Alert archive / Oregon / Mesoscale Discussions in 2012
Mesoscale Discussion 28
The Storm Prediction Center issued this mesoscale discussion at Jan 18, 2012, 3:39 AM PST for 4 counties in Oregon; Clark County, Cowlitz County, Wahkiakum County, Washington. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jan 18, 2012, 3:39 AM PST (11:39 UTC)
- Expired
- Jan 18, 2012, 6:15 AM PST
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
Counties Clatsop County, OR, Columbia County, OR, Multnomah County, OR, Washington County, OR, Clark County, WA, Cowlitz County, WA, Wahkiakum County, WA
The radar
The Portland,OR radar (KRTX), 38 km from the middle of the area, began a volume at 11:42 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 00:00Z, 11.7 hours before the alert went out and 123 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 521 m above ground
- 0-6 km bulk shear
- 102 kt
- 0-1 km storm-relative helicity
- 204 m²/s²
- 0-3 km storm-relative helicity
- 311 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
293
ACUS11 KWNS 181139
SWOMCD
SPC MCD 181139
WAZ000-ORZ000-181415-
MESOSCALE DISCUSSION 0028
NWS STORM PREDICTION CENTER NORMAN OK
0539 AM CST WED JAN 18 2012
AREAS AFFECTED...PARTS OF NWRN OREGON AND SWRN
WASHINGTON...INCLUDING THE PORTLAND METRO AREA
CONCERNING...HEAVY SNOW
VALID 181139Z - 181415Z
MODERATE TO HEAVY SNOW CONTINUES...BUT MAY DIMINISH/COMPLETELY
CHANGEOVER TO RAIN DURING THE 14-16Z TIME FRAME.
LOW-LEVEL WARM ADVECTION AND CORRESPONDING MID-LEVEL HEIGHT RISES
CONTINUE ACROSS MUCH OF THE PACIFIC NORTHWEST...WITH A STRONG WEST
SOUTHWESTERLY 850 MB JET STREAK NOSING INTO THE OREGON COAST. A
ZONE OF ENHANCED LIFT ASSOCIATED WITH THIS FEATURE HAS CONTRIBUTED
TO PERSISTENT PRECIPITATION ALONG AND WEST OF THE SOUTHERN
WASHINGTON/NORTHERN OREGON CASCADES. WHERE TEMPERATURES HAVE
REMAINED CLOSE TO FREEZING NEAR THE SURFACE...FROM THE VICINITY OF
THE COLUMBIA RIVER NORTHWARD...INCLUDING MUCH OF THE PORTLAND
METROPOLITAN AREA...THIS HAS BEEN IN THE FORM OF MODERATE TO HEAVY
SNOW. LOW-LEVEL WARMING MAY BE IN THE PROCESS OF CONTRIBUTING TO A
CHANGEOVER TO RAIN IN SOME AREAS...FROM WEST TO EAST ACROSS COASTAL
AREAS...AND THIS LIKELY WILL BECOME MORE PREVALENT AND PRONOUNCED
AFTER DAYBREAK. VARIABILITY EXISTS AMONG THE MODEL FORECAST
SOUNDINGS...BUT THERE HAS BEEN A GENERAL SUGGESTION THAT WEAKENING
LIFT...AND PERHAPS AT LEAST SOME DRYING...WITHIN A RISING DENDRITIC
GROWTH LAYER MAY OCCUR BY THE 14-16Z TIME FRAME. THIS IS EXPECTED
TO CONTRIBUTE TO A COMPLETE CHANGEOVER TO RAIN ACROSS THE PORTLAND
AREA...AND DIMINISHING SNOW RATES IN SURROUNDING HIGHER ELEVATIONS
REMAINING BELOW FREEZING.
..KERR.. 01/18/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...SEW...PQR...
LAT...LON 46612362 46632338 46392295 46022234 45262232 45312281
45472313 45872361 45792364 46242379 46612362Nearby
Mesoscale Discussions in Oregon, 2012Mesoscale Discussions in Washington, 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.