Thursday, March 12, 2015

When does Spring really start?

We're often asked the question "when does Spring really start?"  The easy answer is to look at your calendar.  It says March 20th.  This is "Astronomical Spring", which is the vernal equinox.  It's defined as the day when the sun is directly over the equator, and the length of a day is 12 hours no matter what your latitude (this isn't quite correct, but we won't go into that here).  But it doesn't take much thought to realize that this definition is only remotely linked to the weather.  And having one date for the entire Northern Hemisphere seems in some ways, ridiculous.  Spring starts in Miami and Fairbanks on the same day?

The "Meteorological Spring" is another definition.  It's defined as the months of March, April, May.  But again, this suffers from a "one size fits all" problem.  Surely there's a better way of defining Spring that varies from one location to another.  The Capital Weather Gang at the Washington Post addressed this same topic, and had some other ideas.  You can read their blog here.  

Some of their suggestions have this natural variability built in, such as the last day of measurable snow, last freeze, soil temperature, and first green leaves.  But many of these would be difficult to apply to all locations.  What about locations that don't receive snow, never freeze, or don't lose all of their leaves?  And if a location receives snow in May, does that mean that it's still Winter?

For central Washington, the Tree Fruit Research Center in Wenatchee tracks the average first bloom of the apple trees.  You can see those dates at this link.  The nice thing about a measure that tracks leaves, flowers, or soil temperatures, is that it will vary year-to-year (i.e. spring doesn't start on the same day every year).

The intriguing measure in the Capital Weather Gang blog was defining seasons based on average temperature.  They took the average daily temperatures at a location, and divided them into the coldest 1/4th (winter) and warmest 1/4th (summer), with spring and fall as the seasons in between.  If we do this for the Spokane Airport, we get the following:

Winter: Nov 11th - Mar 6th (116 days)
Spring: Mar 7th - Jun 8th (93 days)
Summer: Jun 9th - Sep 15th (99 days)
Fall: Sep 16th - Nov 10th (57 days)

While this is somewhat interesting, we're not quite sure if we agree with its accuracy.  Fall is the shortest season, no doubt about that.  But in reality, spring is the longest of all season in the Inland Northwest.  It typically starts in late February or early March, but it often lasts all the way through June.  We have a saying that summer in the Inland Northwest doesn't start until after the 4th of July, in Seattle, they claim that their summer starts on the 12th of July.  This means that in reality, spring lasts about 4 months while summer is just a shade over 2 months long.

For us, it's often easiest to classify the seasons by holidays:

Winter: Thanksgiving to President's Day
Spring: President's Day to the 4th of July
Summer: 4th of July to Labor Day
Fall: Labor Day to Thanksgiving

Friday, March 6, 2015's been warm! Will it continue?

Over the past 30 days the Inland Northwest has been abnormally warm, and indications are the Inland Northwest will experience well above normal temperatures next week, and maybe beyond.  Before we look ahead, take a look at the temperature anomalies over the past 30 days.

Temperatures have been running about 3 to 7 degrees above normal, with the greatest anomalies over North Central Washington, with even higher anomalies over portions of eastern Oregon, and southern Idaho.

The weather pattern ahead appears to be showing a very warm signal.  So what is going to cause this?  The atmosphere often goes through various oscillations that affect our weather pattern.  One of these that we will not dive to deep into is the Arctic Oscillation (AO).  This AO value is forecast to soar next week with the highest value seen in quite some time.  Take a look at the forecast for the AO

The black line is the observed and the red line is the forecast.  As you can see, the highest value seen since November is 3.5, and is forecast to reach a value close to 6 within the next week.
This combined with our current weak El Nino often produces warm temperatures.  Take a look at what typically occurs temperature wise with this pattern:

As you can see nearly the entire US usually sees warmer than normal temperatures in this scenario.

So, let's look at the upcoming pattern.  Here is the GFS model forecast for Tuesday

The model indicates a low pressure system over the eastern Pacific Ocean with a warm southwest flow ahead of it shown by the arrow.  This will usher in warm air from the southwest into Washington, Oregon, and Idaho.

Here is our forecast high temperatures for Tuesday, which is about 15 degrees above normal and near record values for many cities.

Now, here is the GFS model forecast for Thursday

The pattern looks similar.

How about next Saturday?  Does it look any different?

The warm pattern continues.  Regarding precipitation, this flow often brings in increased moisture as well.  At this time, it looks like the heaviest precipitation through the week will remain north of the Canadian Border.  The best threat for rain for the Inland Northwest will be Wednesday into Thursday.  

