Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 846
The Storm Prediction Center issued this mesoscale discussion at Jun 3, 2021, 4:58 PM MDT for 12 counties in Idaho; 13 counties in Montana; 6 counties in Oregon. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 3, 2021, 4:58 PM MDT (22:58 UTC)
- Expired
- Jun 3, 2021, 7:30 PM MDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 31 counties
Ada County, ID, Adams County, ID, Boise County, ID, Canyon County, ID, Clearwater County, ID, Gem County, ID, Idaho County, ID, Lewis County, ID, Nez Perce County, ID, Payette County, ID, Valley County, ID, Washington County, ID, Cascade County, MT, Chouteau County, MT, Deer Lodge County, MT, Granite County, MT, Lake County, MT, Lewis and Clark County, MT, Liberty County, MT, Mineral County, MT, Missoula County, MT, Pondera County, MT, Powell County, MT, Ravalli County, MT, Teton County, MT, Baker County, OR, Grant County, OR, Harney County, OR, Malheur County, OR, Union County, OR, Wallowa County, OR
The radar
The Boise radar (KCBX), 212 km from the middle of the area, began a volume at 23:00 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, 11.0 hours before the alert went out and 202 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 3029 m above ground
- 0-6 km bulk shear
- 12 kt
- 0-1 km storm-relative helicity
- -13 m²/s²
- 0-3 km storm-relative helicity
- -15 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
000
ACUS11 KWNS 032258
SWOMCD
SPC MCD 032258
MTZ000-IDZ000-ORZ000-WAZ000-040130-
Mesoscale Discussion 0846
NWS Storm Prediction Center Norman OK
0558 PM CDT Thu Jun 03 2021
Areas affected...portions of eastern Oregon into western Idaho and
western Montana
Concerning...Severe potential...Watch unlikely
Valid 032258Z - 040130Z
Probability of Watch Issuance...5 percent
SUMMARY...A damaging gust or two remains possible with the stronger
storms into the early evening hours. A WW issuance is not expected.
DISCUSSION...A deep, dry boundary layer has evolved this afternoon
across portions of the Interior West along the periphery of an upper
ridge. Strong heating beneath an 8+ C/km surface-500 mb lapse rate
environment has promoted enough lift and marginal instability (i.e.
at or under 500 J/kg MLCAPE) to support thunderstorm development. A
couple of storms have briefly acquired appreciable intensity over
the past hour (with a 45 kt gust recently measured in Owyhee County,
ID), and a couple more storms may support a strong/damaging gust
through the evening hours given the aforementioned steep lapse rates
in place. However, the sparse and brief nature of the severe threat
precludes a WW issuance.
..Squitieri/Thompson.. 06/03/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TFX...PIH...MSO...BOI...OTX...PDT...MFR...
LAT...LON 42681986 44241930 44821875 46731627 48131312 48591119
48551006 47970976 47251077 46461216 44801474 43621578
42851610 42361684 42241880 42681986Nearby
Mesoscale Discussions in Montana, 2021Mesoscale Discussions in Idaho, 2021Mesoscale Discussions in Oregon, 2021Every mesoscale discussion in 2021
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.