Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 262317
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
617 PM CDT FRI AUG 26 2016

...AVIATION UPDATE...

.SHORT TERM...(This Evening through Saturday)
Issued at 311 PM CDT FRI AUG 26 2016

The main focus for the short-term is on the potential for strong to
severe thunderstorms late this afternoon into this evening,
primarily across northeast and east central KS. Water vapor imagery
shows several bands of moisture continuing to stream northward
across the central U.S., with a shortwave noted across northwest to
north central KS this afternoon. Surface observations show the
frontal boundary that had been stalled out over far southeast KS was
lifting into east central KS as a warm front.  Visible satellite
imagery showed some breaks in the cloud cover across eastern KS,
which allowed afternoon temperatures to reach into the low 80s.  In
contrast, extensive cloud cover remained in place across north
central Kansas today, keeping temperatures cooler near 70 degrees.
Mesoanalysis showed little to no cap in place across eastern KS with
the warming temps and dewpoints near 70 degrees. As a result, 1000-
2500 J/kg of surface-based CAPE was present with 35-45kts of
effective shear. The better 0-1km shear was noted across far
northeast KS at 15-20+kts. With veering low-level flow expected into
this evening, stronger storms may develop rotation and become
supercells. The primary hazards with any strong storms will be
damaging winds and large hail, but cannot rule out the potential for
an isolated tornado as well.  With PWAT values near 2 inches, storms
may also be capable of producing a quick burst of locally heavy
rainfall. As the shortwave passes to the northeast this evening,
expect any remaining storms across eastern KS to become more
elevated, with the better forcing, instability, and shear becoming
more focused across Missouri, thus causing the severe threat to
diminish later this evening. Storms may diminish in coverage
mid/late evening into the early overnight hours, however models show
another embedded shortwave advancing into north central KS overnight
into Saturday morning. With decent isentropic lift and an increasing
low-level jet across central KS, these conditions should support the
development of additional scattered showers and thunderstorms. These
storms should advance into central KS overnight and continue to
track eastward across the outlook area through mid morning. These
storms will be elevated and the potential for any severe weather
from this overnight activity is low.  The main concern will be the
potential for some locally heavy rainfall.

In general, expect precipitation chances to diminish through the day
on Saturday, with the better potential for a few isolated to
scattered storms being focused generally along and south of I-70.
Models show shear being noticeably weaker on Saturday, so the
potential for any severe weather from these isolated Saturday
afternoon storms is low. With expansive cloud cover expected across
much of the outlook area, have lowered high temperatures by a couple
of degrees, into the low/mid 80s.

.LONG TERM...(Saturday Night through Friday)
Issued at 311 PM CDT FRI AUG 26 2016

There is a chance for showers and storms on Sunday and Monday as the
forecast area remains on the western periphery on the high pressure.
Models are hinting at the possibility of a few shortwave troughs to
track just north of the area. So other than that there are no
obvious signs of forcing in this pattern. Soundings are showing an
generally uncapped environment in the afternoon and evening, but
also a lack in warm advection and convergence. Although, the gulf
moisture will continue to stream northward as the high stays locked
over the mid MS valley through the week. So despite the chances for
precip everyday confidence is rather low that any particular
location will receive enough rain for flooding. Deep layer shear
will be on the decreases through the period therefore inhibiting the
severe potential with any storms.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday)
Issued at 617 PM CDT FRI AUG 26 2016

Main concern is whether very weak surface ridging slides into the
KS river valley and allows for some potential IFR CIGS and VSBY
to move south. The NAM appears to be the most aggressive in
bringing the boundary south. Based on current OBs, think the GFS
may be a better solution. Consensus from the models tends to keep
VFR conditions at the terminals so will keep a VFR forecast at
this time. Think if VFR conditions do not hold, that some fog could
develop with light boundary layer winds and a moisture ladened
airmass in place. Will maintain a mention of VCTS overnight as
well. Timing from prev forecast seems to fit with the latest
convection allowing models so that looks fine for now. With no
obvious feature to focus convection, its difficult to be more
specific than VCTS at this time.

&&

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

$$

SHORT TERM...Hennecke
LONG TERM...Sanders
AVIATION...Wolters



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