Early Season Snows

Okay, so there is no snow in sight, but as we come up to the end of August the climatological chances of snow are increasing. And today is the 88th aniversery of the greatest August snow of record, and there are only two autumns with measurable snow before September 10th:

August 29, 1922: 3.0" Measurable snow was recorded at most observing locations in the Interior.
Sept 2-3, 1980 3.1"
Sept 5, 1980 0.2"

For the 1980 event, College 5NW, at 900' MSL, measured 4" of snow.

Trace snowfalls have occurred more often. The last time it snowed before Sept 10th was Aug 31, 2005, when there was a brief mixed rain and snow shower just before midnight at the airport.

All this is of course for in town. This time of year snowfall is usually extremely elevation dependent. The most recent August hill-snow in the Fairbanks area was on Aug 22 1996, when elevations above 2300' had 1 to 2 inches of snow, 0.2" here at Keystone Ridge (1600'), and there were some flurries as low as 800' MSL.

Soaking rains for Fairbanks

5pm update:
rains have been showery but frequent since 9am. Storm totals include:
Eielson AFB: 0.97"
Keystone Ridge: 0.80" [thru 4pm]
Fairbanks Airport 0.73"
1 Mile Chena Hot Springs Road: 0.64"

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The first stratiform rain since June began late Friday evening in the area, and by 9am Saturday had brought generally a third of an inch of rain or more to the area. It's a chilly rain at high elevation; 41F at Munson Ridge (3100'MSL) , but the freezing level is still a fairly high 6200'. Between the rain and the fact that it's the end of August, hopefully the Willow Creek fire will be squashed for good. It was quite stinky in town Friday once the SW winds started up.

Specific amounts include:

Fairbanks airport: 0.41
Eielson AFB: 0.65"
Clearly Summit: 0.57"
UAF West Ridge: 0.54"
Keystone Ridge: 0.44"
College 5NW: 0.40" (above Goldstream Valley)
Fort Wainwright RAWS 0.25"

Growing Degree Days

There have been a couple of articles in the Fairbanks Daily News-Miner of late about what a great growing season summer 2010 has been. Yet neither seasonal temperatures nor precipitation have seemed outstanding. One explanation may be that the summer has been unusually balanced. Rather than six weeks of very warm weather, temperatures have been mild over a long period. This is reflected in the plots above, based on data from Keystone Ridge. The plot on the left shows Growing Degree Days (daily mean temperatures above 50F) May through August, with individual months noted. Like the raw temperature plot, the 2010 total is above the 15 year mean, but not by a lot, and several summers were higher. However, the plot on the right tells a different story. Here, the monthly percentage of total Growing Degree Days is plotted. 2010 has the most even distribution across the four months of any summer.* The contrast with last year, which had almost the same total number of GDD, is remarkable. In 2009, almost half the seasonal GDD are crammed into July.

*The remaining six days in August 2010 will add only a small number of GDD to the total and will slightly increase the balance in the GDD distribution for this year.

Summer Wrap-up

The warmest quarter of the year in Interior Alaska is late May through late August. Here's a plot of recent summers on Keystone Ridge: overall warm, but not extreme. Of course, a 91 day average is a simple way to characterize a season. More on that to follow.

Rain around Town

While the Fortymile and upper Tanana valley have been drenched this summer, in the central Interior its been much more it or miss, what with a complete lack of stratiform rain. Tuesday evening most…but not all… places in Fairbanks-land did get a couple of showers…and a handful of lightning strikes…here at Keystone Ridge there was just a single rumble.

Rain amounts include:

East Fort Wainwright: trace
Fairbanks airport: 0.07", monthly total 0.55 is less than 40% of normal to date
North Pole 0.11"
Keystone Ridge 0.16"
Angel Creek: 0.31" (near Chena Hot Springs)
Chatanika: 0.43"

Wide Open Spaces

MODIS image from this afternoon; sail north from Barrow and you'll go 400 miles til you hit the solid pack ice.

