Incoming Storm

GOES 11 IR image at 730pm ADT Thursday with a nice view of the rapidly deepening storm in the Gulf of Alaska...forecast to deepen below 960mb Friday morning. This will pump more warm air into the Interior.

Yukon Freeze Up

The chinook busted through Thursday afternoon in Fairbanks, but on the other side of the Yukon-Tanana uplands it remained chilly. This photo late in afternoon from Beaver (viathe FAA webcam), with a slough of the Yukon River icing up.

Cold in the Interior

Everything I know...

PUBLIC INFORMATION STATEMENT...CORRECTED
NATIONAL WEATHER SERVICE FAIRBANKS AK
541 PM AKDT TUE SEP 28 2010

...UNUSUALLY COLD TEMPERATURES IN INTERIOR...

...WARM-UP ON THE WAY...

TEMPERATURES THIS MORNING WERE UNUSUALLY LOW FOR SO EARLY IN THE
AUTUMN OVER ALL OF INTERIOR ALASKA. THERE WERE NUMEROUS REPORTS
OF LOW TEMPERATURES BELOW ZERO...AND A FEW RECORDS WERE SET.

THE LOWEST TEMPERATURES WERE REPORTED FROM AUTOMATED WEATHER
STATIONS ON THE YUKON FLATS. A STATION ALONG BEAVER
CREEK...BETWEEN BIRCH CREEK VILLAGE AND BEAVER VILLAGE REPORTED A
LOW OF 11 BELOW...AND AN AUTOMATED STATION BETWEEN FORT YUKON AND
CHALKYITSIK REPORTED 10 BELOW. OTHER LOW TEMPERATURES TUESDAY
MORNING IN THE INTERIOR INCLUDE...

CHICKEN......................................................5 BELOW
CIRCLE HOT SPRINGS.............................5 BELOW
SEVEN MILE DOT (DALTON HIGHWAY).........5 BELOW
DENALI VISITORS CENTER..................4 BELOW
CENTRAL....................................................2 BELOW
BIRCH CREEK (ABOVE THE STEESE BRIDGE)...2 BELOW
BOLIO LAKE (NEAR FORT GREELY)...........2 BELOW
HEALY AIRPORT.............................................ZERO
CHENA HOT SPRINGS...................................ZERO
BETTLES...........................................................ZERO
DRY CREEK.....................................................2 ABOVE
COLDFOOT.........................................................3 ABOVE
FORT YUKON....................................................3 ABOVE
ARCTIC VILLAGE...........................................5 ABOVE

IN THE FAIRBANKS AREA...MOST NOTABLY...THE LOW OF 3 ABOVE AT
EIELSON AFB IS THE LOWEST SEPTEMBER TEMPERATURE OF RECORD
THERE...BREAKING THE PREVIOUS RECORD OF 5 ABOVE SET ON
SEPTEMBER 27 1992.

THE LOW OF 14 ABOVE AT THE AIRPORT...WHILE NOT A RECORD...IS THE
LOWEST SEPTEMBER TEMPERATURE SINCE 1993.

AN AUTOMATED WEATHER STATION ABOUT 15 MILES ABOVE THE RICHARDSON
HIGHWAY BRIDGE ON THE SALCHA RIVER REPORTED A LOW OF 4 BELOW.
OTHER LOW TEMPERATURES TUESDAY MORNING IN THE FAIRBANKS AREA
INCLUDE...

GOLDSTREAM CREEK........................ZERO
GILMORE CREEK...........................5 ABOVE
CHATANILA (MILE 42 STEESE)..............5 ABOVE
NORTH POLE..............................6 ABOVE
EAST FORT WAINWRIGHT....................6 ABOVE
UAF WEST RIDGE.........................11 ABOVE
COLLEGE 5NW (GOLDSTREAM HILLS).........16 ABOVE
KEYSTONE RIDGE.........................20 ABOVE

TONIGHT WILL NOT BE QUITE AS CHILLY IN MOST PLACES...AND MUCH
WARMER WEATHER WILL RETURN TO INTERIOR ALASKA DURING THE NEXT FEW
DAYS AS A SERIES OF STORMS MOVING THROUGH THE GULF OF ALASKA PUMP
MILD AIR BACK INTO THE REGION.

$$
RT SEP 2010..

Point Lay Sunset

Snow showers Monday evening over the Chukchi Sea at Point Lay.

