Alert archive / Oregon / Mesoscale Discussions in 2011

Mesoscale Discussion 177

February 28, 2011Clackamas County, Hood River County, Oregon; Skamania County, Washington

The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2011, 1:56 PM PST for Clackamas County, Hood River County, Oregon; Skamania County, Washington. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Feb 28, 2011, 1:56 PM PST (21:56 UTC)
Expired: Feb 28, 2011, 5:00 PM PST
In force: 3 hr
Issued by: the Storm Prediction Center

Counties Clackamas County, OR, Hood River County, OR, Skamania County, WA

The radar

The Portland,OR radar (KRTX), 95 km from the middle of the area, began a volume at 21:56 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

Salem/Mcnary, OR (KSLE), launched 12:00Z, 9.9 hours before the alert went out and 93 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: 600 m above ground
0-6 km bulk shear: 92 kt
0-1 km storm-relative helicity: 336 m²/s²
0-3 km storm-relative helicity: 435 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.

944 
ACUS11 KWNS 282156
SWOMCD
SPC MCD 282156 
WAZ000-ORZ000-010100-

MESOSCALE DISCUSSION 0177
NWS STORM PREDICTION CENTER NORMAN OK
0356 PM CST MON FEB 28 2011

AREAS AFFECTED...NRN ORE AND SRN WA CASCADES

CONCERNING...HEAVY SNOW 

VALID 282156Z - 010100Z

HEAVY SNOWFALL RATES 1-2 INCHES PER HOUR WILL LIKELY CONTINUE
THROUGH THE AFTERNOON ACROSS THE NRN ORE AND SRN WA CASCADES.

AN UPPER LEVEL LOW OFF THE B.C. COAST IS FORECAST TO MOVE LITTLE
THROUGH THE EVENING HOURS COINCIDENT WITH A STRONG UPPER JET
REMAINING OVER THE PACIFIC NW.  AS SUCH...A FETCH OF HIGHER PW/S
CHARACTERIZED BY EXCEEDING 1/2 INCH--SHOULD REMAIN FOCUSED OVER THE
REGION AIDED BY 30-50 KT FLOW AT 1-2 KM ABOVE SEA LEVEL.

LATEST SURFACE MAP SHOWS TEMPS IN THE UPPER 30S TO NEAR 40 DEG F IN
THE WILLAMETTE VALLEY AND INTERIOR VALLEY LOCATIONS.  HOWEVER...SNOW
LEVELS PER LATEST WEB CAM DATA INDICATE THAT HEAVIER SNOW
ACCUMULATIONS ARE OCCURRING GENERALLY AOA 1000-1500 FT WHERE TEMPS
ARE AOB FREEZING.  RECENT DETERMINISTIC MODEL GUIDANCE SUGGEST
LIQUID EQUIVALENT PRECIPITATION RATES OF 0.10-0.20 INCH WILL
CONTINUE...LEADING TO HEAVY SNOWFALL RATES ON THE WINDWARD SLOPES OF
THE CASCADES.

..SMITH.. 02/28/2011

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

ATTN...WFO...PDT...SEW...PQR...

LAT...LON   44672242 46012210 46392175 46232144 45782141 45002158
            44332185 44362230 44672242

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 27, 5:02 PM PST	Mesoscale Discussion	SPC	Chelan, Clark, Cowlitz, King, Lewis, Skagit and 3 more	6 hr

Nearby

Mesoscale Discussions in Oregon, 2011 Mesoscale Discussions in Washington, 2011 Every mesoscale discussion in 2011

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.