Thursday, November 1, 2018

2018-19 Winter Outlook

It's that time of the year where many are asking what kind of winter we will have.  Many have already heard about this year being an El Nino winter and we will discuss this further.  Let's begin with what the El Nino Pattern typically looks like.

Now often during El Nino years the Pacific Jet Stream sends storm south of our region bringing wet weather to California.  Now the exact placement of this can be different from year to year with some years bringing wet weather up into the Pacific Northwest.  We will come back to this later.

So how strong will this El Nino be?  Well the Climate Prediction Center is favoring a weak event.  Here is the latest forecast from various models.

Nearly all model solutions are showing El Nino conditions this winter.

So with a weak El Nino event, you may be asking what happened in prior weak El Nino years.  That is a great question!  Let's look at six cases since 1950 including 1958-59, 1976-77, 1977-78, 2004-05, 2006-07, 2014-15.  If we average the temperature and precipitation anomalies from these six cases, here is what we get:

Milder than normal in the west, and drier than normal in the northwest.  However looking at these maps doesn't give any insight to the variability that can occur.  So let's begin with temperature anomalies for each weak El Nino event.

As you can see, all six cases brought near to above normal temperatures, so no surprises there.  What about precipitation?

Quite a bit more variability.  The past three cases near or below normal while the 1976-77 winter was our "drought winter".  However 1958-59 and 1977-78 actually brought above normal precipitation.  The latest outlooks from the Climate Prediction fit well with history.  Higher confidence for near to above normal temperatures.  Lower confidence of drier than normal which is only slightly favored over parts of the region.

CPC Temperature Outlook for Dec 2018-Feb 2019 issued Oct 18 2018.

CPC Precipitation Outlook for Dec 2018-Feb 2019 issued Oct 18 2018.

So what about snow?  The milder temperatures typically brings below normal values to the lower elevations.  Here is the percent of normal map.

As you can see most towns receive between 65-80 percent of normal snowfall.  Now for cities not as sensitive to temperature who are often well cold enough for snow, higher values show up such as Republic (91%), Winthrop (96%), and Leavenworth (103%).  For an interactive version of this map, click here.

So does this mean most of the Inland NW will see below normal snowfall this winter?  Well the odds lean this way, but it is worth noting that some El Nino events prior to the 80s were snowy for some towns as the graphs for Spokane and Sandpoint show.

Spokane observed snowfall for weak El Nino events 

Sandpoint observed snowfall for weak El Nino events

Now while milder temperatures are favored, this does NOT mean we won't see any big cold snaps.  For example, the 2006-07 event brought a temperature down to -10F in Spokane.

Spokane Temperature data Fall/Winter of 2006-07.  Solid red line is record highs.  Solid light blue line is record lows. The dark blue lines represent observed temperatures.  The top brown line is normal high while bottom brown is normal low.  

Another important factor is that even in El Nino years, significant weather events can and often due occur!  The 2006-07 weak El Nino brought two wind storms.  The December event brought damaging winds to many areas of the Inland NW.  The January event brought a mountain wave wind storm to Wenatchee.

Even ice storms can occur, like the weak El Nino of 2014-15 in Leavenworth.

So in summary, a mild winter is likely with below normal snowfall in the valleys.  Precipitation is less certain.  And even if the winter as a whole finishes on the mild side, your town could be impacted by a short term significant weather event such as a wind storm, snow storm, ice storm, or even flooding.  Be prepared and keep informed of latest weather forecasts!

Monday, October 29, 2018

Trick or treat? - Weather outlook

Are you wondering about the Halloween forecast?  Will you or your kids get wet trick or treating?  How about temperatures?  Wind? Let's get to it!

First, we are watching a low pressure system south of the Aleutian Islands which is drawing up significant moisture northward from near Hawaii.

Infrared Satellite image from 11 AM PDT Monday, October 29th, 2018.
So will this moisture make it up our way?  Well its hard to tell from a still satellite image, so let's take a look at some model data.  First of all, let's see if this moisture plume is showing up in the models.