Tastes of Winter

A few flurries in the Fairbanks area Sunday. Monday morning low temperatures mostly teens and lower. The low of 19F at Keystone Ridge is the second earliest sub-20 degree temperature in 15 years of observations. The low of 16F at Fairbanks airport is the lowest September temperature since 1993, and the more remarkable with the lack of snow cover today. The cold spots were in the single digits, with 6 above at Goldstream Creek and Chatanika (Mile 43 Steese). The lowest reported temperature in the area was 3 above at the Angel Creek RAWS, near Chena Hot Springs. This site, though on the valley bottom, is not usually a cold spot as there is often a downvalley drainage wind here that breaks the inversion. Not this morning though.

Apparently one record low this morning: 0F in Bettles breaks the old record for Sept 27th of +6F set in 1957 and ties the record low for September. Again all with no snow on the ground.

There also was some snow Sunday in the Anchorage area, including at least a small accumulation on the hillside

Brooks Range Snow

FAA webcam photos from Anaktuvuk Pass (top) and Arctic Village (bottom) this morning. The snow cover at Arctic Village is from the snow Saturday evening. Anaktuvuk has had some snow cover for a few days now.

Surf's Up

6pm Saturday webcam photo from Barrow. Surf's up and a fresh dusting of snow. West wind gusting to 40 mph and pack ice hundreds of miles north and northwest. Note the seaward berm the city has plowed up. Coastal Flood Warning in effect until 6am Sunday.

The 10am ADT Saturday surface analysis from Environment Canada shows the storm northeast of Barrow and the high building across the northern Siberia coast into the Chukchi Sea. This is a classic set-up for Barrow coastal flooding.

First subzero temps of the season

Updated:
Beaver Creek RAWS (Southwest of Fort Yukon) reported a low of 5 below this morning, and the Chalkytisk RAWS (actually half way between Fort Yukon and Chalkytisk) had -3F, and Circle Hot Springs Coop 0F.

In the greater Fairbanks area, winds died off in some, but not all valley locations. Where winds went calm, lows included +2F at the SalchaRiver RAWS, 11F at Chatanika (Mile 43 Steese) and 13F at Goldstream Creek and Birch Lake DOT. Valley locations that kept a wind were mostly in the 20s, including at least some of the usually colder North Pole area sites.

Also, this morning was the first RAOB to be completely below freezing.

Freeze by Day

Looks like many places above 2000' MSL failed to get above freezing today: Eagle Summit 23F, MunsonRidge & Montana Creek DOT 29F, Upper Chena Dome 30F, Cleary Summit 32F. With dew points near 10F and a steady wind, here on Keystone Ridge (high 35F) the puddle at the slop pile never thawed.

Sunshine

So today is the 15th straight day with no precipitation and either clear or mostly clear skies. Such streaks occur in late winter, but it seems quite unusual in the warm season. With the advent of the ASOS as the source of surface observations in December 1996, there are no longer reliable or continuous sky cover statistics, but this is certainly unusual.

More on the Big Plunge

Here's a graphic of the 925 mb temp (typically about 2200' above the ground this time of year) during the mega-ridge and the dramatic change Tuesday night. It's not much hyperbole to say that summer ended at 530pm Tuesday.

Freeze at Last

The Fairbanks Airport made it to freezing late Wednesday evening, so the date of first freeze goes into the books as Sept 22nd, two weeks later than normal and tied for 4th latest of record. Over the past 5 years, the dates of first freeze are:

2006 Sep 25
2007 Sep 21
2008 Sep 21
2009 Sep 23
2010 Sep 22

During this time there have been no instrumental or exposure changes.

What a Differnce a Day Makes

Clear skies and bright sunshine, and…
Fairbanks Airport Tuesday max temperature 64F, Wednesday 48F
McGarth Road (1170' MSL) Tuesday max temperature 60F, Wednesday 43F
Keystone Ridge Tuesday max temperature 55F, Wednesday 39F

End of Summer

Summer in Fairbanks ended late Tuesday afternoon when the dry, cloud free cold front blasted thru the area. Temperatures aloft have fallen quite dramatically, and most higher elevations are now below freezing. The low of 29F here on Keystone Ridge is the first freeze of the autumn. Combined with 15 to 35 mph winds, it feels like autumn too.

Meanwhile, most valley locations are no colder than recent mornings, thanks to the breeze and so little inversion. Fairbanks Airport still hasn't been to freezing, though I suspect that will occur this evening.

Frosty Morning

Frosty webcam shot late Tuesday morning from Ivotuk, southwest of Umiat in the foothills of the Brooks Range.

Snow

Flurries the past 24 hours at Deadhorse and Kaktovik. Freeze coming for Fairbanks. Is this the end of summer?

More record high temps

Updated:
High temperatures of 60F at both Nome and Kotzebue Sunday are new records for Sept 19th. The mega-ridge lives.

