Alert archive / California / Mesoscale Discussions in 2012

Mesoscale Discussion 167

February 28, 2012Siskiyou County, Trinity County, California

The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2012, 1:49 PM PST for Siskiyou County, Trinity County, California. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Feb 28, 2012, 1:49 PM PST (21:49 UTC)
Expired
Feb 28, 2012, 5:45 PM PST
In force
4 hr
Issued by
the Storm Prediction Center

Counties Siskiyou County, CA, Trinity County, CA

The radar

The Medford radar (KMAX), 70 km from the middle of the area, began a volume at 21:52 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

Medford/Jackson, OR (KMFR), launched 12:00Z, 9.8 hours before the alert went out and 101 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-pSkew-T log-p diagram, Medford/Jackson, OR at 12:00Z on 2012-02-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Medford/Jackson, OR at 12:00Z on 2012-02-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 36 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
529 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
36 m²/s²
0-3 km storm-relative helicity
147 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.

446 
ACUS11 KWNS 282149
SWOMCD
SPC MCD 282149 
ORZ000-CAZ000-290145-

MESOSCALE DISCUSSION 0167
NWS STORM PREDICTION CENTER NORMAN OK
0349 PM CST TUE FEB 28 2012

AREAS AFFECTED...NWRN CA...FAR SWRN ORE

CONCERNING...HEAVY SNOW 

VALID 282149Z - 290145Z

SNOW WILL DEVELOP AND BECOME HEAVY OVER THE HIGHER ELEVATIONS OF
NWRN CA AND FAR SWRN ORE...WITH RATES REACHING 2 IN/HR AFTER 23Z
AFFECTING ELEVATIONS AOA 4 KFT.

A DEEP PACIFIC SHORTWAVE TROUGH AND ATTENDANT BELT OF STRONG
MID-LEVEL FLOW WILL CONTINUE APPROACHING THE COAST. IN
RESPONSE...UPSLOPE FLOW...WAA...AND DCVA ARE FORECAST TO INCREASE
LATER THIS AFTERNOON AND CONTINUE INTO THIS EVENING. THE ASSOCIATED
STRONG ASCENT...AND STEEPENING LOW-TO-MID-LEVEL LAPSE RATES...WILL
SUPPORT THE DEVELOPMENT OF HEAVY SNOW WITH RATES REACHING 2 IN/HR
AFTER 23Z INTO THE EVENING...MAINLY FOR ELEVATIONS AOA 4 KFT. THIS
WILL OCCUR AS AN AXIS OF PW VALUES AROUND 0.5-0.7 INCH /130-150
PERCENT OF NORMAL/ PER BLENDED AMSU-SSMI TPW DATA IMPACTS THE
REGION. THE HIGHEST SNOWFALL RATES WILL BE OF GREATEST CONCERN OVER
THE KLAMATH MOUNTAINS AND THE SRN EXTENT OF THE CASCADES.

..COHEN/MOSIER.. 02/28/2012

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

ATTN...WFO...MFR...STO...EKA...

LAT...LON   41002368 41592379 41982358 42192323 42302265 42452239
            42602214 42332198 41942204 41492204 41012221 40662275
            40092293 40072340 40662365 41002368

Nearby

Mesoscale Discussions in California, 2012Every mesoscale discussion in 2012

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.