18z GFS initialization of 500 mb heights and 700-500 mb Relative Humidity valid 18z (11 AM PDT) Monday, October 29th, 2018
Good news!  The GFS model as well as the other models are picking up on this moisture.

Now, let's see where this model takes it.  Here is it's projection for Halloween.

18z GFS forecast of 500 mb heights and 700-500 mb Relative Humidity valid 18z (11 AM PDT) Wednesday, October 31st
Much of this moisture tops the flat ridge (noted by the H west of California) and moves across Washington, Oregon, and Idaho on Halloween.  But the entire day doesn't look like a washout at this time.  Let's take a closer look at when the best rain chances are.

We will take a look at a new set of model data called the National Blend of Models (NBM). This utilizes many numerical weather prediction model data and post-processed model guidance.  If you want to know more about NBM, click on this link for more details.

So let's start with 5 am - 11 am Halloween

It looks wet Halloween morning for most of Eastern Washington and north Idaho as well as near the Cascades.  It is worth noting that the best rain chances for Omak, Wenatchee, and Moses Lake may arrive prior to 5 am (not shown here).

What about Halloween afternoon?  Let's see.

The best rain chances are near the Cascades, far SE Washington, and the Idaho Panhandle.

Now, for the time you really want, Halloween evening (Trick or Treat time)

This would suggest low rain chances and more likely a dry trick or treat for most of Central and NE Washington.  Pullman, Lewiston, St. Maries, and Kellogg area under a higher threat of rain.

What about temperature?  Here is the 6 PM temperature forecast from the NBM

It will be a little on the cool side with values mostly in the mid 40s to lower 50s.  These are very close to normal values for this time of year.

What about wind?

Winds do not look particularly strong, ranging from 5 to 10 mph for most areas.  The Palouse and areas near the foothills of the Blue Mountains in SE Washington could see slightly strong winds of 10 to 15 mph.  The mountains will be breezy.

Now we will continue to fine tune the forecast, please keep informed of the latest forecasts on our home page found here.

Thursday, October 18, 2018

Changes next week and new fall/winter outlooks

Enjoying day after day of sunshine?  How much longer will it last?  In this blog we will address this important question, but also take a brief look ahead into November and briefly touch on the winter outlook.  A more detailed winter outlook blog is coming on or near November 1st. 

So why the abundant sunshine and stretch of dry weather?  A persistent ridge of high pressure is the answer.   Here is one model forecast for this Sunday (Oct 21st) showing high pressure deflecting the jet stream well north of our area.

18z GFS forecast of 500mb heights and 250mb winds valid 5 PM PDT Sunday October 21st
This will be a great weekend for yard work.  Especially raking all those leaves!

There is good model agreement that dry weather will last through at least Tuesday morning.  A weak system tracks through late Tuesday and Wednesday but probably won't produce much rain if any.  Models agree of a wetter pattern developing around Thursday (Oct 25th) of next week.  A low pressure system sets up off the coast resulting a mild but potentially wet southwest flow.  Here is one model depiction of what the pattern should look like next Friday. 

18z GFS forecast of 500mb heights and 250mb winds valid 5 PM PDT Friday October 21st

The jet stream (noted by the green and orange shaded colors) becomes aimed at Washington and north Idaho.  The latest 6-10 day Climate Prediction Center outlooks support a wetter pattern as well.

CPC 6-10 Day Precipitation Outlook issued Oct 18 valid Oct 24-28th, 2018 

It's still too far out to talk about rain amounts and will ultimately depend on the exact placement of the jet stream. 

What about November?  The new outlooks issued today (Oct 18th) favor elevated odds of warmer and drier than normal.

CPC November 2018 Temperature Outlook issued Oct 18 

CPC November 2018 Precipitation Outlook issued Oct 18

And what about the winter you ask?  Well an El Nino winter is forecast which has historically brought mild winters to the Inland NW with precipitation more of a wild card.  The new CPC outlooks issued today (Oct 18) mimic this idea as shown below.

CPC Dec 2018-Feb 2019 Temperature Outlook issued Oct 18 

CPC Dec 2018-Feb 2019 Precipitation Outlook issued Oct 18 

But don't think that a mild winter means no significant weather.  Short term significant weather events can and do occur.  In the next blog we will go into more detail with the past three weak El Nino events (2004-05, 2006-07, 2014-15) and look at what happened.

