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000
FXUS63 KTOP 011127
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
527 AM CST Sun Dec 1 2013

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 335 AM CST SUN DEC 1 2013

Westerly flow in advance of a shortwave trough over the southwest
CONUS this morning continues to stream high clouds just to our
south over far southern Kansas. A weak to nearly stationary
frontal boundary is stretched west to east across northern Kansas.
Ahead of the weak trough over the panhandles, a plume of moisture
has increased dewpoints around 35-40F northward into Oklahoma and
southern Missouri. This slight moisture increase for far east
central areas with a decent surface inversion has prompted some
concern for patchy ground fog to continue and/or develop through
the early morning. While best chances for reduced visibilities are
near bodies of water such as lakes and rivers, cannot rule out a
few areas especially south of Interstate 35 falling around or
below 1 SM at times. Any developing fog should quickly lift by mid
morning.

The surface trough over Texas is expected to shift eastward on
Sunday as area of high pressure slides southeast through the
afternoon. In turn, light winds from the north during the morning
hours, becoming variable through the early evening. Colder temps
noted to the northeast with lack of strong mixing or warm air
advecting in should cool high temps down a few degrees from
Saturday in the lower to middle 50s.

On Sunday evening, a lead shortwave trough ahead of the incoming
potent low pressure system shifts southeastward across the northern
plains. Mid level moisture increasing between 700-500 MB should
result an increase in cloud cover for the northern and eastern half
of the county warning area. Surface flow increases slightly and
veers to the south between 5 and 10 mph. These conditions should
keep overnight lows a tad warmer in the upper 20s to lower 30s.

.LONG TERM...(Monday through Saturday)
Issued at 335 AM CST SUN DEC 1 2013

Monday is looking warm with models showing decent warm air
advection at the surface and 925MB. Because of this have bumped
highs up into the lower 60s for most areas Monday and also nudged
up lows for Tuesday morning expecting a southerly wind to persist
and keep some modest mixing in the boundary layer.

A stark change in temperature will affect central and eastern KS
by Wednesday. While the general consensus is that the GFS remains
to progressive with the Canadian front on Tuesday, the ECMWF has
come in trending faster with the cold air and the NAM is not
terribly different from the ECMWF. Much of the uncertainty in
timing is coming from the models handling of a closed wave moving
down the British Columbia coast and then east across the northern
plains. There remains some spread in solutions with respect to
this wave, with the GFS the fastest and the GEM the slowest. But
there does appear to be some convergence in model solutions with
the ECMWF/UKMET/NAM beginning to cluster. With this in mind, the
forecast weighted the ECMWF/NAM solutions a little more heavily
resulting in the front entering north central KS late Tuesday and
exiting the forecast area to the southeast by Wednesday morning.
The biggest change to the previous forecast was to cool temps
about 10 degrees on Wednesday.

Models do not show much in the way of moisture ahead of the front.
Most solutions show a wave moving across the forecast area with
some forcing for precip on Tuesday, but none of them show any
meaningful mid level moisture for the wave to work with. Then by
the time the front enters the area, the better forcing has passes
to the east and northeast. Because of this have continued with a
dry forecast as the front passes through the area. Did keep a
chance for some light snow Wednesday night through Thursday night.
The GFS and ECMWF suggest an embedded wave withing the southwest
flow aloft could bring enough moisture to saturate the column
while there is still some decent mid level frontogenesis
available. Precip type appears to be of little question as the
ECMWF and GFS show the profile completely below freezing by
Thursday morning. Therefore think there could be a band of light
snow late Wednesday night into Thursday. At this point the forcing
and available moisture appear to be pointing towards minor
accumulations if everything comes together. By Friday and Saturday
think dry air will once again overcome any weak disturbance within
the large scale pattern as the Canadian ridge of high pressure
build south, and have a dry forecast going. Temperatures are not
anticipated to moderate much through the end of the week as cold
air advection persist into Saturday morning.

&&

.AVIATION...(For the 12Z TAFs through 12Z Monday Morning)
Issued at 511 AM CST SUN DEC 1 2013

Occasionally dense and shallow fog at KTOP is showing signs of
improvement to MVFR visibility aft 12Z, gradually lifting to VFR
aft 14Z. VFR prevails at KFOE/KMHK through forecast period. Light
and variable winds through the afternoon gradually shift to the
south aft 00Z below 5 kts with an increase in mid level clouds
overnight.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Wolters
AVIATION...Bowen