Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 220001

Area Forecast Discussion
National Weather Service Topeka KS
548 PM CST Sat Jan 21 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Sunday)
Issued at 258 PM CST Sat Jan 21 2017

20Z water vapor imagery shows an upper level shortwave amplifying as
it moves across the southern Rockies towards the plains. At the
surface, a low pressure system is deepening over the southern high
plains in response to the shortwave. Weak ridging remained over
eastern KS.

For tonight models continue to take the bulk of the dynamics from
the shortwave aloft, mainly to the south of the forecast area.
However the model progs do show some weak forcing, moisture
advection and a diffluent pattern aloft developing over east central
KS this evening. So chances for rain showers this evening appear to
be improving. Although rain amounts will generally be around a tenth
of an inch. The bigger concern is the potential for dense fog to
form along the NEB state line late tonight. The RAP has been
consistent in developing dense fog over Brown and Nemaha counties
and this is supported by the ARW and NMM. Although this is dependent
on how far north mid level clouds advect north as models develop the
fog on the northern fringes of the cloud cover. Additionally surface
winds from the north are expected to freshen towards 12Z which
raises questions about how dense fog may be. Have included a mention
for areas of fog across northeast KS but uncertainty in visibilities
precludes any headline at this time. The next shifts can monitor
trends and reevaluate fog potential. Lows tonight should range from
the lower 30s north where skies may remain clearer longer, to the
lower 40s across east central KS expecting clouds to keep temps from
falling to far.

For Sunday, think skies should clear out by the afternoon as the
system south of the area continues moving east. Some low level cold
air advection is anticipated on the back side of the system so temps
should be cooler than today. Have highs in the lower 40s across
northeast KS where fog and stratus are possible to near 50 in
central KS.

.LONG TERM...(Sunday night through Saturday)
Issued at 258 PM CST Sat Jan 21 2017

Upper ridge building east into the Plains brings clearing skies
Sunday night. Warm air advection increases from the mid to the lower
levels late Monday into Monday night, though still dry through the
bulk of the troposphere so no precip anticipated. Models showing a
significant spread in handling upper energy moving into the central
portions of the CONUS Tuesday, but still keep the local area on the
dry side and precip chances limited, especially south of Interstate
70. Northwest winds behind this system late Tuesday into Tuesday
night brings much colder air in for Wednesday and on into the end of
the week as northwest to northwest flow dominates the column, though
airmass is still modified continental and keeps values near normal.
Will retain some mention of precip Tuesday night into Wednesday as
the trough axis moves through. Any of this appears light at the most
but would turn to wintry phases with time. Dry conditions should be
the rule beyond these periods.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 540 PM CST Sat Jan 21 2017

Light rain showers continue to push northward toward the TAF sites.
These have arrived at the Topeka terminals and should arrive at
within the hour. VFR conditions are expected to prevail at MHK. MVFR
visibilities are expected from 06-10Z at the Topeka terminals as
patchy fog develops within the scattered rain showers. Winds will
increase from the north at 10-15 knots by 15Z Sunday morning. As the
surface low moves southeast of the area, winds will begin to
decrease near the end of the period.




SHORT TERM...Wolters
AVIATION...Baerg is the U.S. government's official web portal to all federal, state and local government web resources and services.