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Area forecast discussion
National Weather Service Topeka Kansas
1237 PM CDT Sat may 27 2017

..update to aviation forecast discussion...

Short term...(today and tonight)
issued at 259 am CDT Sat may 27 2017

Confidence in specifics for today and tonight is fairly low, but
potential for high-end severe weather is in place. Convection
continues to roll east across northwest Kansas early this morning in
area of good elevated cape and moderate low level jet. Other
convection was over southwest Missouri north of a warm front.
Dewpoints south of this front in the lower 70s with southerly flow
over it. Locally, weak near-surface winds and clear skies until
recently allowing for some slightly reduced visibilities, but
increasing cloud should keep widespread fog in check.

Am leaning toward the linear system to the west to slowly decrease
in intensity with time as moisture convergence and available
moisture decrease, with many models very similar in an area of much
lower 850mb dewpoints moving north through the eastern half of the
state in the 10-14z window. Will still likely have at least some
remnant convection through the early morning hours in at least
northern areas with some signals of an mesoscale convective vortex developing just south of
the Nebraska border at 8z, with some potential for a weak surface
low to push northeast into the area. Dewpoints could easily reach
the upper 60s as 850mb dewpoints then rise quickly with 500-700mb
lapse rates near 9 c/km to produce extreme ml cape with little cin.
Specifics of where the surface low end up will play a large role in
low-level shear, but west-southwest 500mb winds around 40kts will supply enough
shear for supercells. Very large hail will be the most apparent
threat, with severe winds and tornadoes also possible, mainly in
southern and eastern areas. Timing and location of overall severe
weather threat very hard to nail down, but could see high surface-
based instability develop by early afternoon. Several hours of at
least east central Kansas being in the warm sector and multiple
sources of weak forcing brings the potential for a few rounds of
storms for locally heavy precip possibilities as well. Upper trough
swings into the area late tonight, which should bring cyclogenesis
well to the east for convection to end by early Sunday morning.

Long term...(sunday through friday)
issued at 259 am CDT Sat may 27 2017

The latter two thirds of the Holiday weekend shape up rather well
as northwesterly flow aloft moves in with surface high pressure
moving southward into the Central Plains. Highs in the upper 70s
Sunday become upper 70s to low 80s on Monday. Overnight lows in
the 50s with northwest winds through the period.

Next chance for rain holding off until late Monday night into
early Tuesday and relegated to our far southern and western
counties where the front resides. Highs again on Tuesday and
Wednesday rise toward 80. Upper pattern starts to shift on
Wednesday from northwesterly to zonal, then the influence of the
trof over the western states into The Rockies starts to shift
eastward as well. This increases rain chances Thursday into Friday
and would likely cool highs a few degrees. Strength of these
storms is a bit far out, but enough cape and shear progged for
strong to severe at times late next week. Watch for updates.

&&

Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1234 PM CDT Sat may 27 2017

Kept thunderstorms in the vicinity due to additional instability today with afternoon
heating although severe threat should be southeast of the taf
locations. Continued forecast of MVFR cigs as cooler air comes in
tonight followed by VFR late tonight and Sunday morning.

&&

Top watches/warnings/advisories...
none.
&&

$$

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