000
FXUS63 KTOP 181734
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1234 PM CDT Fri Apr 18 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 305 AM CDT FRI APR 18 2014

At 07Z this morning, upper ridging seen on water vapor imagery
builds eastward into the region. Broad area of high pressure
stretches from Oklahoma through the southeast half of Kansas into
Missouri. The calm winds and and stout inversion at the sfc has
resulted in areas of smoke and haze from the yesterdays prairie
burns. With the dewpoint temperatures in the low 30s and forecast
lows this morning at or just above freezing, will continue the
Frost Advisory through 8 AM. Across north central into western
Kansas, increased south winds around 10 mph were a result of the
surface trough residing over eastern Colorado.

The upper ridging this afternoon will confine the sfc trough and
tighter pressure gradient to north central Kansas. Strong south
winds pickup over north central Kansas between 15 and 25 mph with
gusts in upwards of 30 mph. Slightly weaker winds between 10 and 20
mph are seen over east central and northeast areas. Gulf moisture
begins to increase by the afternoon lifting dew points to the low
40s by late afternoon. As highs climb to near 70 degrees, minimum RH
values fall to the upper 30s. High fire danger conditions exist for
areas west of highway 75 during the late afternoon.

For tonight, an upper shortwave trough begins to eject the surface
wave into the northern and central plains, maintaining the EML over
north central Kansas. Winds in this area average from 10 to
15 mph sustained while elsewhere south winds below 10 mph are
expected. Forecast lows are much warmer than this morning, generally
in the upper 40s to low 50s.

.LONG TERM...(Saturday through Thursday)
Issued at 305 AM CDT FRI APR 18 2014

Models continue to show a southern stream shortwave, currently off
the southern CA coast, moving into the central plains late
Saturday. The model`s prog of the wave doesn`t look that well
organized as it comes out into the plains and because of the split
flow over the CONUS there is no kicker to move it east very fast.
The relatively weak winds associated with the southern stream also
suggest the deep layer shear will be rather weak through the
weekend. While forcing looks disorganized with the wave, cooler
mid level temps associated with the wave allow for some surface
based instability between 1000 and 2000 J/kg to develop by Sunday
afternoon. However ahead of the upper trough the NAM and GFS show
a decent elevated mixed layer providing a good capping inversion
to surface parcels. With this in mind have backed off on the POPs
for Saturday afternoon and Saturday night thinking the cap will
limit coverage of thunderstorms. The better chances should remains
across north central KS in closer proximity to a surface trough
that could provide a focus for low level convergence. Did not make
many changes to the forecast for Sunday. With no real inhibition
to convection on Sunday, think there could be scattered showers
and thunderstorms developing in the afternoon. It appears as
though rain chances Sunday morning will be dependent on whether an
MCS develops from the Saturday night convection and manages to
slide south into the area. At this point, I don`t have enough
confidence in the model solutions to lower POPs for Sunday morning
but it looks like chances may be better through the afternoon.
Models show southerly surface winds through the day Sunday and so
with a little insolation highs should be able to warm into the mid
and upper 70s. The upper wave finally begins shifting to the east
of the forecast area Monday. Continued with some chance POPs for
Sunday night and Monday as lapse rates stay steep enough for some
positive buoyancy as long as the upper trough remains overhead.

The GFS and ECMWF are showing signs of elevated convection late
Tuesday night as the southerly low level jet redevelops. Am a
little suspicious of the models QPF here due to mid level ridging
over the plains. Also the models strongest moisture return appears
to be around 700MB and isentropic surfaces suggest the better
saturation may set up just south of the NEB state line.
Nevertheless the models have shown some run to run consistency
with this idea, so will maintain some slight chance pops for
Tuesday night and Wednesday. The better chances for precip may end
up being Wednesday night and Thursday as a longer wavelength
trough moves across the CONUS. However there are some timing
differences with this wave between the GFS and ECMWF. Because of
these differences, opted to remain fairly close to the prev
forecast.

Temps through the period look to be rather mild with no signs of a
Canadian airmass intruding south. Therefore generally keep lows in
the 50s and highs in the 70s. Wednesday could end up being the
warmest day with some places hitting 80 as strong southerly flow
brings warmer air into the region.

&&

.AVIATION...(For the 18Z TAFs through 18Z Saturday Afternoon)
Issued at 1217 PM CDT FRI APR 18 2014

Expect VFR conditions for the next 24 hours. Southeast winds will
increase to 8 to 12 KTS this afternoon with some gusts. Southerly
winds will increase to 14 to 16 KTS with gusts 23 to 25 KTS by 15Z SAT.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Wolters
AVIATION...Gargan