Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 201114
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
614 AM CDT Sun Aug 20 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 345 AM CDT Sun Aug 20 2017

There are two shortwaves of interest this morning. One is over
eastern NE and supported the development of an MCS currently moving
into portions of northeast KS. A low level jet around 30 kt out of
the southwest is intersecting this associated cold pool and allowing
additional storms to form. There is a fair amount of instability
ahead of this outflow so expect that convection could continue until
the low level weakens in a few hours. The short term models have
been struggling with the overall coverage and propagation of this
MCS. So far most of the solutions are too far north with the track,
therefore confidence on how far to the south storms will reach is
not certain. There is a chance that storms could reach I-70 by
sunrise. The more intense convection looks to remain over NE, but
wind gusts up to 50 mph could be possible within the strongest cells
across far northeast KS and 35 mph with the gust front the next few
hours. Another shortwave is over OK and moving northeastward through
out the day. It may be providing enough lift for the isolated storms
currently in southeast KS, and could allow them to persist through
the late morning. Therefore have kept the pops in locations near the
I-35 corridor.

The outflow from this MCS could reside in our area through
the afternoon and be the focus for isolated to scattered storms.
There appears to be limited forcing later today besides the weak
shortwave that tracks over southeast KS, so if storms can form
expect mainly isolated coverage. The area of least inhibition
happens to be the area with the most cape, which is east central and
southeast KS. The mucape this afternoon is forecasted to be upwards
of 4000 j/kg, which is enough to support strong convection. There is
very little deep shear so updrafts might not maintain strength for
long, but isolated hail and localized downdrafts could be possible.
Highs today will reach the mid to upper 90s with a few locations
hitting the lower 100s. These temperatures along with dew points in
the mid 60s to mid 70s will cause heat indices to reach the lower to
mid 100s. Tonight southwest flow aloft opens up the potential for
weak shortwaves to track over the region as evident in some of the
models. These waves could provide lift for further development.
Confidence is pops tonight is low given the variability in the model
solutions and the lack of a clear cut scenario.

.LONG TERM...(Monday through Saturday)
Issued at 345 AM CDT Sun Aug 20 2017

Monday continues to bring a variety of forecasting problems. Models
remain consistent in the upper wave now over northwest Mexico
reaching western Kansas late tonight and coming on northeast during
the day. Fairly persistent cirrus over eastern Arizona and New
Mexico early this morning looks to move in during the day, though
could hold off until the mid afternoon. Precipitation chances look
to be generally increasing from the late morning through the
nighttime hours as precipitable water values reach around 2
inches. There is small potential for overnight storms to linger
into the morning, then large-scale forcing ramps up with the
approaching wave and dewpoints again in the upper 60s to mid 70s
contributing to little convective inhibition and 1500-3000 J/kg
ML CAPE for the afternoon. Deep shear is not very strong but
enough with the CAPE for minor severe weather potential. The
western wave then merges with a wave and cold front coming
southeast out of the northern Plains Monday night for more
widespread thunderstorm potential and heavy rain threat. Outside
of precip and deeper cloud, heat index values look to be peaking
in the mid 90s to near 100 Monday afternoon. Overall the potential
for clear and long- term viewing of the eclipse is low though
could see scenarios for at least brief breaks in the clouds.

Cold front should push south of the area by mid afternoon Tuesday
for decreasing precip chances through the day.  Dry conditions then
still anticipated into the late week with surface ridge in place.
Some chance for convection returns Saturday in warm air advection as
the northwest flow aloft backs somewhat.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 609 AM CDT Sun Aug 20 2017

Some convective debris should give way to mostly clear skies by
late morning. The winds are currently our of the northeast, but
will gradually veer to the south through the morning. There is a
slight chance for an isolated storm this afternoon through the
overnight.

&&

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

$$

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



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