Rod's Weather Headlines

 PRELIMINARY LOCAL STORM REPORT...CORRECTED
 NATIONAL WEATHER SERVICE PORTLAND OR
 130 PM PST TUE DEC 14 2010
 
 ..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
 ..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
             ..REMARKS..
 
 1144 AM     TORNADO          AUMSVILLE               44.85N 122.87W
 12/14/2010                   MARION             OR   FIRE DEPT/RESCUE
 
             EAST AND WEST BOUND LANES COVERED WITH DEBRIS NEAR TOWN 
             OF SHAW. MANY AUTO ACCIDENTS BETWEEN MILE POSTS 42 AND 45
             DUE TO HAIL ON ROADS. 
 
 1144 AM     TORNADO          AUMSVILLE               44.85N 122.87W
 12/14/2010                   MARION             OR   BROADCAST MEDIA 
 
             DAMAGE TO MANY HOMES AND BUSINESSES IN AUMSVILLE. 
             OVERTURNED SEMI TRAILER. UPROOTED TREES. ALSO...MANY 
             REPORTS OF FLYING DEBRIS HITTING AUTOS AND OTHER 
             STRUCTURES...SUCH AS TWO BY FOUR LUMBER STUD BLOWN INTO A
             TRUCK. 
 
 1144 AM     TORNADO          AUMSVILLE               44.85N 122.87W
 12/14/2010                   MARION             OR   FIRE DEPT/RESCUE
 
             EMERGENCY PERSONNEL OBSERVED TORNADO. NUMEROUS TREES 
             DOWN. REPORTS OF PEOPLE TRAPPED IN AUTOS DUE TO NUMBEOUS 
             DOWNED POWER LINES. 

___________________________________________________________

The above was issued by the National Weather Service.  A number of stories and videos can be found at:

www.kgw.com

Damage in the videos showing roofs ripped off and walls of homes damaged indicate this was at least an  

F-2 Tornado.  Wind speeds were likely 113 - 157 mph in the vortex of the storm or higher. 

Strong wind shear likely played a role in the tornadic development.  An upper level disturbance tracked through 

Clackamas county this morning, jet stream core winds were near 150 mph from the west/southwest.  5,000'  

winds were near 50 mph mostly from the west.  The shear would have been speed shear, meaning the difference  

in speed from near 5,000' to 30,000' was great and can cause friction, leading to a spinning of air - coupled with   

surface based rising air from a very unstable air mass and some rotation from the passing disturbance.  The pattern  

I just mentioned is not unusual for our area.  As you know, tornadoes are rare.  Oregon does in fact average several 

tornadoes a year.  Unfortunately, the random nature of development means the storms are almost always a complete  

surprise with no warning.  Our area does seem to be a greatest risk for mini - windstorms or in this case a tornado  

when the flow pattern has a southwest component, an upper level disturbance and a strong jet core.  

ALL THREE WERE PRESENT THIS MORNING.

Portland, Oregon (Tuesday, December 14th 2010) 9:05pm PT -- "The strongest tornado to strike Oregon and Washington in 17 years tore through the small western Oregon town of Aumsville just before noon Tuesday. The National Weather Service has preliminarily classified today's tornado as an EF2 on the enhanced fujita scale." Special thanks to the Portland office of the National Weather Service for also posting this radar loop of today's tornado. See: http://www.wrh.noaa.gov/pqr/aumsville.php

"In comparison, today's tornado was the strongest to strike NW Oregon and SW Washington since an F2 tornado rolled through Oregon's Yamhill and Washington counties on December 8th 1993, where no no injuries were reported. The Vancouver, Washington tornado of April 5th 1972, which was an F3, stands alone in the record books. Six people were killed in Vancouver and over 300 people were injured when the deadliest west coast tornado in recorded history struck just before 1pm. Vancouver's Peter S. Ogden Elementary School was demolished. Many students were trapped and injured. The tornado went on to level a nearby bowling alley and shopping center before dissipating after a nearly eight mile long path of destruction. The Vancouver tornado of 1972 was also the deadliest in the United States in 1972."    

"Oregon and Washington have reported a combined total of 202 tornados since records have been kept in 1950. Those totals are split nearly equally between the two states with most registering either an F0 or F1 (called an EF0 and EF1 now days). Only two tornados in Oregon and Washington history have been classified as an F3. The first struck near Seattle on December 12th 1969 with only a few injuries reported. The second was the deadly Vancouver, Washington tornado in 1972."    

