Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 211125

National Weather Service Topeka KS
525 AM CST SAT NOV 21 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 319 AM CST SAT NOV 21 2015

At 08Z the upper level trough axis extended from northeast Nebraska
into south central Kansas. The upper trough axis will move across
northeast and east central Kansas by mid morning. Precipitation
continues to move across east central Kansas in the form of rain and
snow and expect it to move out by 11Z.

Tight pressure gradient was observed across north central and
northeast Kansas this morning at 08Z. North winds were gusting up to
around 40 mph across the area. High pressure will build southeast
today into the area as the surface low continues to move off to the
east into the Ohio Valley. As the drier air works into northeast
Kansas clouds will gradually decrease later this morning with mostly
sunny skies this afternoon. Bulk of the cold air will affect areas
to the east, however temperatures today will only warm into the mid
to upper 30s. Tonight the surface high will be overhead during the
evening then move off to the southeast overnight. Mid level wave
will move southeast across Nebraska and clip northeast Kansas before
moving off into Missouri tonight. Main effect will be an increase in
mid level clouds in the northeast around midnight then decrease by
sunrise Sunday. Lows tonight will dip down into the lower 20s.

.LONG TERM...(Sunday through Friday)
Issued at 319 AM CST SAT NOV 21 2015

By Monday zonal flow aloft continues to modify the temperatures
across the area with highs back in the 50s and lows in the 30s.
Meanwhile a decent upper level low pressure digs over the Pacific
Northwest and into the southwest US into Wednesday. This puts the
area under southwest flow aloft and results in increased low level
moisture starting Tuesday. Isentropic lift within this saturated
layer could lead to drizzle and or light rain Tuesday night mainly
across southeast and east central KS. During this time frame arctic
high pressure will slide southward along the high plains driving a
front towards the region.

Wednesday night the main closed upper low begins to send shortwave
energy over the plains, which partially phases with the northern
stream. This lead shortwave will increase the large scale lift and
enhance the front as it passes through the area. There are some
hints that the overall instability will increase as mid level
temperatures cool so have kept the mention of showers and
thunderstorms out ahead and possibly along the front Wednesday night
and Thursday. The models begin to diverge on the solution causing
low confidence in the forecast beyond this point. The difference in
the models seems to be related to a northern stream kicker, which
would cause the main upper low to progress eastward as a positively
tilted trough. The GFS shows this scenario and is therefore more
progressive pushing the precip east before the sub freezing
temperatures arrive. The ECMWF hangs some energy back west resulting
in a longer duration event, which allows the cold air to reach the

The frontal passage appears to be during the day Thursday with rain
and or storms as the dominate precip type. Late Thursday evening
both models depict the sub freezing surface air arriving in north
central KS and moving southeastward through the overnight. As
previously mentioned the GFS ends most of the precip before this
happens. The ECMWF under cuts the precip and warm nose aloft with
sub freezing air. With warm nose sufficient for melting it would
suggest rain changing to freezing rain and sleet from northwest to
southeast. Possibly followed by a mixture of light snow on the
backside. Slight difference in timing and the amount of post frontal
precip will play a big role in this outcome. There is still time to
analyze the evolution of this system moving forward, but it does
bear watching.


.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 524 AM CST SAT NOV 21 2015

Main focus of this TAF will be on the timing of VFR ceilings and
when gusts subside.  Believe MVFR ceilings will hang on a little
longer (until 15Z) than some short range model guidance suggest as
clouds are just now beginning to scatter out in southern Nebraska.
Have gusts ending in MHK at 16Z, with TOP/FOE slightly later. Expect
VFR conditions the rest of the period with some mid-level clouds
moving in late tonight.


.TOP Watches/Warnings/Advisories...


LONG TERM...Sanders
AVIATION...Heller is the U.S. government's official web portal to all federal, state and local government web resources and services.