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SPC MD 1383

MD 1383 CONCERNING SEVERE THUNDERSTORM WATCH 428... FOR PORTIONS OF NORTHWEST MN...SOUTHEAST ND...NORTH CENTRAL AND NORTHEAST SD
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Mesoscale Discussion 1383
NWS Storm Prediction Center Norman OK
0353 PM CDT Fri Jul 21 2017

Areas affected...Portions of northwest MN...southeast ND...north
central and northeast SD

Concerning...Severe Thunderstorm Watch 428...

Valid 212053Z - 212230Z

The severe weather threat for Severe Thunderstorm Watch 428
continues.

SUMMARY...The severe weather threat for Watch 428 continues.

DISCUSSION...A threat for severe wind gusts and hail continues in
the Watch area, with the main threat in the short term ahead of the
supercell in Griggs County, ND, which is expected to maintain a
threat for significant hail and wind gusts in the next hour or so.

Convective coverage is increasing rapidly in much of the MN portion
of the Watch under the influence of the approaching short wave
trough. Initial storm development appears as scattered discrete
cells in this area, so a limited tornado threat continues with any
cells that can attain supercell structures, but is mostly confined
to a narrow region between the surface trough and a region of much
drier air over north central MN. Severe wind gusts and hail are also
possible with this activity.

Farther south, the convective inhibition has eroded over most of the
area, and scattered thunderstorms are expected to develop in the
next hour, mainly along a weak surface trough over central SD.  An
initial mode of discrete cells is expected that will pose the threat
for severe wind gusts and hail.  The tornado threat is much lower in
this portion of the Watch given weak low-level winds/shear and a
more deeply-mixed boundary layer.

..Coniglio/Cohen.. 07/21/2017

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

ATTN...WFO...DLH...FGF...ABR...BIS...UNR...

LAT...LON   48159887 48159431 44649833 44630254 48159887 

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SPC MD 1382

MD 1382 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR CENTRAL NEBRASKA...NORTHWEST KANSAS
MD 1382 Image


Mesoscale Discussion 1382
NWS Storm Prediction Center Norman OK
0343 PM CDT Fri Jul 21 2017

Areas affected...Central Nebraska...northwest Kansas

Concerning...Severe potential...Watch unlikely 

Valid 212043Z - 212215Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms are expected to develop the remainder of
this afternoon and continue into the evening hours.  Isolated
instances of damaging winds and perhaps hail can be expected.  A
watch is not anticipated due to the isolated nature of the threat.

DISCUSSION...Towering cumulus clouds were increasing in vertical
extent in the vicinity of a surface trough across northeast through
central Nebraska at 2030Z, and a small area of thunderstorms has
developed across northwest Kansas.  Intense diurnal heating of a
moist (PW values of 1.5 to 1.9 inches) air mass has resulted in
strong surface-based instability with MLCAPE of 3000-4000 j/kg. 
Modest westerly mid-level flow has contributed to effective shear of
20-35 kts, sufficient for some degree of organization, including
isolated supercell structures given the degree of instability. 
Water loading in updrafts and strong DCAPE will promote a risk for
damaging gusts with the strongest storms through early evening, and
a few instances of hail will also be possible.  Overall risk appears
to be relatively confined in space and time, and a watch is not
currently anticipated.

..Bunting/Dial.. 07/21/2017

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

ATTN...WFO...OAX...GID...LBF...GLD...

LAT...LON   40049903 39730048 39780104 40450066 40940023 41250014
            41590001 41859997 42109964 42239889 42279843 42279812
            42109781 41769753 41139758 40329794 40049903 

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