Alert archive / Washington / Mesoscale Discussions in 2020

Mesoscale Discussion 511

May 2, 20206 counties in Idaho; 10 counties in Oregon; 12 counties in Washington

The Storm Prediction Center issued this mesoscale discussion at May 2, 2020, 2:19 PM MDT for 6 counties in Idaho; 10 counties in Oregon; 12 counties in Washington. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 2, 2020, 2:19 PM MDT (20:19 UTC)
Expired: May 2, 2020, 4:45 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 28 counties

Adams County, ID, Benewah County, ID, Clearwater County, ID, Latah County, ID, Lewis County, ID, Nez Perce County, ID, Baker County, OR, Crook County, OR, Gilliam County, OR, Grant County, OR, Morrow County, OR, Sherman County, OR, Umatilla County, OR, Union County, OR, Wallowa County, OR, Wheeler County, OR, Adams County, WA, Asotin County, WA, Benton County, WA, Columbia County, WA, Franklin County, WA, Garfield County, WA, Klickitat County, WA, Lincoln County, WA, Spokane County, WA, Walla Walla County, WA, Whitman County, WA, Yakima County, WA

The radar

The Pendleton radar (KPDT), 35 km from the middle of the area, began a volume at 20:19 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.

The nearest sounding before it

Boise Airport, ID (KBOI), launched 12:00Z, 8.3 hours before the alert went out and 303 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2759 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: -9 m²/s²
0-3 km storm-relative helicity: 87 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

021 
ACUS11 KWNS 022020
SWOMCD
SPC MCD 022019 
IDZ000-ORZ000-WAZ000-022245-

Mesoscale Discussion 0511
NWS Storm Prediction Center Norman OK
0319 PM CDT Sat May 02 2020

Areas affected...Northeast OR...Southeast WA...Western ID

Concerning...Severe potential...Watch unlikely 

Valid 022019Z - 022245Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms capable of isolated severe wind/hail will be
possible later this afternoon into the early evening. Watch issuance
is considered unlikely.

DISCUSSION...At 20Z, WV imagery shows a well-defined shortwave
trough beginning to move over inland portions of the Pacific
Northwest. In advance of this system, a broad surface low is located
over northeast OR/southeast WA, and a cold front is beginning to
advance eastward from western into central WA/OR. Thunderstorms have
recently developed across portions of northeast OR, with additional
development expected into portions of far southeast WA and adjacent
western ID later this afternoon, in conjunction with increasing
large-scale ascent and continued boundary-layer heating. 

SBCAPE of 500-1000 J/kg and effective shear increasing into the
30-40 kt range will support some storm organization with the initial
widely scattered activity, with a corresponding risk of isolated
marginally severe hail and locally strong downburst winds. Later
this afternoon into the early evening, coverage of convection may
increase in conjunction with the eastward-moving cold front,
potentially posing a threat for more widespread strong to locally
severe wind gusts, especially from far northeast OR into southeast
WA. At this time, the overall threat appears too marginal for watch
issuance.

..Dean/Hart.. 05/02/2020

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

ATTN...WFO...MSO...BOI...OTX...PDT...

LAT...LON   44552068 45302121 45702132 46172121 46732059 47691826
            47661645 46381526 45051618 44731650 43681883 43681920
            43722012 44552068

Nearby

Mesoscale Discussions in Washington, 2020 Mesoscale Discussions in Oregon, 2020 Mesoscale Discussions in Idaho, 2020 Every mesoscale discussion in 2020

Sources

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.