Rod's Weather Headlines

For weeks, I have been talking about what has turned into an amazing dry streak since January first.  Following a wet October - December, Portland has only seen 54 percent of normal rainfall this calendar year.  With a 2013 rain total to date of 6.21 inches, this is the 3rd driest January - March three month period since PDX records began in 1940.  Up to .15 inches of rain looks possible through the end of the month, but parts of the metro may stay dry. 

As of noon yesterday, March 25th, Vancouver, Hillsboro and Salem report the driest precipitation totals on record for the first quarter of the year.  Here are the totals, along with the date of first record:

Vancouver:  6.10 inches - driest on record, dating back to 1890

Hillsboro:  5.08 inches - driest on record, dating back to 1929

Salem:  5.19 inches - driest on record, dating back to 1892

The above numbers will be the all-time record for first quarter precipitation, if no more rain falls through March 31st.  Forecast outlooks continue to project below normal rainfall through mid-April.

As promised a morning cold front is starting our spring season with a raindrop splat!  Here are the totals as of 5:00 this morning:

Astoria .96" / Newport .59" / Portland .61" / Vancouver .71" / Kelso .56" / Hillsboro .71" / McMinnville .63" / Salem .76" / Hood River .46" / The Dalles .18"

As spring begins, the normal high temperature for Portland is 58 degrees and the normal low is 40 degrees.  All daily records moving forward show high temperatures in the 70s or warmer, while record lows can still be in the 20s through May 1st! 

Despite this morning's rainfall, forecast charts continue to indicate near normal to below precipitation for the spring months.  March is likely to finish with below normal rainfall, becoming the third consecutive month to do so. 

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The Vernal Equinox kicked-off spring this morning, March 20th at 4:02 a.m. PDT.  The Equinox is the day on which both the north and south pole are equal distance to the sun (92.6 million miles).  The sun will stand directly over the Earth's equator, bringing equal hours of darkness and daylight.  The term vernal means green and equinox means equal night.  The coming days will see minutes of daylight begin to out number minutes of darkness as we march toward the summer season.

The chill you felt this morning was the coldest air since January!  Here are a few of the coldest unofficial low temperatures:  Brush Prairie, (Clark County), 26 degrees, Hillsboro & Scappoose 27, Salem 28 and Portland 29 degrees.  For Portland, today's chill was the coldest since January 22nd when the low temperature was 24 degrees.  By the way, this morning's record low stands at 26 degrees.

So far, this has been a winter with little cold.  February at PDX only had one freezing morning.  The lowest temperature last month was 30 degrees on Feb. 8th.  You may remember, the airport did not see it's first freeze until December 29th.  Since that late Dec. day, only 18 more days have seen freezing temperatures, nearly all were recorded during our colder than normal January.  Portland's annual average for freezing temperatures is 37 days.  A typical March has three freezing starts.  The average final Portland freeze is March 30th.  The record latest freeze is 32 degrees, back on May 2nd, 1964. 

Stay warm and enjoy today's sunshine!

Meteorological spring begins!

The scientific community considers March 1st through May as the spring season.  The National Weather Service is calling for cool -- meaning below normal temperatures -- and gives little confidence of projected precipitation for the Northwest. 

The national map would suggest increased confidence toward normal to slightly below rainfall averages over the next three months.  Much of the western United States is expected to see a dry spring.  There is no reason to believe at this time, that we will see any record "wet" months this spring or summer. 

Portland is coming off of three consecutive wet springs with all three years featuring at least one top 5 wet record month, including the wettest March on record at PDX in 2012 when 7.89 inches of rain fell.  2011 featured the 3rd wettest April at PDX and 2010 recorded the 3rd wettest May and a new record wet for June with 4.27 inches of precipitation. 

I think it is safe to say, many of us are hoping for a somewhat normal or even dry spring.  The last spring to see March, April and May all have below normal rainfall was 2007.

The so called "Enso" state of the atmosphere, which is the tracking of La Nina and El Nino conditions shows a neutral to very weak La Nina holding into early summer. 

Developing El Nino conditions may begin to take hold early next fall.  I looked at the last 10 years of data for Portland and found a strong correlation between temperatures and El Nino and La Nina episodes.  Nine of the last ten years show a positive correlation when looking at temperature. 

