Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 270041 AAA
AFDTOP

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TOPEKA KS
741 PM CDT Tue Aug 26 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Wednesday)
Issued at 322 PM CDT TUE AUG 26 2014

Another period of complex mesoscale and storm scale local weather is
in store through Wednesday. On Tuesday afternoon, a weak short wave
trough seemed apparent in satellite imagery over central KS and was
moving northeast. Scattered storms, a few now becoming strong, have
developed on the leading edge of this disturbance in an atmosphere
characterized by 1500 to 2000 J/kg of surface CAPE and about 20 kts
of 0-6 km shear. Thunderstorm coverage in advance of this wave is
expected to remain scattered and steadily progress toward the
northeast into this evening before likely dissipating.

The stronger upper disturbance tonight will be displaced north of
the area tonight while the low level jet will be focused slightly
farther west than last night. This should keep the bulk of
convection west and north of the local forecast area as well, at
least through 06Z or even 09Z. However, by around 09Z, the LLJ will
be veering more into north central KS and could support another
round of early morning convective enhancement especially across
northern Kansas. Most model guidance has a history of poor
performance in handling the time period between 06Z and 18Z in the
past few days, and the forecast reflects that. Have leaned closely
to a solution provided by the WRF-ARW which builds the MCS in
eastern Nebraska toward northwest Missouri by sunrise and then
suggests backbuilding into northern KS. This seems plausible based
on orientation of the LLJ and likely progression of the MCS. But, it
should be said that confidence is rather low.

Wednesday morning may see the early storm activity, especially in
northeast KS, with a decrease through around noon. By afternoon, the
forecast will depend once again on small scale features such as
outflow and weak waves aloft. One feature with a bit higher
confidence is the likelihood for more widespread thunderstorm
development in parts of central KS by late afternoon into early
evening while other scattered activity may be possible across the
entire area on the more localized features. Given likelihood for
outflow from morning storms, tomorrow looks to be a couple of
degrees cooler than today, although more ample sunshine than
forecast would make low to mid 90s more likely especially south of
I-70.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 322 PM CDT TUE AUG 26 2014

By Wednesday night the upper low will be centered over CO as a lead
shortwave trough tracks over the northern plains and into the upper
Midwest. In the lower levels a cold front will form along the front
range and progress eastward. Ahead of the cold front the low level
jet strengthens during the overnight hours. The convergence
associated with the jet focuses convection north of the area into
NE, and portions of central KS. The front should begin to push into
the forecast area during the day Thursday. As the upper level trough
exits the Rockies and large scale lift increases Thursday night and
Friday. This is when widespread rainfall is more likely across the
entire area. Organized severe weather will be limited during this
period without sufficient deep layer shear. Although despite weak
lapse rates instability still ranges from 1500 to 2000 j/kg. This
instability and higher bases pose a risk for isolated strong wind
gusts and marginal hail. There is much better agreement that the
upper low tracks overhead Saturday and the front exits shortly
after. Have kept slight pops in far east central KS on Saturday
night for any lingering precip. The models then advertise several
shortwaves tracking over the northern plains causing another front
to pass through Monday and Tuesday.

&&

.AVIATION...(For the 00Z TAFs through 00Z Wednesday Evening)
Issued at 734 PM CDT TUE AUG 26 2014

Thunderstorms in the KTOP/KFOE vcnty with gusty winds to 35 kts
and brief mvfr cigs/ifr vsbys in rain will end by 01z...but
remain in the vcnty until 02z. Otherwise will go with a dry and
vfr taf for all terminals through the period as next convective
event later tonight should remain more north of the terminals.
Will maintain east to southeast winds thru the fcst period
generally under 10 kts.

&&

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

$$

SHORT TERM...Barjenbruch
LONG TERM...Sanders
AVIATION...63





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