Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 212058

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

.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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1139 AM CST Sat Jan 21 2017

Models show moisture advection through the evening as an upper
level shortwave passes south of the area. With some weak forcing
and upper level divergence, there should be some scattered showers
across east central KS this evening. Think the terminals may see
some MVFR VSBY with the moisture advection but forecast soundings
keep CIGS above 3KFT. The bigger uncertainty is whether dense fog
redevelops on the northern fringes of the cloud cover and
eventually moves back into the terminals once the rain and cloud
cover passes east. Some of the high resolution solutions show this
potential. Went with the consensus which keeps any dense fog north
along the MO river, but will need to monitor trends in the models.




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