Area forecast discussion
National Weather Service Kansas City/Pleasant Hill MO
1240 PM CDT sun may 19 2013
Update...
issued at 1045 am CDT sun may 19 2013
Convective complex that tracked into western MO around sunrise is now
rapidly weakening across central and northeast Missouri. A weak
mesoscale convective vortex can be seen in the wake of this system
tracking into southwest Iowa. Subsidence behind this feature has
allowed skies to rapidly clear out across eastern Kansas and western MO,
and this trend will continue through the rest of the morning leaving
the region in good shape to warm up into the 80s today.
Good conditions for heating this afternoon will allow the airmass to
become strongly unstable, although last night's convective complexes
scoured out some of the high moisture that was in place yesterday
afternoon. Dewpoints that were in the upper 60s and low 70s have now
dropped into the lower and middle 60s across much of Kansas and
western MO. However, moisture return is already getting underway
across Oklahoma, and 12z soundings from oun and sgf depict plenty of
moisture above the surface and below 850 hpa that should advect into
the area this afternoon and mix down to give surface dewpoints in the
upper 60s, possibly lower 70s. Dewpoints could also be boosted by the
ground moisture left over from last night's rain that will evaporate
into the boundary layer.
How high dewpoints get this afternoon will be a key factor in
determining severe potential, especially tornado potential. As mid-
level flow becomes supportive of organized severe storms this
afternoon, low-level flow will also increase near and east of the
Kansas/MO state line, particularly early this evening. This could set a
short window favorable for tornadoes and even strong tornadoes if local
heights can become low enough and 0-3 km cape supportive of strong
low-level updrafts. These conditions are likely to be met near the
Kansas/MO state line around 00z if dewpoints can rise to near 70 degrees.
Regardless of tornado threat, we still expect supercells capable of
very large hail to develop over eastern Kansas this afternoon and
gradually merge into a convective line over western MO through the
evening. This line will be capable of widespread damaging winds. Will
also need to watch for embedded mesovortices and tornadoes within
this line as it spreads into strong low-level shear across central MO
later this evening.
&&
Short term...(today and tonight)
issued at 338 am CDT sun may 19 2013
Main concern in the short term revolves around the potential for all
modes of severe weather late Sunday afternoon through Sunday night
as well as the potential for a second round of severe weather on
Monday.
A broad, slightly negatively-tilted upper level trough is moving
through the eastern rockies this morning. This trough will move out
into the northern plains today with an upper level low developing
across South Dakota. However, a lead wave in the base of the trough
will rotate into the Central Plains by tomorrow afternoon. This will
force a Stout cold front into eastern Kansas. As this wave over
takes the front this should allow for initiation during the late
afternoon across eastern Kansas. Model soundings show that when
storms initiate there will be a very moist environment to work with
as dewpoints will be in the upper 60s to near 70. Also, there will
be steep lapses rates across the region as well as cape values of
2000-3000j/kg. So, the ingredients are there for severe weather
however the caveat will be if early morning convection across
central and southeastern Kansas continues to lift northeastward this
could led to increased cloud cover and may not allow the
environment to recover and realize that potential instability. That
being said if cloud cover does break and we do realize the forecast
highs of the mid 80s tomorrow there is a good potential for severe
weather. Models in good agreement in trying to develop supercells
across eastern Kansas during the late afternoon tomorrow. Early in
the evolution of these storm all modes, large hail, damaging winds
and even an isolated tornado will be possible. As these storms move
eastward into the western County Warning Area they will begin to form a line of
storms as which point the main threats would then become large hail
and damaging winds. This line of storms is then expected to move
eastward across the entire County Warning Area tomorrow night.
The severe weather potential on Monday becomes even more uncertain
based on whether the environment can recover during the afternoon
hours. The set up however is similar to Sunday only with a slight
shift south and east to severe potential. The upper level low will
continue to rotate across South Dakota and northern Nebraska. A
secondary cold front will develop across the plains states early
Monday and shift eastward into eastern Kansas by Monday evening.
Again, conditions will be favorable for severe weather with steep
mid level lapse rates, dewpoints in the mid 60s, and cape values
between 2500-3500j/kg. Also, of interest is models show a jet streak
moving through the area Monday evening which would aid in supercell
development with again all three Mode of severe weather possible.
Long term...(monday through saturday)
issued at 338 am CDT sun may 19 2013
Monday night into Tuesday...convection will be ongoing Monday night
across the County Warning Area with strong to severe weather possible as discussed
during the short term. Thunderstorms will gradually shift east of
the area by Tuesday morning. The upper low will only make slow
progress eastward, with the surface cold front located from north
central to southwest Missouri by Tuesday afternoon. Another round of
thunderstorms will be possible along and east of the boundary
Tuesday afternoon and evening. Severe weather will once again be
possible, mainly in the eastern quarter of the County Warning Area. Thereafter, the
front is expected to clear the area by Tuesday night, ending chances
for precipitation. The front will sag southward and stall near
southern Missouri into south central Kansas by Wednesday into the
end of the work week. Likewise, slight chances of showers and
thunderstorms will be possible mainly across southern sections of
the County Warning Area through Friday, in areas closest to the frontal boundary.
Near seasonal temperatures can be expected through the period, with
highs in the 70s and lows in the 50s.
&&
Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1238 PM CDT sun may 19 2013
Line of storms is expected to rapidly develop later this afternoon
across eastern Kansas, ahead of a weak wave that is currently visible
as a band of altocumulus from gri to sln and west of ict. While
timing is still somewhat uncertain, best guess at this time is that
this line of storms will approach the Kansas/MO state line around 00z,
progressing toward irk and cou toward 04z, give or take a couple of
hours. These storms may be strong with large hail and severe wind
gusts.
&&
Eax watches/warnings/advisories...
Kansas...none.
MO...none.
&&
$$
Update...hawblitzel
short term...73
long term...Blair
aviation...hawblitzel
