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Area forecast discussion 
National Weather Service Topeka Kansas
632 am CDT Tuesday Aug 4 2015

..update to aviation forecast discussion...

Short term...(today and tonight)
issued at 330 am CDT Tuesday Aug 4 2015

Convection this morning ongoing just to the north and east of the
forecast area...following what is likely the better convergence of
the low level jet and lift along the 305k surface. Surface frontal
boundary is settled generally from northwest to southeast along the i70 corridor.

Most guidance suggests current area of convergence stays just to the
north of the area...but will keep some slight chances along the NE
border this morning where its possible outflow may be enough to
overcome weak capping that far north. Rest of the area will likely
have to wait until later this afternoon when upper wave currently
over western Kansas makes its way eastward. Think there will be
enough time for sunshine to build up instability to the 1000-1500
j/kg range...but shear is weak and still think slow moving storms
and locally heavy rain is the most likely hazard from these
storms...although could see some gusty winds early as storms come in
over a heated up late morning air mass. Better rain chances move
across the south and into the east later this evening and overnight.
Daytime highs in the 80s may be slightly cooler out west if the rain
gets in faster...with nighttime lows from the middle to upper 60s

Long term...(wednesday through monday)
issued at 330 am CDT Tuesday Aug 4 2015

Periods of most concern look to be Wednesday and Wednesday night.
Convection will likely linger and refire into the daytime hours of
Wednesday with upper wave still making its way through and rather
impressive upper flow, thermal gradient, and thus isentropic lift
for late Summer. Specific trends in convection remain unclear, but
at least a few areas of heavy rain seem possible in northwest flow
and synoptic boundary of similar orientation. There will also be
some potential for severe storms if a middle-late day break can occur
for mainly eastern locations. If decent boundary layer mixing can
become established, cape/shear combo would easily support supercell
storms with impressive wind fields over the the 5000-15000 foot
layer. Upper trough's passage Wednesday night should keep much of
the next period or two dry. Exact temperatures will largely depend on
precipitation trends with sref T spread around 7 degrees.

Next wave in the northwest flow brings another modest boundary
through the area Thursday evening with flow over the boundary
developing by Friday night, and likely staying near to not far south
of the area into early next week in stagnant large scale regime. Will
continue small thunderstorm chances for several periods with a
slight warming trend given no certain day to expect precipitation at this


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 629 am CDT Tuesday Aug 4 2015

Primary concerns for the forecast are convective chances. Wave
coming out of western Kansas increases coverage later this afternoon
and continues through the did not pick one
particular time for heaviest storms and will carry VFR prevailing
ts. Will need to watch for lower ceilings and visbys later in the
forecast period.


Top watches/warnings/advisories...


Short term...67
long term...65

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