2007 Weather Year in Review

By the middle of the month the weather had changed markedly. Cold Canadian air had moved into the region for our chilliest week of the winter. Highs were generally in the teens with sub-zero overnight lows. Priest Lake and Spokane dropped to -10 while Mazama bottomed out at -12. But the cold spell was short-lived and temperatures rebounded back to their more normal values. As is often the case, the transition from cold to warm resulted in significant snowfall. The Coeur d'Alene area picked up 5-10” of snow on the night of the 19th . A large ridge of high pressure developed over the western U.S. putting an end to the stormy weather for the month.

February

The month started off cold but quickly warmed as a front moved through on the 3rd. Sub-freezing daytime temperatures were replaced by nights where the temperature failed to drop below freezing. Winter snow packs began to melt as most of the precipitation was in the form of rain. A warm front moved into the region on the 15th. While initially this provided 4-6" of snow in the valleys of northeast Washington, eventually the warm air arrived as temperatures warmed considerably. On the 17th temperature readings reached into the 50s across the area with Lewiston and Pomeroy reaching 64 degrees. A wet and windy system arrived on the 19th and 20th. Spokane gusted to 44 mph on the 20th while the Waterville Plateau region gusted to 52 mph. Area ski resorts picked up over a foot of snow. Winter still had one more gasp as a cold unstable trough of low pressure moved over the Pacific NW during the last week of the month. Showers of fluffy snow were quite common, with 2 to 4 inches accumulating in just an hour or two. The area surrounding Wenatchee picked up 4 to 8 inches on the 24th, Similar amounts fell in the Spokane and surround areas on the 25th and 28th.

March

The wet and somewhat snowy February weather persisted into the first few days of March. Snow advisories were issued for much of the Idaho Panhandle and extreme eastern Washington on the first and second of March. Daytime temperatures were about 10 degrees below average for the beginning of March. In fact, the Wenatchee airport failed to warm above freezing on the 2nd with a high of only 31 degrees. But temperatures quickly rebounded into the 50s and 60s by the end of the first week and largely stayed at or above normal for the remainder of the month. In fact, by the 11th Wenatchee was setting a record high for the day with a reading of 72 degrees. One cool and showery period around the 26th lowered snow levels below 4000 feet, bringing 2.3 inches of snow to Winchester in the southern Panhandle. This storm also brought Wenatchee nearly all of it's precipitation for the whole month, as it was the 11th driest March out of 48 years of record keeping. The first thunderstorms of the season occurred on the last day of the month in the Columbia Basin, another harbinger of the arrival of spring.

April

Similar to March, the first few days of April were cool and unsettled. Scattered snow light snow showers were observed mainly north and east of Spokane on the 2nd . The first truly “warm spell” of the spring arrived shortly after this, as temperatures warmed into the lower 70s for the first time at many locations. As usual, these warm ups are short-lived and followed by a cool and wetter period. The cold front that swept through the area on the 9th brought a few thunderstorms as well as some gusty winds. The strongest winds observed were 54 mph near Vantage and 48 mph at Uniontown. Behind this front temperatures dropped back below freezing at night. Colville and Davenport set record lows on the 12th of 15 and 20 degrees respectively. As April came to a close it was becoming obvious that we were in for a dry spring. The 2-month total of 0.21” at Wenatchee was the 2nd driest March/April on record.

May

While better known for flowers and Mother's Day, May in the Inland Northwest is often filled with several wet, cloudy and cool days. It's actually the wettest month of the year in Lewiston. But this year May was noteworthy for its sunny skies and mild temperatures. Instead of the typical swings between 80s one day and 50s the next, temperatures were generally in the 60s and 70s throughout the month. Similar to the 2 preceding months, May started out on a cool and wet note. But the weather quickly warmed with abundant sunshine. A mainly dry cold front moved through on the 12th , causing the development of a few dry thunderstorms near the Spokane area. One storm produced a wind gust to 51 mph at the Spokane Felts Field airport. But the cool temperatures only lasted a day or two as high pressure built into the area for more sunshine and warmth.

Then the first significant storm system of the season moved into the area. A deep low pressure system moved onshore over northern Oregon. This set up a good pattern for Wenatchee to finally get some much needed rain. The 2-day total of 1.51” was the wettest 2 day rain event in May ever observed since airport records began in 1959. As the storm moved out of the area, a line of thunderstorms developed over northeast Washington on the 21st and moved southward over the Spokane area. The Spokane Airport received 1.11” of rainfall from these storms. The cold temperatures resulted in snow over the mountains, with 6-10” of snow reported in the Cascades and Idaho mountains.

While the wet event in late May made up for the large precipitation deficit in many locations, the Lewiston area was still well below average at the end of May. The 3-month total of 2.16 was just over half of their normal amount. This was the 7th driest spring on record for Lewiston, with records going all the way back to 1881.

June

Temperatures in June were very close to those for an average June, although they were a bit warmer than usual in Lewiston. The month started off downright hot, with temperatures in the 90s for the first few days, which was about 20 degrees warmer than normal for that time of year. But as usual in early June, the heat didn't last and more moderate temperatures returned for the bulk of the month. Instead of temperatures, it was the continuation of dry weather that was the noteworthy aspect. After a disappointing spring, there was still a chance for June rainfall to make up for the recent dry spell. Unfortunately it was not to be. Most locations had less than half of their normal rainfall for the month. The rainfall also was spotty rather than widespread, so the precipitation numbers tended to be a bit deceiving. In contrast to last summer's active thunderstorm season, this year's was rather lacking. The only notable event for June was on the last day of the month. Strong thunderstorms caused wind damage in the Idaho Panhandle from Coeur d'Alene up to the Canadian border. Golfball-sized hail was also reported southeast of Lewiston.

