Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 122329

Area Forecast Discussion
National Weather Service Topeka KS
529 PM CST Thu Jan 12 2017


.SHORT TERM...(This evening through Friday)
Issued at 427 PM CST Thu Jan 12 2017

Main upper low responsible for this weekend`s storm system is
currently centered across northern California. Mid level moisture
and high clouds were streaming across the southwest CONUS into the
region, expected to increase in coverage later tonight as the system
deepens straight southward. Currently towards the sfc, expansive
area of high pressure has chilled temps down to the 20s this
afternoon, falling into the teens tonight as the ridge axis
gradually slides eastward on Friday. This will in turn increase
northeasterly winds to near 10 mph overnight into Friday morning.

Main focus was on the ice storm potential across the area on Friday
and through the weekend. Details regarding the exact location of
each swath of precipitation that is possible is hard to nail down at
this point. The models are still struggling with how far north to
bring the freezing rain on Friday and Saturday. The 12Z GFS has the
QPF amounts and placement that makes the most sense conceptually
when compared to past ice storms under similar synoptic patterns.
Usually there is an elongated swath of precip from southwest to
northeast across the central US with embedded convection. Therefore
I`m not sure why some of the models have limited QPF until the main
low pressure lifts out. Moisture does not seem to be an issue
especially in the elevated warm layer. The surface temperatures are
also tricky to forecast due to the shallow nature of the cold air
and the warm air advection in place. Therefore some models are
eroding the cold air faster than others, which is mainly the GFS.
Light freezing rain and possibly freezing drizzle looks to stay
confined to south east and east central KS late Friday morning and
afternoon. Amounts appear to generally be light during this time

.LONG TERM...(Friday night through Thursday)
Issued at 427 PM CST Thu Jan 12 2017

Another round of freezing rain looks likely at some point on
Saturday. It could be as early as mid day or as late as the evening.
The best chances for widespread freezing rain with significant
accumulations will be Saturday evening through Sunday. The
consensus for temperatures during this time frame is to keep most
of the area below freezing with the exception of south east and
east central KS. During the day Sunday the freezing line may
gradually migrate northward as the mid level low pressure lifts
out of the southwest US and warm air advection increases. There is
still time to adjust timing and amounts, but generally there is a
very good chance that some location in the forecast area receives
significant ice accumulations of 0.50" to 1.00" by Sunday evening.

By Monday morning, upper low is centered across southwest Kansas
with maximum lift and qpf amounts occurring through mid morning.
Light freezing rain remains the likely precipitation type across far
north central Kansas until they transition to all rain by mid
afternoon. Strong WAA ahead of the upper low will quickly raise
highs to the low 50s in east central areas, and the middle 30s in
north central Kansas. The warm air advects around the backside of
the low Monday night, generating a decent trowal where additional
precipitation impacts north central Kansas. Amounts are uncertain at
this time, however forecast soundings suggest a wintry mix of snow,
sleet, and freezing rain will be possible. Will continue to monitor
how models trend with the upper trough track, but believe that it is
possible that headlines may need to be extended or added for north
central areas. The system finally lifts out on Tuesday with dry and
mild weather conditions returning for the remainder of the week.


.AVIATION...(For the 00Z TAFS through 00Z Saturday)
Issued at 529 PM CST Thu Jan 12 2017

Models show surface ridging with dry air remaining over the area
with pressures rising through the night. It isn`t until towards
12Z Fri when isentropic lift and overrunning setup. So VFR
conditions are expected into Friday morning. There appears to be
a consensus in solutions for MVFR CIGS moving in to the termainals
around 19Z. However once the low clouds move in, models weaken the
isentropic lift. So it is not a given that there will be much
lift in the cloud Fri afternoon for -FZDZ or -FZRA. Models QPF
proggs suggest FOE may be the most likely terminal to see some
-FZRA so have included a PROB30 at this time given limited
confidence in vertical motion for precip.


Ice Storm Warning from 6 PM Friday to midnight CST Sunday night
for KSZ008>012-020>024-034>038.

Ice Storm Warning from 9 AM Friday to midnight CST Sunday night
for KSZ026-039-040-054>056-058-059.



SHORT TERM...Prieto/Sanders
LONG TERM...Prieto/Sanders
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