Arctic Sea Ice update

Here is the false color image of Arctic Sea Ice coverage as of Sunday from the University of Illinois's Cryosphere Today web site:

According the the National Snow and Ice Data Center, this amounts to just under 6 million square kilometers of ice coverage, and as of August 16th the total Arctic Sea Ice coverage was third lowest of record, less than last year but more than 2007 and 2008. The annual ice minimum will be sometime in September and will not be far from the ARUS median June forecast of 5.1 million square kilometers.

More Frost Info

I should note that only one of the long-term climate sites in the Fairbanks area have a freeze yet:

Lows Saturday morning:
Eielson AFB: 33F
North Pole: 36F
College Observatory 38F aka UAF West Ridge
Fairbanks Airport: 40F

Lows this morning were similar or a little cooler.
Fairbanks airport kept a breeze most of the night and wound up with a min of 41F
College Observatory: 36F
North Pole: 33F
Goldstream Creek: 27F
Salcha River RAWS: 21F

Hillsides are way above freezing: 47F Saturday morning and 46F this morning here on Keystone Ridge; the CRN site near Fox had 44F Saturday morning and 41F this morning

Eielson did report a min of 30F, about 12 days earlier than average.

The long term Tok coop reported a min of 29F Saturday, the first freeze of the autumn and a week or so later than average.

Autumn Cometh

A nice dawn webcam shot from atop Knob Ridge, near Dot Lake in the upper Tanana Valley.

Temperatures fell to freezing in many of the usually cooler valleys this morning, including the Fairbanks area. Goldstream Creek had 28F, Woodsmoke coop station near North Pole and Chena Hot Springs reported 30F and Eielson AFB 33F. This is around the average date of first freeze in these areas. Somewhat to my surprise, there was no frost evident in Goldstream Valley about 730am on the way home this morning.

East of Fairbanks, Tok #2 coop 28F (same location as the Tok CWOP) and OBrien Creek on the Taylor Hwy 28F. The lowest reliable temperature reported this morning was 23F from the RAWS on the Salcha River, about 15 miles upriver from the Richardson Hwy bridge.

Fire Season Winding Down

As we move toward the end of August, the 2010 wildfire season is winding down. After a very early and active start in May, the season slowed down markedly, and in spite of some warm and dry weather, especially over the central Interior, never really picked up steam again. As of August 19th, total acreage burned is at 1.07 million acres, with only a couple of fires in the Upper Yukon Valley, west of Fort Yukon, still reasonably active. While this is the 5th year in the past 10 with more than one million acres burned, this is less than half of last years total. Regrettably for Fairbanks, the Willow Creek fire, just southwest of town, continues to smolder and occasionally smoke up town. Unless and until there is a several day period of cool rainy weather, this may remain an irritant until the snow comes.

Autumn temperature changes

When I moved up onto Keystone Ridge in June 1996, I figured that June would be the month when, on average Keystone Ridge, at 1600' MSL, daily maximum temps would coolest compared to town (i.e. Fairbanks International, 440' MSL). After all, June has the maximum solar insolation and climatologically the fewest days of rainy cool weather; many Junes have no stratiform rain events at all. Well after 15 years of data, I can safely say I was wrong, as the plot at the right shows.

In fact, other contributions make as much or more of an impact on the non-inversion season max temperatures. In the spring, a much longer lasting snowpack on the Ridge helps suppress temps, while in the late summer and early autumn more persistent fog and stratus AND the much lower sun angle, amplified by the northeast aspect of the Keystone Ridge weather station contribute to an even greater deficit. I would not have guessed that in fact September is the month when Ridge is coolest compared to town.

Big Change

Like most late summer heat, Sunday's record event has been quickly replaced by more seasonable weather. Freezing level at 6200' this morning, down from nearly 13,000' Sunday afternoon. The Munson Ridge SNOTEL, at 3100' south of Chena Hot Springs, was 40F at raining this morning, while here at Keystone Ridge, 45F, light rain and in cloud at 8am. Even Fairbanks International made into into the 40s. Combined with the increasing colors in the birch trees and the first end of nautical twilight since late April last night, NOW it's starting to feel like Autumn.

