Alert archive / Oregon / Mesoscale Discussions in 2012

Mesoscale Discussion 2164

December 16, 2012Nevada County, Plumas County, Sierra County, California; 9 counties in Oregon

The Storm Prediction Center issued this mesoscale discussion at Dec 16, 2012, 12:39 PM PST for Nevada County, Plumas County, Sierra County, California; 9 counties in Oregon. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Dec 16, 2012, 12:39 PM PST (20:39 UTC)
Expired
Dec 16, 2012, 6:15 PM PST
In force
6 hr
Issued by
the Storm Prediction Center

Counties Nevada County, CA, Plumas County, CA, Sierra County, CA, Baker County, OR, Crook County, OR, Deschutes County, OR, Grant County, OR, Harney County, OR, Klamath County, OR, Lake County, OR, Union County, OR, Wheeler County, OR

The radar

The Medford radar (KMAX), 217 km from the middle of the area, began a volume at 20:41 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, 8.7 hours before the alert went out and 208 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 2012-12-16Temperature 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 2012-12-16The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 123 square meters per square second.1939587897117136Sfc1 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
586 m above ground
0-6 km bulk shear
62 kt
0-1 km storm-relative helicity
123 m²/s²
0-3 km storm-relative helicity
353 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.

584 
ACUS11 KWNS 162039
SWOMCD
SPC MCD 162039 
ORZ000-CAZ000-170215-

MESOSCALE DISCUSSION 2164
NWS STORM PREDICTION CENTER NORMAN OK
0239 PM CST SUN DEC 16 2012

AREAS AFFECTED...PARTS OF THE SRN CASCADES EWD ACROSS CNTRL/ERN ORE
AND PARTS OF THE NRN SIERRAS

CONCERNING...HEAVY SNOW 

VALID 162039Z - 170215Z

SUMMARY...AREAS OF SNOW WITH RATES POTENTIALLY REACHING 1 IN/HR...
AND PERHAPS 2 IN/HR OVER THE CASCADES AND SIERRAS...WILL IMPACT THE
AREA LATE THIS AFTERNOON INTO TONIGHT. LOCALIZED BLIZZARD CONDITIONS
WILL ALSO BE POSSIBLE.

DISCUSSION...A STRONG UPPER JET STREAK AND ACCOMPANYING ZONE OF
ENHANCED DEEP TROPOSPHERIC FLOW CONTINUE APPROACHING THE COAST PER
RECENT WATER VAPOR IMAGERY. AS THE FLOW BELOW 700 MB IMPINGES ON A
NW/SE-ORIENTED BAROCLINIC ZONE AT AN OBLIQUE ANGLE...WAA/ISENTROPIC
ASCENT WILL ALLOW SNOW TO SPREAD ACROSS CNTRL/ERN ORE TO THE E OF
THE ORE CASCADES AFTER 22Z...WHILE SNOW CONTINUES WITH INCREASING
RATES OVER PARTS OF THE CASCADES/SIERRAS. SNOWFALL RATES REACHING 
1 IN/HR WILL BE POSSIBLE AOA 3500 FT ELEVATION...WHILE RATES LOCALLY
REACHING 2 IN/HR MAY OCCUR OVER PARTS OF THE CASCADES/SIERRAS. AFTER
A LULL IN THIS PRECIPITATION BETWEEN 02Z AND 04Z...SNOWFALL RATES
POTENTIALLY REACHING 1 IN/HR -- EXCEPT TO 2 IN/HR OVER THE
CASCADES/SIERRAS -- WILL ONCE AGAIN IMPACT THE AREA. THIS WILL OCCUR
AS AN AMPLIFYING MID-LEVEL IMPULSE -- DEPICTED FROM 43N TO 49N
BETWEEN 127W AND 135W PER RECENT WATER VAPOR LOOPS -- CROSSES THE
AREA.

ACROSS THE CASCADES OF ORE AND FAR NRN CA EWD ACROSS CNTRL/ERN
ORE...THE COMBINATION OF A STRENGTHENING SFC PRESSURE GRADIENT AND
700-MB FLOW INCREASING TO 60-80 KT WILL SUPPORT SFC WIND SPEEDS OF
20-35 KT WITH HIGHER GUSTS AFTER 00Z. THESE WINDS WILL COMBINE WITH
THE SNOW IN SOME AREAS TO SUPPORT BLOWING/DRIFTING SNOW WITH
VISIBILITIES AOB ONE-QUARTER MILE AND LOCALIZED BLIZZARD CONDITIONS
THIS EVENING THROUGH TONIGHT. FURTHERMORE...FORECAST SOUNDINGS
SUGGEST THE DEVELOPMENT OF A STABLE LAYER ABOVE RIDGE-TOP LEVEL
ACROSS PARTS OF THE AREA TONIGHT. THIS MAY FOSTER MOUNTAIN WAVE
DEVELOPMENT AND ENHANCED WINDS/LOCALIZED BLIZZARD CONDITIONS...
PARTICULARLY IN THE LEE OF NNW/SSE-ORIENTED RANGES.

..COHEN.. 12/16/2012

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

ATTN...WFO...BOI...PDT...REV...MFR...STO...PQR...

LAT...LON   42711909 42152034 41402126 39712051 38982019 38812030
            39032061 39772108 40672179 41562216 42542228 42942231
            44142211 44952193 45492172 45472139 45042132 44692136
            44302135 44242108 44882067 45062001 45371891 45901766
            45621722 45071714 43581784 42711909

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 16, 3:12 PM PSTMesoscale DiscussionSPCHood River5 hr

Nearby

Mesoscale Discussions in Oregon, 2012Mesoscale 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.