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SPC United States Convective Summary



RSS Mesoscale Discussions from Storm Prediction Center

SPC MD 1171

MD 1171 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN WY...WESTERN SD...EASTERN MT
MD 1171 Image


Mesoscale Discussion 1171
NWS Storm Prediction Center Norman OK
0328 PM CDT Wed Jun 28 2017

Areas affected...Eastern WY...Western SD...Eastern MT

Concerning...Severe potential...Watch unlikely 

Valid 282028Z - 282230Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated severe thunderstorms are possible this afternoon,
with a threat of hail and locally damaging wind.

DISCUSSION...Widely scattered thunderstorms have developed from
eastern MT/WY into western SD, in conjunction with diurnal heating
and in advance of a low-amplitude upper trough moving through the
interior Northwest. 

The strongest convection within the MCD area has thus far been
across northeast MT, in the vicinity of a weak surface boundary
where winds are favorably backed out of the east, resulting in
effective shear of 35-45 kt and effective helicity of 100-150 m2/s2.
In conjunction with SBCAPE of 500-1000 J/kg, the wind profile in
this area will continue to support organized convection in the short
term, including transient supercell structures with a threat of
large hail and locally damaging wind. Strong drying/mixing across
far eastern MT and western ND should limit the severe threat with
eastward extent across this area. 

Further south, additional clusters of thunderstorms are moving
across southeast MT and eastern WY, and an isolated strong cell has
recently developed south of Rapid City. While wind profiles are not
quite as favorable compared to northeast MT, effective shear of
25-35 kt in conjunction with SBCAPE of 500-1250 J/kg will support
the potential for modestly organized clusters and perhaps a
supercell or two, capable of large hail and locally damaging wind. 

In general, the magnitude and coverage of the severe threat across
these areas are expected to remain too low for watch issuance.

..Dean/Guyer.. 06/28/2017

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

ATTN...WFO...UNR...CYS...BYZ...GGW...

LAT...LON   42970449 43020476 43200505 43760506 44570517 46620596
            47940612 48090449 45770401 44050259 43140254 43100273
            43050316 43030410 42970449 

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SPC MD 1170

MD 1170 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PARTS OF EAST CENTRAL AND SOUTHEAST MINNESOTA INTO WESTERN/CENTRAL WISCONSIN
MD 1170 Image


Mesoscale Discussion 1170
NWS Storm Prediction Center Norman OK
0249 PM CDT Wed Jun 28 2017

Areas affected...Parts of east central and southeast Minnesota into
western/central Wisconsin

Concerning...Severe potential...Watch likely 

Valid 281949Z - 282145Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorms are expected to develop and intensify across
the region through late afternoon, accompanied by increasing severe
weather potential as early as the 4-5 PM CDT time frame.  A watch
issuance seems probable within the next hour or two.

DISCUSSION...Within the warm sector of a sub-1000 mb surface cyclone
now migrating across central Minnesota, insolation and low-level
moistening beneath modestly steep mid-level lapse rates are
contributing to considerable boundary layer destabilization.  Mixed
layer CAPE now appears on the order of 1000-2000 J/kg, along and
south of a warm frontal zone extending east southeast of the low
center, and objective analysis suggests that mid-level inhibition is
in the process of becoming increasingly negligible.

Aided by forcing for ascent associated with a mid-level cyclonic
vorticity center, progressing through larger-scale upper troughing
now shifting across the upper Mississippi Valley and Upper Midwest,
thunderstorms are expected to develop and increase across the region
through late afternoon.  Initial attempts at this may already be
underway near/southeast of the Minneapolis area.  Activity seems
likely to generally focus and propagate along the warm frontal zone,
and may include discrete supercells before possibly growing upscale
into an organizing convective system, in the presence of strong deep
layer shear.

..Kerr/Guyer.. 06/28/2017

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

ATTN...WFO...GRB...DLH...ARX...MPX...