Nearly all warm Enso springs showed above normal temperatures and nearly all cool Enso patterns show below normal temperatures. 

The findings would support a somewhat cooler than average spring this year.  However, when looking at rainfall totals, the data is split nearly 50-50 percent, meaning zero confidence for projecting spring rainfall.

The conclusion for our March through May spring outlook is the following:  Expect temperatures to average slightly cooler than normal.  Rainfall will likely be near normal with a greater chance of averaging dry than wet over the three months. 

Current forecast charts show below-normal rainfall through the first half of March.

No sharp transitions of weather pattern due to a change of equatorial water temperatures that drive El Nino and La Nina are expected through this summer.  If true, we should expect somewhat normal and pleasant Northwest weather in the months ahead.

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Here is a list of what the above likely means, if the Spring Outlook proves correct:  High temperature averages would be 54-65 degrees.  We would see few warm days with highs in the 70s & 80s and lots of cloudy days into afternoon.  The spring months would be the driest in four years!  No record wet months, but still 40-50% of days would see some rainfall.  The last few years have see measurable rainfall days during spring 60-70% of the time, meaning 6 of 7 days.  

If you are a valley snow lover or a child at heart wishing for a Portland snow day, your chance of building a snowman is quickly vanishing.  As the final days of February begin, forecast charts show now metro snow in sight.  In fact, snow levels as March begins may go as high as 8,000 feet! 

March has brought snow before, but more than 1-2 inches is rare.  The largest March snowstorm dropped 8 inches back on March 7 & 8th of 1951.   April has never produced more than a trace of snow in the air or on the ground.  The latest trace of PDX snow in the record back fell on April 9th back in 1980.  You may remember a trace of snow on a chilly day back on March 28th, 2008.

My Portland winter forecast last fall stated an unfavorable pattern for any significant snowfall this winter season.  Of course, there is always time for the forecaster to be proven wrong!

Today's winter storm brings active weather to the Northwest for the first time in weeks.  Timberline lodge reports a foot of new snow since yesterday and two more feet are likely through Saturday morning!  Before the flakes started to fall yesterday, the lodge had only seen 30 inches of snow since February 1st.

This weekend's snowstorm will leave Timberline with more than 420 inches of total snow for the season, which is considered normal for the entire winter.  Thanks to a snowy December & early January that saw 100 inches of snowfall, this winter will go into the books as a good season.  Of course, the snowpack will be measured through May 1st, meaning a 500 inch season looks likely at 6,000 feet.

Despite a below normal January and to date a dry February, PDX continues to see a water year surplus of more than 4.00 inches, which means we still have roughly an extra month of rain in the bucket.  The water year is measured October 1st - September 30th and parallels the Cascade snow season.  Of course the million dollar question is whether or not we will see a soaking wet spring.  As of today, most signs point to normal rainfall March - May, but of course we won't truly know until we live it.

Travelers this weekend should check conditions.  Snow covered roads will be likely tonight & Saturday morning down to 1,000 feet or lower.  Both the Coast Range & Cascades will be slow going at times.  

So far this month, there's been only a trace in the rain bucket and forecast charts, which are often too wet, give Portland just 1.62-inches of moisture through the first 20 days of this month.

 February average rainfall over the past 30 years is 3.66 inches - an average that ten years ago was 4.18 inches.  Over the past 10 years, groundhog month has averaged nearly 1.50 inches below normal.  All but one February as seen below-average precipitation. 

The period of change is long enough for meteorologists to identify as a mini climate-shift. In fact, the so-called 'Big 4' rain months for Portland's rainy season used to be November through February.  That period, for decades, represented roughly half of the cities' annual rainfall and were the wettest four months of the year.

  Not any more, in fact March is now the 4th-wettest month of the year with an average of 3.68 inches. 

Perhaps the mini climate-shift that catches your eye the most is the increasing trend of wet spring months.  April, May and June all have higher rainfall averages then 10 years ago.  In fact, recent years have shown little difference in total rainfall between November through February when compared to March, April, May and June.

For now, enjoy a dry day and wonder if this spring will be another soaker.

