Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 261723
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1223 PM CDT Sat Jul 26 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 308 AM CDT SAT JUL 26 2014

At 3 AM, there were several features of interest located across the
region. First, a frontal zone extending from near Concordia into far
southeastern Nebraska. Temperatures were only slightly cooler north
of the front with some low level convergence along the boundary. The
low-level moisture was a bit deeper north of the front, and also
with eastward extent in the CWA while there was a relatively dry
zone with Td`s in the low/mid 60s in parts of the Flint Hills. There
was also a zone of weak isentropic ascent within a sharply veered
low level jet stream across the southeastern half of Kansas. A belt
of 300 to 500 J/kg of MUCAPE rooted around 8000 feet was in place
across east central KS, and the LLJ lift coincided with the MU
lifted parcel level in this area...resulting in scattered shower
development with a few t-storms possible through sunrise from
Emporia over toward Ottawa.

Another feature which will have a substantial impact on today`s
forecast was a short wave trough with an embedded MCV moving into
central KS at 3 AM. The wave was moving into a more stable airmass
and convection has been dissipating early this morning. At the same
time, the lift with the compact system remains strong enough to
produce precipitation albeit with little to no lightning. Expect an
area (likely shrinking with time) of light to moderate rain and
embedded thunder to move across the forecast area this morning, and
have timed the POPs with recent movement of the MCV. This precip
could very well come to an end before it reaches eastern KS, or
another lower-likelihood scenario would be a slight increase in
coverage and intensity from mid morning into the afternoon as
instability increases a bit ahead of the system. For now will run
with slight chances of accumulating precip, and widespread mid/high
clouds. The clouds will obviously impact the temperature and
dewpoint forecasts, and could provide relief from the intense heat.
However, expect these clouds to be exiting the area and decreasing
west to east by early afternoon, which should leave plenty of time
for afternoon heating. Dewpoints may remain a bit higher, but the
strongly veered flow pattern should eventually mix more of a
westerly component to the surface along with lower dewpoints. The
current heat index forecast remains in the 103 to 108 range across
the entire area but with a small potential to hold lower.

Late today into tonight, the region will begin to feel the effects
of a strong short wave trough moving into the Great Lakes region.
Will see gradual height falls after 00Z along with a gradual
increase in cold advection. The surface front will drift south and
additional mid-level moisture will move into the area. There is a
slight chance for storms in the vicinity of the front late afternoon
into early evening, but the mixed layer parcels are likely to have
fair amount of inhibition and the forcing is just not very strong so
convection is questionable and isolated if it develops. If storms
develop, localized damaging downburst winds would be possible. Will
also keep an eye on northern Nebraska where there is some chance for
an MCS to develop this afternoon and propagate southeast into
northeast KS. This is a low confidence scenario, but possible.
Otherwise, look for a slightly better (but still slight) chance of
storms during the overnight hours as the glancing short wave may
provide lift for moderately unstable elevated parcels. There would
be a small chance of strong winds with overnight activity, but
severe weather is unlikely.

.LONG TERM...(Sunday through Friday)
Issued at 308 AM CDT SAT JUL 26 2014

A mostly quiet period expected in the extended forecast for
northeast Kansas. Dry northwest flow aloft spreads southward behind
the front, quickly clearing out precipitation on Sunday. Dewpoints
are expected to mix down into the low 60s while cool air advecting
southward behind the departing trough will hold highs 10 degrees
cooler than Saturday in the low 90s. Northerly winds aloft remain
rather strong, prompting sfc gusts around 25 mph in the afternoon.

The below normal temperatures are here to stay for next week as
light winds and cool high pressure settles over the central and high
plains. Best chances for more scattered rainfall is on Tuesday
evening and especially Wednesday as a shortwave trough dropping south
over western KS develops a cluster of storms expected to push south
and east through the state. At this time, elevated instability is
very weak with MLCAPE values at 200 J/KG at best so believe much of
the activity would be in the form of showers with perhaps an
isolated thunderstorm or two. Meanwhile a potent upper trough is
progged to deepen southward through mid week over the upper Great
Lakes region. Latest runs of the GFS and ECMWF still having a
difficult time discerning the depth of this wave and subsequent
minor weak waves, in addition to the lack of decent moisture across
our cwa. For now, sided with the consensus blend that keeps slight
chances for isolated afternoon thunderstorms on Thursday and Friday.
Believe most areas should stay dry with temperatures being
noticeably cooler in the low 80s for highs and overnight lows in the
upper 50s and lower 60s.

&&

.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1223 PM CDT SAT JUL 26 2014

VFR conditions continue to be expected. High-based precipitation
should be ending shortly at KTOP and KFOE with passage of an upper
level wave. Strong convection currently in NE Nebraska will need
to be monitored as it could reach the terminals around 0Z, but at
this point confidence remains too low for inclusion.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY until 8 PM CDT this evening FOR KSZ008>012-020>024-
026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Barjenbruch
LONG TERM...Bowen
AVIATION...65





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