LAT...LON   45929211 45568954 44538940 43579118 43819304 44839393
            45929211 

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SPC MD 1169

MD 1169 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR MUCH OF CENTRAL AND SOUTHERN IOWA AND ADJACENT PORTIONS OF NORTHWESTERN ILINOIS...NORTHERN MISSOURI AND SOUTHEASTERN NEBRASKA
MD 1169 Image


Mesoscale Discussion 1169
NWS Storm Prediction Center Norman OK
0214 PM CDT Wed Jun 28 2017

Areas affected...Much of central and southern Iowa and adjacent
portions of northwestern Ilinois...northern Missouri and
southeastern Nebraska

Concerning...Severe potential...Watch likely 

Valid 281914Z - 282115Z

Probability of Watch Issuance...80 percent

SUMMARY...A rapid increase in thunderstorm activity and intensity
appears possible late this afternoon, perhaps as early as the 3-5 pm
CDT time frame.  The latest trends are being closely monitored for
increasing severe weather potential which likely will require a
watch issuance.

DISCUSSION...Potential convective evolution late this afternoon
remains a little unclear, but objective analysis suggests that
mid-level inhibition is becoming increasingly negligible across much
of the region.  This is occurring in response to both continued
insolation and low-level moistening, with surface dew points
currently increasing through the upper 60s and lower 70s F.  Beneath
a corridor of modestly steep mid-level lapse rates, associated with
a thermal ridge extending east northeast of a plume of warmer and
more strongly capping elevated mixed-layer air across the central
Plains, moderately large mixed layer CAPE (2000-3000 J/kg) appears
to be developing.

Given this magnitude of potential instability, in the presence of
weakening inhibition, rapid thunderstorm development and
intensification appears possible within the next few hours.  Forcing
for ascent to support initiation, however, remains a bit unclear. 

Deepening convective development is currently evident along the
surface trough axis, to the west of a persistent area of elevated
thunderstorm activity now spreading east northeastward across north
central Iowa.  Additional attempts at deepening convective
development also appear ongoing around and east of the Omaha area,
beneath a somewhat warmer mid-level environment, in the presence of
enhanced lower/mid tropospheric warm advection.  As a lingering
mid-level speed maximum (associated with larger-scale upper
troughing shifting into the Upper Midwest) gradually noses east of
the mid Missouri Valley late this afternoon, a general increase in
convective development seems probable, in the presence of sufficient
vertical shear for supercells, and, eventually, an upscale growing
thunderstorm cluster or two.

..Kerr/Guyer.. 06/28/2017

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

ATTN...WFO...DVN...DMX...EAX...OAX...

LAT...LON   41709558 42559466 42409363 42649219 42179114 40609089
            40099460 40599631 41709558 

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SPC MD 1168

MD 1168 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHERN MT...CENTRAL/EASTERN ID...NORTHERN WY...FAR NORTHERN UT/NORTHEAST NV
MD 1168 Image


Mesoscale Discussion 1168
NWS Storm Prediction Center Norman OK
0139 PM CDT Wed Jun 28 2017

Areas affected...Southern MT...Central/eastern ID...Northern
WY...Far northern UT/northeast NV

Concerning...Severe potential...Watch unlikely 

Valid 281839Z - 282115Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorm clusters capable of isolated hail and strong
wind gusts will continue into this afternoon.

DISCUSSION...Thunderstorm activity has recently increased across
portions of southern MT, eastern ID, and western WY, in conjunction
with a low-amplitude upper trough moving through the interior
Northwest. As heating continues this afternoon in an environment
characterized by relatively steep low-midlevel lapse rates and
effective shear of 25-35 kt, thunderstorm coverage is expected to
increase, with some weakly rotating cells or organized clusters
possible. 

The strong thunderstorm cluster over currently over the Wind River
Range in western WY will likely pose some threat of marginally
severe hail and strong wind in the short term, with wind threat
potentially extending further east into lower elevations if a
sufficiently strong cold pool can become established. Additional
redevelopment is likely over eastern ID/southwest MT and also across
far northeast NV/northern UT, with eastward-moving clusters
resulting in a similar risk of isolated hail/strong wind gusts. In
general, the magnitude of the threat is expected to remain too low
for watch issuance.

..Dean/Guyer.. 06/28/2017

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

ATTN...WFO...UNR...CYS...BYZ...RIW...TFX...SLC...PIH...MSO...
BOI...LKN...

LAT...LON   41801277 41561453 43301477 45011483 45651408 46171137
            46130834 45610583 44710523 43620525 42560684 42400847
            42251013 42061121 41801277 

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