Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 302327
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
627 PM CDT SAT JUL 30 2016

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Sunday)
Issued at 330 PM CDT SAT JUL 30 2016

The little MCS that was over central NEB at the start of the day has
now just about moves all the way through the forecast area. Limited
instability and shear down stream of the system prevented it from
strengthening. But with a lack of inhibition to a surface parcel,
lift from the rain cooled air has been enough for the MCS to
persist. Looking at the 20Z water vapor imagery, there doesn`t
appear to be an obvious shortwave upstream from the forecast area
and surface obs indicate the surface ridge continues to weaken while
a lee trough over the central high plains gradually deepens.

For tonight and Sunday, models show the low level jet increasing and
veering to the southwest late tonight and into Sunday morning with
warm air and moisture advecting back into northeast KS. With the
outflow boundary laid down by this afternoons MCS, the expectation
is for elevated storms to redevelop by the late evening within the
warm air advection pattern as the low level jet veers to the
southwest. The high resolution models have done a poor job with
the convection today and the GFS/ECMWF/NAM haven`t faired much
better. However the GFS/ECMWF/NAM seem to show a signal for elevated
storms in about the same location and time. This would fit the
current conditions with the outflow over the area. So while
confidence is not terribly high, the setup appears favorable and
have increased POPs into the 60 to 70 percent range. The storms are
expected to linger through part of the morning Sunday so have POPs
tapering off by the afternoon. Mid level lapse rates do not appear
to be significantly steeper than this afternoon (6 to 6.5 C/km) and
deep layer shear vectors are progged to remain on the weak side
between 20KT and 30KT. So widespread severe storms appears unlikely,
we`ll need to keep a look out for an isolated strong storms.

Lows tonight may be a little tricky in that elevated storms could
cause lows to be cooler by a southerly wind and increasing clouds
may act to hold temps up. Stayed close to the model consensus with
lows around 70s for the most part. Increasing warm air advection and
clearing skies during the afternoon should help Sunday`s highs warm
into the lower and middle 90s. If the rain lingers over eastern KS
later into the day, these highs may be a touch on the warm side.

.LONG TERM...(Sunday Night through Saturday)
Issued at 330 PM CDT SAT JUL 30 2016

Weak elevated instability with still some decent isentropic upglide
around 750mb is suggested by the NAM and GFS to persist into the
evening hours near STJ. Will keep small pops going here but expect
most action to be on northeast by this time. Stronger zonal flow
develops over the Northern Rockies Monday with areas of cyclogenesis
to the west and northwest. At this point believe any convergence in
and near northern Kansas would be too limited to break the
developing cap for daytime convection. Monday night into Tuesday
night however there are indications of increasing moisture aloft as
southwest flow persists and will keep small precipitation chances
for these periods. Next best precip chances come from Thursday into
Friday with still suggestions of a boundary settling in. Main
concern for these periods continues to be heat with 850mb temps
solidly in the mid to upper 20s C and dewpoints well into the 60s to
lower 70s. The potential for convective episodes brings questions on
the persistence of realizing these apparent temps in time and space.
Models diverge aloft by Saturday with handling of where ridge will
attempt to re-amplify. Will go with conditions near early August
normals for now.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 622 PM CDT SAT JUL 30 2016

For the 00Z TAFs, no need to make major changes to the going
forecast as some consistency in guidance suggests that isolated
storms form after midnight and work from west to east by early
morning Sunday as the LLJ veers. Have tried to narrow down the most
probable times at this point in the forecast. Do expect that VFR
outside of storms will still be the case. MVFR still expected with
storms as they move through mainly due to VIS restrictions as
storms should be high based.

&&

.TOP Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Wolters
LONG TERM...65
AVIATION...Drake


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