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
 www.weather.gov/otx for the most current forecast. 

   

Monday, June 11, 2018

Hot temperatures likely next week

After a very warm May, the weather has changed for the first half of June with periods of cooler temperatures, rain showers, and thunderstorms. Computer models have remained fairly consistent over the past several days showing strong high pressure developing next week which could bring an extended period of much above normal temperatures. The latest image showing U.S. risk of hazardous temperatures says it all.


This experimental product from the Climate Prediction Center issued today (Jun 11th) shows a high risk (60%) of excessive heat across the Columbia Basin on June 19th and 20th, with a moderate risk (40%) over this same area June 21st and 22nd.  The remainder of Central and Eastern Washington is in a moderate risk June 19-22nd. 

But before the heat, let's talk about the weather this upcoming weekend and how quickly the weather pattern transitions next week.

Here is the pattern for Saturday and Sunday:

12z/June 11th GFS model forecast of 500mb heights and 700-500mb Relative Humidity (image) valid 5 PM PDT Saturday June 16
12z/June 11th GFS model forecast of 500mb heights and 700-500mb Relative Humidity (image) valid 5 PM PDT Sunday June 17

Not good if you have outdoor plans.  A low pressure system moves little, bringing the potential for showers each day and maybe even a few thunderstorms.  Previous model solutions were quicker to move the low out, but now the weekend looks showery.  Note the images above depict relative humidity with the green colors over our region indicating high values of moisture.

After that, models show a quick transition in the weather pattern. The low over Idaho takes a quick jaunt to the southwest, setting up off the California coast with strong high pressure over the Inland NW. 
12z/June 11th GFS model forecast of 500mb heights and 700-500mb Relative Humidity (image) valid 5 PM PDT WED June 20th.

This results in a hot/dry conditions over our region while the low off the California coast possibly draws in much needed precipitation into the southwest.  A large area of heat expands into much of the west as the image below shows.

12z/June 11th GFS model forecast of 500mb heights and 850 mb temperatures (image) valid 5 PM PDT WED June 20

The European model shows a similar pattern

00z/June 11th ECMWF model forecast of 500mb heights and 850 mb temperatures (image) valid 5 PM PDT WED June 20

How hot will it be?  Well it's too far out to narrow down the numbers, but 90s are a good bet for many valleys, possibly touching close to 100° in the hottest locations.  Note that this event is still 8-10 days out, and the details will probably change.  But, don't be surprised by an extended spell of heat starting around Tuesday, June 19th.

Wednesday, June 6, 2018

May 2018 Recap & Summer Outlook

May 2018 brought above normal temperatures, with some new records, to much of the eastern half of Washington and the Idaho Panhandle. Wenatchee, WA; Winthrop, WA; Mazama, WA; and Bonners Ferry, ID all experienced their warmest May on record. Spokane, WA and Lewiston, ID also had some of their warmer Mays on record; it was in the top 5 warmest Mays for both cities. It was not the typical wet and cool May that we are used to. Many locations received below normal precipitation, but did not reach any new record low totals. However, due to the above average temperatures and remaining snow pack, some lakes and rivers rose to significant heights. Numerous lakes and rivers experienced flooding. The Kettle River, near Ferry, reached a historic crest of 22.54 ft. on May 11th

Monthly Weather Summary - May 2018
Table 1. Average May temperatures with their rank when looking at the previous/current May records
*It is important to note that due to long periods of record, sites of observations may have changed.

Table 2. May 2018 high and low temperatures with date and total monthly precipitation

Temperature and Precipitation Anomalies


When looking at May mean temperature anomalies above, much of Washington east of the Cascades, the Idaho Panhandle, and northwestern Montana had the biggest warm-anomalies in the western United States.


A closer look at May percentile rankings shows that some record warm mean temperatures occurred in the Eastern slopes of the Cascades, which is where you can find record setting Mazama, Winthrop, and Wenatchee in Washington. Most of the Pacific NW was much above normal.

In the Pacific Northwest, the map of May precipitation anomalies displays the drier than normal conditions in much of the region. 


Looking closely at Spokane

For the entire month of May, there were no days with temperatures below 40°F at Spokane Intl. Airport. 
xmACIS Plot showing number of days in May with min temperatures below 40°F (1947-2018)


There have only been two previous years where Spokane's low temperature has failed to fall below 40° F in the month of May: 1957 & 1980. The last time the temperatures dropped below 40°F this year was April 23rd with a low of 34°F.  This year had the second warmest May low temperature, just below 1957’s record of 42°. 
Summer Outlook

CPC summer temperature outlook issued May 17, 2018


CPC Summer precipitation outlook issued May 17, 2018
The Climate Prediction Center (CPC) outlook is favoring elevated odds of a warmer than average and drier summer (June-July-August) this year for the Northwest. However, this does not mean there will not be periods of cooler weather and precipitation, like we will be seeing this weekend.

