Area forecast discussion
National Weather Service Topeka Kansas
1145 PM CDT Thursday may 23 2013
Short term...(this evening through friday)
issued at 341 PM CDT Thursday may 23 2013
Although the surface low that impacted the region this past weekend
has progressed east of the Great Lakes region...an associated cold
front still stretched westward across northern Missouri and into
eastern Nebraska. Enough moisture and lift was present near this
boundary to keep much of northeastern Kansas under cloud cover
through much of the day today. Visible satellite imagery showed
some scattering out with the cloud cover by middle afternoon...which
allowed afternoon temperatures to reach into the upper 60s to lower
70s.
Surface high pressure over the northern plains has spilled southward
into the Central Plains today and will shift east of the area
tonight into Friday as the upper level ridge continues to build over
the central and Southern Plains. Expect another cooler night across
the County Warning Area this evening as overnight lows look to drop into the
upper 40s to lower 50s. Models continue to show several embedded
shortwaves developing along the northern extent of this ridge over
the upcoming days...the first looking to develop tonight into Friday
across eastern Colorado and western Kansas. This shortwave also
looks to coincide with a frontal boundary stretching southward from
a surface low over Montana into western Nebraska and western Kansas.
Better chances for precipitation look to be across the western half
of Kansas in the vicinity of this boundary and shortwave. There is
still some uncertainty amongst the models regarding how much
moisture and lift will be able to spread eastward into the forecast
area on Friday to support the development of some scattered showers
and thunderstorms. Due to this uncertainty...have chance probability of precipitation
primarily focused over north central and central Kansas through the
day with a mostly dry forecast for far eastern Kansas. Could start
seeing any scattered precipitation that develops shift into
northeastern Kansas by Friday evening as the shortwave pivots a bit
further east along the ridge. The increased cloud cover across the
area on Friday will keep temperatures on the cooler side once
again...with afternoon highs looking to top out in the upper 60s to
lower 70s.
Long term...(friday night through thursday)
issued at 341 PM CDT Thursday may 23 2013
The middle and long term forecast period remains rather uncertain
regarding specific details of location and timing of thunderstorm
potential...but confident in some of the general features as well as
a temperature pattern.
The upper level flow pattern this weekend will actually be
characterized by a rather Sharp Ridge axis centered over eastern
Kansas with a long wave trough firmly in place over the western
Continental U.S.. several pieces of energy will translate out of the western
trough from Saturday through next week...providing numerous chances
for thunderstorms through the period. The primary challenge with
this forecast seems to be in interpreting which of these impulses
will be strong enough to overcome a capping inversion across eastern
Kansas...as well as any periods during which the deep layer shear
markedly increases coincident with the short wave trough passage.
Otherwise...temperatures are expected to be generally in the 80s for
highs and 60s for lows through the entire period...with cloud cover
largely dependent upon convective systems...and a rather moist low
level airmass in place.
In terms of specifics...it would appear that a short wave trough
passage will weaken the upper ridge enough on Friday night to
support an mesoscale convective system across Nebraska...and perhaps even into northern
Kansas. The remnants of this mesoscale convective system may impact mainly northeast Kansas
on Saturday morning...but perhaps more importantly are expected to
place an outflow boundary across the forecast area by afternoon. The
exact location of any outflow will focus any thunderstorm activity
initially to that location and remains uncertain...but instability
will be maximized along the boundary with inhibition minimized and
expect at least a few storms to develop along any remnant outflow if
it does indeed exist. The deep layer shear profile is not particularly
strong although it may support at least some brief storm
organization before cold pools interact. Saturday night convection
may also track along this boundary across the area out of central
Nebraska. Will need to monitor this activity for late night
wind/hail potential should it organize into an mesoscale convective system. Upper ridging is
forecast to build back in over central Kansas in the wake of this
activity...with any Sunday afternoon convective potential depending
upon a cap break. Instability should still be strong on Sunday and
the deep shear profile should be a bit more impressive than
Saturday...and could see some severe weather potential late Sunday
into Sunday night. Locally heavy rainfall will also be possible
through this period given moderate to high precipitable water values and potential
for storms to focus repeatedly over the same general areas.
Beyond Sunday...the uncertainty regarding specifics is just too
great to get bogged down in any details. Operational models maintain
the broad southwesterly upper flow pattern but diverge regarding the
evolution of the ejection date of the primary upper low itself.
Whenever The Heart of this system does enter the Central Plains...
would expect a greater potential of severe weather with increased
deep layer shear and perhaps a more organized focus for development.
Have maintained several rather small chances for precipitation
through the long term period but there is a chance that much of the
area could be dry until the main trough approaches...it all really
depends on whether cap strength can outlast weak short wave trough
strength on a day to day basis. Even after the main trough crosses
the plains...it looks like the weather pattern will remain active
with southwest flow remaining in place and a new long wave trough
settling over the western U.S.
Barjenbruch
&&
Aviation...(for the 06z tafs through 06z Friday night)
issued at 1145 PM CDT Thursday may 23 2013
Models continue to show increasing moisture advection up through
central Kansas as the low level jet veers around more to the south.
Latest satellite shows a band of ac within the axis of moisture
advection. Therefore will continue with a mention of vcsh at mhk
by middle morning as isentropic forecasts show some lift with lowering
conditions pressure def developing across north central Kansas. Think top and foe
will remain mainly to the east of the better moisture advection.
The NAM has backed off on the low level saturation and MVFR ceilings.
With the RUC showing some consistency in keeping ceilings VFR...have
taken out the mention of MVFR ceilings at mhk.
&&
Top watches/warnings/advisories...
none.
&&
$$
Short term...hennecke
long term...barjenbruch
aviation...wolters