McGrath Heat

The big ridge aloft that has brought more than a week of sunny and warm weather to much of the Interior is drifting westward and weakening. McGrath set or a tied a record high every day Sunday through Friday. The five days this month in the 70s in McGrath is the most ever in September.

Denali Sunrise

I just can't resist another gorgeous Denali sunrise shot at 816am Saturday, from the NPS webcam at Wonder Lake:

Endless Summer

Snow Friday evening in Bismark, ND, snow on Mt Washington, NH, and Fairbanks awaits the first freeze. So it is with life under the mega-ridge. Notice the nearly continuous above normal temperatures since late July.

Persistant Inversion

Here's a plot of daily high and low temperatures for three different locations in the Fairbanks area since the big ridge build in over the weekend. With clear skies and no wind to speak of, every night radiationally cooled air pools in the valleys, and each afternoon the sunshine is still strong enough to mix out the morning inversion. As a result, valley bottom locations have big diurnal ranges (46 degrees Wednesday at Goldstream Valley Bottom), while the high elevation sites have much smaller ranges (13 degrees Wednesday at Keystone Ridge). So, it's not there is so much heating from the sun that it raises the temperature by 40 some degrees; rather, the heating is enough to mix down the warm air that is lying just above the surface. The overall heating is reflected in the high elevation diurnal ranges: 15 degrees or less with 100 percent of the 13 hours of possible sunshine.

Fires and fog

Fires continuing to smolder away on the Yukon Flats, and dense fog engulfing Cook Inlet show up beautifully on this 148 pm Wednesday NOAA-18 visible image, with the mega-ridge providing wonderful clear skies.

Big Ridge

Here's a plot of 500 mb heights at Fairbanks and the morning inversion strength since the big ridge aloft built in. The inversion strength is simply the warmest temperature in the boundary layer minus the surface temperature. This is a simple but useful way to quantify the inversion strength. This morning's 11.8C is the strongest of the event so far. On the ground, lows range from the lower 20s (Salcha River RAWS) to the lower 50s (most automated sites above 2000' MSL)

Apparent Arctic Sea Ice Minimum

The National Snow and Ice Data Center has tentatively called the Arctic sea ice minimum for 2010 as 4.76 million sq. km on September 10th. It is possible that this could dip lower, but given that nearly all of the sea ice is north of 75N, this is probably the minimum. This is the third lowest extent of Arctic Sea Ice in the satellite era (since 1979), and about seven percent lower than last summer's minimum of 5.10 million sq km.

Record Highs

Three record high temperatures Monday in the west and central Interior: 69F at Tanana breaks the old record of 67F set in 1965, Galena's 69F broke the record of 66F also set in 1965 and McGrath had 71F, breaking the previous record 68F in 1968.

Strong Inversion

Inversions having been growing under the big ridge aloft the last few days. This morning's sounding has an inversion strength of 11.0C (20F) in 391 meters (1282 ft). The lowest few hundred meters will mix out this afternoon.

Latest "First Freeze" at North Pole

North Pole's long term climate site finally got down to freezing Sunday morning (after a low of 33F August 22nd), with a low of 30F. This is the first freeze of the season there, and is by four days the latest first freeze in the autumn in 42 years of records. The previous latest first freeze was September 8, 1990. The histogram at the left shows the distribution of first freeze dates at North Pole. The growing season (number of days between freezing temperatures) this summer of 118 days is the longest of record in North Pole, 10 days more than the 1990 season. Other lows so far this autumn include 33F at UAF West Ridge, 34 at the Experiment Station, 35F at the Airport, and 39F on Keystone Ridge.

Frosty Morn

This was the frostiest morning in the valley thus far this autumn, with some frost on lawns even in urban Fairbanks. Leaving work at 7am there was a bit of frozen dew on the car windshield. Most valley stations had the lowest temperatures thus far season: Fairbanks Airport 35F, UAF West Ridge 33F, Goldstream Creek 26F, Salcha River RAWS 22F. North Pole finally made it to freezing, with a low of 30F, the latest first freeze there in more than 40 years of records. The frosty photo is from the corner of Murphy Dome and Sheep Creek Roads about 725 am.

Meanwhile, under the warm ridge, temperatures at elevation remain balmy: low of 47F here on Keystone Ridge, and the Caribou Peak RAWS, at 2500' MSL north of Chatanika, had a low of 50F.

