Alert archive / California / Mesoscale Discussions in 2007

Mesoscale Discussion 2139

October 29, 200713 counties in California

The Storm Prediction Center issued this mesoscale discussion at Oct 29, 2007, 12:46 PM PDT for 13 counties in California. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Oct 29, 2007, 12:46 PM PDT (19:46 UTC)
Expired: Oct 29, 2007, 2:15 PM PDT
In force: 89 min
Issued by: the Storm Prediction Center

Counties Amador County, CA, Butte County, CA, Calaveras County, CA, El Dorado County, CA, Fresno County, CA, Madera County, CA, Mariposa County, CA, Nevada County, CA, Placer County, CA, Plumas County, CA, Sierra County, CA, Tuolumne County, CA, Yuba County, CA

The radar

The Sacramento radar (KDAX), 105 km from the middle of the area, began a volume at 19:47 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, 7.8 hours before the alert went out and 172 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: 1240 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 75 m²/s²
0-3 km storm-relative helicity: 151 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
ACUS11 KWNS 291946
SWOMCD
SPC MCD 291946 
CAZ000-292115-

MESOSCALE DISCUSSION 2139
NWS STORM PREDICTION CENTER NORMAN OK
0246 PM CDT MON OCT 29 2007

AREAS AFFECTED...SIERRA NEVADA RANGE

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 291946Z - 292115Z

TSTMS ARE EXPECTED TO INCREASE IN COVERAGE ACROSS DISCUSSION AREA
THIS AFTERNOON WITH THE POTENTIAL FOR SOME MARGINALLY SEVERE HAIL
WITH THE MOST INTENSE CORES.  A WW IS NOT ANTICIPATED.

A PLUME OF RELATIVELY STEEP MID-LEVEL LAPSE RATES OF 7-8 C/KM
COUPLED WITH DAYTIME HEATING ARE CONTRIBUTING TO AIR MASS
DESTABILIZATION OVER THE SACRAMENTO VALLEY EWD INTO SIERRA NEVADAS
WHERE MUCAPES HAVE INCREASED TO 500-1000 J/KG.  RECENT TRENDS IN
RADAR...SATELLITE AND LIGHTNING DATA SETS INDICATE TSTMS SLOWLY
INCREASING IN AREAL COVERAGE OVER THE SACRAMENTO VALLEY...NAMELY
GLENN...TEHAMA AND MORE RECENTLY SACRAMENTO COUNTIES.  FORCING FOR
ASCENT ATTENDANT TO MOBILE UPPER TROUGH APPROACHING THE CA COAST
APPEARS TO BE THE PRIMARY MECHANISM SUPPORTING THIS MORE RECENT
STORM DEVELOPMENT.

AS THIS SYSTEM CONTINUES EWD...EXPECT AN INCREASE IN STORM COVERAGE
OVER PORTIONS OF THE SACRAMENTO INTO SAN JOAQUIN VALLEYS...AND
EVENTUALLY THE HIGHER TERRAIN OF THE SIERRAS.  RUC PROXIMITY
FORECAST SOUNDINGS SUGGEST THAT AMBIENT THERMODYNAMIC ENVIRONMENT
OVER THE SIERRAS WILL BE MOST FAVORABLE FOR THE DEVELOPMENT OF A
COUPLE MARGINALLY SEVERE STORMS CAPABLE OF SOME HAIL.  THIS THREAT
SHOULD TEND TO DIMINISH BY MID TO LATE EVENING AS BOUNDARY LAYER
COOLS AND STABILIZES.

..MEAD.. 10/29/2007

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...VEF...REV...HNX...STO...

36751987 38852153 39722187 39982194 40372155 40282084
38321964 37241862 36541904

Nearby

Mesoscale Discussions in California, 2007 Every mesoscale discussion in 2007

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.