Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 112333
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
533 PM CST Thu Jan 11 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday)
Issued at 228 PM CST Thu Jan 11 2018

The mid-level shortwave trough has become an open wave as it lifts
northeastward over IA. The associated frontogenetical forcing has
also weakened significantly, but is still strong enough for a
band of light snow across far eastern KS. The snow should be light
and brief enough that the additional accumulations should remain
under a dusting. The latest observational and model data suggests
that the snow should come to an end by 2 pm this afternoon. The
post-frontal pressure gradient remains modest and therefore wind
gusts 30 to 40 mph are still possible through the afternoon. By
this evening the gradient is forecasted to relax, causing a
decrease in the winds. Locations that received over one inch of
snow could experience additional drifting as the strong northwest
winds continue. Temperatures are much lower than anticipated so
have trended them much lower through tonight. Wind chills as a
result are already in the single digits and single digits below
zero, which continue through tomorrow morning. Low temperatures
could reach near zero to slightly below zero give this air mass
and the recent snow cover.

.LONG TERM...(Friday night through Thursday)
Issued at 228 PM CST Thu Jan 11 2018

A longer wave length upper level trough will amplify across the east-
central US and remain in place through the middle of next week
before shifting eastward off the Atlantic coast. This pattern will
keep the central plains in northwesterly flow at mid and upper
levels of the atmosphere.

A series of shorter wave length troughs will dig southeast across
the plains. The first upper trough will dig southeast across the
central high plains into the southern plains Friday afternoon
through Friday night. The low-levels of the atmosphere will be dry
but there may be enough ascent for snow flurries or light snow
across the western counties Friday afternoon through Friday
evening. Snow accumulations across the western counties will be a
dusting at best. The continue low-level CAA will only allow highs
on Saturday to reach the mid teens to lower 20s. Overnight lows
will drop into the single digits friday night.

A second more intense H5 trough will dig southeast across the
plains Sunday night into Monday. Once again the low-levels will be
dry but stronger ascent along with a reinforcing shot of arctic air
will provide for higher liquid to snow ratios. Therefore, some
areas of northeast and east central KS may see 1 to 2 inches of
light fluffy snow Sunday night into Monday. However, the GFS model
solution is less amplified and tracks the H5 trough farther east.
If the GFS solution were to verify then any minor snow
accumulations will remain in far northeast KS with most of the
snow fall along the central MO river valley southeast across
western MO. Both the GFS, GEM and ECMWF show much colder air
advecting southward across eastern KS on Monday with the center of
a 1045 mb ridge axis over the CWA on Tuesday. Highs Sunday ahead
of the next arctic airmass will reach into the 30s with most areas
getting into the mid to upper 30s Sunday afternoon. Highs Monday
may occur during the morning hours with temperatures falling
through the teens during the afternoon. Highs on Tuesday may only
reach around 10 degrees along the NE border with mid teens across
the southern counties. Overnight lows Monday night and Tuesday
night will drop into the lower single digits along the southern
counties and 5 to 10 below along the NE border. Monday night
northwest winds will remain in the 5 to 15 MPH range which will
cause wind chill indices to drop to the 15 to 20 below range north
of I-70.

Wednesday through Thursday, the cold surface ridge will shift east
of the plains and southerly winds will moderate high temperatures
into the mid to upper 20s on Wednesday and mid 30s to lower 40s by
Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 529 PM CST Thu Jan 11 2018

Predominantly VFR conditions are expected through the TAF period
with a few areas of MVFR ceilings in the east early this evening
and in north central KS late Friday afternoon. Current gusty
northwesterly winds of 15 to 25 kts will gradually subside to
around 5 to 10 kts by tomorrow morning as high pressure
approaches the region.

&&

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

$$

SHORT TERM...Sanders
LONG TERM...Gargan
AVIATION...Skow



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