-038>040-054>056-058-059.

Winter Weather Advisory until 6 AM CST Saturday for KSZ008>010-
020>022.

Winter Weather Advisory from 3 PM this afternoon to 6 AM CST 
Saturday for KSZ034>037.

&&

$$

SHORT TERM...Drake
LONG TERM...53
AVIATION...Drake