Please monitor our website for all of the latest updates: https://weather.gov/spokane

Wednesday, May 30, 2018

Friday, March 2, 2018

Major snowstorm strikes Republic, Conconully and surrounding mountains

A major snowstorm struck portions of the Inland Northwest over the past two days.  It all started during the late afternoon and early evening on February 28th.  The Okanogan Highlands as well as Conconully and the Loup Loup area were especially hard hit with several reports of 14-21".

Here is the scene from Sherman Pass east of Republic this morning.


The snow stick shows 5 feet on the ground.  Below is a map showing snowfall totals that have been reported to us as well as a few SNOTEL sites.  Thank you for all your reports!

2 day snowfall reports (inches) ending Friday, March 2nd, 2018

As you can see there were huge variations in amounts.  For example around 1" in Omak but just to the northwest of there 19" in Conconully!  Also no snow accumulation in Oroville.  Why the difference?  Well temperatures in the lowest valleys generally stayed slightly above freezing through the event with rain, rain/snow mix, or a wet non-accumulating snow.  Snow began to accumulate above 1500 feet with heavy snow totals for most areas above 2000 feet.

So why did this area get so much snow this time?  Let's take a look at the pattern.

00z/1st UW WRF-GFS forecast of 500mb heights/vorticity valid 18z (10 AM PST) Monday March 1st

An unseasonably deep upper low sat off the coast before slowly inching its way into the region.  Situational awareness tables (not shown) indicate lows of this magnitude occur about once every 10 years for this time of year.  This flow pattern was very favorable for precipitation as southerly flow on the east side of the low provides no precipitation shadowing from the Cascades.  Here is a series of satellite images showing multiple waves coming into the region from the south.

GOES-16 Infrared Satellite image valid 8 AM PST March 1st, 2018
GOES-16 Infrared Satellite image valid 9 PM PST March 1st, 2018



GOES-16 Infrared Satellite image valid 8 AM PST March 2nd, 2018

Note that on the latest image (8 AM March 2nd) there was still another wave lifting north.  Good news is that after today, accumulating snow should be done for several days.

So why was this flow pattern so favorable?  Here is one model depiction of moisture and wind during a portion of the event.

Model depiction of 700-500mb RH and 850 mb winds valid 6z Mar 1st (10 PM PST Feb 28th, 2018)

As you can see all the green means lots of moisture.  Then note the wind vectors out of the south-southeast.  The next image below shows these same wind vectors overlayed with the terrain.


The green colors indicate lower valleys and plateaus while the brown colors are the mountains.  Notice how the winds run generally from the lower elevations of the Columbia Basin into the higher terrain of the Okanogan Highlands.  This provides added lift to generate more precipitation. In contrast, for weather systems with strong westerly flow, a large area of downslope off the higher terrain of the Cascades can create a precipitation shadow over this same area.  The flow pattern is very important for snow totals in this area!

Republic has seen worse.  For this event the official 2 day snow total of 14.0 inches tied for the 6th greatest 2 day snowfall on record.  The Republic observation from Jan 2nd and 3rd of 1965 showed a total of 26.5" fell which is the snowiest 2 day period on record.




Saturday, February 10, 2018

What a difference a year makes!

It has been stated before that each La Niña year is different.  Last year was a La Niña year, and this winter is yet another La Niña.  However this winter so far has been a far cry from what last winter brought.  Let's take a look at where we are this year compared to last.  Also, don't give up on winter, as temperatures have turned colder: we'll briefly discuss what lies ahead.

This winter so far
Let's begin with this winter.  Above normal temperatures and precipitation for Washington and northern Idaho.  Drier than normal and very mild to our south in Oregon.  December actually brought normal temperatures; it was the very mild January that contributed to the warmth on the map below.

December 2017-January 2018 Temperature anomaly
December 2017-January 2018 Precipitation Percent of Normal



Last Winter
And last winter, well it was a cold one especially in the Columbia Basin!  Precipitation was just the opposite compared to this winter.  Drier than normal in Washington and northern Idaho and wetter than normal to our south.

December 2016-January 2017 Temperature anomaly

December 2016-January 2017 Precipitation Percent of Normal

Snowpack
The milder temperatures this winter, especially in January and the first part of February have led to quite the difference in lower elevation snow pack this winter compared to last.  Below are maps showing the differences in SWE (Snow Water Equivalent) for February 10th, 2018 vs 2017.

This winter

Modeled SWE (Snow Water Equivalent) 12z (4 AM PST) February 10th, 2018 

As you can see, not much snow is left in the valleys.  Good news is mountain snow pack in Washington is looking good.  Oregon, not so much.  Mountain snowpack typically peaks around April 1st, so these maps could still change by then, stay tuned!

And last winter
Modeled SWE (Snow Water Equivalent) 12z (4 AM PST) February 10th, 2017 

Much more lower elevation snow pack, and Oregon was doing much better.

How does this look with regards to percent of normal?  Here is the February 10th map showing the west.

