Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
FXUS63 KEAX 171729
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1229 PM CDT Fri May 17 2013
.SHORT TERM...(Today through Saturday night)
Issued at 403 AM CDT FRI MAY 17 2013
Closed upper low over extreme north central AR will continue an
eastward track and move away from the CWA today. Could see an
isolated shower or storm over the far eastern counties later this
morning and early afternoon as any remaining vorticity lobes rotate
cyclonically westward. Stratus has formed over the southern CWA.
These clouds on the northwest side of the upper low an increasingly
moist boundary layer. 06z RAP has best handle on the current low
cloud trends and followed. Airmass over the CWA is very similar to
yesterday. However, except for the far northwest corner of MO believe
max temperatures today may be a few degrees cooler than yesterday due
to increased cloud cover.
The earlier upstream convection over KS and NE was tied to a couple
of weak vorticity lobes. Convection has all but dissipated and dont`
expect it to reform today.
Shortwave ridging aloft is progged to amplify as it moves east
across the Central and Southern Plains this afternoon through
Saturday. This should yield dry and warmer conditions on Saturday.
Expect max temperatures in the middle to upper 80s.
Saturday night is looking a tad more interesting as it no longer
looks dry. NAM/GFS/ECMWF/GEM have been giving signals for the past
couple of runs that elevated convection will form Saturday evening
over eastern KS/western MO and quickly advance northeast Saturday
night. With a stout elevated mixed layer providing an impediment to
surface based convection, any activity will need to rely on
isentropic ascent and a ramping up of the h8 low level jet.....and
we have that. So, have no qualms in adding at least slight chance
PoPs for Saturday night to most of the CWA. Even went with chance
PoPs over the northeastern CWA as the initial activity will have had
time to increase in coverage as it moves quickly northeast.
.LONG TERM...(Sunday through Thursday)
Issued at 403 AM CDT FRI MAY 17 2013
For Sunday, there remains a good chance for severe weather from the
afternoon into the overnight hours. A trough is expected to move
into the Plains by Sunday afternoon leading to a surface low that
will move to our north. This will result in the entire area being in
a broad warm sector with dewpoints likely in the mid to upper 60s.
Model soundings show a strong CAP over the region but also with the
potential for elevated showers/storms earlier in the day. This
possible area of precipitation should move east into the Mississippi
Valley by the afternoon leaving eastern Kansas and western Missouri
to see better destabilization during the afternoon. CAPE values in
the 2500 to 3500 J/kg range look likely given forecast dewpoints so
we will see moderate to strong instability build across our western
zones. The finer scale details of what impact the convection earlier
in day will have will only be able to be resolved during the nowcast
period. But strong instability and 0-6KM shear in the 40 to 50 kt
range, oriented more normal to any initiating boundary, indicates
supercells would be the most likely convective mode initially.
Hodographs show a good amount of curvature by the afternoon and this
is increased during the evening as the low level jet restrengthens
overhead. Storms will likely initiate over eastern Kansas during the
afternoon hours and become supercells. As winds veer into the
evening and overnight hours storms should organize into more of a
line/ convective complex. Large hail, damaging winds and a few
tornadoes are possible with the initial storms before the convective
mode changes and damaging winds becomes the primary concern.
Monday will be greatly dependent upon what happens Sunday night, and
as such confidence is quite a bit lower. Latest guidance suggest
that the front will be nearly east of us by the evening hours with
winds across the area veered southwesterly. Shear and instability
are still supportive of severe weather, but the chances should be
either across our eastern to southern zones or even east of the
forecast area. We will really need to see how the weather pans out
Sunday before a saying anything with any level of certainty.
For the remainder of the extended forecast, the upper trough that
affected the area Sunday and Monday should have cutoff over the
Upper Midwest. Another segment of the upper trough will move through
Wednesday and as a result there may be a few showers or storms
across northern Missouri into central and eastern Missouri. A few
showers and storm will remain a possibility into Thursday as
northern portions of the forecast are still under the influence of
the Upper Midwest upper low. The effects of the upper low will
diminish by Friday as upper ridging spreads into the Plains. This
will result in a warm up with drier conditions more likely for the
weekend. The severe potential looks rather low for this stretch of
.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1228 PM CDT FRI MAY 17 2013
Widespread MVFR cigs are gradually lifting and scattering, and expect
cumulus field to lift into VFR across the entire region by late
afternoon. Most guidance is suggesting the possibility of IFR
cigs/vsbys redeveloping a bit further north and east late tonight,
possibly affecting the KC terminals and parts of ern KS/wrn MO.
Confidence on this is not high, and increased SE flow should prevent
widespread vsby restrictions, but probabilities for IFR cigs are high
enough for now to introduce this into the TAFs right around sunrise.