Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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000
FXUS63 KEAX 240917
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
417 AM CDT SUN APR 24 2016

.Discussion...
Issued at 417 AM CDT SUN APR 24 2016

Today - Tonight:

The first in a series of upper level systems will bring scattered
convection to at least the northwest half of the CWA starting late
this afternoon. A closed upper low now over WY is progged to track
east and reach the central SD/NE border by late afternoon. A
nocturnal low-level jet over the Central Plains and modest
isentropic ascent are currently aiding a narrow band of elevated
convection from central KS into south central NE. This activity is
expected to lift northeast and possibly graze the northwest tip of
MO this morning before dissipating.

Several additional features will generate strong/severe convection
from western OK through central KS and into far northwest MO. A
dryline will set up from central KS through far western OK this
afternoon while a cold front swings southeast from under the WY
system. As a h7 vorticity max/lobe emerges from under the WY system
and ejects northeast across KS scattered surface-based convection
will form along the KS/OK portion of the dryline. In addition storms
will form over southeast NE/northeast KS where a weak boundary left
by this mornings convection or a pre-frontal convergence zone lies.
The NE/KS convection should affect the northwest 1/3 of the CWA late
this afternoon and early evening. Moderate instability around 1500
J/kg with 30kt 0-6km shear may be sufficient to support a few
marginally severe storms. The primary threat will be large hail. The
severe threat will last several hours ending a few hours after
sunset as the storms weaken as they move east into a less favorable
environment. Coverage and intensity will gradually decrease with
time such that most of the convection will have dissipated by the
pre-dawn hours of Monday morning.

The severe storms which form along the KS/OK dryline may never reach
the CWA as they will weaken and tend to decrease in coverage as they
lift northeast and off the dryline. Accept the model trends in
slowing the arrival of the convection into the CWA as well as
decreasing it in coverage. So, have lowered PoPs for all but the
northwest 1/3 of the CWA as well as limit the QPF.

Monday - Saturday:

As noted in yesterday`s discussion this will be a very active period
with several additional periods of strong/possibly severe convection
as well as the potential for heavy rainfall Tuesday night/Wednesday.

While Monday looks relatively quiet isolated convection is still
possible as the earlier mentioned cold front stalls over the CWA and
around 1000 J/kg of instability will be available. Increasing mid
level heights and the lack of an upper level feature should greatly
limit convection.

By Tuesday the next closed upper system will move out of the Central
High Plains. This system will be much larger with a better defined
negatively tilted shortwave ejecting northeast across KS. With
surface dewpoints likely well into the 60s advecting into the region
there will be ample instability, in excess of 2500 J/kg, to supply
the needed energy for severe convection Tuesday evening. Will need
to keep a close eye on where the warm front will be as it will be a
primary focus for severe storm development. However, the shear will
be near the lower end of the threshold with 0-6km shear in the 25-
30kt range. Heavy rainfall will also be a concern Tuesday
night/Wednesday as precipitable water values between 1.25 and 1.5
inches are near the 99% percentile.

Should see at least a one day break in the rain on Thursday,
possibly carrying over into the first part of Friday before the next
upper trough sends the first wave of warm air advection convection
into the CWA by Friday evening. Timing differences between the ECMWF
and the GFS by the end of the week requires more of a broadbrush
approach on rain chances. Even then PoPs will be rather high this
far out. Should we get as much rain as the models are advertising in
the upcoming week we should eliminate the yearly shortage in
precipitation.


&&

.Aviation...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1046 PM CDT SAT APR 23 2016

VFR conditions expected through much of the fcst period. Latest
model runs suggesting the bulk of thunderstorm activity will remain
west of the forecast area. Cannot rule out some isolated convection
holding itself together as it moves east off the dryline in central
Kansas...but activity will be moving into a more and more unfavorable
environment with further eastward progress. In any event...have
inserted a VCTS mention for STJ...and later updates can address the
KC terminals if trends begin to change. The other main concern
remains the likelihood for LLWS early this morning thanks to a strong
southwesterly low-level jet...and have maintained mention for all
terminals with the 06z package. Meanwhile...southerly winds of 10-15
kts overnight will increase after 16z on Sunday with gusts up to 30
kts possible during the afternoon hours.


&&

.EAX Watches/Warnings/Advisories...
KS...None.
MO...None.
&&

$$

Discussion...MJ
Aviation...32



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