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SPC MD 1314

MD 1314 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PORTIONS OF THE WESTERN GREAT BASIN

MD 1314 Image


Mesoscale Discussion 1314
NWS Storm Prediction Center Norman OK
0133 PM CDT Wed Jul 22 2020

Areas affected...portions of the western Great Basin

Concerning...Severe potential...Watch unlikely 

Valid 221833Z - 222030Z

Probability of Watch Issuance...5 percent

SUMMARY...Scattered thunderstorm development is expected by the mid
afternoon hours, and will pose an isolated risk for strong downburst
winds and perhaps severe hail.

DISCUSSION...Recent GOES visible and IR imagery across the western
Great Basin show deepening cumulus with cooling cloud top
temperatures developing off of higher terrain across eastern NV as
well as within a broad deformation zone ahead of an approaching
upper-level low off the CA coast. A few transient lightning strikes
have also been noted over the past hour. While sustained convection
has yet to develop, these trends suggest that more robust convective
initiation is probable in the next 1-2 hours. Elevated instability
remains somewhat marginal (widespread MUCAPE values near 500 J/kg),
but low-level lapse rates have already steepened to 8-9 C/km across
a broad region as a result of deep boundary-layer mixing. 

Once convection becomes established, a gradual increase in storm
intensity is expected through the late afternoon hours as continued
boundary-layer warming, coupled with the steep mid-level lapse rates
noted in morning soundings, helps augment instability. Additionally,
the approach of stronger flow aloft associated with the upper-level
wave will help strengthen deep layer shear through the afternoon.
The aforementioned steep low-level lapse rates will support the
potential for sporadic strong to severe downburst winds. A few
instances of severe hail will be possible with any stronger, more
organized storm, but widespread severe convection does not appear
likely and precludes the need for a watch.

..Hart/Moore.. 07/22/2020

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

ATTN...WFO...BOI...LKN...REV...MFR...STO...

LAT...LON   39921770 40191866 40302023 40292108 40912140 41472089
            41992003 42311903 42311769 42351689 41731478 40711426
            39041435 39231540 39521662 39921770 

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from SPC Mesoscale Discussions https://bit.ly/2amcay0

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