Warm Day up North

Photo courtesy of the FAA

Temperatures Tuesday made it into the 70s almost right to the Beaufort Sea coast. High temperatures included 74F at Deadhorse and Kuparuk, 73F at Nuiiqsut and 72F at Alpine. Colville Village, north of Nuiquit, held at 69F. Continued southwest winds kept the offshore wind going overnight, so overnight lows were mostly in the 50s. The photo from Deadhorse this morning shows lots of water showing up on the Prudhoe Bay area lakes.

Wonder Lake View

Nice photo of Denali from the near the Wonder Lake rangers station Tuesday morning. Photo courtesy of the National Park Service.

Arctic Sea Ice

Sea ice coverage in the Arctic Basin was pretty close to normal during the spring, but has been decreasing much faster than usual the past several weeks. To the right below is the Alaska-centric view of coverage as of Monday, June 18th. Notice that the Bering Sea is nearly ice free now. On the left is the plot of total areal coverage from the National Snow and Ice Data Center, illustrating the dramatic decrease since the end of May, and is a result of so much of the Arctic sea ice now being first year ice, that is, ice that formed this past winter, which is not very thick and susceptible to summer melt.This is evidently the lowest total sea ice coverage for mid June in the satellite era (1979-present)

Courtesy of the University of Illinois

Courtesy of NSIDC

Nice photo Saturday afternoon from the Ester Dome webcam, looking southeast across town and the Flats, with a flat topped cumulus producing some light rain down toward North Pole. Image courtesy of the FAA.

Fairbanks Temperatures

Here's an update on Fairbanks temperatures, with my preferred standardized anomaly plot. The three to four week cycle that temperature  followed over the winter has, as expected, somewhat broken down. The chart also illustrates that the warm weather earlier this month (mean temperature of 69F on the 8th), was, relative to the typically variability for a given time of year, the farthest above normal for any day this year.

Catching Up

Back in town. Some highlights:

Keystone Ridge had 16 days in May with exactly a trace of precip. Only eight days with measurable precip.

As of Thursday morning, Jun 14, total acreage burned in Alaska so far is just of 33,000 acres.

More to come as I get caught up.

Even Bigger Lightning Day

This has been an active week for thunder, with Monday being the first day of the season with more than 1000 strikes. Tuesday was even more active, with more than 4000 strikes in the Interior, with many fire starts.

Traveling

I'm traveling for a couple weeks so posting will be light o rmaybe none, depending on connectivity issues.

First Big Lightning Day

The thunder season has gotten off to an early, but otherwise slow start. Up until Tuesday, there had not yet been a day with even 100 strikes state-wide. That changed big-time Tuesday as a strong trough aloft touched off more than 700 strikes, most of them in an arc from Old Crow, YT southwest to the Nulato Hills. The trough passed through Fairbanks-land mid-AM, too early to touch off thunder. There were very few early afternoon in the uplands north of the Steese Highway. This is the latest date for the first 100 strike day since 2001.

High Water Follow-up

Here's an update on the high water over the holiday weekend. At the left are Monday morning hydrographs for the upper Chena and lower Salcha Rivers. The peak stage Saturday on the Salcha was the highest stage in four years, and on the Chena the highest since 2003. The Chena at Fairbanks crested Sunday at 6.4 feet, which is notable mostly in that it's a five foot rise since last week.

It's a Soaker

 May only rarely brings soaking stratiform rains that send Interior Rivers out of their banks, but this is one of them. Here is the Saturday morning hydrograph from the Chena River near the Mile 40 Bridge. In addition to much more rain than anticipated, this rain also accelerated high elevation snowmelt. At the Munson Ridge SNOTEL, at 3100' MSL south of Chena Hot Springs, there was still a snow depth of four inches being reported Friday morning, which is now down to one inch, which is at the noise level. Fairbanks Airport set a new precipitation record Friday with 0.52 inches of rain.

