Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 311116
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
616 AM CDT Tue Mar 31 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 401 AM CDT TUE MAR 31 2015

Main upper PV anomaly to impact the region Wednesday is beginning to
enter British Columbia this morning. A broad, southern stream wave
is also noted shifting northeast towards Baja California. Ahead of
this system, sfc dewpoints were increasing northward over Oklahoma
and southern Kansas into the 40s and 50s. Across northeast Kansas, a
weak boundary was centered over northeast Kansas with weak northerly
winds towards the Nebraska border, and variable winds south of
Interstate 70. Temperatures were overall starting out in the 40s.

Another warm afternoon expected today with clear skies and highs
into the upper 70s and lower 80s. Surface high builds southeast into
the area, shunting the higher dewpoints towards the south and east.
While a slight increase in moisture is possible initially this
morning over east central areas, believe increased mixing during the
afternoon will lower dewpoints back to the 30s. Observed forecast
soundings are fairly similar of the drier air aloft at 800 mb mixing to
the sfc. Veering winds through the day from north to east by late
afternoon are on average weaker compared to yesterday at 10 mph. See
Fire Weather Discussion below for more information on concerns.

Weak upper ridging quickly passes through the plains region tonight.
In its wake a surface trough develops in its wake over the western
high plains. Winds increase after midnight over north central areas
as they veer to the south by sunrise. Return flow also brings a
surge of moisture northward over central Kansas with dewpoints
reaching the 50s. As a result, overnight lows are not as cool with
readings in the lower 50s.

.LONG TERM...(Wednesday through Monday)
Issued at 401 AM CDT TUE MAR 31 2015

Wednesday remains on track to be windy and quite warm with moisture
streaming northward into eastern KS through the day. While there is
likely to be some mixing in the afternoon, still appears likely that
dewpoints in the middle to upper 50s will be widespread in the area,
and this should help prevent extreme fire conditions with MinRH in
the 30-40% range although will need to watch closely for potential
to mix drier air down to the surface. By late day, a cold front is
expected to stretch from northeast NE back into southwest KS while a
weakly formed dry line develops into central KS. The warm sector
airmass is likely to have 1500+ J/kg of MLCAPE by late afternoon,
with much of the region moderately capped. Strong convergence along
the cold front is likely to cause widespread convective development
from north central KS to the northeast, while more isolated
development is likely farther southwest. There is a small chance
that convergence near the weak dry line could initiate a few storms
as well. The front will steadily move into the forecast area, but
may not arrive until late evening, and by that time the surface
based parcels are likely to become more capped with slightly
elevated parcels favored. Storm mode is somewhat difficult to
forecast at this point, as much of the warm sector has only 25-35
kts of 0-6 shear but with a looped hodograph through the layer so
any semi-isolated storms will have at least some potential to take
on supercell character if storm motion is slow enough to avoid
downdrafts. Otherwise forcing along the front as the night goes on
is likely to favor numerous storm mergers and interference...and
while deep shear increases dramatically near/behind the front, the
effective shear for elevated parcels is not very impressive. So feel
there is potential for line segments and perhaps some embedded
supercell structure. The main hazards from any stronger storms would
be hail and possible some damaging wind as stronger downdrafts could
transport some momentum from a 60 kt LLJ to the sfc. Could also see
some heavier rainfall amounts in excess of an inch, particularly in
northeast KS where strong moisture transport, elevated PW, and some
potential for backbuilding will focus.

The front will continue south into Thursday morning, but elevated
convection may linger in east central KS beyond sunrise. A second
short wave trough then enters the area from the west on Thursday
night with strong model agreement in moderate to strong forcing for
ascent across the forecast area. However, there is disagreement in
whether low level dry air can be overcome for precip to reach the
ground. Have kept precip chances across the area for this period
with the best potential in north central and east central KS.
Temperature profiles will cool markedly, but a cold rain appears
more likely than any snow if precip does develop.

Friday into the weekend looks mainly dry. It will be cooler on
Friday with widespread cold advection and some cloud cover expected,
but will see a warming trend Saturday and Sunday. An upper trough
deepens across the western CONUS by Sunday with increased
southwesterly flow aloft and low level moisture advection possibly
bringing a slight chance for a few storms to the area for Monday.

&&

.AVIATION...(For the 12Z TAFs through 12Z Wednesday Morning)
Issued at 609 AM CDT TUE MAR 31 2015

MVFR visibilities are expected at KFOE where smoke has lingered
underneath the inversion. Weak mixing may linger the haze through
16Z. VFR prevails at terminals thereafter. High pressure shifting
southeast through the region veers light north winds to the east
during the afternoon where speeds may peak near 10 mph.

&&

.FIRE WEATHER...
Issued at 609 AM CDT TUE MAR 31 2015

Very high fire danger conditions exist for this afternoon as
temperatures once again peak in the upper 70s to lower 80s. Fairly
confident in drier air above the surface to mix down from around 800
mb to the surface. This would lower the minimum humidity values in
the late afternoon between 20 and 27 percent. Main area of
uncertainty are the wind speeds and potential gusts as it appears
there is some indication from short term guidance of easterly winds
approaching 15 mph south of Interstate 70 in the mid afternoon.
Gusts therefore may occasionally reach 20 mph. High pressure in the
area however should hinder winds from being as strong as yesterday
for most of the area. Will not mention headlines at this time and
plan to monitor for any changes.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Barjenbruch
AVIATION...Bowen
FIRE WEATHER...Bowen






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