So far this month, there's been only a trace in the rain bucket and forecast charts, which are often too wet, give Portland just 1.62-inches of moisture through the first 20 days of this month.

 February average rainfall over the past 30 years is 3.66 inches - an average that ten years ago was 4.18 inches.  Over the past 10 years, groundhog month has averaged nearly 1.50 inches below normal.  All but one February as seen below-average precipitation. 

The period of change is long enough for meteorologists to identify as a mini climate-shift. In fact, the so-called 'Big 4' rain months for Portland's rainy season used to be November through February.  That period, for decades, represented roughly half of the cities' annual rainfall and were the wettest four months of the year.

  Not any more, in fact March is now the 4th-wettest month of the year with an average of 3.68 inches. 

Perhaps the mini climate-shift that catches your eye the most is the increasing trend of wet spring months.  April, May and June all have higher rainfall averages then 10 years ago.  In fact, recent years have shown little difference in total rainfall between November through February when compared to March, April, May and June.

For now, enjoy a dry day and wonder if this spring will be another soaker.

Mt. Hood resorts are thrilled to pick up fresh powder this weekend.  The  heavy snows of mid-December left a snow depth at Timberline of 114 inches, Meadows 105 inches and Skibowl 64 inches.  Total snowfall at 6,000' through Christmas day was 266 inches.  Since that day, just 53 inches of snow has fallen at Timberline.  Today's snow base is lower than four week's ago and ranges from 44 inches at Skibowl to 83 at Meadows and 102 inches at Timberline Lodge.  The snow pack at the Mt. Hood test site is 76 percent of normal to date. 

Of course we still have many weeks of snow to go.  A typical winter season transitions through heavy snow weeks to dry weeks to heavy again.   Compared to one year ago, Mt. Hood above 5,000 feet has received 100 more inches of snow this far through the season.  Remember last year saw a booming 222 inches of snow fall on Mt. Hood from March 1st - May 10th.  The 2011-2012 snow season ended up exactly normal with 65.5 inches of melted snow water equivalency.  Here is hoping for a good 2nd half of the Mt. Hood snow season.

With talk of freezing rain in some spots today, especially the Columbia River Gorge, I want to clarify the differences between frozen precipitation types. 

Freezing Rain:  Simply liquid rain in the air that freezes into a glaze of ice when the drops make contact with freezing objects on the ground.  This is the precipitation type that can cause the most damage, coating trees and power lines with ice until the weight brings them crashing down.  Freezing rain is the classic ice-storm.  Just more than a trace of freezing rain can coat roadways and sidewalks with a sheet of ice making driving and walking impossible.  Forecast models give meteorologist a temperature profile showing all warm air just above the surface.  Under such conditions, when ground temps are 32 degrees or less, freezing rain will be in the forecast.  The worst ice storms usually occur with ground temperatures in the 20s.

Sleet:  A warmer layer of air in the atmosphere melts snowflakes into raindrops, after which the rain then falls into a freezing layer, turning the raindrops into ice balls or pellets.  The frozen pellets then fall to the ground.  Sleet, although formed differently does appear similar to hail stones to the casual observer.  Sleet can fall onto a frozen or above freezing ground surface.  Heavy sleet falling onto frozen roadways and lawns can coat the surface with thick ice, also making driving nearly impossible.

Hail:  As mentioned above, hail appears at ground level much the same as sleet.  The difference between sleet and hail is how the two are formed.  Hail is formed through convective weather and for much of the country is most common in severe spring and summer thunderstorms.  Liquid droplets in a cumulus cloud formation are carried high in the atmosphere into freezing temperatures where the droplets freeze into icy balls known as hail stones.  The hail stones then fall from the top of the cloud to the bottom and back into above freezing temperatures where the icy stones are coated with liquid then carried by updraft winds back to the top of the cloud into freezing temperatures.  The new liquid coating freezes into ice, making the hail stone larger.  The process repeats until the hail stone is too heavy to be supported by updraft winds and falls to the ground.  Single hail stones can be as small as peas and as large as soft balls!  Here in the Northwest, hail is most common during the fall, winter and spring months when cold upper level lows, lower the freezing level and cause convective activity.