Other rain amounts in the area include
Salcha River RAWS: 1.23 inches
Mile 40 Chena Hot Springs Road: 0.99 inches
Birch Lake RWIS: 0.94 inches
Woodsmoke near North Pole: 0.77 inches
Fort Knox Mine: 0.70 inches
Keystone Ridge: 0.68 inches
Aurora: 0.62 inches
Fairbanks Mid-town: 0.59 inches

Summer Rains

It's a sure sign on summer when I start posting hydrographs. Here is the plot of observed and forecast stages on the Salcha River at the Richardson Highway bridge. Water levels have been rising in response to showers the last few days, and will rise more with the steady rains today. Since late Thursday evening, rainfall amounts of a quarter to one inch of rain has been common, with the highest amounts east of Fairbanks and the lowest west of town.

Rain

After two weeks of sprinkles, most parts of Fairbanks-land received measurable rain Wednesday from showers. However, as expected in showery precipitation, amounts were highly variable. Photo from Thursday morning looking south from UAF West Ridge, courtsey of the Alaska Climate Research Center

Rainfall Wednesday included:

Keystone Ridge: 0.28 inches
UAF West Ridge: 0.20 inches
Fort Knox Mine: 0.17 inches
Goldstream Creek: 0.15 inches
Fairbanks Airport: 0.04 inches
East Farmers Loop: 0.02 inches
Aurora: 0.02 inches
Eielson AFB: 0.01 inches
North Pole: Trace

First 70 in Fairbanks

Fairbanks Airport made 70F today for the first time this year. This is exactly the average date (1930-2011) for the first 70º temperature.

Winter Hangs on

Temperatures are warming up across northern Alaska and snow cover is starting to go at low elevations even on the North Slope and Bering and Chukchi Sea coasts. Not so much yet though at higher elevations in of the Brooks Range. The photo at the right taken Sunday morning is from Ivotuk, southwest of Umiat at about 2000 feet elevation.

Warming Up

Temperatures so far this this month have been significantly below normal, as the updated standardized daily temperature anomaly chart at the left shows. Through Wednesday, the high temperature at the Fairbanks Airport for the spring has been 61º on April 16th and again on May 12th. However, that's set to change as the first really warm weather of the season is in the cards, as high pressure aloft builds and has already put an end to the daily convection. Over the past 80 years the mean date for the first 70º temperature in Fairbanks is May 21st, and this year will be very close to that date. 

Cool May Morn

Temperatures fell overnight as skies cleared and the airmass remains on the cool side. Low temperatures Monday morning were near or below freezing in much of Fairbanks-land, including

Updated...
Goldstream Creek: 22F
Eielson AFB: 28F
UAF West Ridge: 28F
Fort Wainwright: 30F
Fairbanks Airport: 30F
Keystone Ridge: 32F
Cleary Summit: 35F
 (Photo Monday morning courtesy of the Alaska Climate Research Center)

The snowpack is getting pretty dirty at Barrow, as this late morning photo  from the UAF Sea Ice groups shows. it's been a cool spring in Barrow, with the temperature the first nine days of May averaging 8 degrees below normal. On the bright side, Barrow had their last sunset of for the summer last night at 12:59am. The next time the sun goes below the horizon at Barrow will be at August first at 220am

Thunder in Fairbanks

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
706 PM AKDT SAT MAY 5 2012
 ...THUNDER AT FAIRBANKS AIRPORT...
...EARLIEST IN 28 YEARS...

A 20 MINUTE THUNDERSTORM AT THE FAIRBANKS AIRPORT EARLY SATURDAY EVENING WAS THE EARLIEST THUNDERSTORM OF THE SEASON SINCE 1984...WHEN THERE WAS A THUNDERSTORM ON MAY 3RD. THUNDER IN THE FIRST HALF OF MAY IS NOT UNCOMMON OVER THE HILLS NORTH AND EAST TOWN...BUT IS QUITE UNUSUAL TO OCCUR SO EARLY IN THE SEASON IN THE FAIRBANKS BOWL. REPORTS OF UP TO ONE TENTH OF AN INCH OF RAIN AND SMALL HAIL HAVE BEEN RECEIVED FROM AREAS ON THE EAST SIDE OF TOWN. $$ RT MAY 2012

(Photo from the FAA's Ester Dome webcam looking southeast at 554pm ADT Saturday)

Chilly on the North Slope...but...