**The above is courtesy of the best weather researcher in our area!  Mr. Steve Pierce,  Local A.M.S Chapter Officer

Windstorm Anniversary --- "It was 15 years ago today (12/12/1995) that many locations from California to the Canadian boarder experienced one of the strongest windstorms since the Columbus Day storm of Oct 1962. The windstorm of December 12th 1995 eventually took a track to the NW tip of Washington. At one point the central pressure of the storm was down to 953-954mb, besting both the Nov 13th-14th 1981 storm and the Columbus Day Storm with regards to central pressure. Winds were clocked as high as 120mph along the Oregon coast and between 60-80mph in the valley near Portland. Some have suggested there may be a general "return cycle" of approximately 15 years between storms of that magnitude. If so, the Pacific Northwest is due for another."Windstorm Anniversary --- "It was 15 years ago today (12/12/1995) that many locations from California to the Canadian boarder experienced one of the strongest windstorms since the Columbus Day storm of Oct 1962. The windstorm of December 12th 1995 eventually took a track to the NW tip of Washington. At one point the central pressure of the storm was down to 953-954mb, besting both the Nov 13th-14th 1981 storm and the Columbus Day Storm with regards to central pressure. Winds were clocked as high as 120mph along the Oregon coast and between 60-80mph in the valley near Portland. Some have suggested there may be a general "return cycle" of approximately 15 years between storms of that magnitude. If so, the Pacific Northwest is due for another."

The above historical data is courtesy of Mr. Steve Pierce, Local A.M.S.  Chapter Officer

Here are some of the heaviest weekend rain totals:

Lee's Camp, Coast Range:  6.70"

Bonneville Dam:  3.80"

Mt. Hood:  3.50"

Astoria:  3.16"

Gresham:  1.50"

Portland, PDX:  1.41"

Vancouver:  1.35"

Salem:  .93"

 

.A MOIST STORM SYSTEM AND WARM FRONT WILL BRING HEAVY RAIN TO
MUCH OF NORTHWEST OREGON AND SOUTHWEST WASHINGTON ON SATURDAY...
WITH ADDITIONAL PERIODS OF HEAVY RAIN ON SUNDAY AND MONDAY. ON
SATURDAY...THE HEAVIEST RAIN IS LIKELY TO BE IN THE NORTH OREGON
COAST RANGE...WILLAPA HILLS...AND SOUTH WASHINGTON CASCADES...WITH
6-HOUR AMOUNTS AS HIGH AS 3 INCHES AND 24-HOUR AMOUNTS AS HIGH AS
6 INCHES. THERE IS AN EXPECTED BREAK IN THE RAINFALL ON SUNDAY...
AND THEN ANOTHER FRONT WILL BRING ADDITIONAL RAINFALL FROM SUNDAY
EVENING THROUGH MONDAY. FREEZING LEVELS WILL BE ABOVE 6000 FEET
FROM MID-DAY SATURDAY THROUGH MONDAY. MANY RIVERS WILL RISE
SHARPLY SATURDAY...WITH FLOODING POSSIBLY AS EARLY AS LATE
SATURDAY AFTERNOON. FLOODING OF CREEKS AND PONDING IN URBAN AREAS
IS ALSO LIKELY.

* HEAVY RAIN SATURDAY WILL DRIVE RIVER LEVELS UP SHARPLY STARTING
  SATURDAY AFTERNOON AND INTO SUNDAY.

* SEVERAL RIVERS MAY REACH FLOOD STAGE AS EARLY AS SATURDAY
  AFTERNOON...WITH THE FLOOD THREAT CONTINUING INTO MONDAY.

SOUTHWEST WASHINGTON RIVERS OF MOST CONCERN INCLUDE...
THE GRAYS RIVER IN WAHKIAKUM COUNTY
THE COWLITZ RIVER IN COWLITZ COUNTY

NORTHWEST OREGON RIVERS OF MOST CONCERN INCLUDE...
NEHALEM RIVER IN TILLAMOOK COUNTY
WILSON RIVER IN TILLAMOOK COUNTY
TRASK RIVER IN TILLAMOOK COUNTY
SILETZ RIVER IN LINCOLN COUNTY
UPPER TUALATIN RIVER IN WASHINGTON COUNTY
LUCKIAMUTE RIVER IN POLK AND BENTON COUNTIES
JOHNSON CREEK IN MULTNOMAH COUNTY
PUDDING RIVER IN CLACKAMAS AND MARION COUNTIES

 Record rain in Portland Thursday of 1.42 inches.  A second of push of heavy rain will fall Saturday and Saturday night.  

