Alert archive / Washington / Mesoscale Discussions in 2021
Mesoscale Discussion 957
The Storm Prediction Center issued this mesoscale discussion at Jun 13, 2021, 3:20 PM PDT for 9 counties in Oregon; 11 counties in Washington. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- Jun 13, 2021, 3:20 PM PDT (22:20 UTC)
- Expired
- Jun 13, 2021, 5:15 PM PDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Crook County, OR, Deschutes County, OR, Gilliam County, OR, Jefferson County, OR, Morrow County, OR, Sherman County, OR, Umatilla County, OR, Wasco County, OR, Wheeler County, OR, Adams County, WA, Benton County, WA, Douglas County, WA, Franklin County, WA, Grant County, WA, Kittitas County, WA, Klickitat County, WA, Lincoln County, WA, Spokane County, WA, Walla Walla County, WA, Yakima County, WA
The nearest sounding before it
Salem/Mcnary, OR (KSLE), launched 12:00Z, 10.3 hours before the alert went out and 211 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
- 5 J/kg
- Mixed-layer CIN
- -19 J/kg
- Mixed-layer LCL
- 585 m above ground
- 0-6 km bulk shear
- 63 kt
- 0-1 km storm-relative helicity
- 112 m²/s²
- 0-3 km storm-relative helicity
- 136 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
703
ACUS11 KWNS 132220
SWOMCD
SPC MCD 132220
WAZ000-ORZ000-140015-
Mesoscale Discussion 0957
NWS Storm Prediction Center Norman OK
0520 PM CDT Sun Jun 13 2021
Areas affected...Northern Oregon into eastern Washington
Concerning...Severe potential...Watch unlikely
Valid 132220Z - 140015Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated thunderstorms are expected to develop through the
late afternoon and into the early evening, and will likely pose a
hail/wind threat. This risk is expected to remain too isolated for a
watch issuance.
DISCUSSION...GOES visible imagery shows a growing field of deepening
cumulus across central to north-central OR. This is likely
associated with modest warm air advection near 700 mb ahead of an
approaching upper-level shortwave trough (which is currently moving
up the West Coast per water-vapor imagery). A few stronger, but
transient reflectivity cores have been noted within this field in
regional radar imagery, and the potential for sustained convection
will increase over the next 1-2 hours as stronger forcing for ascent
arrives. Strong deep-layer flow over the region is supporting 50-60
knots of 0-6 km bulk shear, which will help organize any persistent
convection. One limiting factor is the limited instability with only
250-500 J/kg MUCAPE noted in mesoanalysis estimates. Continued
daytime heating should yield sufficient instability for a few
isolated storms by late afternoon into the early evening, which may
pose a hail/wind risk, but the overall threat should be too limited
to warrant a watch.
Further east across the ID/MT border, greater instability is noted
and a few scattered convective showers have developed along the
Sawtooth Mountains. However, this region is displaced from more
favorable deep-layer shear and stronger forcing for ascent, yielding
low confidence in the overall severe potential.
..Moore/Dial.. 06/13/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OTX...PDT...MFR...PQR...
LAT...LON 43992233 45292168 47402069 48031996 48001857 47811737
47491710 46581786 45601861 44571928 43962000 43602098
43112154 42492208 42472269 43252262 43992233Nearby
Mesoscale Discussions in Washington, 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.