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FXUS63 KTOP 101138

Area Forecast Discussion
National Weather Service Topeka KS
538 AM CST Tue Dec 10 2019

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 330 AM CST Tue Dec 10 2019

Quiet and cool weather is on the docket for today and tonight.

The morning surface analysis shows a 1023mb ridge axis sliding 
east of the forecast area. With a fresh Canadian airmass in place,
combined with light winds and clear skies, temperatures under the
ridge fell into the mid to upper teens. West of the Flint Hills, 
weak southwesterly flow over the higher terrain enabled 
temperatures to remain steady or even slightly rise into the mid-
20s. However, winds veer to the north once again later this 
morning as a secondary surge of negative theta-e advection takes 
place ahead of a 1033 mb high pressure dropping southeastward 
along the mid-Missouri River Valley. While the bulk of the CAA 
takes place east of the forecast area, the northerly winds will 
undoubtedly keep temperatures confined in the 30s for highs today.
Southerly flow sets in overnight on the backside of the high, 
stabilizing low temperatures in the low to mid 30s and setting up 
a warmer day on Wednesday.

There will be an increase in cloud cover later today as a region 
of weak H800-700 frontogenetical forcing slides through from 
northwest to southeast. With this shallow region of decaying lift 
centered in the DGZ and within a region of low static stability, 
did introduce a slight chance of flurries in north-central Kansas 
this afternoon. However, with ample lower-tropospheric dry air in 
place under this saturated zone (surface Td depression of 10 C), 
there is a good chance that any ice crystals sublimate before 
reaching the surface. No accumulation or impacts are expected.

.LONG TERM...(Wednesday through Monday)
Issued at 330 AM CST Tue Dec 10 2019

A gradual warmup ensues for the middle to latter part of the week
with an active weather pattern returning this weekend.

A quasi-stationary zonal surface trough sets up over the forecast
area on Wednesday in-between two high pressure cells, enabling 
southerly flow and WAA to increase over the southern portions of 
the forecast area. Highs north of the boundary are progged to 
reach the low 40s, with around 50 possible further south. There is
some uncertainty in the exact behavior of this trough, which 
should oscillate over the area before lifting northward as a warm 
front Wednesday night. The NAM core solutions in particular are 
further south with the boundary on Wednesday, while the GFS/EC/CMC
solutions focus the trough over the northern forecast area. 
Increasing WAA takes place overnight Wednesday ahead of a sharp 
meridional shortwave plowing eastward within a WNW zonal flow. The
corresponding surface low lifts northeastward through Nebraska 
and Iowa, with little in the way of impacts over the forecast 

Continued southerly flow remains in place through the day on 
Thursday and Friday before a vertically stacked trough sweeps 
through, ushering in colder air for the weekend. As with the 
earlier system, any appreciable precipitation should track east of
the region. The focus then shifts to Sunday and Monday as a 
digging upper tropospheric shortwave arrives over the western U.S.
The evolution of the lower tropospheric lee cyclone will play a 
key role in shaping the resulting surface precipitation shield 
over the Central Plains. The latest 00Z guidance suite are now 
focusing the surface pressure trough track over Texas, a pattern 
that would struggle to produce appreciable impacts over the 
forecast area. However, with the energy associated with the system
still situated over far eastern Russia, this forecast will change
and still bears watching over the coming days.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 535 AM CST Tue Dec 10 2019

VFR conditions are forecast for the TAF periods with north winds
of 5 to 15 kts today becoming light and backing to the south
tonight. A few light flurries are possible towards north-central
KS midday today, but no restrictions are forecast. Marginal LLWS
is also possible early Wednesday morning, but confidence was not
high enough to mention in the TAFs.



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