What about after that, here is the 8-14 day outlook from the Climate Prediction Center:
The pattern refuses to budge!  What about after that, what is the spring looking like?  Here is the CPC outlook for March, April, and May.

It appears that this warm weather pattern may last for awhile, with elevated odds of warmer than normal temperatures.  Of course, occasional rounds of cooler and unsettled weather typically occur in the spring.  But when all is said and done, we will probably look back at this being a warm spring.

Saturday, February 28, 2015

Update on Snow Chances

In our last blog, we talked about the chances for snow in our area on Monday and/or Tuesday.  Our conclusions were:

  • Any precipitation would fall as snow.
  • The overall weather pattern was not a good one for snow in the Inland Northwest.
  • Not all of the computer guidance agreed on exactly what was going to happen.
Two days later, those conclusions still hold true.  Usually at this point we have a pretty good idea of what's going to happen.  But in this situation, we're still no more confident than we were two days ago.  Here's why.

Here's the GFS forecast for Sunday evening.  The low is way up in northern Canada with a trailing cold front (blue line).

GFS forecast of precipitation (green shading) and sea-level pressure (thin lines) for Sunday evening.

Here's the forecast for Monday afternoon.

GFS forecast of precipitation (green shading) and sea-level pressure (thin lines) for Monday afternoon.

As you can see, the front splits.  Half of it goes into the upper plains while the other half drops down the West coast.  This leaves the Inland Northwest dry, which is pretty common for this kind of storm moving down from the northwest.

Let's look at the Canadian GEM model:

Canadian forecast of precipitation (blue green shading) and sea-level pressure (thin lines) for Monday afternoon

This looks very similar to the GFS model.  The GEM does bring a bit more snow into the Panhandle, but keeps eastern Washington dry.

So why isn't our confidence higher?  Because the ECMWF has a slightly different scenario.  It thinks the cold front will hold together as it passes over our area.  So much so, that it gives about 1-2" of snow to the Panhandle and eastern Washington, east of Moses Lake.

What's more is that each model has been consistent with itself.  Often, we'll see forecasts from the computer models that will change 12 hours later.  In those situations, our confidence is lower.  But in this case, each forecast from each model is very similar to its previous forecast.  So the GEM and GFS insist that the Inland Northwest won't see much from this storm, while the ECMWF continues to insist that we will see 1-2" of snow.  

So, are there any other computer forecast models?  Yes, there are.  Here's the UKMET forecast:

UKMET forecast of precipitation (blue and green shading), sea-level pressure (thin black lines) and 500mb heights (red lines) for Monday afternoon.

You can see that the UKMET has light precipitation over all of Washington.  This is similar to the ECMWF, just lighter on the precipitation.  If this were to verify, eastern Washington might see a dusting of snow.

The SREF model is an ensemble, which means that it's actually a group of 23 similar models.  Here's a display of the SREF forecast snowfall for Spokane:

SREF forecast of snow for Spokane

Of the 23 SREF models, only 6 of them have any snow for Spokane, and only one has nearly an inch of snow.

So given all of this, the odds are slim that eastern Washington will see any snow on Monday.  Not impossible, just not likely.  Thus, the forecast of "a 40% chance of snow showers" for Spokane.  The northern Panhandle has a bit better odds, but still not a slam dunk.

After that, we don't see any significant precipitation for at least another week.

Thursday, February 26, 2015

Is There Snow in our Future?

It's been so long since we've seen snow around here, that most of us have put away the boots and snow shovels for the season.  Is there any chance we'll have to get them back out of storage?  It's not likely, but there is a chance.  Let's take a look.

First, the stage will be set in the next couple of days.  A somewhat weak storm is moving down from the north today (Thursday), but this will largely miss our area to the west.  Some folks are getting some rain and high elevation snow, but mostly it's just clouds.  As this storm moves south of the region on Friday, it will pull down some cold and dry air from Canada.

GFS forecast precipitation (green shading) and surface pressure (thin black lines) for Saturday morning

Saturday  will be a rather raw day, with temperatures in the upper 30s to lower 40s and a brisk north wind.  This new air mass will mean that any precipitation from the next weather system will fall as snow instead of rain.  That next system will arrive Monday and Monday night.  There are three computer models that we look at for the weather 5 days out: the GFS (US model), the GEM (Canadian model) and the ECMWF (European model). 

