Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 070522
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1222 AM CDT Mon Jul 7 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday)
Issued at 259 PM CDT SUN JUL 6 2014

Current setup across the region this afternoon features the cluster
of cloud cover and thunderstorms pushing southeast over southern MO.
Cumulus field was seen building over east central KS ahead of a
surface trough axis stretched from southwest to northeast over
central NE. Gusty southwest winds are gradually waning as they veer to
the southwest and eventually north over southern NE where the weak
cold front resides.

The cold front is progged to progress southeast before becoming
nearly stationary over the CWA late this evening. This will be the
focus for isolated thunderstorms near the KS and NE border beginning
late this afternoon through the overnight period. Current
environment shows plenty of sfc instability in upwards of 2000 J/KG
and effective shear near 20 kts. Limiting factors are the lack of
strong convergence near the boundary with little to no forcing aloft
to support widespread convection. Latest runs of the HRRR, NMM and
ARW are supportive of this thinking with perhaps an isolated updraft
or two evolving into a thunderstorm cluster late this evening into
Monday morning over northern and northeast areas. Main hazards,
if storms develop, would be gusty winds, small hail, and heavy
rainfall. Most areas, especially over far northeast and east
central, will see an increase in mid level clouds once again holding
overnight lows to the lower 70s.

Frontal boundary lifts northward to southern NE tomorrow, increasing
southerly warm air advection into the area. Highs range from the low
90s near the front over northern KS, to the middle and upper 90s
elsewhere. High dewpoints boost heat indices anywhere from 100 to
104 degrees, just below advisory criteria. A much stronger PV
anomaly will round the upper ridge and track south over the northern
plains during the afternoon. This will help reinforce the surface
front for thunderstorm development beginning late afternoon. Timing
of this shortwave trough is slightly varied with the NAM bringing it
across northern KS by late afternoon while the GEM/GFS/ECMWF center
between 00Z and 06Z. Will side closer to the consensus with
maintaining a chance for thunderstorms in the afternoon, becoming
more likely in the next period. Increasing effective shear, high
instability and a well mixed boundary layer near the front may
produce severe storms capable of strong winds, large hail, and
localized heavy rain.

.LONG TERM...(Monday Night through Sunday)
Issued at 259 PM CDT SUN JUL 6 2014

Convection may be ongoing Tuesday late afternoon into the evening
hours as storms continue along an incoming front. As previously
mentioned, considerable instability south of the front will make
plenty of energy available for large hail, damaging winds, and
locally heavy rainfall through the evening hours. 0-6km shear of
50kts along a boundary could bring a tornado threat, although
setup is not conducive for isolated supercell development, but
rather a strong MCS pattern. Will need to keep watchful eye on
this time period with these ingredients in place, as timing of
front, low level jet development, and impulses in the flow will
influence timing and spatial development of a complex. Higher
concerns at this time are for areas along and north of I70. Have
likely PoPs north with scattered south and decreasing rapidly
after 12z.

As storms and clouds move south of the area Tuesday night, sunshine
and high pressure return with enough time for highs to reach into
the middle 80s for most areas on Tuesday afternoon. Would
anticipate cooler lows in the 60s as this pattern continues for
Tuesday night. By early Wednesday, front begins a northward push
back across the high plains, and may bring a round of return flow
convection from west to east across our area for Wednesday night
into Thursday. Think mid level cap building back in through the
night Thursday night into Friday will relegate most precip chances
to our north, and will carry just a slight chance PoP early Friday
as mid level temperatures are still competing with convective
development potential. Hot temperatures are quick to come back as
the mid level warming mixes temperatures in the 90s down to the
surface for Friday into Saturday. Systems passing through the NW
flow on Sunday may be enough to push a frontal boundary near the
KS/NE border by late Sunday, so will carry a slight chance there,
but still hot with highs remaining in the middle 90s to finish out
the weekend.

&&

.AVIATION...(For the 06Z TAFs through 06Z Monday Night)
Issued at 1222 AM CDT MON JUL 7 2014

For the 06z TAFs, VFR conditions are expected for today. There is a
slight chance for a few very isolated showers and thunderstorms to
pop up near the TAF sites overnight into Monday morning, however the
confidence in occurrence is too low to warrant a mention in the
TAFs. Light and variable winds will shift to the northwest overnight
and towards the east and southeast through the TAF period. There is a
chance for showers and thunderstorms to develop and track southward
over the TAF sites by early to mid evening, so have added the
mention of VCTS. Soundings suggest that borderline MVFR/IFR cigs
will be possible with these storms, so will need to monitor this
potential in future updates.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...67
AVIATION...Hennecke






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