One more Record

College 5NW, which holds the distinction for longest hillside climate obs in the Fairbanks area (since the mid 1970s), set a new August record high Sunday, with a max of 90F. And of course warmest so late in the season.

North Slope Heat

Heat Sunday was not confined to to the Interior. Much of the North Slope was hot too, except where a cooling sea-breeze keep it more pleasant.

Highs include:
Umiat: 80F
Ivotuk: 77F (SW of Umiat)
Inigok: 76F (NW of Umiat)
Atqasuk: 74F
Wainwright: 73F
Point Lay: 72F
Marsh Creek: 71F (SE of Prudhoe Bay)
Nuiqsut: 70F
Ikpikpuk: 68F (well NW of Umiat)

Barrow held at 56F thanks to the sea-breeze. 900' up on the 00Z RAOB it was 66F.

More Heat Numbers

The high temp of 92F in North Pole on Sunday is a new August record. The previous record high was 90F in 1994 . Max temp at Denali National Park HQ was 81F, probably a daily record.

Other highs from the Fairbanks area:

Aurora: 92F
Ester: 91F
Chena Hot Springs: 91F
Goldstream Creek: 90F (CWOP site had 94F but that's a different thermometer, close to the house)
Mile 42 Steese: 88F
Keystone Ridge: 84F (highest August temp in 15 years of records)
Ester Dome: 81F (2200' MSL)

Montana Creek DOT 84F (2100' MSL)
Cleary Summit 84F (2200')

Recod Heat Update

930pm ADT update:
91F Fairbanks
90F Eielson AFB
90F UAF West Ridge (College Observatory)
86F Fort Greely
86F Tok
85F Northway
83F Bettles

All are record highs for the date and hottest so late in the summer except Tok, which has a couple of days with 86F later in August.

85F at Nenana was one degree shy of the 1923 record of 86F for the date.

COOP obs: 92F at Aurora in Fairbanks, 88F at Kobe Hill north of Healy and at Chena Ridge.

Records Falling

530pm ADT: Here's the RAOB

500pm ADT: 91F at Fairbanks, hottest ever so late in the season. 850mb temp +19.0C, warmest of record for August. 86F at Fort Greely, a new daily record.

2PM ADT: Eielson AFB 88F, Fairbanks 87F, and Northway 82F are all daily records. Eielson is the hottest this late in the summer (data since the early 1940s).

Return of the Heat

There is going to be a lot to talk about today, but for starters, overnight lows at elevation and breezy spots widely in the 60s overnight. THE Antler Creek RWIS, between Healy and Denali National Park was 70F at 5am with winds gusting to 35 mph. The low of 59F at Fairbanks Airport was one degree above the record high min of 60F set in 1974.

Fairbanks 850mb temp at 12Z +15.2C, 500mb height 578dm, freezing level 11.4K. No records but getting close.

Picture's worth a Blog

Imformative IR GOES-West image from Saturday evening; well-defined storms and associated fronts that are bringing rain and winds to western Alaska, with the hot ridge to the east. Yet another sign of things to come.

Damp in the Big Town

Anchorage has evidently set a new record for consecutive days with precipitation: as of today 28 days straight days with a trace or more of rain. I say evidently, as there seems to be some confusion as to whether the NWS Forecast Office at Sand Lake (just south of ANC International Airport) or the ASOS at the airport is the "official" Anchorage site. The Anchorage forecast office thinks they are; NCDC is using the ASOS. In any event, it has been damp in the Big Town. The Fairbanks record is also is also 28 consecutive days.

Sign of the Times

Midnight last night, from the Alaska Climate Research Center webcam lookign south from UAF West Ridge.

Late Season Heat

The numerical guidance is united in forecasting at a one or two day hot spell this weekend, with Sunday being the hottest day...with highs well into the 80s. So what's the history of late season heat in Fairbanks? Well, the temperature has been 85F or above exactly six times August 15th or later, most recently in 1977. The highest is 90F, is August 20, 1923. While I'm skeptical of much of the pre-1930 data for Fairbanks, this one looks plausible, with most sites in the Interior reporting highs in the mid 80s for that event.

