SPC MD 859

MD 0859 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PARTS OF SOUTHWESTERN NEBRASKA AND ADJACENT NORTHERN KANSAS
MD 0859 Image


Mesoscale Discussion 0859
NWS Storm Prediction Center Norman OK
0825 PM CDT Mon May 20 2024

Areas affected...parts of southwestern Nebraska and adjacent
northern Kansas

Concerning...Severe potential...Watch likely 

Valid 210125Z - 210300Z

Probability of Watch Issuance...80 percent

SUMMARY...An intensifying supercell and perhaps small upscale
growing convective cluster appears likely to continue developing
eastward along a frontal zone into portions of southwestern Nebraska
and adjacent northern Kansas through 10 PM-Midnight CDT.  This will
be accompanied by increasing potential for large hail, severe wind
gusts and a few tornadoes.  A new watch likely will be issued within
the next hour or so.

DISCUSSION...More substantive intensification of convection across
northeastern Colorado is now underway, including one supercell now
propagating eastward across the Akron CO vicinity.  As activity
continues eastward, strengthening easterly low-level updraft inflow
will become increasingly unstable with deeper progression into the
plains.  This likely will support further upscale growth, including,
at least initially, an enlarging supercell, then perhaps a gradually
upscale growing cluster focused along the baroclinic zone (roughly
centered around 700 mb) extending eastward near/north of the
Kansas/Nebraska border vicinity.

..Kerr/Thompson.. 05/21/2024

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...GID...LBF...GLD...BOU...

LAT...LON   40930201 41000060 40679972 39699985 39580095 39680163
            40140214 40930201 

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SPC MD 858

MD 0858 CONCERNING TORNADO WATCH 269... FOR PARTS OF NORTHEASTERN COLORADO
        
MD 0858 Image

Mesoscale Discussion 0858
NWS Storm Prediction Center Norman OK
0713 PM CDT Mon May 20 2024

Areas affected...parts of  northeastern Colorado

Concerning...Tornado Watch 269...

Valid 210013Z - 210215Z

The severe weather threat for Tornado Watch 269 continues.

SUMMARY...Ongoing thunderstorms may begin to consolidate into at
least one increasingly prominent supercell across and east of the
Akron CO vicinity of northeastern Colorado through 7-9 PM MDT.  This
may be accompanied by a risk for large hail in excess of 2 inches in
diameter, locally damaging wind gusts and increasing potential for a
tornado or two.

DISCUSSION...Thunderstorms development has been slowly increasing to
the north of the Palmer Ridge, with intensification initially slowed
by rather modest boundary-layer instability.  Downstream of
large-scale mid-level troughing crossing the Intermountain West,
cyclogenesis is underway to the lee of the southern Rockies.  A
corridor of strengthening warm advection centered around around the
700 mb level is becoming focused across northeastern Colorado into
southwestern Nebraska, and associated forcing for ascent may
contribute to consolidation of ongoing storms approaching areas
near/northwest of Akron CO through 01-03Z.  At the same time,
continued boundary-layer moistening on easterly low-level flow
beneath steepening lapse rates may contribute to mixed-layer CAPE
increasing in excess of 1000-1500 J/kg.

Vertical shear beneath a strong west-southwesterly jet nosing across
the southern Rockies into the central Great Plains will support
substantive intensification as inflow into convection becomes
increasingly unstable.  It seems probable that this will include the
evolution of at least one prominent supercell, which may tend to
remain focused along the baroclinic zone as it propagates eastward
within 30+ kt southwesterly deep-layer ambient mean flow.

..Kerr.. 05/21/2024

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...GLD...BOU...

LAT...LON   40300373 40720246 39970166 39580236 39750338 40300373 

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