Rod's Weather Headlines

Our wet March weather is yet another reason to belief Portland's rainy season could be on the move from winter into spring.  A few years ago I did a comparison of recent rainfall from November through February to the spring months of March through June.  The result was a nearly equal average, meaning spring months over the past decade are seeing nearly the same total amount of rainfall as winter as well as a near equal number of days with measurable precipitation. 

What caught my eye to wright this article is the number of top 5 wet spring months in the record book.  A record book that has simply been re-written since 1980.  You will notice when looking at the top 5 wet months for March, April, June and May,  all but four years have occurred over the past three decades.  In other wards, 16 of the wettest 20 spring months on record for PDX have recently taken place.  In fact, 7 of the wettest months have occurred since the year 2000.   The month of March has seen a dramatic increase in rainfall average over the past 10 years and is on average Portland's 4th wettest month during a typical calendar year. 

To be fair, the PDX record book only dates back to 1941, meaning you could make the argument that the first 40 years of record were actually under value.  However, it is undeniable that recent decades have seen a consistent increase in spring rain.  It is important to note, that overall Portland rainfall has declined.  I am noticing a shift of the heaviest rainy season, not an increase in total moisture overall.

PDX ends March tied for the 2nd wettest on record with 7.52" of total rainfall.  March of 1957 also had the same amount of total precipitation.  March of 2014 was the wettest at the airport since December of 2012.  The wettest day was last Friday, the 28th, when 1.69 inches set the all-time record for daily March rainfall at PDX.  The all-time record for March rain was set two years ago when 7.89 inches fell. 

I have written several articles the past few year talking about an apparent climate shift in Portland's rainy season.  The change I am noticing is a shift of our wettest months moving from winter into spring.  The March rainfall average over the last 10 years is 4.36 inches, well above the 1981-2000 average of 3.68 inches.  March on average, is Portland's 4th wettest month.  Current trends open the possibility of March averaging as much rainfall as December or January in the coming decades, but for now the thought is pure speculation. 

Spring weather outlooks from the National Weather Service show Portland to be warm and dry when compared to normal for the months of April, May and June.  However, forecast models show above normal April rainfall through the first two weeks of the month.

A wet weather pattern with most days seeing measurable rainfall is expected through the first full week of April.  Forecast models show high pressure ridging developing around April 10th.  Outlooks from the National Weather Service call for Portland to see above normal temperatures and below normal rainfall mid-April through the end of May. 

Eight 60 degree days this month and counting has spring fever in full bloom across the Rose City.  Only for now, cherry blossoms are stealing the show.   

The official start of the spring season will take place Thursday March 20, at 9:57 a.m.  local time.   The Vernal Equinox marks the day on which the north and south pole are equal distances towards the sun at 92.6 million miles.  At the time of Equinox, the sun stands directly over the Earth's equator.  The word vernal means green and equinox means equal as in equal daylight and darkness.  It is interesting to note, that Portland's equal day of 12 hours of daylight and darkness occurred on Monday, March 17th.  The beginning of spring will be our cities 3rd day of more brightness than darkness. 

The day of the equinox will find the sunrise at due east and sunset at due west. 

Today's sun breaks will likely be the kick-off to a stretch of warm, mostly dry spring-like days for much of the Northwest.  The 7day forecast shows mostly dry weather this week, Tuesday through Sunday.  In fact, current forecast models show zero strong storm fronts through March 21st.  The next 10 plus days will likely bring a number of dry, warm days with highs warming into the 60s!  Longer range weather models project an above normal temperature average for the months of March, April and May.   

To date, Portland has warmed into the 60s three times this year.  Our first 70 degree temperature looks possible in the coming week or two. The forecast for pleasant weather is a sharp contrast to the spring of 2011.  You may recall the cold, wet weather of three years ago, set records for cold and wet conditions.  Portland did not reach 60 degrees that year until March 31st, which set the record for latest in the year to reach the spring milestone.  April of 2011 went on to be the 3rd wettest at PDX.

Sunday night's storm met the challenge of being the strongest in a series of February weather fronts to pass Portland.  The photo above shows high water over highway 30.  Localized flooding has been reported from the coast to the valley.  Portland saw nearly an inch of rain fall during the overnight, early morning storm.  Crews also spent Monday cleaning up from high winds.  The peak south wind gust of 55 mph at PDX was the strongest recorded since March 13th of 2011 when a mini-windstorm reported a west gust of the same speed.