Here's the GFS forecast for Monday night:
GFS forecast precipitation (green shading) and surface pressure (thin black lines) for Monday night
The GFS shows the majority of the next system sliding down east of the Rockies, which is what most of these storms do.  But you can see that the GFS does indicate some snow making it into the Panhandle and extreme eastern Washington.

Now take a look at the GEM model for this same time:

GEM forecast precipitation (shaded) and surface pressure (solid lines) for Monday evening

Not identical to the GFS, but similar.  The ECMWF (not shown) actually has a bit more precipitation for eastern Washington than the GEM or GFS.  Earlier runs of the ECMWF were showing a more significant storm for the Inland Northwest, but the more recent model forecasts have backed off on that idea.

Unlike storms in December or January, this system will be more spring-like.  What does that mean?  In the heart of winter, our atmosphere is typically very stable.  Snow tends to be more widespread and light.  But in the spring, the surface is warmer while the upper-atmosphere is colder.  This causes a more unstable atmosphere.  The result is precipitation which is more showery but can be heavier.  But it also can be more difficult to accumulate snow on the ground during the afternoon hours.

Temperatures on Tuesday might be rather chilly, with some locations not making it above the freezing mark.  If this happens, it would be the coldest day since January 3rd.

GFS forecast high temperatures for Tuesday March 3rd

Thus, at this point it doesn't look like a widespread heavy snow event.  Rather, some locations in the Panhandle and extreme eastern Washington could see a few inches of snow.  It's too early to have much confidence in this scenario.  In fact, it's more likely that this storm will stay to the east of our area, as they typically do.  

Stay tuned and we'll update this blog in a day or two as the forecast becomes clearer.

Monday, February 23, 2015

Mountain snow at record lows? Any relief in sight?

Many across the Inland Northwest may be wondering if our mountain snow pack is at near record levels and if there is any relief in sight.  We'll answer those questions in this blog.

First, let's look at precipitation in the mountains.  Given the lack of snow pack in the mountains, the assumption might be we haven't had much moisture.  As the image below shows, this is clearly not the case.  All of the Pacific Northwest mountains have received their normal precipitation since the start of what we call the Water Year (October 1st).

So, how does our snow pack look - not good!

Clearly, a good portion of what has fallen in the mountains has been in the form of rain.  This is especially true across the central and southern Washington Cascades, and Oregon.  Much of this rain fell early in the season (October and November) before a snow pack had been established.  There have been more mountain-rain events during the winter as well. 

So, now let's answer the question, is this a record for low snow pack?  Let's break it down by region, starting with Northeast Washington and North Idaho.  Each dot is a SNOTEL site showing where we are at this year compared to normal.  

More simply put...

red = awful snow pack
orange = not good
yellow = a little low on snow
green = doing well

As you can see, the snow pack is not good, and downright awful in spots.  Now, to see if this is a record we need to look at individual sites.  Let's look at Mount Spokane (Quartz Peak) and Lookout Pass.

Blue Line = highest recorded snow pack
Green Line = where we should be
Black Line = this season's trace (2014-2015)
Red Line = lowest recorded snow pack

So looking at the black line (this year's trace), both sites are close to a record low, but not quite there.  It's important to note that SNOTEL data started in the late 1970s and early 1980s.  Thus, the traces for "lowest" and "highest" snow pack ever only go back about 35 years at most.

How about Southeast Washington, it looks very bad.  See for yourself...

Let's look in the Blue Mountains at Touchet...

Also well below normal, just above the record low value.

And finally, the Cascades, how do they look?  The West Slopes are in bad shape.  Mission Ridge area also in bad shape.  Further north however, the mountains surrounding the Methow Valley are doing much better.

Let's see the traces from Stevens and Harts Pass

Stevens Pass isn't looking good, but is above record low value.  Harts Pass in the North Cascades is actually running right where they should be for this time of year.

So, while the snow pack is low this year, most areas are not at record levels.  You may be asking yourself "what's the problem?" since the mountains have received their normal precipitation, just in the form of rain instead of snow.  The mountain snow pack acts like summer precipitation in the western US.  By that we mean, in the West, we don't get a lot of rain in the summer.  But the mountain snow pack acts like rain in the mountains, and keeps our rivers running through the dry summer/fall months.  With a low snow pack, it will likely melt earlier than normal.  This will likely result in low stream flows in the late summer and fall months.  Whether this has an impact (e.g. irrigation, fish, etc) remains to be seen.

