Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 301749

1249 PM CDT Tue Sep 30 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 252 AM CDT TUE SEP 30 2014

The upper low was located over the Nebraska Panhandle and moving
northward at 08Z. Trailing lobe of energy extended southeast into
northwest Kansas. Another embedded wave was moving across Colorado
at 08Z.

Scattered thunderstorms had developed in southwest Kansas within the
low level jet and theta-e axis. The moisture and instability axis
extends northeast into north Central Kansas.

Expect scattered thunderstorms to affect parts of north central
Kansas this morning into parts of northeast Kansas as trailing wave
pivots northeast across the area as the upper low lifts north into
the Dakotas. This afternoon may see an initial lull in convection
with subsidence the wake of the initial wave before increasing
toward late afternoon and evening. Models suggest that around 1000
J/kg of MUCAPE will be present along with 35 kts of bulk shear.
However mid level lapse rates are marginal. May see a few strong to
severe storms late afternoon through mid evening with mainly hail
and wind the main hazards.

Expect convection to be on the increase tonight as the low level jet
increases across the Central Plains with deep moisture advection
across northeast Kansas. Another wave ejects out of the longwave
trough across Kansas increasing forcing for ascent. Given good
moisture transport tonight along with diffluent upper flow over
eastern Kansas after 06Z, locally heavy rainfall will be possible.
Elevated thunderstorms are expected to be widespread and have
maintained highest probabilities from late evening onward.

.LONG TERM...(Wednesday through Monday)
Issued at 252 AM CDT TUE SEP 30 2014

Showers and thunderstorms should be ongoing across the area early
Weds as another upper wave passes across the region late Tues
night into early Weds. 40KT LLJ along with WAA and moisture
advection should lead to widespread convection at least into mid
morning. By afternoon would expect some clearing and instability
to increase across Central KS closer to the low level dry surge.
The sfc low should remain nearly stationary across SW KS as the
main upper wave digs into the Rockies by Weds evening. This will
act to back the low level wind fields and help re-focus
convergence along any outflow boundaries/warm front which should
be located somewhere across the CWA. 6KM shear of 40-50kts along
with 1500-2500 MLCAPE and increasing directional shear by sunset
should set the stage for severe storms capable of hail...damaging
winds and perhaps tornadoes given the forecast 3KM direction shear.

ECMWF and GFS both suggest that storms will evolve into a cluster
with some training possible given the orientation of the 50kt
LLJ across the 850mb moisture axis Weds night. This could lead to
locally excessive rains of 2+ inches and perhaps some minor
flooding across the CWA.

By Thursday the upper trough axis will gradually shift east with
lingering showers and storms likely at least through midday before
the cold front passes through by afternoon. At this time it
appears that the front should pass through most of the CWA before
peak heating however if the front slows some parts of eastern KS
could see another round of storms Thurs PM.

Thankfully the weather will transition to a cooler and drier
pattern by the weekend and into next week as a ridge builds over
the Rockies and a trough remains in place across the Great Lakes.


.AVIATION...(For the 18Z TAFs through 18Z Wednesday Afternoon)
Issued at 1233 PM CDT TUE SEP 30 2014

Main issue through the period will be timing and intensity of
TS. Area of storms west of MHK should stay west in the short
term. May see additional development near MHK through the rest of
the afternoon. Any TS would have VFR cigs with short periods of
lower VIS. While there is a chance of TS through the evening, most
likely timing of TS with more persistent IFR VIS and occasional
lower CIGS is expected after 05Z (MHK) and 09Z (TOP/FOE) with
+TSRA possible. These storms should exit the area between 15Z-18Z.




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