This month's stormy weather has pushed total PDX rainfall to more than 3.75 inches for the month, which is above the February average of 3.66 inches.  To date, Portland's water year total is only 56% of normal, but on the right track!  The news is better for the Mt. Hood snowpack where a snow depth of 98 inches at 5,400 feet is holding 36 inches of water.  The Mt. Hood snowpack is currently 84% of normal for the season!   Highway 26 at Government Camp will likely be snow covered at times through Thursday with more heavy snow to come this week!

Looking forward, the first 10 days of March are likely to see above normal rainfall.  There are signs that March and April precipitation will be at least close to normal.  

Saturday afternoon update:   Metro rain totals could exceed .75" through early evening.  Rain will break into showers tonight. 

Total rainfall Sunday - Monday noon:  1.25 - 1.75" possible

Tuesday:  Rainfall may exceed .50".   

The threat of heavy rainfall will end Tuesday evening.  The forecast the rest of the week calls for scattered precipitation. 

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Steady rainfall ends for now, but will return Saturday.  Heaviest weekend rain will fall Sunday evening and night.  The National Weather Service has issued a Flood Watch from the coast to the Cascades.  Large rivers such as the Willamette and Clackamas are expected to rise 3-5 feet through Monday, but remain below flood stage.  The Willamette river at Salem will likely rise to near bankfull Sunday night, while the Willamette at Portland is forecast to raise to near 11 feet, well below the flood stage of 18 feet.  Smaller streams draining out of the Coast Range should be watched closely.  Current projections show the Wilson River at Tillamook to rise within 2 feet of flood stage. Please be alert for areas of high water, especially Saturday & Sunday nights.

Satellite photos shows a stream of moisture aimed at the Northwest.  Combined Portland rainfall from last night through this coming Monday morning could reach 2-3.00 inches, which would be the heaviest rain since more than 3 inches fell the last three days of September!

Possible rain totals including last night through this coming Monday could reach 2-4 inches at the coast, 4-6" over the Coast Range, 2-3 inches across the metro valley and 4-7 inches over the Cascades. 

Current forecast models show long enough dry breaks between periods of steady rain to reduce the risk of any widespread flooding.  However, motorist should be aware of likely high water spots, especially at night and small streams should be closely watched. 

Six days of Arctic air triggered more than 2 feet of new snowfall on Mt. Hood.  Both Mt. Hood Meadows and Timberline resorts report 26 inches of new snow.  Low snow levels also helped Mt. Hood Skibowl build a two feet base over the resort's front slope.  The Mt. Hood snowpack has grown from 40 percent of normal back on January 1st, to 64 percent of normal as of today, February 9th. 

Forecast models show several storm systems this coming week and heavy snowfall above 5,000 feet of 2 - 3 feet.  Snow projections through next weekend would build the Mt. Hood snowpack to more than 70 percent of normal for the season to date.  While we might not catch up completely, it is for the first time looking more likely that the north Oregon Cascades will see better than 50 percent snowpack for the season, which ends April 30th in terms of the main snow season.

Keep an eye on the forecast this week as heavy mountain snow, high coast winds and heavy valley rain are all expected!

The Portland Airport measured 3.8 inches of snow on the ground from yesterday's storm, the most for any February since nearly 7 inches fell over the entire month back in 1993.  In fact, Thursday's snowfall becomes the first time February has picked up any measurable snowfall since 1995.  If Portland's snow depth reaches more than 8.3 inches this weekend, this month would become the snowiest Feb.  since 1949 when 13 inches fell. Portland's all-time record for February snowfall is 20 inches back in 1893!

The Arctic air has set 3 temperature records.  The high of 29 degrees Wednesday and the high of 23 degrees Thursday were the coldest high temps on record for each date.  Also, the low temperature this morning of 20 degrees or colder sets a new record low for the date.  It is likely that this afternoon's high temperature will set a 4th record for cold air!   The all-time record low temperature for February is -3 back in 1950.  The all-time coldest high temp for the month is 15 degrees back in 1989. 

Keep an eye on the forecast as more snow accumulates through tonight.  A sleet mix may develop Saturday and icy weather still looks possible Sunday before all warms and changes to rain.

Likely Thursday snow in Salem of 3-6", starting in the morning & falling through the day. Portland will see increasing afternoon snow into early evening. East winds may dry the air, producing only a trace or dusting in parts of the metro area. However, if 1-4" fall, the Portland evening commute would be a mess. Accumulations north of Vancouver could reach 3-6".

A change in the orientation of Saturday's warm front has made the snow and ice forecast for Friday night & Saturday very uncertain.

Portland could see 3-6" of snow through the day Saturday depending on how much sleet or ice mixes with the snow. Accumulations will be possible into Sunday morning.

All of the valley metro will warm Sunday and transition into rain showers. The Columbia River Gorge may see snow and ice accumulations all weekend. Travel on I-84 will likely become very difficult.