The power of the ridge

POES-19 image from 240 pm ADT Saturday. The lack of any appreciable snow cover of the Brooks Range this late in September is unusual. Also note there is a smoke plume from the Pat Creek fire, just north of the Yukon River near Stevens Village. Temperatures on the North Slope are extremely mild; through 3pm, Atqasuk, south of Barrow, has been up 60F, in the upper 50s at Deadhorse., and 66 at the Umiat RAWS. The record high at Barrow today is 60F, which is probably out of reach but still, pretty warm for this late in the season.

Another Upper Tanana Deluge

Wednesday night and Thursday brought another heavy rain event to the Upper Tanana Valley. The cooperative observer at Tok reported 1.46 inches of rain, which is the highest daily precip of record for September in Tok. The previous record was 1.33 inches on Sept 2, 2001. Northway, with 0.84 inches of rain, set a new record for the calendar day of Sept 8th. Happily, there was not much rain on Taylor Highway, with less than a quarter inch at Chicken.

More on First Freeze

Here is a plot of the past 40 years of the first date in the autumn at the Fairbanks Airport (bottom) and North Pole (top) with a low temperature at or below freezing. The black line is the five year running average. So the lack of a freeze at the Airport is not unusual yet, especially given that in the past four falls the first freeze didn't occur until after September 20th. However, the lack of a freeze at North Pole this late is unprecedented. Also note the lack of correlation in the dates and trends!

Overnight Soaker

Heavy showers moved through the Fairbanks area late Tuesday evening and early Wednesday. The ASOS at airport recorded 0.98" between 10pm and 4am. So far no other site has reported quite that much; 0.62" at Keystone Ridge, 0.58" near College and University, 0.54" at UAF West Ridge, when generally less than 0.40" in the North Pole and Eielson AFB areas.

This amount of rain in such a short time of time (0.72" at the airport in just two hours) is quite unusual this late in the season, but there was a lot of moisture available. The afternooon RAOB Tuesday had 1.03" of precipitable water, and dew points got up to 56F early Tuesday evening, before the rain started in earnest.

Update:
The maximum 24 hour rainfall at the Airport of 1.05" Sept 7-8th appears to be the third highest September since 1930.

Arctic Sea Ice update: Now third lowest

The National Snow and Ice Data Center reported that as of Sept 3rd the sea ice coverage in the Arctic was now lower than any point in 2009 and the third lowest of record (since 1979). As of Sept 6th, about 5.0 million sq km of ice, about 2 million below the late 20th century average. The annual minimum coverage will probably be in the next week or two.

CPC Plots

From our friends at the Climate Prediction Center, some useful plots of temperatures the past three months. With the ice pack hundreds of miles north of Barrow, I expect Barrow to get a lot more "red" in the next eight weeks.

Lack of freezing becoming significant

While the coolest valley spots are now regularly dropping below freezing on clear nights, of the long-term climate sites in the Fairbanks area only Eielson AFB has reached 32F. At North Pole, the low so far has been 33F, which makes this now the latest "first freeze" of record there (data since 1969). Both the Experimental Station and College Observatory have had multiple days with lows in the mid 30s, but again no freeze. For both these sites the median date for the first freeze is around Sept 1. The median date for the first at the airport is approaching, but no sign yet of any freeze outside of the low spots.

Another factoid:

The last freeze at Eagle Summit, 3650' MSL, was May 14th

Golden Autumn

A view from Fort Yukon Friday afternoon, showing the golden birch.

Cooling off

This morning's POES IR imagery (610AM ADT) shows a fair amount of clear skies over Interior Alaska, and with the rapidly lengthening nights, this can only mean one thing…down go the temperatures.

Subfreezing minimums are now routine in the cold valley bottom locations: 28F this morning at Goldstream Creek, and 22F at the Beaver Creek RAWS on the Yukon Flats. Even the "routine" valley places are getting colder: 31F at Eielson AFB, 35F at UAF West Ridge, and even Fairbanks International dipped to 38F, the first sub-40F temperature this autumn. It's pure radiative cooling: 850 mb temp +5.0C this morning on the Fairbanks RAOB and higher elevation min temps were well up in the 40s: 45F here at Keystone Ridge and 48F at Clearly Summit.

Summer Review: Rain

The climatological highlight for Summer 2010 in Interior Alaska must be the extreme rainfall over the upper Tanana Valley and Fortymile country in late June and July and the attendant flooding.

Northway measured 13.85" of rain June through August. This is almost 2 and half times normal, and is 4" more than the annual normal! This by far the wettest summer of record in Northway. Eagle, with 10.09" of rain also recorded the wettest summer of record. The flooding on the Fortymile River in July was the greatest of record, and the Taylor Highway beyond the Top of the World Cutoff was closed more often than open due to mudslides and the roadbed simply sloughing away.