Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 230943
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
343 AM CST Tue Dec 23 2014

.SHORT TERM...(Today and Tonight)
Issued at 343 AM CST TUE DEC 23 2014

Water vapor imagery at 0830Z showing an upper level low with
center over eastern NE/southwest IA with a shortwave trough
extending west/southwest from the into northeast CO. Drier air
aloft is evident from southwest into east central KS on the south
side of the circulation. Light snow continues to wrap south and
southeastward with the trough across west and northern NE and
should gradually work south and eastward across the CWA through
the day. Temperatures vary significantly across the CWA due to
various amounts of clouds and mixing. Overall...expect
temperatures to start out in the low to middle 30s and rise very
little across the northwest half of the CWA as clouds and the
effects of evaporative cooling from precip limit highs to the
middle 30s. Less cloud cover and a later arrival of the colder
air/precip potential should still allow for readings to reach the
lower 40s along and south of the Kansas Turnpike...which will
offset the colder start due to less clouds early this morning.
Colder air aloft will move across the CWA through the day and
precip associated with frontogenetical forcing should reach the
ground primarily as snow from northwest to southeast through the
mid and latter portions of the day...although if drying aloft
increases resulting in the loss of ice...precip could fall as
drizzle or very light rain with temperatures above freezing. This
is especially true along and east of the Turnpike. Models are not
in agreement on how much saturation persists through the day...so
have worded forecast as rain or snow across the southeast half of
the CWA through the day with an overall snow potential across the
northwest. Although precipitation will taper off across the
western CWA tonight...it will linger as snow across the eastern
CWA. Another concern is snow amounts with the ground still
relatively warm from the recent milder temperatures. There is
concern that if snowfall rates remain light...it will primarily
melt as it hits the ground before temperatures fall below freezing
tonight. Either way...as frontogenetical forcing and overall lift
with the trough weakens with time through tonight...snowfall
amounts across the CWA are expected to be less than an inch. Lows
tonight will range from near 30 in the far eastern CWA to the
middle 20s in the far north central.

.LONG TERM...(Wednesday through Monday)
Issued at 343 AM CST TUE DEC 23 2014

There may be some lingering snow Wednesday morning as the GFS and
ECMWF hint at in the QPF progs. However think any snow Wednesday
morning will be short lived as the upper trough remains
progressive in moving east. What little forcing there may be
Wednesday morning should come to an end pretty quickly. Models
show a west wind with some weak warm air advection by the
afternoon. Low clouds may also try to mix out as subsidence
increases through the day. Because of this, have trended highs for
Wednesday a little warmer.

Wednesday night and Thursday should be dry as shortwave ridging
moves overhead. Models deepen a surface low over eastern CO on
Thursday. This should cause the pressure gradient to strengthen
and south winds to advect warmer air north. Think that with only
some highs clouds to contend with, insolation combined with strong
warm air advection could help push afternoon highs on Christmas
day to around 50. If the low level lapse rates can become dry
adiabatic, highs could several degrees warmer.

Have continued with a dry forecast for Thursday night through
Friday night as models track a shortwave lifting northeast through
central NEB and the strongest forcing remaining northwest of the
area. Additionally, moisture return ahead of the system is not
very good and models fail to saturate the column to the east of
the surface low track Thursday night. So what forcing there will
be should not have much moisture to work with. The one question
mark is on Friday afternoon across east central KS where some
better low level moisture may surge northeast. At this point it
looks like a low chance for some light QPF so have opted to keep
the POPs below 20 percent for now.

Think the weekend will also be dry as the next wave passes through
the southern plains and cold dry air builds in with a surface high
pressure system. Am a little skeptical of the ECMWF`s prog of
precip over eastern KS on Saturday as it shows the 850MB front
into northeastern OK and southern MO with dry air advecting south.
The precip seems to be a function of strong frontogenesis, but I
don`t see the moisture availability. So think the weekend will be
cold and dry with Canadian airmass building south. Monday appears
to be dry as well as mid level energy digs southwest over NV and a
reinforcing Canadian airmass build south. Moisture continues to
look limited with a quasi zonal flow aloft and no obvious forcing
for precip. Highs Saturday through Monday are expected to be in
the 30s. Lows should be in the teens and lower 20s.

&&

.AVIATION...(For the 06Z TAFs through 06Z Tuesday Night)
Issued at 1142 PM CST MON DEC 22 2014

Could see brief very light precip at the terminals over the next
few hours from mid cloud. Reductions from low cloud still expected
for much of the period from 15Z through the end of the forecast,
likely MVFR. There is enough potential for precip development for
an inclusion, but will keep MVFR going with still some doubts on
intensity and duration.


&&

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

&&

$$

SHORT TERM...63
LONG TERM...Wolters
AVIATION...65





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