Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 302305
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
605 PM CDT Thu Apr 30 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 302 PM CDT THU APR 30 2015

19Z water vapor shows a closed low over IL and a mid level ridge
centered over AZ. A shortwave trough was moving across MT and WY
towards the northern plains with shortwave ridging extending from
the southwest through the central plains and into MN. At the
surface, weak ridging extended from the upper Midwest through
eastern KS.

For tonight, moisture is expected to remain limited with the surface
ridge axis moving towards the central MS river valley. Models also
indicate there is little in the way of large scale forcing with the
mid level shortwave ridging overhead. Therefore a dry night is
expected with skies remaining mostly clear. The dry air associated
with the surface ridge may allow for temps to drop off quickly this
evening and eventually fall into the mid and upper 40s. Think there
should be some mixing through the night with the ridge to the east
and a surface trough to the west, so do not expect lows to be to
cold but would not be surprised if a few favored locations fall into
the lower 40s.

The shortwave trough currently moving towards the northern plains is
expected to shear out as it approaches the forecast area Friday.
Initially moisture for precip is pretty limited but there are some
signals from the models of better moisture within a surface trough
axis. However this trough axis is also forecast to become less
defined as the day progresses. Overall there is no large scale
forcing to generate thunderstorms, but there could be enough
convergence and lift along the surface trough for an isolated storm
or two if the trough doesn`t dissipate. Therefore have continued
with some 20 to 30 percent chance POPs generally across the far
northern counties near the NEB state line. Instability and shear
parameters are marginal for thunderstorms, so I do not foresee much
risk for severe weather. Have kept highs in the mid and upper 70s
since there is no real change in airmass. Increasing mid level
clouds may limit insolation across the north enough to keep highs in
the lower 70s. Otherwise think highs should be back into the mid
70s.

.LONG TERM...(Friday Night through Thursday)
Issued at 302 PM CDT THU APR 30 2015

Return flow will organize Friday night producing temp/moisture
advection overnight on the nose of a modest LLJ. MUCAPE will also
be marginal in the 500j/kg range but should still see sct to
widely sct elevated thunderstorms mainly near the NE/KS border
after midnight so will leave current low pops. Lack of low level
boundaries and stronger theta e advection focused north of KS on
Sat/Sat night should lead to a dry period that should last through
the day Sunday with breezy warmer and more humid conds. Next chc
for more widespread precip appears to be Sun night as initial
energy from western U.S. trough will begin to impact the area. A
low level boundary fcst to be in the area Monday will lift north
by Tues into Weds however an upper wave will eject into the Plains
so expect a broad area of sct convection to increase especially on
Weds as the upper wave moves over KS. The initial wave will cause
a front to sag into the area by Thu and with continued SW flow
aloft expect precip chcs to persist. All in all a wet pattern will
develop next week and perhaps beyond as the upper trough remains
in place across the West by next weekend.

&&

.AVIATION...(For the 00Z TAFs through 00Z Friday Evening)
Issued at 603 PM CDT THU APR 30 2015

VFR conditions are expected throughout the period.  After 18Z, VCTS
are possible for all terminals; however, any storms that form would
be isolated and confidence with storm location is low.  Therefore,
have left the mention of storms out of this TAF package.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Wolters
LONG TERM...Omitt
AVIATION...Heller





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