Alert archive / California / Mesoscale Discussions in 2021

Mesoscale Discussion 11

January 4, 20215 counties in California

The Storm Prediction Center issued this mesoscale discussion at Jan 4, 2021, 2:48 PM PST for 5 counties in California. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Jan 4, 2021, 2:48 PM PST (22:48 UTC)
Expired: Jan 4, 2021, 4:15 PM PST
In force: 87 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

Counties Butte County, CA, Shasta County, CA, Sutter County, CA, Tehama County, CA, Yuba County, CA

The radar

The Beale AFB radar (KBBX), 19 km from the middle of the area, began a volume at 22:49 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

Oakland, CA (KOAK), launched 12:00Z, 10.8 hours before the alert went out and 219 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: 890 m above ground
0-6 km bulk shear: 60 kt
0-1 km storm-relative helicity: 182 m²/s²
0-3 km storm-relative helicity: 243 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

992 
ACUS11 KWNS 042249
SWOMCD
SPC MCD 042248 
CAZ000-050015-

Mesoscale Discussion 0011
NWS Storm Prediction Center Norman OK
0448 PM CST Mon Jan 04 2021

Areas affected...portions of northern California

Concerning...Severe potential...Watch unlikely 

Valid 042248Z - 050015Z

Probability of Watch Issuance...5 percent

SUMMARY...A few of the stronger cells may support a damaging gust or
brief tornado through around 00Z. The sparse severe threat is
expected to diminish shortly after sunset. A WW issuance is not
anticipated.

DISCUSSION...KBBX radar depicts strong semi-discrete cells ongoing
across southern Tehama County, CA. These storms are occurring within
a broad region of confluence, where ascent will promote the
continuation of the ongoing storms as well as some potential for
additional convective development. The ambient environment may be
characterized by relatively steep (around 7 C/km) 0-3 km lapse
rates, with associated 100 J/kg 0-3 km CAPE. Ambient vertically
oriented surface/near surface vorticity appears juxtaposed to the
favorable low-level buoyancy per latest Mesoanalysis. As such, any
of the more intense, long-lived storms that manage to develop or
sustain themselves may produce a brief tornado or perhaps a damaging
gust or two. The severe threat is expected to diminish after sunset
as the surface flow continues to veer/weaken, and as boundary layer
decouples and low-level buoyancy diminishes.

..Squitieri/Grams.. 01/04/2021

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

ATTN...WFO...STO...

LAT...LON   38442151 39372222 40342244 40742245 40942220 40772183
            40122151 39522121 38942091 38612079 38442151

Nearby

Mesoscale Discussions in California, 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; radar from the NEXRAD Level II archive.