The Rewetting of the Western U.S.

The last two weeks have been a major turnaround for water resources along the west coast of the U.S.  And a decided end of California's dry season and enough water to end the wildfire threat over central and northern CA.

Here are the precipitation totals for the past two weeks from the National Weather Service official analysis for the western U.S..   Significant totals, ranging from around 15 inches in the northern Cascades to 5-10 inches in the higher terrain of California.

But how much has this differed from normal for the past 2 weeks?  The figure below has the answer!  Most of Washington has been near normal, but California is another story....way above normal (3-7 inches)

The latest streamflow levels show most of our state has normal to above normal streamflow, with the exception of a few rivers over SW Washington.

California has normal to above normal streamflows after all the rains.

Reservoir storage in California is in good shape, most at or near normal (the red line), except for Lake Orville, the heavily damaged reservoir in which water levels have been held low).  There is plenty of room to store more water, and the recent rains are starting the process.

For example, there has been a huge surge upwards in the storage at Trinity Lake in northern CA (see below)

Here in Seattle, both cumulative precipitation and reservoir levels are close to normal (see below)

The bottom line is that worries about drought are now fading, as substantial precipitation has reached the west coast of the U.S.



from Cliff Mass Weather and Climate Blog https://ift.tt/2U1ds85

The Rewetting of the Western U.S.

The last two weeks have been a major turnaround for water resources along the west coast of the U.S.  And a decided end of California's dry season and enough water to end the wildfire threat over central and northern CA.

Here are the precipitation totals for the past two weeks from the National Weather Service official analysis for the western U.S..   Significant totals, ranging from around 15 inches in the northern Cascades to 5-10 inches in the higher terrain of California.

But how much has this differed from normal for the past 2 weeks?  The figure below has the answer!  Most of Washington has been near normal, but California is another story....way above normal (3-7 inches)

The latest streamflow levels show most of our state has normal to above normal streamflow, with the exception of a few rivers over SW Washington.

California has normal to above normal streamflows after all the rains.

Reservoir storage in California is in good shape, most at or near normal (the red line), except for Lake Orville, the heavily damaged reservoir in which water levels have been held low).  There is plenty of room to store more water, and the recent rains are starting the process.

For example, there has been a huge surge upwards in the storage at Trinity Lake in northern CA (see below)

Here in Seattle, both cumulative precipitation and reservoir levels are close to normal (see below)

The bottom line is that worries about drought are now fading, as substantial precipitation has reached the west coast of the U.S.



from Cliff Mass Weather and Climate Blog https://ift.tt/2U1ds85

Finally some snow over the Pacific Northwest

There has been a substantial increase in our snowpack during November.  To illustrate, here are the snow depths on November 1 and last night.  Notable increases, particularly over the north Cascades and southern BC..

But even with increases, the snowpack is less than at  the same time last year (see below).

In fact, although there have been considerable increases in higher elevation snowpack the past few weeks, the latest USDA Snotel data shows that the Cascades are still below normal (about 40%), while the northern Sierra Nevada is above normal, as are the western slopes of the Rockies.

The last day has not been kind to our mountain snowpack, with warm, rainy conditions caused by a moderate atmospheric river.  But that is past now and we have been experiencing cooler, unstable conditions, with decent snow showers in the mountains.

The forecast for the next 72 hr  (ending 4 AM Saturday), suggests another half a foot at higher elevations in the  Washington Cascades and huge snow dumps over northern CA and southern Oregon.

Now modern ski areas have considerable capabilities for making snow if the temperatures are cold enough, and there is good news on that front--we are heading into a period of much cooler lower atmosphere temperatures. 

To show this, here are the NOAA/NWS GEFS ensemble air temperature forecasts at the surface for Stampede Pass in the central WA Cascades around 4000 ft  (remember that in an ensemble system we run the forecast model many times to explore uncertainty).  The black line is the average of the forecasts, the ensemble mean, which is usually a very good forecast.  Temperatures really drop the next few days and generally stay below freezing.   Any snow won't be melting and snow making should be fine about 3500 ft.

Crystal Mountain will reopen on Friday, Baker  and Stevens are getting close, and Whistler is open with early season conditions.  Enjoy.

from Cliff Mass Weather and Climate Blog https://ift.tt/2AsU4rA

Finally some snow over the Pacific Northwest

There has been a substantial increase in our snowpack during November.  To illustrate, here are the snow depths on November 1 and last night.  Notable increases, particularly over the north Cascades and southern BC..

But even with increases, the snowpack is less than at  the same time last year (see below).

In fact, although there have been considerable increases in higher elevation snowpack the past few weeks, the latest USDA Snotel data shows that the Cascades are still below normal (about 40%), while the northern Sierra Nevada is above normal, as are the western slopes of the Rockies.

The last day has not been kind to our mountain snowpack, with warm, rainy conditions caused by a moderate atmospheric river.  But that is past now and we have been experiencing cooler, unstable conditions, with decent snow showers in the mountains.

