Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 280528

1128 PM CST Thu Nov 27 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 217 PM CST THU NOV 27 2014

Surface high pressure ridge moved off to the east into Missouri
today allowing the return of southerly winds to northeast Kansas.
Winds were stronger across western and central Kansas where the
pressure gradient was stronger.

Tonight expect some high clouds to move across the forecast area through
the early morning hours Friday as a system moves southeast across
the northern and central Plains. Lower boundary layer remains
mixed overnight and expect temperatures to be about 6 to 13
degrees warmer than Thursday morning lows, ranging from 26 to 31

Max temperatures Friday likewise will rebound into the mid 50s to
lower 60s. Southwest winds are expected with the tightest pressure
gradient across east central Kansas where winds will gust to
around 25 mph in the afternoon.

.LONG TERM...(Friday Night through Thursday)
Issued at 217 PM CST THU NOV 27 2014

Most significant forecast challenges are frontal timing on Sunday,
and precip chances Wed/Thur.

Zonal flow aloft Friday night and Saturday result in a lee trough
over the High Plains and southerly/southwesterly low-level flow
bringing in warmer temperatures. Temps at 850 mb forecast to be in
the 15-17C range and max temps are expected to be in the lower to
middle 60s across the area. Mild conditions should continue
overnight Saturday night.

A positive tilt upper trough moving eastward across the Northern
Plains/Upper Midwest will result in a surging cold front entering
northern KS about 12Z Sun. Timing of this front is an issue in
forecasting temperatures as NAM and GFS move front through entire
area by noon on Sunday. GEM and ECMWF are a few hours slower,
which could lead to warmer highs in east central KS. Have gone
with a compromise on timing for frontal position and wind shift
given by the SREF mean, but bumped up winds behind front over what
SREF would have. Highs in east central KS south of I35 could reach
the lower 50s if that scenario plays out, but if faster NAM/GFS are
a better forecast, would only get into the 40s there.

Surface high ridge axis moves across eastern Kansas on Monday with
max temperatures not expected to make it out of the lower 30s most
places. As ridge translates off to the east, temperatures
moderate back into the 40s for Tue and Wed.

Both GFS and ECMWF continue with their run to run consistency by
mid-week. Unfortunately, that means there are considerable
differences between these models by Wednesday. These differences
seem to be due to the handling of system that cuts off off the
California coast early in the week. ECMWF has been slow to bring
this system into the western U.S. while GFS has brought it east as
a decent trough into the Rockies by Wed. Downstream for us, that
means 12Z ECMWF persists with northwest flow aloft and subsidence
over the area on Wednesday and Wednesday night while the GFS
continues to have more west-southwesterly flow aloft and develops a
lee trough with isentropic lift in eastern KS by Wed afternoon.
Given this variability, confidence is low, although slight chance
POPs are still being included.


.AVIATION...(For the 06Z TAFs through 06Z Friday Night)
Issued at 1127 PM CST THU NOV 27 2014

For the 06z TAFs, VFR conditions are expected through the period.
Surface low pressure situated over the High Plains will gradually
shift a bit further eastward across Kansas, resulting in an increasing
pressure gradient through the day on Friday. As a result, could see
some wind gusts during the afternoon hours of 15-20mph before
diminishing during the evening hours.




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