Alert archive / Oregon / Mesoscale Discussions in 2021

Mesoscale Discussion 1417

August 2, 20217 counties in Oregon

The Storm Prediction Center issued this mesoscale discussion at Aug 2, 2021, 12:51 PM PDT for 7 counties in Oregon. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 2, 2021, 12:51 PM PDT (19:51 UTC)
Expired: Aug 2, 2021, 3:15 PM PDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

Counties Crook County, OR, Deschutes County, OR, Grant County, OR, Harney County, OR, Jefferson County, OR, Lake County, OR, Wheeler County, OR

The nearest sounding before it

Medford/Jackson, OR (KMFR), launched 12:00Z, 7.9 hours before the alert went out and 258 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: 1714 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 42 m²/s²
0-3 km storm-relative helicity: 115 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

967 
ACUS11 KWNS 021952
SWOMCD
SPC MCD 021951 
ORZ000-022215-

Mesoscale Discussion 1417
NWS Storm Prediction Center Norman OK
0251 PM CDT Mon Aug 02 2021

Areas affected...portions of central into southeast Oregon

Concerning...Severe potential...Watch unlikely 

Valid 021951Z - 022215Z

Probability of Watch Issuance...5 percent

SUMMARY...A damaging gust or two may occur with the strongest storms
this afternoon into early evening. The overall severe threat is
expected to be quite sparse and short-lived, and a WW issuance is
not expected.

DISCUSSION...Mostly clear skies have allowed for ample diurnal
heating, with surface temperatures/dewpoints exceeding 80/50 F per
latest METAR observations, contributing to 500-1000 J/kg MLCAPE
(when modifying 17Z RAP forecast soundings). Latest visible
satellite imagery shows CU field growth over the higher terrain of
the southern Cascades, and MRMS mosaic radar data shows convective
initiation in progress. Further heating into the 85-90F range should
support more robust convective initiation over the next couple of
hours.

By 21Z, a well-mixed boundary layer will be in place, fostering
8.5-10 C/km 0-3km lapse rates. Mainly high-based, pulse-cellular
storms are expected this afternoon into early evening. The presence
of 0.75 inch precipitable water values suggests that enough water
loading in convective downdrafts and subsequent evaporative cooling
in the deep sub-cloud layer will support some potential for gusty
winds. However, dewpoints are expected to mix out some by afternoon
peak heating, constricting skinny CAPE profiles to the 600-300 mb
layer/above the freezing level. As such, the stronger (potentially
severe) wind gusts are expected to be quite isolated and brief, and
a Severe Thunderstorm Watch issuance is not anticipated.

..Squitieri/Grams.. 08/02/2021

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

ATTN...WFO...BOI...PDT...MFR...PQR...

LAT...LON   43002145 43582225 44322233 44452228 44902177 45132102
            45201994 45211933 45021918 44161855 43501808 43071778
            42571798 42171849 42151902 42222000 42512064 42672101
            43002145

Nearby

Mesoscale Discussions in Oregon, 2021 Every 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.