The forecast for the next 72 hr  (ending 4 AM Saturday), suggests another half a foot at higher elevations in the  Washington Cascades and huge snow dumps over northern CA and southern Oregon.

Now modern ski areas have considerable capabilities for making snow if the temperatures are cold enough, and there is good news on that front--we are heading into a period of much cooler lower atmosphere temperatures. 

To show this, here are the NOAA/NWS GEFS ensemble air temperature forecasts at the surface for Stampede Pass in the central WA Cascades around 4000 ft  (remember that in an ensemble system we run the forecast model many times to explore uncertainty).  The black line is the average of the forecasts, the ensemble mean, which is usually a very good forecast.  Temperatures really drop the next few days and generally stay below freezing.   Any snow won't be melting and snow making should be fine about 3500 ft.

Crystal Mountain will reopen on Friday, Baker  and Stevens are getting close, and Whistler is open with early season conditions.  Enjoy.

from Cliff Mass Weather and Climate Blog https://ift.tt/2AsU4rA

Strong Winds and an Atmospheric River Hit the Northwest

Strong winds, some exceeding 50 mph, are hitting some parts of the Northwest today.  And a moderate atmospheric river promises substantial rain in the mountains.

The maximum wind gusts over the past 24 h, shows a fascinating picture of very strong wind in some locations, while lighter winds are evident in others. 45-55 mph gusts in the San Juans and along the coast.  And 40 mph gusts east of North Bend as one ascends towards Snoqualmie Pass.   But light winds around Puget Sound.

Such huge differences result from our terrain and land-water contrasts.

A forecast from the UW WRF modeling system of sustained winds (not gusts) for 10 AM this morning shows the pattern (see below).  In particular, look at the strong winds from the eastern Strait of Juan de Fuca across the San Juans. 

Why are they there?  Blame the Olympic Mountains!   The sea level pressure forecast is shown by the light brown lines.  There is relatively high pressure on the windward (south side) of the Olympics and a leeside pressure trough on the northern side.   This pressure pressure pattern results in a strong pressure difference on the northeast side of the Olympics that accelerates the winds from the southeast.  And strong winds are found on the western side of Snoqualmie Pass because there is a large pressure difference across the Cascades and air is accelerating towards lower pressure to the west.

Smith Island, just west of Whidbey Island, has had recent gusts to 48 knots (SISW1) and  similar winds are being experienced along the coast, such as at Destruction Island (DESW1).   Destruction winds are particularly vicious because of the Olympics as well, since the barrier enhances the pressure gradients in the area.

But winds are only part of the story today.   A moist flow, known as an atmospheric river, is heading right into us, as shown by the infrared satellite image at 7:30 AM (below).  A really juicy frontal cloud band that stretches well into the Pacific.

We can see the plume of moisture clearly in a short-term forecast of total atmospheric water vapor in vertical column of air:

The resulting precipitation over our region during the next 24h  will be substantial, with parts of the Olympics and north Cascades getting over 5 inches of liquid water equivalent:

Note the light precipitation to the NE of the Olympics?   A world-class rainshadow is happening as the air sinks on the lee side of the barrier.  Here is the latest weather radar image--the rainshadow is spectacular:

And then mid-week the jet stream goes south and California gets hit hard by precipitation and mountain snows.  Fire season is over for central and northern CA.

from Cliff Mass Weather and Climate Blog https://ift.tt/2FHNELa

Strong Winds and an Atmospheric River Hit the Northwest

Strong winds, some exceeding 50 mph, are hitting some parts of the Northwest today.  And a moderate atmospheric river promises substantial rain in the mountains.

The maximum wind gusts over the past 24 h, shows a fascinating picture of very strong wind in some locations, while lighter winds are evident in others. 45-55 mph gusts in the San Juans and along the coast.  And 40 mph gusts east of North Bend as one ascends towards Snoqualmie Pass.   But light winds around Puget Sound.

Such huge differences result from our terrain and land-water contrasts.

A forecast from the UW WRF modeling system of sustained winds (not gusts) for 10 AM this morning shows the pattern (see below).  In particular, look at the strong winds from the eastern Strait of Juan de Fuca across the San Juans. 

Why are they there?  Blame the Olympic Mountains!   The sea level pressure forecast is shown by the light brown lines.  There is relatively high pressure on the windward (south side) of the Olympics and a leeside pressure trough on the northern side.   This pressure pressure pattern results in a strong pressure difference on the northeast side of the Olympics that accelerates the winds from the southeast.  And strong winds are found on the western side of Snoqualmie Pass because there is a large pressure difference across the Cascades and air is accelerating towards lower pressure to the west.

Smith Island, just west of Whidbey Island, has had recent gusts to 48 knots (SISW1) and  similar winds are being experienced along the coast, such as at Destruction Island (DESW1).   Destruction winds are particularly vicious because of the Olympics as well, since the barrier enhances the pressure gradients in the area.