Wednesday, October 3, 2018

Record dry summer for some, relief in site?

Now that it's October, let's reflect back on the past three months.  Has this summer seemed dry to you?  Summer is after all the driest time of the year and many of our recent summers have been very dry.  Let's take a closer look.

July through September finished much drier than normal over much of the region as the image below shows.

As you can see, just about everyone finished in the bottom 10% (orange shading) in terms of total precipitation.  And several locations in and near the Columbia Basin reported their driest (red shading) July through September on record.  Here is the data below to prove it

You can see from the table above that Wenatchee, Ephrata, Grand Coulee, Lind, and Davenport reported a new record (or record tie) for the lowest July through September precipitation.  Ritzville and Omak came in 2nd, with Spokane and Pullman 3rd place.

And we still have that dry steak going in Ephrata.  After today it will be 109 consecutive days without measurable precipitation.

We are watching a weather system that will spread rain into portions of the area Friday afternoon into Friday night.  Right now the brunt of it should pass south of Interstate 90.  Ephrata will be on the edge.  Here is one model run from late this evening (Oct 3rd) showing rain amounts for Friday.

00z (Oct 4th) GFS Model 12 hour precipitation forecast valid 11 AM - 11 PM PDT Friday, October 5th.

Looking ahead to next week models are advertising a cold trough settling into the region with a possible increased threat of precipitation.   The long range outlooks from the Climate Prediction Center valid Oct 9-13th show high confidence of colder than normal temperatures with slightly elevated odds of wetter than normal. 

Wondering about the winter outlook?  We plan on updating the blog later this month talking about El Nino and its potential impacts for the Inland Northwest.

Sunday, August 19, 2018

Weekend of Smoke: Aug 18-19

Washington and north Idaho experienced the worst smoke of the summer (so far) during the weekend of August 18-19. The smoke reduced visibility to a mile or less in many areas and drove air quality into the "unhealty" or "hazardous" range across the Pacific Northwest. By Sunday, the smoke forced many residents indoors. Reduced visibility from the smoke even caused delays at Seatac airport.

The smoke produced an eerie feeling of darkness during the middle of a summer day. Motorists used headlights throughout the day due to the poor visibility. Check out the picture of Coeur d'Alene at 4 PM on Sunday the 19th.

August 19 at 4 PM: Vehicles Using Headlights. Idaho Transportation Department Camera in Couer D'Alene ID
At times, it was tough to see the sun through the thick veil of smoke. The sun is the little bright dot to the left of the radar tower. This picture was taken at the National Weather Service Office just west of Spokane at 6 PM on the 19th. The nearby Spokane International Airport reported 1 mile of horizontal visibility at the time of this photo. 

August 19 at 6 PM: NWS Spokane.
Where are the fires producing all of this smoke? The map below shows the "hot spots" detected by satellites. The red and orange dots indicate active fires across British Columbia, Washington, and Oregon. Other large fires are burning over northern portions of Vancouver Island.

The map below is a computer simulation produced by NASA that forecasts smoke in the atmosphere. The oranges, reds, and pinks indicate high concentrations of smoke. Atmospheric winds have created a huge reservoir of smoke over the western United States with some of the highest concentrations of smoke over Washington, north Idaho, and southern British Columbia.

NASA/GMAO - GOES-5 Forecast CO Biomass Burning valid 00 UTC 20 August, 2018

Air quality across the Pacific Northwest was affected by the smoke. The red dots on the map below represent sensors reporting "Unhealthy" air quality. The purple and dark purple dots are indicative of "Very Unhealthy" and "Hazardous" air quality. The map also has active fires plotted with flame icons.

August 19 at 7 PM: Air Quality Sensors and Active Fires. Pacific Northwest Smoke Cooperators

This high resolution MODIS satellite image shows the thick grey smoke over the Pacific Northwest. The image was taken around noon PDT, and it shows how the air in southeast Washington and the southern Idaho Panhandle was "cleaner" than central and northeast Washington.