The Northwest snow pack typically peaks around April 1st, so we still have about a month to at least ease the bleeding.  Looking ahead, are changes in store?  Yes, but not in a big way.  Here's the GFS precipitation forecast for Thursday night and Friday.

GFS 24-hour Precipitation forecast ending Friday morning

The light green shading represents 0.01" to 0.10" of liquid, which isn't much.  The low pressure system (red L near Portland) is actually moving from north-to-south, meaning that most of the precipitation will stay west of our area.  For the mountains, all of this will fall in the form of snow.  In the lower elevations, the precipitation could be in the form of rain or snow.  But as is typical with spring weather here, snow that falls during the afternoon/evening hours probably won't accumulate.

Looking farther into the future, we get another chance of some light precipitation early next week.  Here's the same GFS forecast for next Monday and Monday night.

GFS forecast of 24 hour precipitation ending Tuesday morning, March 3rd

Again, not a strong storm by any means.  Other models (Canadian, ECMWF) are even less excited about this system.  So there's nothing coming in the next week that will bring much mountain snow.

How about farther into the future?  The 6-10 day outlook isn't encouraging.  Here's the expected temperature pattern:

Just about the entire lower-48 states will be below normal next week.  So that's encouraging.  But here's the precipitation outlook:

The dry weather continues for the western US.  That doesn't mean we won't see any more snow.  The GFS does show some other potential for snow into March.  But suffice to say, the weather pattern doesn't look cold and wet.

Wednesday, February 18, 2015

Rare and Beautiful Clouds Over the Inland Northwest

If you live in Eastern Washington or Northern Idaho and looked up to the skies the morning of February 18, 2015 between 6:30 and 8am, you may have observed a rare and spectacular phenomenon!  This morning, many folks (including us at the NWS Spokane office) couldn't help but be in awe of these amazing clouds.
Photo courtesy of Jon Fox


But what are they and why do they form?  

This phenomenon is often referred to as fallstreaks or cloud holes.  Much research has been done on the subject dating back to the late 1950s.  Since this phenomenon is relatively rare, it's easy to conclude that the atmospheric conditions in which it forms are also very specific.  Research has shown that the holes or fallstreaks mostly commonly form in altocumulus or stratocumulus clouds.

After several days of mostly clear skies over the Inland Northwest, moisture was approaching from the west bringing the region a layer of altocomulus stratiformis.  As we do every morning at 3am, we launched a radiosonde that sampled the atmospheric conditions just a few hours prior to the sunrise and cloud punch holes.  This image below shows that sounding.
The area on the sounding circled shows increased moisture where the cloud layer most likely formed a few hours later.  The approximate height of this cloud is at about 400 mb, 7 kilometers, or 23,000 feet.   According to the sounding, the temperature at that layer is approximately -30° Celsius.

On visible satellite imagery, we captured a few images as the sun came up and illuminated the feature from above.
So what's the explanation??  I'm going to quote one of many articles and papers that have been written on the subject.  This excerpt comes from an article that appeared in Weather - December 2008, Vol. 63, No.12 by David E. Pedgely.

"These circular (or sometimes cylindrical) holes are formed when aircraft penetrate supercooled liquid cloud layers such as altocumulus.  The passage of the aircraft is believed to produce large numbers of ice crystals, which then grow quickly by the Bergeron-Findeison mechanism in the vapor-rich conditions (water-saturated air is supersaturated relative to ice).  This growth depletes the cloud of water vapor, causing the liquid droplets to evaporate and the formation of a hole in the liquid cloud layer with a visible trail of ice crystals falling out beneath."

"It seems that their most likely explanation is the penetration of shallow, highly supercooled altocumulus clouds by aircraft whose wakes freeze some droplets over a radius of about 100 m.  These ice particles are then spread by wake turbulence over a radius of 1 km or so in about 10 minutes within the cloud, where they grow at the expense of the droplets.  The resulting crystals fall into, and continue to grow in, clear but ice-suspersaturated air, and gravity sorts them into a fallstreak, where a weak downdraft develops through drag and evaporation."

In short, an aircraft traveled directly above or through the cloud layer.  It has been proven that it is not a result of anything the aircraft is emitting, instead it's the sudden and drastic decrease in pressure over the wing or propeller tip that initiates the process of  depleting the cloud and causing the liquid droplets to evaporate.  The result is the appearance of a hole that has been created with trailing ice crystals falling out beneath.