July

It's typically the pattern around here that the consistent hot weather of summer doesn't start until after the 4th of July. This year, it was a day or two early. Temperatures for the mid-summer holiday were in the 90s, and reached the triple digits in most places on the 5th. The heat subsided a bit after a few days but returned quickly. This time it broke with mainly dry thunderstorms on the 13th. Wind gusts from these storms reached 53 mph at the Spokane International Airport. For the remainder of the month daytime readings typically reached the 90s, but the extreme heat wasn't seen again. For the month overall, July 2007 was the 2nd hottest month (any month of the year) ever for both Spokane and Lewiston, bested only by July 1906. While the number of 90+ degree days at Spokane this year (16) was much higher than normal (9), it was well below the record of 20 days in 1985. The heat wasn't confined to the Inland Northwest. Many locations such as Missoula, Boise and Salt Lake City experienced their hottest month ever.

August

An analysis of hot July's showed that not all August's follow suit. In fact, just the opposite often occurs. Hot July's are more often followed by near or below normal Augusts. And this was the case for 2007. In fact, it was cooler than the past 4 Augusts. There were only 3 hot spells in the month, each lasting only a couple of days. And a very cool air mass on the 20th and 21st kept daytime temperatures below 70 at nearly every location, a welcome relief from the summer heat. This event also brought some much-needed rainfall to the area. Precipitation amounts ranged from just a few hundredths in the Cascades to nearly one-half inch at Ritzville and La Crosse. Another round of rainfall arrived on the last day of the month. This time strong thunderstorms accompanied the rain. Hail and strong winds were felt over many communities of extreme eastern Washington and the Idaho Panhandle.

September

The month began in its usual fashion, with temperatures in the 80s and even lower 90s as summer tried to hold on for a few more days. This weather lasted until the middle of the month when our first Pacific front moved into the area. While there wasn't a lot of precipitation with this system, the temperatures dropped considerably. 80s were replaced by 60s and upper 50s. This event really marked an end to the warm summer temperatures and ushered in autumn weather. A couple of colder and wetter fronts arrived by the end of the month. Ahead of these temperatures warmed back up into the 70s and lower 80s but were quickly replaced by 50s and 60s. The mountains received their first dusting of snow as the freezing levels dropped to around 4500 feet. September wound up very close to average for temperatures but on the dry side with precipitation.

October

The cool showery weather of late September continued into the first part of October. Temperatures hovered in the 50s with rain showers. There was even some graupel (small hail) from the showers on the 4th . This is fairly common in March, but a rare sight for October. The rain was also quite heavy for early October. Chelan picked up ¾ of an inch on the 1st and Bonners Ferry received 0.62” of rain on the 4th . A break in the Pacific storms allowed the area to dry out and warm up a bit. Lewiston reached 87 degrees on the 9th with Pullman topping out at 81F. More cold and wet weather arrived in the middle of the month. Daytime temperatures stayed in the 40s in some locations. Meanwhile the mountains picked up some significant snow, with 5-10” falling in the Cascades and Panhandle mountains. Any thoughts of an early ski season were dashed as valley temperatures once again rebounded into the 60s and 70s, melting all of the mountain snow. Ritzville set a new record high on the 23rd with a maximum temperature of 78 degrees. But just as quickly as it warmed up, cooler air came in from the north. Nighttime temperatures dropped into the teens in the northern valleys. When it was all said and done, October came in a bit cooler and wetter than normal.

November

The first few days of November were dry and sunny. But that didn't last. Wet weather set in on the 7th and continued through the 19th . This round of storms ended with a strong low pressure system moving across northern Oregon. This storm brought the first real snow to the lowlands. Spokane picked up less than ½ inch, but southeast Washington and the southern Idaho panhandle were the big winners. Winchester, ID (south of Lewiston) received 14.1” of the white stuff, and Pomeroy, WA received 6.5”. But all of the clouds and storminess actually kept temperatures rather mild. Then the first wintry air mass moved in behind this last storm. Nighttime temperatures dropped into the teens while daytime temperatures stayed below freezing in most locations for the rest of the month. More storms moved into the area at the end of the month bringing more snow. Valley locations north and east of Spokane received 4-8” of snow on the 27th . Then just about every location picked up 1-3” of snow on the 29th . So at the end of the month, the Inland Northwest was covered in a blanket of white.

December

The cold and snowy pattern of late November was destined to end. A very warm and moist plume of air from the subtropics took aim at the Pacific Northwest. Subfreezing temperatures on the 1st climbed into the 50s by the 4th, accompanied by copious rainfall and gusty winds. As the warm air rode over the cold air, heavy snow fell in the valleys of the Cascades and near the Canadian border. Moyie Springs near Bonners Ferry picked up 18", while Mazama received nearly 3 feet of snow. West of the Cascades record flooding occurred. Interstate-5 near Chehalis was closed by floodwaters. In the mountains, heavy snow resulted in avalanches, closing Highway 2 east of Stevens Pass.

After this rapid warm-up event the weather calmed down for a few days as a high pressure ridge developed over the Gulf of Alaska, closing the storm door. Eventually a few weak systems moved over the ridge and dropped into the area from the northwest bringing light snow to most locations. After a few days the ridge broke down and the Pacific storm door was open again. Storms moved through the area every 1 to 3 days. The image below shows the procession of storms beginning near Japan and moving across the Pacific Ocean, heading for the Inland Northwest.