Alert archive / Idaho / Mesoscale Discussions in 2021
Mesoscale Discussion 1421
The Storm Prediction Center issued this mesoscale discussion at Aug 5, 2021, 2:45 PM MDT for 13 counties in Idaho. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 5, 2021, 2:45 PM MDT (20:45 UTC)
- Expired
- Aug 5, 2021, 4:45 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Ada County, ID, Blaine County, ID, Boise County, ID, Butte County, ID, Camas County, ID, Cassia County, ID, Elmore County, ID, Gooding County, ID, Jerome County, ID, Lincoln County, ID, Minidoka County, ID, Power County, ID, Twin Falls County, ID
The radar
The Boise radar (KCBX), 128 km from the middle of the area, began a volume at 20:46 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, 8.8 hours before the alert went out and 128 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
- 87 J/kg
- Mixed-layer CIN
- -488 J/kg
- Mixed-layer LCL
- 3177 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 63 m²/s²
- 0-3 km storm-relative helicity
- 146 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
639
ACUS11 KWNS 052045
SWOMCD
SPC MCD 052045
IDZ000-UTZ000-NVZ000-052245-
Mesoscale Discussion 1421
NWS Storm Prediction Center Norman OK
0345 PM CDT Thu Aug 05 2021
Areas affected...southern Idaho and extreme northeast Nevada and
northwest Utah
Concerning...Severe potential...Watch unlikely
Valid 052045Z - 052245Z
Probability of Watch Issuance...5 percent
SUMMARY...High-based convection may pose a risk for isolated
downburst winds this afternoon into the early evening hours. It
appears coverage of any severe events will probably remain too
sparse to warrant a WW.
DISCUSSION...This afternoon high-based convection is in the process
of developing from northeast NV through northern UT and southern ID.
Most of this activity has yet to produce lightning. Strong diabatic
heating is occurring in the wake of the morning clouds and showers,
boosting temperatures into the 90s F, but with surface dewpoints
likely to mix into the 40s and upper 30s F over much of this region.
Deeply mixed boundary layers with steep lapse rates will
characterize the atmosphere, but instability will remain marginal
with 300-600 J/kg MLCAPE. Scattered showers and thunderstorms will
continue developing within the zone of upper diffluence and ascent
downstream from a shortwave trough situated over northern CA.
High-based updrafts rooted near 600 mb atop deep inverted-V boundary
layers will promote a threat for isolated downburst winds as
activity spreads northward into the early evening.
..Dial/Grams.. 08/05/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...SLC...PIH...BOI...LKN...
LAT...LON 44191554 44101389 43521271 42741238 41971294 41011479
41931531 42881645 43491655 43941627 44191554Nearby
Mesoscale Discussions in Idaho, 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.