Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 251741
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1141 AM CST Thu Dec 25 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 333 AM CST THU DEC 25 2014

Water vapor and IR satellite imagery high level moisture
streaming northeastward across the central plains. A sfc low over
the high plains continues to deepen and has resulted in an
increase in surface winds and temperatures with the mixing and
high clouds. Models in good agreement that the corridor of
strongest pressure gradient and surface winds will be across the
Flint Hills of the southern/southwest portions of the county
warning area. By late morning expect south winds to increase into
the 25 to 35 mph range with gusts near 45 mph before slowly
decreasing after 2 pm as the pressure gradient will gradually
start to relax. Feel that wind speeds should be lowering by 4
pm...so have decided to issue a wind advisory for 6
south/southwest counties of the CWA from 11 am to 4 pm.

With the good warm air advection and strong mixing...highs from the
upper 40s north to low to mid 50s south look good despite the
presence of some high clouds. As the front moves eastward and
bisects the county warning area tonight...should see an increase in
low level moisture and stratus across the northwest CWA behind the
front and ahead of the front across the southeast. This will also
set the stage for temperature gradient with lows ranging from the
middle 20s north central to the low 40s across the far southeast
corner of the CWA. Will maintain a dry forecast through the period.

.LONG TERM...(Friday through Wednesday)
Issued at 333 AM CST THU DEC 25 2014

The models continue to show the potential for light precipitation
Friday afternoon and into the morning Saturday. Moisture
availability appears to be the biggest question mark. Models prog
the better forcing to move overhead during the day Friday while
they try to saturate the airmass. Nevertheless most model
solutions bring light QPF into the area by Friday evening, so have
maintained chance POPs mainly for Friday evening. Initially temps
may be warm enough at the surface for precip to be mainly rain or
drizzle through the afternoon. As the front slowly moves southeast
and cold air advection increases, there should be a change over to
snow. Forcing and moisture overnight Friday night suggest any snow
amounts will be an inch or less. However the biggest concern
Friday night is some of the models showing mid level dry air
suggesting the dendritic growth zone may not be saturated and
there could be some light freezing drizzle or light freezing rain.
Cross sections show possible CSI or even upright instability so
for now think precip may be driven more by frontogenesis and
instability such that there would be enough vertical motion to
keep the dendritic zone saturated. But precip type will be
something to keep an eye on. All of the models show the airmass
drying out rather quickly on Saturday. Because of this think that
any precip will be coming to an end by mid morning and have
trended POPs down through the morning.

Sunday is expected to be dry before another front and arctic
airmass move through the area on Monday. With the cold air
advection and frontogenesis likely with the front, there could be some
light snow accumulations late Monday and Monday night. With much
of the upper level energy digging southwest towards southern CA,
there doesn`t appear to be a great amount of forcing or moisture,
so snow should be light. Think by Tuesday much of the snowfall
should come to an end as models diminish the mid level
frontogenesis. Tuesday afternoon through Wednesday should be dry
with cold arctic air moving in place and the forecast area between
a closed low over the southwest and northwest flow over the Great
Lakes.

Continued with much colder temps for Tuesday and Wednesday as
models modify a 1050MB surface ridge over the central plains.
Highs in the teens and 20s appears plausible.

&&

.AVIATION...(For the 18Z TAFs through 18Z Friday Afternoon)
Issued at 1138 AM CST THU DEC 25 2014

VFR conditions are expected for the majority of the period.  Gusty
winds will continue throughout the afternoon until 00Z when the
pressure gradient begins to weaken.  The cold front will begin move
through the CWA from NW to SE by 06Z tomorrow causing southerly winds
to veer from the north.  At 15Z, stratus will begin to affect all
sites moving in from both north and south of the area.  Some models
are indicating the potential for fog formation, but will leave that
out until there is more confidence.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY until 4 PM CST this afternoon FOR KSZ037-038-054-
055-058-059.

&&

$$

SHORT TERM...63
LONG TERM...Wolters
AVIATION...Heller





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