Mesoscale Discussion 656

Issued

May 5, 2017, 3:16 PM MDT (21:16 UTC)

Expired

May 5, 2017, 5:15 PM MDT

In force

119 min

Issued by

the Storm Prediction Center

Chance of a watch

20%

The Boise radar (KCBX), 63 km from the middle of the area, began a volume at 21:16 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

083 
ACUS11 KWNS 052117
SWOMCD
SPC MCD 052116 
IDZ000-NVZ000-ORZ000-WAZ000-052315-

Mesoscale Discussion 0656
NWS Storm Prediction Center Norman OK
0416 PM CDT Fri May 05 2017

Areas affected...Far north central Nevada...southwest and west
central Idaho...far eastern Oregon...far southeast Washington

Concerning...Severe potential...Watch unlikely 

Valid 052116Z - 052315Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms will increase the next few hours and pose a
threat for severe wind gusts and severe hail.  Coverage of severe is
not expected to warrant a watch at this time.

DISCUSSION...Despite thin cirrus overspreading the area within a
plume of deep Pacific moisture, strong early day heating has
resulted in 500-1000 J/kg of MUCAPE along a north-south corridor
from north-central Nevada into western Idaho.  Widely scattered
thunderstorms have developed within the Pacific frontal zone pushing
east over the area, most concentrated in north-central Nevada.
Deep-layer shear in the 35-45 kt range has supported some updraft
organization with these initial storms. Weak updraft rotation and
sustained updrafts within steep mid-level lapse rates should support
some potential for severe hail in the stronger storms.  

Additionally, dewpoints in the 40s and 50s holding within a
deeply-mixed boundary layer will support strong to scattered severe
wind gusts with the stronger downdrafts.  Recent HRRR guidance
suggests some loosely organized wind threat with consolidating
storms with a cold pool moving into southwest Idaho after 22z, which
is a reasonable scenario given the somewhat more concentrated area
of storms currently over north-central Nevada.  The coverage of
severe is currently expected to be too low to require a watch, but
convective trends will be monitored for an increase in storm
intensity, coverage, and longevity that could increase watch
potential into the evening.

..Coniglio/Edwards.. 05/05/2017

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

ATTN...WFO...PIH...MSO...BOI...LKN...OTX...PDT...REV...

LAT...LON   44121854 45171850 46431808 46901710 46961587 46561496
            45431470 44821490 44061507 43051546 41591570 40761648
            40621728 41161773 41811814 42661839 44121854

Mesoscale Discussions in Idaho, 2017Mesoscale Discussions in Oregon, 2017Mesoscale Discussions in Washington, 2017Every mesoscale discussion in 2017

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.