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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

                            
000
FXUS63 KTOP 190543
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1143 PM CST Mon Feb 18 2019

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 340 PM CST Mon Feb 18 2019

Minor PV anomalies were moving northeast across southwest and 
central Kansas this afternoon at 20Z per satellite and profilers. 
Main upper trough resided over Arizona and Utah this afternoon with 
a 160 kt H250 jet across the southern and central Plains. A surface 
high pressure extended from the Dakotas southward into Texas this 
afternoon. Winds will gradually become easterly tonight as the high 
slides off to the northeast by 12Z Tuesday. 

Weak isentropic lift in the 280K-290K layer along with weak theta 
advection will continue through about 03Z this evening. Also mid 
level frontogenetic forcing is forecast to overspread north central 
Kansas late this afternoon through mid evening. Convective allowing 
models continue to show light snow or flurries across parts of 
central and north central Kansas this evening, but recent runs have 
backed off some from a few hours ago. Elsewhere expect clouds to 
overspread the area and have adjusted lows upward from blended 
guidance a few degrees.

The system forecast to bring measurable snowfall to central and 
northeastern KS late Tuesday into early Wednesday still looks on 
track. 

By Tuesday morning a deep longwave trough will be in place 
over the eastern portion of the Intermountain West. Precipitation 
will likely be ongoing over the CO Rockies with a southern stream of 
moisture and precipitation in place over TX. Broad, synoptic scale 
ascent associated with the upper jet and isentropic upglide will 
work into the area ahead of the system Tuesday afternoon, allowing 
for a widespread area of precipitation to move in. The most likely 
form of precip expected to impact the region with this round of 
weather will be snow. However, have noticed some differences in the 
amount of mid-level dry air that models try to bring in. The GFS 
forecast soundings maintain deep low and mid level saturation for 
the majority of event. NAM, on the other hand, wants to bring some 
dry air into the dendritic growth zone earlier than other models, 
which would indicate the possibility of a mix over to some 
freezing rain/drizzle. Currently leaning more toward a GFS 
solution with snow being the primary precipitation type Tuesday 
evening and night. East-central KS is the most likely region to 
see a switch to freezing rain/drizzle overnight, thus snow amounts
there will be a little lower but a glaze of ice is possible on 
top of the snow. 

QPF is currently forecast to be between three and forth tenths of an 
inch across the entire forecast area. Snow ratios are expected to 
range from near 10:1 in east-central KS to near 16:1 in north-
central KS. All things considered, snow amounts are forecast to be 
between two and four inches in east-central KS and between four and 
six inches near and north of I-70. A Winter Storm Watch has been 
issued for counties bordering NE where the highest totals are 
expected. The rest of the area will be in a Winter Weather Advisory 
starting Tuesday afternoon. Precipitation should move out Wednesday 
morning.  

.LONG TERM...(Tuesday night through Monday)
Issued at 340 PM CST Mon Feb 18 2019

Mother Nature will give us a brief break in precipitation until the 
end of the week. Sunshine should return and a warming trend is 
expected into the weekend. Highs are expected to reach the 40s for 
portions of northeast KS Friday and Saturday. 

The next system to keep an eye on will quickly approach the area on 
Friday as another deep trough across the western US. Moisture will 
stream northward into KS ahead of the approaching trough and will 
bring a chance for precip back to our forecast Friday. Model 
guidance depicts a cut-off upper low pivoting northeast from the 
Four Corners region into KS on Saturday. The strong dynamics of the 
system could produce some instability and thunderstorms before 
cooler air arrives behind the system. Models are starting to come 
into better agreement with the timing and placement of this next 
system, but will need to monitor as this event is still several days 
away.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1139 PM CST Mon Feb 18 2019

For the 06z TAFs, VFR conditions are expected overnight before 
the next system moves into the region on Tuesday, bringing 
chances for snow to the TAF sites. Snow chances will increase 
Tuesday afternoon through Tuesday evening, with MVFR cigs/vis 
likely by mid to late afternoon. With widespread snow likely by
Tuesday evening, models show cigs/vis dropping to IFR conditions
through the end of the period. Cannot rule out the potential for
some periods of LIFR cigs/vis with any moderate snow bands, so
will need to monitor this potential in future TAF updates. 

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 PM Tuesday to 9 AM CST Wednesday 
for KSZ020>024-026-034>040-054>056-058-059.

Winter Storm Watch from Tuesday afternoon through Wednesday 
morning for KSZ008>012.

&&

$$

SHORT TERM...53/Teefey
LONG TERM...Teefey
AVIATION...Hennecke