Rain Forecast Saturday, Saturday night:

Salem, Portland Metro:  1.25" - 2.00"

Coast:  2 - 3.00"

Coast Range:  3 - 6.00"

______________________________

Many area streams and rivers are running high.  The National Weather Service is monitoring water levels and believes area rivers and streams will rise to near flood stage Saturday night.  The best chance of river flooding with be those coming out of the Coast Range.  

Drier weather with lighter rain totals Sunday.  Rain may be heavy at times Monday night, Tuesday and Wednesday. 

As a forecaster, much of the coming ten days look wet!  The pattern continues to support above normal rainfall, but no "big" storms.  Meaning, the threat of flooding or high winds looks minimal, with the exception of this coming Saturday night.  Heavy rain amounts of an inch or more Saturday, coupled with high snow levels and already high river levels may push streams to flood stage.  The best chance of flooding will likely be rivers draining from the Coast Range.  It is interesting to note, that so far this La Nina season has not developed what I would call extreme weather.  The headline is simply above normal rainfall for the valley and good mountain snows over the Cascades.  

Rain projections for the metro indicate:

1" +    Saturday - Saturday, night

.30"     Monday

.50" + Tuesday

.25"    Wednesday

.15"     Thursday

1" +     Friday - Saturday

_______________________________

Some rain looks likely each day all the way to Dec. 25th, Christmas Day.  Right now, Christmas looks cloudy with rain showers and highs in the 40s.  If the forecast holds true, snow levels the next two weeks will remain above 2,000 feet with most days near and above 3,000  feet.   

By the way, I do not post advance rain totals very often, despite requests.  The reason is that the data is not reliable past 5 days and holds no consistency.  

I want to take a second and clarify the meaning of the snow level I list on the 5-Day Snow Forecast, found on the Mt. Hood Weather page.  

The snow level is the elevation at which all precipitation will fall as snow.  The snow level is typically 1,000 feet below the freezing level in the atmosphere and is also the ground elevation that snow will stick and accumulate.  

The last few days, the true snow level has been near and above 4,000 feet, although surface freezing temperatures have been closer to 2,000 feet at times.  What this means is that an icy wintry mix of moisture is possible at elevations near freezing and up to the snow level.  At snow level and above, no mix, simply all snow.

So,  if the snow level is 6,000 feet and Government Camp at 4,000' reports a temperature of 28 degrees, you know that a mix of sleet and or freezing rain will be possible until you reach 6,000 feet when all moisture will become snow. 

Hope this makes sense!

As promised Tuesday's storm was a wet one!  Tillamook had more than 2.00" of rain, Salem had over an inch, PDX .84" and Timberline picked up 18" of snow!  The Portland rain total closed November at 6.63" for the month, more than inch above the average of 5.61 inches.  Not a "super" wet month, but our trend of above normal precipitation that began in September continues.  Total precipitation since September 1st is 12.84", which is 121% of normal!  

As you may know, December is the start of meteorological winter.  (Yes, meteorologists have their own seasons - it's an ego thing!)  All outlooks call for above normal precipitation through at least February.  Temperatures are expected to be near normal for December and slightly below in January and February.  La Nina, which began back in June will likely continue into the early spring months.  Slightly more than 50% of forecast models project La Nina conditions will continue to strengthen through the month of December.  If correct, January and February could be very active months!  At present, Pacific ocean temperatures in the equatorial belt off of south America, average 3-5 degrees F below normal, which is considered to be a STRONG LA NINA and continues to have the possibility of being one of the strongest in the last 60 years.  Strong La Nina's are associated with wet, cool and very active winters across the Northwest.  It is interesting to note that the heaviest moisture so far in terms of departure from normal has been across central California, Nevada, Idaho and Montana.  La Nina's typically produce a moisture bulls-eye over the Northwest.  However, so far, this event has produced a deep trough to our south, which has supported heavier amounts south and east of our region.  If the flow pattern changes, we will really get wet!

Snow Totals as of Tuesday Morning:

Santiam Pass 33"

Government Camp 19"

Sunset Coast Range Pass 10"

Longview 4"

Sandy 3"

Woodland, Wa. 3"

Portland (PDX) .3" dusting