Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 211756
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1256 PM CDT Thu May 21 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 341 AM CDT THU MAY 21 2015

Northern stream shortwave is currently progressing eastward over the
Midwest this morning as an upper ridge builds in behind the wave.
Lower cloud cover has broken up across portions of the area this
morning leaving mostly clear skies with the exception of near the
MO/KS state line. Surface high pressure was still located northwest
of the forecast area, and will build southward through out the day.
This means a slight pressure gradient is still in place, which could
offset the radiational cooling. Although, fog is still possible at
some locations especially northern KS where the clouds have cleared
out early and winds are overall lighter. Some higher level clouds
spread in from the west later today and high temperatures reach the
mid to upper 60s. Winds will become fairly calm as the center of the
high slides through this afternoon and evening. Models are in good
agreement that a lead shortwave trough will kick out of the SW US
tonight. This trough will support moisture return and isentropic
lift over western and central KS early tomorrow morning. There are
some indications that this precip could reach southwest portions of
the forecast area around sunrise therefore have included a slight
chance for showers.

.LONG TERM...(Friday through Wednesday)
Issued at 341 AM CDT THU MAY 21 2015

Friday through Wednesday, a longer wave length upper level trough
embedded within the southern stream of the upper level jet will
remain across the southwest US through next week. Expect scattered
to numerous showers and thunderstorms through the period. The
southern stream jet looks rather weak, thus the vertical wind shear
will not be supportive of more intense organized storm updrafts.

Friday, the first H5 trough will lift northeast across NM into
western KS and NE. The mid and upper level flow will be stronger,
however a cool and stable low-level airmass will be in place. There
may not even be enough instability for thunder. skies will be mostly
cloudy and easterly winds will keep Highs only in the lower to mid
60s.

Friday night through Saturday, An upper low across the four corners
region will amplify slightly. This will cause a downstream upper
ridge to amplify across the eastern plains and southern MS river
valley. Deeper moisture advection will provide enough isentropic
lift for scattered showers and thunderstorms. The instability may
increase to around 1200 J/KG Saturday afternoon across the western
counties of the CWA for some strong pulse storms. Highs Saturday
will warm up a bit into the upper 60s to around 70.

Saturday Night through Sunday, Another shortwave trough will lift
northeast across west TX into western OK and central KS, rotating around
the upper low over southwest CO. Our chances for showers and
thunderstorms will increase late Saturday night into Sunday. The
primary hazard would be heavy rainfall. Highs will warm into the

Sunday night and Monday, There may be a break in the showers and
thunderstorms as eastern KS will be between two shortwave
troughs. I cannot rule out isolated showers or thunderstorms due
to the deeper moisture in place, weak cap and afternoon
insolation. Highs will warm into the mid to upper 70s.

Monday night and Tuesday, An upper level trough over NM will fill as
it lifts northeast across southwest KS into southeast NE and western
IA. Stronger ascent will provide a better chance for showers and
thunderstorms across the CWA. The 0-6KM effective shear looks weak
with only 35 KTS at 500 MB and veered 850mb winds. If the
instability increases then there could be a few strong pulse storms
during the afternoon and evening hours of Tuesday. Highs will be
around 80 Tuesday afternoon.

Wednesday, west-southwest mid and upper level flow with deeper
moisture in place may allow for a few showers and thunderstorms to
develop during the afternoon hours. The better chance will be
closer to the surface trough in western KS. Highs will reach the
lower 80s.

&&

.AVIATION...(For the 18Z TAFs through 18Z Friday Afternoon)
Issued at 1256 PM CDT THU MAY 21 2015

VFR conditions are expected through the period. Winds will be
light and variable becoming southeast around 8 kts after 15Z
Friday. SHRA are expected to move into the MHK terminal by 16Z.

&&

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

$$

SHORT TERM...Sanders
LONG TERM...Gargan
AVIATION...53






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