February 10th, 2018 SWE (Snow Water Equivalent) Percent of Normal

It's not just Oregon, but much of California, Nevada, Utah, New Mexico, and SW Colorado also have much below normal snow pack.

Why?
So what has caused this pattern?  Abnormally strong high pressure over the west.  Typically with La Niña this high pressure is centered further to the west.  Here is this year's pattern.

Mean 500mb heights Dec 1, 2017 to Jan 29th, 2018

And the map below shows the anomaly, with higher than normal pressure over our region as noted by the yellow and orange colors.

Mean 500mb height anomaly Dec 1, 2017 to Jan 29th, 2018

Compared that to last year, which was just the opposite with anomalous ridging to our west with a trough over us as noted by the purple and blue colors.

Mean 500mb height anomaly Dec 1, 2017 to Jan 29th, 2017
This goes to show you that each La Niña is different.  Other factors that we will not get into right now impact the orientation, placement, and strength of the jet steam.

Winter is back!
Now the pattern has shifted a bit with high pressure shifting to our west allowing colder air to drop in from the north.    A reinforcing shot of cooler air arrives Monday (Feb 12) and some models suggest this pattern may stick around for a while.  Here is the Canadian model for next Sunday (Feb 18).

12z/10th Canadian model forecast of 500mb heights, MSLP valid 12z February 18th (4 AM PST)

This model shows a very amplified pattern with a strong ridge in the eastern Pacific and a deep trough over our region.  Other models such as the GFS and European show a similar pattern.  While this pattern looks like a cold one, moisture is the wild card.  This is still a long ways out so stay tuned to the latest forecasts.

And here are the latest 8-14 day outlooks from the Climate Prediction Center which also favor elevated odds for below normal temperatures with about normal precipitation.

CPC 8-14 day temperature outlook issued Feb 10th valid Feb 18-24, 2018

CPC 8-14 day Precipitation outlook issued Feb 10th valid Feb 18-24, 2018

So, despite the mild December, January, and early February, more winter like weather (at least temperature-wise) is expected for the next few weeks.


Sunday, December 31, 2017

Top Weather Events of 2017


As 2017 comes to a close, let's take a look at the weather of the past calendar year. The year began with a cold and snowy January. Then, spring was marred by flooding and landslides. Our summer featured long periods of dry weather with many smoky days during August and September. The fall was relatively quiet followed by a couple of big winter storms during the second half of December.

This chronological list takes a look at ten or the Inland Northwest's top weather events of 2017.



#1. The Central Washington and Palouse Blizzard of Jan 10, 2017 is the first on our list. Drifting snow closed several highways and left cars stranded over portions of Douglas and Grant counties.



#2. The Central Washington Ice Storm: January 17-18. Freezing rain coated the I-90 corridor from Snoqualmie Pass to east of Moses Lake with more than a half inch of ice.



#3. February Ice Jam Flooding. The St Joe River, the Grand Ronde River, and several other creeks and streams in Spokane and Shoshone counties experienced ice jam flooding. Arctic cold in January gave way to heavy rains in February. The subsequent ice jams caused flooding and threatened to damage bridges in southeast Washington and the southern Idaho Panhandle.



#4. March Flooding. Above average rain on top of a deep snowpack pushed many rivers in Idaho and Washington above flood stage. Sprague Washington experienced weeks of high water as the creek entering town flooded fields and streets.


#5. April Landslides. Record amounts of precipitation over the winter combined with the release of frost in our soils caused landslides over the steep terrain of Washington and Idaho.


#6. Number 6 on our list of Top Ten Weather Events of 2017 actually features a day of beautiful weather. During a summer plagued by wildfire smoke and grey skies, eastern Washington and north Idaho enjoyed perfect conditions for viewing the solar eclipse.



#7. Camas Prairie Thunderstorm Wind. Residents of the southern Idaho Panhandle will likely remember number 7 on our list of Top Weather Events of 2017.  Back to back days of damaging thunderstorm winds hit the Camas Prairie on August 29 - 30. Trees were damaged and lightning sparked wildfires.



#8. September Smoke. Number 8 on our list of Top Weather Events of 2017 is a period of weather many of us would like to forget...the wildfire smoke. Cough!  Smoke flooded the Inland Northwest on Labor Day and lingered for the next 4 or 5 days. Spokane experienced some of the worst air quality on record during the first week of September. 



#9. Spokane Record Dry Streak. Our winter and spring featured record amounts of precipitation. Mother Nature did an about face during the summer. From June 29th through September 16th, the Spokane International Airport received no measurable precipitation. 80 consecutive dry days...a new record. 



#10. Heavy Wet Snow: December 19th. A big dump of heavy wet snow rounds out or list of Top Weather Events of 2017. For residents of Sandpoint, Bonners Ferry, and Naples, this storm is still fresh in your memory.  Bonner, Boundary, and Pend Oreille counties receive a foot of heavy wet snow.