Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 241144
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
544 AM CST Tue Feb 24 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 336 AM CST TUE FEB 24 2015

Quiet and temporarily warmer forecast for the next 24 hours across
northeast Kansas. Upper cutoff low remains over the southwest U.S.
this afternoon while a shortwave trough digs southeast over the
Midwest. In its wake, winds across the area shift from the southwest
to the northwest around 10 to 15 mph in the late afternoon. Decent
downsloping winds at 850 mb carry warmer temperatures to the surface
today while sunny skies will result in the warmest day this week.
Thinking mixing will be a bit stronger than operational guidance, so
sided closer to MOS guidance with slightly warmer highs in the
middle to upper 40s for the CWA.

A positively tilted mid level trough tracks southeast across the
inter-mountain west this evening, ingesting the cutoff low and
pushing it eastward.  Winds and temps quickly drop off after sunset
with good radiational cooling to drop lows to the lower and middle
20s. Increased cloud cover from the north with the approaching wave
will steady temps or slightly increase them after midnight.

.LONG TERM...(Wednesday through Monday)
Issued at 336 AM CST TUE FEB 24 2015

A quick-hitting storm system is still on track to impact the area
late Wednesday into early Thursday. This is a complex system and
really seems to be composed of two key parts for the local
forecast area. The primary source of lift will be a compact short
wave trough that focuses deep vertical motion mainly just east of
the forecast area, although it may influence the far eastern
counties of Kansas. The second part is a band of frontogenesis
that will track south across the entire forecast area as the short
wave passes by to the east. Current thinking is that the
combination of these two sources of lift, amidst decent moisture
content, will bring precipitation to the entire forecast area. The
precip associated with the trough will be more persistent while
the precip with the frontogenesis will be in the form of a band
with movement perpendicular to its orientation...resulting in a
quick burst of precip. Temperatures will be a complicating factor
with this system as Wednesday afternoon temps will approach or
exceed 40 degrees for the entire area. Even with the warm day,
believe that they will quickly cool enough to support snow shortly
after precipitation begins to wet bulb down. Given the expectation
for short lived snow and warm ground temps especially in the
western half of the area, have only forecast very light snow
amounts as it will likely melt shortly after falling. Farther
east, the slightly cooler temps may combine with slightly higher
snowfall rates to allow minor accumulation. Expect it to total
under an inch for most, although far eastern counties could see a
bit more depending on the exact track of the upper short wave.
Night fall could support a bit more accumulation too depending on
the timing of the precipitation in conjunction with sunset.

Very cold temperatures will move into the area behind this system
with highs in the upper teens to lower 20s Thursday and
Friday...and Friday morning low in the single digits.

Next weekend is on track to present a broad swath of winter
weather across Nebraska, Kansas, and points east. The storm system
responsible for this is currently just south of the Aleutian
Islands and forecast to drop into the southwestern CONUS by late
week. There seems to be model consistency in bringing a pair of
lead waves across the Plains Friday night and Saturday. All
indications suggest that lift with the first system will be
devoted mainly to cloud cover and saturation...and have held off
any actual precip chances until during the day on Saturday. The
second wave crosses the region on Saturday with a broad area of
moderate to strong isentropic ascent in a deep layer along with
support from a strong upper jet. Temperatures will be plenty cold
on Saturday to support snow and could pick up a few inches over
the course of the day.

Complexity increases Saturday night into Sunday as all current
model guidance brings warmer air into the region both aloft and at
the surface. There are indications that a weak warm nose may
develop over parts of the forecast area while surface temperatures
could be slower to warm above freezing. This gives reason to
continue mention of a mix of snow, freezing rain, sleet, and even
rain as temperatures may eventually climb above freezing south of
I-70. Models are also consistent in keeping areas of northern
Kansas persistently in the snow. There are likely going to be
changes in the coming days, but the take away point from this is
that mixed precipitation types will be possible...and more likely
with southern extent. At the same time, due to the long duration
of the event from Saturday into Sunday and perhaps even into
Monday with more upper energy entering the Plains, and also due to
potential for periods of moderate to heavy precipitation...this
weekend could be a mess with significant winter accumulations
possible.

&&

.AVIATION...(For the 12Z TAFs through 12Z Wednesday Morning)
Issued at 536 AM CST TUE FEB 24 2015

VFR prevails at terminals this forecast period with southwest
winds shifting to the west this afternoon at or above 10 kts.
As winds in the first few thousand feet drop off in the 22Z to 23Z
range...a few short term guidance solutions show a thin layer of
lower cigs developing between 3500 ft and 4000 feet. This deck
gradually increases overnight as the next system with categorical
impacts to terminals arrive after 12Z Wednesday.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Barjenbruch
AVIATION...Bowen






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