Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

000 
FXUS63 KTOP 112354 CCA
AFDTOP

Area Forecast Discussion...CORRECTED
National Weather Service Topeka KS
554 PM CST Wed Dec 11 2019

...CORRECTED TO ADD OMITTED FIRST PARAGRAPH IN LONG TERM...

.SHORT TERM...(This evening through Thursday)
Issued at 334 PM CST Wed Dec 11 2019

Warm air advection continues across the area this afternoon as low 
pressure deepens over the Colorado Front Range. As a result of the 
WAA, temperatures warmed nicely into the upper 40s and low 50s today 
under sunny skies. Into this evening and tonight, the Colorado low 
will kick out of the Front Range as an upper trough traverses the 
region. The low will track over northwestern KS, then into eastern 
NE by early tomorrow morning. A 60 kt LLJ is expected to develop 
over northeast KS ahead of the main wave, and strong low level 
southerly flow will allow more moisture to advect into the area 
tonight. Additionally, low and mid-level ascent aided by slight 
theta-e advection, the LLJ and PVA ahead of the trough will develop 
over the area tonight. Some of the CAMS are producing light 
precipitation as a result, but I have decided to keep POPS to less 
than 15 percent due to an overall lack of saturation in the column. 
Skies will be cloudy and winds will be breezy through the overnight 
period.

Tomorrow looks to be a touch warmer than today with highs reaching 
the mid 50s in most locations. It should be an overall decent day 
despite a bit of cloud cover. No impactful conditions are expected 
during this timeframe.

.LONG TERM...(Thursday night through Wednesday)
Issued at 334 PM CST Wed Dec 11 2019

The surface trough over central Kansas will stall and weaken through 
Friday, with little sensible weather impacts expected. By Saturday, 
a clipper system moving through the Northern Plains will push a cold 
front through the area, with temperatures hovering in the 30s.

This cold air will set the stage for a potential wintry system, 
though exact details are still uncertain. A broad upper trough will 
move onto the West Coast late Saturday and onto the Plains by Sunday 
evening. This will allow for lee surface cyclone development in the 
southern High Plains, with an inverted surface trough extending east 
from the low along a stationary front. To the north of this 
stationary front, isentropic ascent should lead to an initial zone 
of precipitation Saturday night into Sunday. A second wave of 
precipitation is possible late Sunday into early Monday as the low 
moves east into eastern portions of the Southern Plains along the 
stationary front. 

With the entire atmospheric profile remaining below freezing and 
generally saturated through a deep layer, at this point the bulk of 
precipitation is expected to remain snow. The main uncertainty at 
this point is a result of the position of the inverted 
trough/stationary front, along with the amplitude of the upper 
trough and associated strength of the surface low. The GFS maintains 
a stronger surface cyclone with a more northward inverted trough, 
leading to stronger frontogenesis and more precipitation across 
northeast Kansas. On the other hand, the ECMWF is weaker and farther 
south with the surface cyclone and inverted trough, leading to the 
heaviest precipitation staying well south of the area. The CMC is 
more of a middle ground. While accumulating snowfall is certainly 
possible for much of the area this weekend, it is not a slam dunk at 
this point, so continue to monitor in future updates.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 544 PM CST Wed Dec 11 2019

Low-level wind shear remains on track to develop in the next 
several hours and intensify after 06Z as a 60-65 knot low-level 
jet forms. Increasing moisture on these winds brings some 
potential for MVFR stratus development but this potential appears 
less likely in recent guidance. Have kept a high MVFR BKN 
inclusion for now. The passage of a modest cold front brings high 
potential for VFR conditions and weaker winds at the end of this 
forecast. 

&&

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

$$

National Weather Service Glossary of Abbreviations