Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 280453

1153 PM CDT Wed Aug 27 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Thursday)
Issued at 321 PM CDT WED AUG 27 2014

Scattered convection once again popping up over the Central Plains
this afternoon as peak afternoon heating sets in and shortwave trofs
embedded in the flow rotate out of the southwest.  Topeka area is in
between areas at this time, with morning convective outflow
boundaries having set up NW to SE across the forecast area.  Light
showers continue across the western areas with isolated heavier
showers/isolated thunder developing north, east and southeast.

For tonight and tomorrow, sensible weather conditions will be
somewhat dependent on clouds and precipitation across the area. Rain
chances this afternoon and evening are somewhat higher out west and
taper to isolated in the east. After midnight as the low level jet
increases and the warm front remains over our northern counties,
greater chances spread eastward near the Nebraska border and perhaps
slightly farther south where outflow may act as shallow front and
lifting mechanism as well. Plus there are at least two small
shortwave trofs visible in current WV imagery to our southwest.
Nearly two inches of precipitable water in the morning sounding
suggest potential for locally heavy rainfall, and will need to be
particularly vigilant about storms over Brown/Nemaha county where as
much as 4 inches of rain fell last night.  Will carry lows generally
in the lower 70s.  Precipitation chances continue in a similar
fashion for Thursday as larger scale upper trof advances eastward
out of the Rockies into western Kansas by late afternoon.  Shear
remains weak but heavy rain potential continues.  Will carry highs
around 90 for the southeast counties but cooler into the
lower/middle 80s north northwest where rain and clouds should

.LONG TERM...(Thursday Night through Wednesday)
Issued at 321 PM CDT WED AUG 27 2014

Center of the upper trough axis slides southeastward Thursday
evening into Friday increasing chances for widespread precipitation
across the area. Warm and steady isentropic ascent ahead of the
wave is progged to develop a swath of light to moderate showers
and thunderstorms across central Kansas, spreading into north
central areas during the evening and overnight hours. Chance to
likely precipitation continues eastward for the entire CWA Friday as
another cluster of light to moderate showers and thunderstorms
develops over southern KS...lifting northeast into east central
areas during the late afternoon and evening hours. Heavy rain is of
highest concern with this system as increasing saturation through
the column carries PWAT values between 1.50 and 2 inches over the
CWA. Good moisture transport and the support of the LLJ on Thursday
evening should sustain or develop scattered convection. Severe
potential is isolated as MLCAPE averages between 1200 and 2000 J/KG.
Bulk shear from 0-6 KM is on the order of 20 to 30 kts early
Thursday evening and late Friday afternoon where strong winds and
hail are possible. Convective cloud debris along and ahead of the
cold front cools highs on Friday to the lower and middle 80s and
overnight lows in the 60s.

Model consensus is coming into better agreement with the open wave
exiting late Friday evening. Will maintain slight chances for
thunderstorms through Saturday morning over the far eastern counties,
however think most areas will become dry by this time. Drier air and
high pressure filling in on Saturday will quickly clear clouds from
west to east. Have opted to raise highs a few degrees to account for
this change in cloud cover. Mid to upper 80s are common for much of
the area. Confidence is low in precip for the remainder of the
weekend as zonal flow ushers in another upper trough over the inter-
mountain west through the high plains. Will maintain slight chances
Saturday evening and Sunday as the GFS increases isentropic ascent
along the LLJ. Thermal ridge centered over the area and periods of
sunshine during the peak heating lead to raise highs a few degrees
in the upper 80s to lower 90s Sunday afternoon.

The upper trough axis and attendant cold front pushes southeast into
the area Sunday evening and Monday where better confidence for
thunderstorms exists. Upper flow becomes zonal through Wednesday as
the front becomes stationary over southern KS. Showers and
thunderstorms remain possible as weak waves traverse through the
mean flow. Temperatures for next week remain near normal values in
the mid to upper 80s for highs and lows in the 60s.


.AVIATION...(For the 06Z TAFs through 06Z Thursday Night)
Issued at 1144 PM CDT WED AUG 27 2014

Will continue with a dry and VFR forecast for TAFS but also
kept VCTS with the terminals in the 08Z-13Z timeframe as the
North Central KS MCS passes/backbuilds just north of the area.
Will steadily veer winds from easterly to southeast by 10z and
leave thru the day with the expectations that an outflow boundary
will keep somewhat of a more easterly component to the winds
through the day.




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