A quick search of aircraft routes this morning show how many flights follow a similar path departing out of Seattle and head east-southeast near the origin of the fallstreaks.  

Many folks also noticed a sun dog (or parhelion) as shown in the picture below to the right of the sun.  This also has to do with atmospheric optics.  The plate-like hexagonal ice crystals falling through the hole refract the light from the sun.  This halo is fairly common with cirrostratus clouds present.

While the cloud hole punch or fallstreak phonemena are rare because of the very specific atmospheric conditions necessary, there are numerous examples available online from around the world.  Many of the meteorologists (including myself) here at the National Weather Service have never seen this in person so we certainly understand the curiosity that this ignited.

The combination of cloud physics and optics can result in stunning scenery.  Here are a few more photos from NWS employees.

Sunday, February 8, 2015

Milky Rain

The February 6th "Milky Rain"

**** Updated on 9 February with additional information at the end of post ****

A Possible Explanation

A highly unusual "milky rain" occurred over much of eastern Washington and Northeast Oregon on Friday, February 6th. Periods of light rain during the morning and afternoon left cars spotted and smeared with a white or grey residue. 

Picture from a Facebook Friend of the NWS Pendleton OR 
Picture taken at the NWS Spokane office 

Picture taken at the NWS Spokane office

It is not unusual to experience "muddy rain" in the Inland Northwest. During the summer months, dirty brown water marks are frequently deposited on our cars. However, muddy rains rarely occur in the winter. And why the unusual milky white color?

Most plausible explanation: A large dust storm in Northwest Nevada occurred Thursday night into Friday. The dust caused traffic accidents and poor visibility in the Reno area. Winds gusting in excess of 60 mph were reported across the northwest Nevada desert. Here are some peak wind gusts documented by the NWS office in Reno Thursday night into Friday.

     LOCATION                                 REPORT
                JANESVILLE                    62.00 MPH              
                SUSANVILLE  2 NE              66.00 MPH
                ANTELOPE LAKE  5 NNW          70.00 MPH
                PITTVILLE  17 S               73.00 MPH
                HONEY LAKE  15 NE             77.00 MPH
                DOYLE  3 N                    79.00 MPH
                SIERRAVILLE  8 SSE            93.00 MPH

                MONO LAKE  1 NW               63.00 MPH
                CROWLEY LAKE  5 W             76.00 MPH
                COLEVILLE  3 E                82.00 MPH
                BRIDGEPORT  4 WNW             91.00 MPH

                SILVER SPRINGS AIRPORT        62.00 MPH
                SMITH VALLEY                  63.00 MPH
                YERINGTON MUNICIPAL AIR       63.00 MPH
                LOVELOCK DERBY                64.00 MPH
                SWEETWATER SUMMIT             86.00 MPH

                FOX MOUNTAIN  12 WNW          60.00 MPH
                LAKE CITY  3 ESE              70.00 MPH

                SOUTH LAKE TAHOE  3 SSW       64.00 MPH
                RENO  16 SSW                  134 MPH

                RENO  4 SE                    58.00 MPH
                GARDNERVILLE  4 S             59.00 MPH
                MINDEN-TAHOE AIRPORT          64.00 MPH
                COLD SPRINGS VALLEY  2 W      65.00 MPH
                RENO  18 S                    66.00 MPH
                SPOONER SUMMIT  3 E           68.00 MPH
                GARDNERVILLE  5 E             71.00 MPH
                RENO  5 N                     73.00 MPH
                GARDNERVILLE  5 NNW           73.00 MPH
                WASHOE CITY  2 WSW            77.00 MPH
                NEW WASHOE CITY  3 SW         79.00 MPH
                RENO  9 SW                    82.00 MPH
                VIRGINIA CITY  4 NNW          88.00 MPH
                GARDNERVILLE  5 WSW           90.00 MPH
                E GALENA                        109 MPH

Pay particular attention to the reports from Washoe, Humboldt, Pershing, Churchill, and Lyon counties. These generally sparsely populated counties are part of the "desert of Northwest Nevada" and are experiencing a multi-year drought. Numerous reports of blowing dust came from these counties Thursday night into Friday.

Check out some of the pictures from the Reno Gazette-Journal posted in a Saturday story about the storm that pounded the Sierra Mountains with snow and produced strong winds in western Nevada. Note the milky white or grey color of the blowing dust.

 Reno Gazette Journal

Reno Gazette Journal

Reno Gazette Journal

The white colored soil does not appear to be unique to a small area near Reno. Look at this Google Earth Satellite image. Dry lake beds appear bright white in the northwest Nevada desert and throughout the state.