But winds are only part of the story today.   A moist flow, known as an atmospheric river, is heading right into us, as shown by the infrared satellite image at 7:30 AM (below).  A really juicy frontal cloud band that stretches well into the Pacific.

We can see the plume of moisture clearly in a short-term forecast of total atmospheric water vapor in vertical column of air:

The resulting precipitation over our region during the next 24h  will be substantial, with parts of the Olympics and north Cascades getting over 5 inches of liquid water equivalent:

Note the light precipitation to the NE of the Olympics?   A world-class rainshadow is happening as the air sinks on the lee side of the barrier.  Here is the latest weather radar image--the rainshadow is spectacular:

And then mid-week the jet stream goes south and California gets hit hard by precipitation and mountain snows.  Fire season is over for central and northern CA.

from Cliff Mass Weather and Climate Blog https://ift.tt/2FHNELa

Fog and Roadway Icing: The Warning of the Husky Bus Crash

Yesterday, a bus with a number of students of the Husky Band overturned on Interstate 90 just west of the town of George, Washington (see map  below) as they headed to the Apple Cup game in Pullman.   A number of students sustained injuries, but thankfully none were life threatening.

As I will discuss below, severe icing conditions occurred due to fog and freezing temperatures, and with modern observing, modeling, and warning technologies, coupled with cautious driving, the number of  such events can be greatly reduced.

The accident occurred around 5:30 PM Thursday.  A plot of temperatures at 5 PM (with the accident location indicated by the red circle) shows freezing and below freezing surface air temperatures, with 31F reported in the immediate vicinity, while to the southeast temperatures were in the 40s.

A 13-h model forecast of winds and surface air temperature valid at 4 PM was very realistic, showing the threatening cool temperatures over the accident region, while warmer temperatures were predicted over SE Washington.

The cool temperatures were accompanied by low clouds and fog, something shown by a high resolution visible satellite image around 1 PM (see below).

The nearby Grant County Airport (MWH) reported dense fog all day and FREEZING FOG starting around 435 PM (times in UTC, with 0000 UTC being 4 PM)

I have spent a large amount of time studying and working with WSDOT (Washington State Department of Transportation) and SDOT (Seattle Department of Transportation) on the issue of roadway icing.  And I have occasionally done some forensic work on roadway icing accidents.  Roadway icing is probably the greatest meteorological threat faced by WA State citizens.  More than windstorms, flooding, thunderstorms and everything else (I have checked the numbers).

One thing I learned:  freezing fog can be a huge threat.  Fog has lots of water content and when fog droplets contact a cool  roadway surface, substantial icing can occur rapidly.  

When air temperatures are below 35 F and you see fog, you should immediately slow down. 

Why 35F?  Because air temperatures are measured at roughly 6 ft above the surface (car thermometers are at roughly 2 ft above the surface) and surface temperatures can be cooler that air temperatures, particularly at night.  

The threat of icy roads was already evident that morning with the Grant County Sheriff reported icy roads.

Reducing Roadway Icing Injuries and Deaths

There has been substantial progress in reducing roadway icing injuries and deaths.  WA State WSDOT has made large strides, putting up RWIS roadway weather stations around state roadways, educating their plow operators (e.g., bridges ice up first!), using aggressive anti-icing pretreatments on vulnerable roads, and working with us at the UW to build the road temperatures prediction capabilities and public websites that would provide guidance to their staff and warn drivers.  One application I am particularly proud of is our Road-Weather web displays, such as the I-90 page (see
below)

But unfortunately, Washington State efforts are beginning to slide and new technologies that would promote roadway safety are not moving forward.   Recently I learned that Washington DOT (WSDOT) is going to cut all funding to the roadway weather pages and data streams produced by the UW (e.g., I-90, SR-20, I-5, Ferry Weather), substantially cutting back the information available to the public.

Just as serious, we are not moving forward with protective warning technologies that could produce timely warnings of dangerous road condition for WSDOT personnel and the motoring public.  

 Today, there are immense amounts of information describing, in real-time, weather and surface conditions around the State.  Thousands of surface stations, weather radar information, amazing new weather satellite capabilities, smartphone pressures, to name only a few.  Plus, high resolution weather modeling has improved rapidly, with new rapid-fresh forecasts being made every hour.   And soon cars and trucks will serve as massive data sources.    

This huge potential is magnified by the fact that most folks have smartphones, and thus we could provide real-time, vehicle specific warnings of threats on the roads ahead.  I believe we can stop many of the fatal/injuring accidents caused by snow and ice on the roadway, such as the tragic accident of a pregnant woman on I-90 last year.

Unfortunately, the Washington State transportation bureaucracy is not pushing forward on such technological advances, with the explanation that WSDOT lacks the funds to do so.  Hopefully that will change someday.   The effective use of weather information, coupled with smartphone distribution of warnings, has the potential to save many lives and to substantially lessen weather-related carnage on our roads.

from Cliff Mass Weather and Climate Blog https://ift.tt/2TC9FOa