Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 091747

1247 PM CDT Wed Jul 9 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 313 AM CDT WED JUL 9 2014

Surface high pressure has taken over the region leaving clear skies
and light winds through this morning. Morning low temps still on
track to reach the low 60s and upper 50s in a few locations. Patchy
fog may develop shortly before and after sunrise especially in low
lying areas. The high pressure gradually retreats eastward today
allowing return flow to become established later in the evening.
Tonight a shortwave embedded within the northwest flow aloft is
forecast to slide over the area. Isolated thunderstorms could
develop across parts of north central KS and south central NE late
in the afternoon as surface heating erodes the cap. Although the
chances remain low due to the lack of mid level support and surface
convergence. As the shortwave drops in the central plains the mid
level lift increases, mid level lapse rates steepen, and the low
level jet develops over KS and NE. MU cape ranging from 500 to 1000
j/kg spreads eastward into the forecast area, and deep layer flow
supports the possibility of organized severe convection. The more
likely thunderstorm develop will take place in western/central NE
around sunset as the wave approaches. This activity could then form
into an organized line or MCS that tracks southeastward into central
KS. The low level jet is forecast to veer through out the night
which may focus the lift more into portions of eastern KS through
the morning hours. Soundings indicate storms will be high based with
wind and hail as the main threats especially during the evening
across north central KS. There is still uncertainty as to where
exactly this possible complex could track and where isentropic
activity could form later in the night therefore have kept likely
pops out of the forecast for now.

.LONG TERM...(Thursday through Tuesday)
Issued at 313 AM CDT WED JUL 9 2014

Thursday, the ongoing remnants of a nighttime MCS, that developed
across the central high plains Wednesday evening, will be moving
across portions of eastern KS. At this time it is difficult to
pinpoint the highest pops. Most operational models show at least a
tenth of an inch of QPF across much of the CWA during the 12Z to
18Z period. The GFS model shows the bulk of the QPF across central and south
central KS. Isentropic lift/WAA will probably help expand the
remnants of the MCS to at least provide measurable QPF across much
of the CWA Thursday morning. At this time I will carry 40 to 50
POPS but these may have to be increased if mesoscale models
continue to show higher QPF. Most of the showers and thunderstorms
should move east of the CWA by 17Z THU. Any left over OFB boundaries
or MCV may initiate at least isolated showers and thunderstorms
across the CWA during the late afternoon hours, so I kept slight
pops through the afternoon hours. Highs on Thursday will be
dependent on cloud cover. The clouds will probably linger over
east central and northeast KS, so I kept highs in the mid 80s. The
western counties will see more insolation and highs should reach
the upper 80s to around 90 degrees.

Thursday night and Friday...most of the extended range models show
another MCS developing Thursday evening across eastern WY and
western NE. The ECMWF...GFS and GEM take this complex of storms
north and east of the CWA during the overnight hours into the early
morning hours of Friday. The NAM model expands the complex of storms
farther west across the eastern counties of the CWA. ATTM, I`m
leaning towards the ECMWF which just clips the northeast counties of
the CWA with the thunderstorm complex.

The thunderstorm complex will move east across northern MO into
the upper Midwest during the afternoon hours of Friday. A broad
upper level ridge will amplify across the southern plains. High
temperatures will warm into the mid to upper 90s, may be a few 100
degree readings across the southwest counties of the CWA. Heat
indices may reach to near 105 degrees across east central and northeast KS
if dewpoints remain in the lower to mid 70s during the afternoon hours.

Friday night through Saturday, the upper level ridge continue to
remain in place across the southern plains. Most of the CWA will
remain dry as minor upper H5 troughs move around the periphery of
the upper level ridge axis across NE.

Saturday night through Tuesday, an intense upper level trough across
central Canada will gradually dig southeast into the upper Great Lakes by
Tuesday. The first weak cold front will move southward into the
northern counties of the CWA late Saturday night, then through the
remainder of the CWA during the day Sunday. This front may bring
enough surface convergence combined with any weak H5 troughs
digging southeast across the northern and central plains for a
chance of thunderstorms. The first front will move south of the
CWA Monday and may wash out across northern OK. A second stronger
cold front will push through the area Monday night into Tuesday
bringing a chance for showers and thunderstorms as a more
amplified H5 trough digs southeast across the plains, rotating
southeast around the deep upper low over the northern Great Lakes
States. Highs next Wednesday may only reach into the 70s behind
the stronger cold front.


.AVIATION...(For the 18Z TAFs through 18Z Thursday Afternoon)
Issued at 1247 PM CDT WED JUL 9 2014

Potential for thunderstorms remains the main challenge. Ongoing
convection in central Nebraska could enter MHK area around 01Z but
too little confidence in this persisting for inclusion. Better
chances still on track for after 06Z but limited large scale
forcing and instability may keep activity just west of TOP and
FOE and backed off to PROB. Confidence on timing of onset and end
of convection remains somewhat limited.




SHORT TERM...Sanders
LONG TERM...Gargan
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