Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 230001
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
601 PM CST Sat Nov 22 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Sunday Noon)
Issued at 259 PM CST SAT NOV 22 2014

Many locations across the area have reached 60 degrees today, as
warm air streams northward across Kansas ahead of the southern
upper trof. Convection remains across Texas and Oklahoma, while
morning low clouds and drizzle have started to thin in afternoon
mixing.

Expect clouds and rain chances to return overnight, although
chances should be slight. By around sunrise, piece of the southern
wave lifts over the eastern part of the state and increases rain
chances. Even some elevated instability and a rumble of thunder is
possible especially east. Next cold front races into the north
central counties through the morning hours. Expect strong winds
and rain chances along with it.

.LONG TERM...(Sunday Afternoon through Saturday)
Issued at 259 PM CST SAT NOV 22 2014

By mid day Sunday the shortwave associated with the main trough
swings over the plains. This advancing trough will drive a cold
front into the forecast area from the northwest, which looks to
arrive in north central KS around 15Z. Further south a low pressure
will form over northeast OK and lift northeastward into MO. Strong
cold air advection behind the front will usher in temperatures into
the low 40s and upper 30s. A decent layer of frontogenesis will
coincide with the large scale lift to produce a post frontal band of
precipitation. This band will move into north central KS around 18Z
and progress eastward through the afternoon and early evening hours.
The predominate precipitation type will be rain especially
initially. As colder air filters in the sounding becomes almost
fully sub freezing with the exception of the boundary layer. Some of
the lift will occur in the dendritic growth layer with a deep layer
of saturation in place increasing the chances for ice crystals in
the cloud. These ice crystals have a good chance of melting in the
1500 ft warm layer at the surface. With full saturation wet bulb
temperatures may only cool the air to around 3 C. Although, if the
frontogenesis band precipitation is intense enough then you could
potentially cool this warm layer due to melting causing a brief
change over to a wet snow. Especially if the better lift
concentrates in the snow growth layer. At the moment I only
mentioned a chance for a rain snow mix. Do not expect any
accumulations at this time given temperatures in the morning will be
in the upper 50s and low 60s, and QPF generally under a quarter of
an inch.

The other issue behind the front will be the strong northwest flow.
Expect surface winds will quickly increase with the frontal passage
given winds at the top of the mixing layer will be around 45 kts and
a decent pressure gradient moves through. It does not appear that
winds will reach advisory criteria, but can not rule out 35 mph
gusts. Northwest flow aloft will dominate the extended, which will
be characterized by a few shortwaves translating across the northern
US. The most notable wave passes well north of us on Wednesday
dragging a cold front through the area bringing only an outside
chance of light precipitation. The GFS is less impressive with this
wave and therefore the cold air is slightly delayed until Thurs.
Surface pressure from Canada looks to take over for the remaining
period as the pattern aloft becomes more zonal. Temperatures will
generally be characterized by highs in the 40s and lows in the
20s.

&&

.AVIATION...(For the 00Z TAFs through 00Z Sunday Evening)
Issued at 539 PM CST SAT NOV 22 2014

This TAF period will remain challenging much like the previous
one. CIGS/VIS continue to hinder some ops at all terminals.
IFR/LIFR conditions are a strong possibility during the overnight
hours affecting all terminals. Confidence in exact timing is low,
but strong low level moisture will remain in play with a favorable
setup otherwise. There is a window of opportunity, albeit small
with some uncertainty, for some general elevated convection to take
place with weak lift after the 0900Z time frame from KMHK then
building east into the KTOP/KFOE terminals. The largest change
with this TAF period will come near the end with a frontal system
causing a shift in winds that will be gusty from the northwest but
with a trend suggesting improving CIGS/VIS. A small possibility of
a rain/snow mix will begin to show up near KMHK near the end of
the period late Sunday afternoon.

&&

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

$$

SHORT TERM...67
LONG TERM...Sanders
AVIATION...Drake





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