Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 282333
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
533 PM CST Wed Jan 28 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Thursday)
Issued at 309 PM CST WED JAN 28 2015

Shortwave over the central Rockies is now moving over the plains and
eventually into the longwave trough over the eastern US. There is
very limited moisture and lift with this system therefore expect dry
conditions as it tracks across KS. Ahead of the system a front
currently located over central KS will gradually shift eastward. The
deepest mixing today has occurred ahead of the front with
temperatures reaching the mid to upper 70s. In north central KS
cloud cover and shallow mixing along the front has kept temperatures
in the upper 50s. High level clouds have spread over the entire
area, which may limit any further warming beyond a few degrees. With
the deep mixing RH values have managed the mid to lower 20 percent
range. Winds in the same regions are gusting 25 to 35 mph causing
very high fire danger for the rest of the afternoon. As the front
sweeps across the area winds shift to the northwest and increase
especially after midnight when the shortwave exits the region. Wind
gusts around 25 to 35 mph are expected to last through early
afternoon tomorrow. Cold air advection overnight will cause the
boundary layer to remain mixed and low temperatures to stay in the
mid to upper 30s. Tomorrow will be much cooler, and lower cloud
cover moves in from the north. High temperatures range from 45 to 50
degrees with the warmest temps over central KS where cloud cover may
be less than far northeast and eastern KS.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 309 PM CST WED JAN 28 2015

An upper trough will be shifting slowly east across southern
California on Friday with southwesterly flow aloft streaming mid
and upper level moisture toward the Plains. A northern stream
trough will also be diving southeast out of Montana by Saturday
morning and taking aim on the Central Plains by late Saturday.

Friday will be seasonal with temperatures in the lower to middle
40s for highs, and somewhat limited by incoming cloud cover from
the southwest as moisture streams into the area. Temperatures will
fall into the lower 30s on Friday evening but should then remain
nearly steady or even rise a bit overnight as cloud cover and
south winds increase a bit. Lead short wave energy will approach
the area from the southwest after midnight, bringing enhanced lift
into central KS before sunrise. Dry air in the low levels should
preclude much precip from reaching the surface through sunrise,
but have included a slight chance in central KS.

During the day on Saturday, the initial lead short wave will move
across the area with a secondary piece of energy impacting the
area by later in the day. Should note here that model guidance has
been highly variable regarding precip Saturday into Saturday night
given that only minor fluctuations in timing of the SW and NW
systems will impact phasing and resultant precip. Current
indication is that the bulk of precip will be focused south of
I-70 where temperatures will also be a bit warmer, favoring more
of a rain event...but this is still subject to change.

The early waves should provide enough lift in conjunction with the
ample mid and upper moisture to saturate the column down and bring
rounds of precipitation. Temperature profiles are walking a very
fine line between rain and snow, and could see the precip type
fluctuate based on precipitation intensity and dendritic flake
size as the near-surface melting layer should remain with similar
temperatures through the day. Given the current expected profile,
have maintained the forecast for a rain or snow mix through the
day on Saturday and into the evening. Currently expect air and
ground temperatures to be warm enough to preclude any decent snow
accumulation, although there could be occasional slushy build-up
on the roads if any bands of moderate snow can develop. Warm
temperatures continue into the evening, but the system coming from
the northwest eventually brings a stout cold front into the area
by late evening and overnight. This front could bring a band of
enhanced frontogenesis and a period of snow as it moves northwest
to southeast across the area. Additionally, any wet roads from
early precip will be likely to freeze up with patches of ice
developing. Precip will come to an end across the area by Sunday
morning.

In the wake of this system temperatures will be much
cooler...colder than normal even...through the end of the
forecast. Northwest upper flow will remain overhead through the
period with occasional weak disturbances bringing rounds of weak
vertical motion but likely insufficient to produce any
precipitation so have kept the remainder of the forecast dry at
this time.

&&

.AVIATION...(For the 00Z TAFs through 00Z Thursday Evening)
Issued at 533 PM CST WED JAN 28 2015

Initial boundary pushing through and diurnal trends brings winds
down to start, but reinforcing cold fronts causing veering and
increasing winds in the 03Z through 10Z periods. Hard to argue
much with previous timing of MVFR ceilings arriving with the
second front. When the ceilings diminish is uncertain, but went on
the conservative side at this point.

&&

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

$$

SHORT TERM...Sanders
LONG TERM...Barjenbruch
AVIATION...65





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