Google Earth Satellite Image

How does dust from as far away as Nevada get to northeast Oregon and eastern Washington? It would take many hours of a prolonged strong south wind to push dust that far. Below are some images from the University of Washington GFS MM5 weather model. These graphics are tough to read. Our apologies. We may be able to update these graphics with some better ones later.

The next two images are 850 millibar model wind and temperature forecasts. This is roughly 4700 feet above sea level. These images show a constant average wind of roughly 40 knots (46 mph) from 10 PM on Thursday to 7 AM on Friday. This is a period of 15 hours of a constant south wind at 4700 feet above sea level.

10 PM on Thursday:  The small arrows on this graph show show south winds of 30-50 knots over the eastern half of Oregon

7 AM on Thursday:  The small arrows on this graph show show south winds of 30-45 knots over the eastern half of Oregon and up to 50 knots in Washington.

A forecast sounding for John Day (central Oregon) at 4 AM from the University of Washington GFS MM5 shows the wind speed even stronger above 850 millibars...up to 60 knots (69 mph) out of the south/southwest.

How long would it take for dust to travel from northwest Nevada to the Inland Northwest?  Gerlach, Nevada is near some of those dry lake beds in Nevada.
  • Spokane to Gerlach:  Distance - 490 miles
    • 490 miles / 40 miles per hour = 12.25 hours
    • 490 miles / 50 miles per hour =  9.8 hours
  • Pasco to Gerlach: Distance - 380 miles
    • 380 miles / 40 miles per hour =  9.5 hours
    • 380 miles / 50 miles per hour =  7.6 hours
So, if dust were to arrive in the Inland Northwest by mid day Friday, we would expect it to originate in Nevada between midnight and 5 AM. 

What time did the strong winds start in Nevada?  The first wind damage reports started to come into the NWS Reno as early as 925 PM on Thursday night and continued through the night. Here is an excerpt from the Local Storm Report issued by the NWS Reno. High wind reports continued into Friday afternoon.

 1107 AM PST SAT FEB 07 2015

 ..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
 ..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....

 0925 PM     NON-TSTM WND GST 5 N RENO                39.61N 119.82W
 02/05/2015  M73.00 MPH       WASHOE             NV   OFFICIAL NWS OBS


 1255 AM     NON-TSTM WND DMG 2 SW SOUTH LAKE TAHOE   38.92N 120.01W
 02/06/2015                   EL DORADO          CA   LAW ENFORCEMENT


 1256 AM     NON-TSTM WND GST 3 SSW SOUTH LAKE TAHOE  38.90N 120.00W
 02/06/2015  M64.00 MPH       EL DORADO          CA   ASOS           

 0431 AM     NON-TSTM WND DMG 2 ENE SOUTH LAKE TAHOE  38.95N 119.95W
 02/06/2015                   EL DORADO          CA   LAW ENFORCEMENT


 0445 AM     NON-TSTM WND DMG 4 SW SOUTH LAKE TAHOE   38.90N 120.04W
 02/06/2015                   EL DORADO          CA   LAW ENFORCEMENT

             6 TREES BLOWN OVER.

 0450 AM     NON-TSTM WND GST 16 SSW RENO             39.32N 119.94W
 02/06/2015  M134 MPH         WASHOE             NV   MESONET        


 0545 AM     NON-TSTM WND GST 5 WSW GARDNERVILLE      38.91N 119.83W
 02/06/2015  M70.00 MPH       DOUGLAS            NV   TRAINED SPOTTER


 0550 AM     NON-TSTM WND GST 9 SW RENO               39.45N 119.94W
 02/06/2015  M82.00 MPH       WASHOE             NV   PARK/FOREST SRVC


Other explanations for the blowing dust have been "floating around". Excuse the pun. Here are a few of them.

Volcanic activity in Russia. Maybe, but concentrations of ash would probably be only trace amounts given the distance required to get here. You would also expect western Washington and western Oregon to have reports of "milky rain" in this scenario.

Ash from burn scars in the Western U.S.  Another maybe. Burn scars are relatively small compared to the Nevada desert, so the source region would be limited. Burn scars in northern California, central Oregon and western Washington have received an abundance of moisture recently. Northwest Nevada has not. Soggy or snow covered ash will not blow around like dry ash or dust.

Observed 60 Day Rainfall from

60 Day Percent of Normal Precipitation