- Day Three
acus01 kwns 161958
Storm Prediction Center ac 161957
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0257 PM CDT Thu may 16 2019
Valid 162000z - 171200z
..there is a slight risk of severe thunderstorms from the Great
Lakes and Ohio Valley through the Central Plains and northern
Severe storms remain possible from the Great Lakes, Ohio Valley and
westward through the Central Plains and a portion of the northern
Only minor adjustments have been made to previous outlook. Mesoscale convective system will
continue southeast along instability gradient into southern in and
possibly northern Kentucky where it should weaken. Will maintain slight risk
area over the Great Lakes upstream from Ohio Valley mesoscale convective system.
Stabilization has occurred in the wake of this feature. However,
moist advection associated with southwesterly winds and diabatic
warming will allow for the atmosphere to recover in pre-frontal warm
sector from southern WI into Michigan where additional storms may develop
by early evening with damaging wind and large hail possible. Farther
west high-based storms are developing south of the stationary front
over western NE and these may intensify as they continue northeast
into zone of greater destabilization and higher surface dewpoints
near the front. Other storms will develop tonight along and north of
this boundary as the low-level jet strengthens and enhances
isentropic ascent in frontal zone.
Previous discussion... /issued 1130 am CDT Thu may 16 2019/
Considered increasing tornado probabilities and adding significant
hail but low confidence exists in whether supercells can be
sustained in the warm sector across IL/in.
A slowly decaying mesoscale convective system is ongoing near the Illinois/WI border within a warm
advection regime. Morning cam guidance has poorly handled with most
struggling to maintain any semblance of convection beyond
initialization. The stratiform region across Lake Michigan should have an
impact on downstream destabilization in lower Michigan given that Richer
boundary-layer moisture characterized by low to mid 60s surface dew
points is currently confined from Illinois west. It is possible that the
mesoscale convective system may not entirely dissipate as warm advection persists through
the period. Renewed development on the upshear side would seemingly
be most likely along trailing convective outflow. Along the eastern
extent of the Great Plains elevated mixed layer at peak heating,
robust upstream diabatic heating should result in large buoyancy
with MLCAPE of 2000-3000 j/kg. Veering of the wind profile with
height on the periphery of moderate mid-level northwesterlies will
favor supercell structures. An evolution to another mesoscale convective system with
wind/hail risks appears probable tonight towards the Ohio Valley.
Minimal change this outlook beyond adding low tornado probabilities
across the northern/eastern Wyoming vicinity.
Easterly upslope flow will be maintained through the period on the
cool side of the stalled front (just north of the Lee cyclone), with
the somewhat Richer low-level moisture/buoyancy confined mainly to
central NE east. Gradual height falls in advance of the expansive
western trough will combine with the upslope flow and daytime
heating in cloud breaks to support scattered thunderstorm
development along the Lee of the central rockies during late
afternoon, which will persist into this evening. The storm
environment will support a few high-based supercells capable of
mainly producing large hail and isolated severe wind gusts.
Strengthening warm advection this evening yielding isentropic ascent
along the largely west/east-oriented front across Iowa towards
northern Illinois should result in scattered to widespread storms with a
mix of isolated severe hail/wind amid a cluster convective Mode.
Have added a small slight risk for the expectation of a few
supercells around peak heating.
Increasing mid-level height falls and DCVA downstream of the
expansive Pacific coast trough will Foster substantial ascent across
the region at peak heating. With mid 40s to low 50s surface dew
points prevalent, a corridor of modest buoyancy should develop where
diabatic heating is greatest across northern Idaho into far western Montana.
Veering of the low-level wind profile with height beneath moderate
mid-level southerlies should support a few supercell structures
capable of mainly isolated severe hail.
..eastern Great Basin...
The zone of strongest forcing for ascent in advance of the mid-level
trough and along the cold front will reach western Utah and eastern Idaho
later this afternoon through this evening. Though low-level moisture
will be limited, weak buoyancy is expected ahead of the front.
Thunderstorms will be capable of producing isolated
strong/damaging gusts in an environment characterized by weak
buoyancy, steep low-level lapse rates, and strong deep-layer
..southeast nm and far West Texas...
The surface Lee trough will sharpen today in response to increasing
southwest flow aloft over the southern rockies. This area will lie
along the northwest edge of the Richer returning low-level moisture,
which will likely be offset today by deep mixing. Still, some
increase in deep-layer shear and sufficient buoyancy suggest that a
couple of high-based supercells will be possible immediately east of
the high terrain in the late afternoon and evening. Marginally
severe hail and strong outflow gusts will be the main threats.
acus11 kwns 161947
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 161947
Mesoscale discussion 0640
National Weather Service Storm Prediction Center Norman OK
0247 PM CDT Thu may 16 2019
Areas affected...parts of central Illinois into central Indiana
Concerning...Severe Thunderstorm Watch 168...
Valid 161947z - 162145z
The severe weather threat for Severe Thunderstorm Watch 168
Summary...the risk for severe thunderstorms continues, with rapid
new thunderstorm development possible near the Champaign vicinity by
4-5 PM CDT. Trends will continue to be monitored for the
possibility of an additional watch, or southward watch extension.
Discussion...the leading edge of the convective outflow and stronger
associated thunderstorm development continue to progress
southeastward at 30+ kt (across and southeast of the central
Illinois/Indiana state border area). At least some recent general
weakening of ongoing convection is evident in latest mrms cappi
data, and this may continue with activity spreading into the less
unstable environment across Indiana. However, mixed-layer cape has
increased in excess of 3000 j/kg along and to the southwest of the
southwestern flank of the convective outflow, northeast of
Springfield through the Decatur, Champaign and Mattoon vicinities,
where it appears that mid-level inhibition has yet to increase
substantially. As weak mid-level convection, now evident in
satellite imagery south through east of Peoria, progresses
southeastward along the outflow boundary, there appears potential
for rapid new intense thunderstorm development by 21-22z. This may
include a supercell or two initially, with a risk for severe hail
and perhaps a tornado.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 40398677 40698628 40128581 39678633 39348788 39888934
40488904 40228792 40398677