Scientific Forecaster Discussion
fxus63 ktop 291958
Area forecast discussion
National Weather Service Topeka Kansas
258 PM CDT Mon may 29 2017
Short term...(this evening through tuesday)
issued at 258 PM CDT Mon may 29 2017
A beautiful Memorial Day is ongoing across the entire area!
As of 19z, a pesky upper low continues to spin across southern
Ontario. At the surface, a weak front was oriented from near St.
Louis into portions of southern Kansas. A weak cu field was noted along
the boundary. A shower or two is possible along the boundary this
afternoon, however they should remain south of the outlook area.
With plentiful sunshine expected the remainder of the day, high
temps will top out in the upper 70s to lower 80s. Isentropic lift
is expected to increase over parts of SW Kansas this evening, which
could spark a few showers or thunderstorms. Given the mean wind
vectors to the east-southeast I expect the vast majority of activity to stay
south of the area. Isentropic lift will increase along a secondary
front near dawn Tuesday morning for areas mainly along and north of
I-70. Most short term guidance is meager with precipitation given
the dry bl. The outcome of any morning precipitation/cloud cover
will play a factor in Tuesday afternoon's thunderstorm potential.
The aforementioned front will sag southward across the County Warning Area by early
afternoon. A subtle weak upper wave will traverse the Central Plains
by afternoon, which should spark thunderstorms along the boundary.
Decent mid level lapse rates near 7c will contribute to 1000-2000
j/kg of ml cape. Effective bulk shear vectors will be in 30-40 knot
range, therefore organized updrafts can be expected. Any sustained
updraft will be capable of large hail. Given the high local heights
and well mixed bl (inverted v soundings), evaporative cooling may
contribute to isolated damaging wind gusts.
Long term...(tuesday night through monday)
issued at 258 PM CDT Mon may 29 2017
Tuesday night with northwest flow aloft and high pressure sliding
through the northern plains return flow becomes established across
portions of southern Kansas. Convergence associated with the low level
jet and isentropic lift on the 305 k surface should support showers
and scattered storms given elevated instability on the order of a
few hundred j/kg. The models are consistent in keeping this area of
convergence around the same area through the day Wednesday. Coverage
does not appear that widespread, but ongoing precipitation and cloud
cover will dictate if any instability can build from surface
heating. If modest instability can be realized the deep layer shear
would be sufficient for some stronger storms capable of large hail
and damaging wind gusts. Soundings in central Kansas show boundary layer
mixing fairly deep if surface heating can be realized, which would
increase the downburst wind potential during the afternoon and early
evening. On Wednesday night the isentropic lift and low level jet
shift to the north and support more widespread showers and storms
across eastern NE and portions of northern Kansas. The southern edge of
storm development appears to be near and along the state line. This
complex of convection will progress eastward through out the night,
and could linger in far northeast Kansas Thursday morning. On Friday a
weak upper low pressure will lift out over the Southern Plains and
approach the forecast area. As this wave becomes absorbed into the
northern stream precipitation chances increase, and the severe
potential appears low given the better shear will be over the Great
Lakes region. The weekend becomes less clear as the models are have
trouble agreeing with the pattern aloft.
Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1243 PM CDT Mon may 29 2017
VFR conditions are expected throughout the period. A few rain
showers are possible after dawn Tuesday morning at all terminals,
although confidence is too low at this point to mention in taf.
Winds will remain light through the period as well.