Porcupine River Crest

The Porcupine River, the largest tributary of the Yukon, has been running high for weeks now. The recent crest at the gauge near the Alaska/Yukon border is the highest non-break-up related crest in more than a decade. Here is the hydrograph from the Alaska-Pacific RFC showing the crest on Wednesday.

The Little August that Couldn't

Since the end of the heatwave late in the 3rd, it has rained every day but one, just like August is “suppose to be”. But wait…precip is less than half of normal for the first 10 days of the month. Why? Rainfall amounts have been consistently very light almost everywhere. At the airport, 7 of the past 8 days have had rain, totaling a whopping 0.24". Here at Keystone Ridge, just 0.31".

The Bane of Summer

Now that the heat wave is behind us…

Until like most areas in mid-latitudes, the solar forcing on Interior Alaska temperatures is dominant enough to keep August from ever being the warmest month of the summer. The histogram at the left shows that the warmest Augusts are warmer than the coolest Junes and Julys, but it turns out that warm Augusts tend to follow warm Julys (1930-2009 correlation of 0.46). This is quite different than in winter, when there is no statistically significant month to month temperature correlation.

Warm Tidbits

Odds and ends from the heat wave just ended...

The low of 63F on Monday (Aug 2) at Fairbanks Airport is the warmest Weather Bureau/Weather Service era (1930-present) daily low temperature in August. A low of 64 was recorded Aug 16 1912.

Keystone Ridge hit 80F Wednesday...making this the warmest temp of the summer. This is the first time in 15 years of obs that the high for the summer was in August.

July Precip around Fairbanks

Precip was highly variable in July: Here are some observed values as a percentage of normal:

45% at Munson Ridge, south of Chena Hot Springs at 3100'MSL
61% at Salcha
67% at Monument Creek near Chena Hot Springs
85% at North Pole
100% at Eielson AFB and Keystone Ridge
121% at College 5NW, above Goldstream Valley
174% at UAF West Ridge
180% at Fairbanks airport.

If there were normals at Fairbanks Midtown they would probably be around 200%!

Warm night in the Arctic

Barrow celebrated the first sunset of the summer with a very mild night…low temp just 51F. Even warmer away from the relatively cold water, with a low of just 56 at Umiat and 59F at Atqasuk.

All this brought about by the warm winds from Siberia. At least the smoke as cleared out!

Smoke over NW Alaska

From the fine folks at GINA

http://www.gina.alaska.edu/data/gina-modis-images/


Here is a MODIS image from Sunday afternoon showing a large slug of Siberian smoke over the Chukchi Sea and inland into NW Alaska. NWS Barrow reports a smoke smell is evident as of early Sunday evening.

Inversions and Diurnal Ranges

With growing early morning inversions, diurnal ranges in the nighttime cool spots are growing too. Amongst the cooperative observations, Clear Sky Lodge, on the Parks Highway south of Anderson had a 40F spread on Saturday, 42F to 82F, and Chena Hot Springs made 81F Saturday, then back to 43F this morning. Goldstream Creek still looks like it's running a bit too warm for max temps, but for what it's worth, 86F Saturday, down to 43F this morning. Some RAWS have even bigger spreads, but these are artifacts of the too warm temps that RAWS run on brite sunny summer days.

In contrast, higher elevation ridge and slope sites are running diurnals of 20F or less. Here on Keystone Ridge, 78F Saturday, down to 58F this morning. The Nenana Hills RWIS at 1400' MSL had 78F Sat, 62F this morning, and the Cleary Summit RWIS, at 2200', had 75F Sat, 62F this morning. Note though that on RWIS platforms the thermometer is 10-15' above the ground.

Above is a plot of temperatures from Keystone Ridge and Goldstream Valley Bottom over the past day, illustrating the difference. Note that later times are too the left.