MODIS Satellite Imagery: August 19 Noon PDT.

Places like Pullman and Lewiston not only experienced more sunshine on Sunday (Aug 19), but also got much hotter than places shrouded in smoke. The Pullman airport had a high temperature of 90 degrees on Sunday, and Lewiston topped out at 97 degrees. Spokane is only 70 miles from Pullman and was 13 degrees cooler with a high of 77 degrees.

By the evening, smoke spread into southeast Washington and the southern Idaho Panhandle. This animation from Pullman WA shows a wall of smoke arriving before sunset.

When will our smoke situation improve? North Idaho and much of eastern Washington should experience improved air quality by mid to late morning on Monday. The arrival of a cold front will produce gusty north/northeast winds. "Cleaner" air from central Canada combined with the mixing from 15 to 25 mph winds should push smoke toward Oregon and western Washington on Monday. The three images below is a smoke forecast model. The initial is the model smoke depiction for 5 PM Sunday, August 19th.

By 11 AM on Monday, increasing northeast winds should push the thickest smoke into Oregon and western Washington.

By 5 PM on Monday, the reds and pinks representing thick surface smoke should be pushed into western and central Oregon.

Friday, July 13, 2018

June 2018

Much of the United States spent June breaking high temperature records and experiencing a heatwave. The Inland Northwest wasn’t so unfortunate and had yet to reach 90°F in many inland stations, such as Spokane and Pullman. Wenatchee, Omak, and Moses Lake reached a monthly high of 91°F or 92°F, which wasn’t until the last half of June. Eastern Washington and the Idaho Panhandle saw many cool mornings with some low temperatures falling below 40° F in mid-June. For most of the area, it was a dry month with below normal total precipitation values. 

June 2018
Table 1. High & low temperatures and total precipitation for June 2018 with dates

People throughout Washington, especially Spokane, were anticipating the day we broke 90°F. Many say in Spokane that summer doesn’t start until after Fourth of July. While June wasn’t as warm as many expected, most temperatures throughout the month were near normal. So, how did these June temperatures compare to normal? 

Figure 1. Pacific Northwest Average Temperature Departure from Normal

What about the past few years? Let’s take a look at the last six years compared to normal (1981-2010) for a some locations in the area. (All temperatures in degrees Fahrenheit.)

Table 2. Average June Temperatures (2013-2018) vs. Normal 

June 2018 was cooler than last year, but near normal. Considering monthly average temperatures are not expected to be the same, many locations had an average June temperature with very little departure, close to one degree less or greater, from normal.

When comparing average June temperatures, don't forget that 2015 was an abnormally warm month, with numerous stations breaking, or near-breaking, records held for decades. Lewiston's previous record June high temperature of 103°F, from 1925, was broken in 2015 with a high of 111°F on June 28th. With an average almost ten degrees above normal June, this was just one of many locations reaching triple digits (100°F+) and/or breaking a record high June temperature.

Figure 2. Pacific Northwest Percent of Normal Precipitation 

Much of the Inland Northwest (Eastern Washington and Idaho Panhandle) had a much drier than normal month, with many locations not even reaching a monthly total precipitation of half an inch. Lewiston and Pullman received more precipitation than most of the region. They saw more on June 1, 2018 than many locations did all month. In June, Spokane barely broke half an inch, with 0.55", which was not even half the normal total of 1.25". 

Severe Thunderstorm Event: June 25, 2018
An early morning cold front brought strong winds and lightning to northeastern Washington's Ferry and Stevens Counties. Wind gusts reaching speeds above 50 mph brought damage to homes and land north of Spokane near locations such as Republic, WA. Many people confirmed this event's damage with pictures of buildings and hundreds of trees lost in small, localized areas.

CPC 8-14 Day Outlook: Temperature and Precipitation

The Climate Prediction Center 8-14 day outlook (valid July 21-27) continues to show a moderate chance of below normal precipitation (approx. 40-50%) for the end of July. The temperature 8-14 day outlook shows a moderate chance of above normal value (approx. 40-50%). 

The NWS Spokane website, Facebook, and Twitter will always keep you updated. See for the most current forecast.