Area Forecast Discussion
Issued by NWS Topeka, KS

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956
FXUS63 KTOP 180901
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
301 AM CST Mon Dec 18 2017

.SHORT TERM...(Today and tonight)
Issued at 256 AM CST Mon Dec 18 2017

Split upper level flow continued across the central conus. The
northern branch of the upper jet was located across the northern US
and southern Canada where it phases with the subtropical jet across
the mid Atlantic States. An upper low was embedded within the
subtropical jet and was located over northern Mexico early this
morning. The upper low over northern Mexico will gradually lift
northeast into eastern NM and far west TX by 12Z TUE. A broad upper
level trough was located across the upper midwest this morning and
will amplify across the Great Lakes states.

Early this morning there may be some patchy dense fog across far
northeast Kasas. The visibility has dropped at Marysville to one
quarter of a mile. The denser fog across northeast KS will be in the
clearing area behind the low stratus clouds, which are moving east
across the eastern counties of the CWA and should move out of the
CWA after 12Z. Any patchy fog will mix out by 14Z.

Today, eastern KS will remain in weaker zonal flow between both the
northern and southern stream jet maxes. At the surface a lee surface
trough will deepen a bit and cause surface winds to remain from a
southwest to southerly direction. The resulting WAA and insolation
will help high temperatures to warm into the mid to upper 50s, which
is about 17 degrees above our normal high of 41 degrees at TOP.

Tonight, southwesterly surface winds will only allow overnight lows
to drop into the lower 30s across north central KS with mid to upper
30s across east central KS.

.LONG TERM...(Tuesday through Sunday)
Issued at 256 AM CST Mon Dec 18 2017

Early to mid week, the southern stream Westerly energy in the form
of an upper closed low will begin a more progressive evolution
partially filling and transitioning into an open wave but still
forecast to pass south of the forecast area.  This leaves upper
zonal flow in place over the central Plains in Kansas.  Therefore, a
dry and above normal temperature regime still in place into the
Thursday time frame with overall higher heights in place.

Model trends have continued from past runs to lift the Thursday
developing mid-latitude cyclone deformation zone to the north of the
forecast area.  At this time, seeing wrap around frontogenetical
band of snow extending back into the forecast area seems to be
smaller and smaller chances.  Therefore much of the expected
snowfall that does develop will likely remain in Nebraska as Kansas
is more influenced by the developing dry slot area.  Progressive
nature of the GFS does deepen the system more quickly as elongated
shortwave rotates through the Rockies into the Plains states. ECMWF
meanwhile is slightly slower with this evolution and not quite as
strong.  Still thinking that most precipitation will be east and
north of the area as developing fronts sharpen and push out of the
area.  Also, more northerly track of the system probably doesn`t
allow for CAA to filter into the region as quickly as previous
forecasts.

Friday should see the below normal temps working into the area as
the upper trough rotates through.  This will set the stage for a
more uncertain period into the weekend and Christmas Eve in
particular.  The upper pattern becomes more highly amplified with a
Pacific ridge again along the California coast into western Canada.
This in return causes an elongated lobe of energy to dig into the
northern Plains extending into portions of the inter-mountain west
and the Four Corners region by Sunday.  GFS operational solution and
GEFS members have been suggesting that incipient wave developing
within a region of strong ascent ahead of this deepening trough may
move just to the south of the forecast area.  Only 2 GEFS members at
this time have the weather feature moving over the forecast area.
The Canadian and ECMWF have kept with the idea of sending a weather
system over the area for Christmas Eve.  Amounts still not too
evident as spreads are just too large and inconsistent.  Regardless,
the ECMWF and Canadian forecast a large positively tilted trough set
up over the northern CONUS into the Central Rockies.  This could
reinforce of frontogenetical band that sets up for a good portion of
the Sunday time frame.  Precipitation would be all snow for this
period if this all materializes with very cold temperatures in
place.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1131 PM CST Sun Dec 17 2017

Clouds should gradually move off to the east early this morning
with clouds exiting from west to east. Satellite trends suggest
that stratus should move out of MHK by 07Z and TOP and FOE in the
08Z-09Z period. Some mvfr vsbys with fog are possible through 14Z
then VFR is expected thereafter.


&&

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

$$

SHORT TERM...Gargan
LONG TERM...Drake
AVIATION...53



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