Low temperatures Saturday morning on the North Slope were nearly or a bit below zero, including zero at Barrow, 2 below at Kaktovik and 8 below at Anaktuvuk.

How unusual is this? Not at all. Over the past 50 years, the average date of the last zero temperature in the spring at Barrow is May 3rd.

Webcam photo looking northeast from the Barrow Airport, courtesy of the FAA.

Precip Type in Dry Air

Friday afternoon and evening brought convective showers to Fairbanks-land. However, with a dry and still cool-ish airmass in place, the form of the (light) precipitation that did occur was perhaps not as might be expected. There were a few reports of light rain in the Fairbanks bowl. However, snow was reported near the Chatanika River on the Elliott Highway, below 800 feet elevation. Here on Keystone ridge, it snowed between 330pm and 4pm, with temperatures no lower than 38F. Unsurprisingly, light snow was also reported on Wickersham Dome, elevation 2600 feet.

The graphic shows a plot of the 00Z May 05 Fairbanks upper sounding (heights are in geopotential meters: for practical purposes, just think of the y-axis as in meters). The freezing level was over 3000 feet above the ground. However, the elevation of the "wet-bulb zero" (the elevation that if you saturate the air the temperature would be at freezing) was only 1400 feet above the ground. In at least some of the precipitation shafts, the air was not saturated, allowing snow to fall perhaps as much as 2500 feet below the nominal freezing level.

Spring in the Brooks Range

Noontime Friday photo from Chandalar DOT Mile 239 on the Dalton Highway at 3000' elevation , courtesy of the FAA. With high temperatures below freezing, snowmelt has a long ways to go in the central Brooks Range.

Here's an update of the 2012 standardized temperature anomaly chart for here on Keystone Ridge. The mean temperature Wednesday of 21F was 2.5 standard deviations below normal, the most for any single day since the coldsnap before Thanksgiving. On Tuesday, Fairbanks Airport set a new record low max temperature of 32F.

It's a cold May morning in Interior Alaska, with most places having low temperatures in the teens and lower 20s. Here on Keystone Ridge the low 11F is the lowest temperature in 16 years of record here and probably the lowest May temperature since 1992. Other lows include: 15F at Goldstream Creek, 19F at UAF West Ridge, 19F Mile 43 Steese Highway, 21F at Fairbanks Airport and 22F at Fort Wainwright. Webcam photo from Bettles Tuesday morning, courtesy of the FAA

More on April

As Corey noted in the April summary, this was 13th warmest April of record. This was mostly due to the persistence mild weather, with the warmth mid-month being the only really outstanding daily anomaly. Here's a plot of daily high temperatures in April, normals and the daily departure from normal. From the 18th through the 29th there was hardly any daily to day change in the actual high temperature. However, because normals are rising steadily, overall the departure from normal lowered with time.

And below is a plot of the mean April temperatures in Fairbanks over the past century. The linear regression for the full period 1905-2012 (not plotted) shows an increase of about 5 degrees AND is statistically significant. However, nearly all of that trend has come since the PDO shift in 1976. There is no significant trend from 1905 to 1976.

April Summary

PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE FAIRBANKS AK 451 AM AKDT TUE MAY 1 2012 ...APRIL WEATHER SUMMARY FOR FAIRBANKS... ...MILD AND DRY... FOLLOWING A COLD MARCH...APRIL CONTINUED THE TREND OF THE LAST 6 MONTHS OF ALTERNATING COLD AND WARM MONTHS AND WENT INTO THE RECORD BOOKS WITH WELL ABOVE NORMAL TEMPERATURES. THE AVERAGE TEMPERATURE OF 36.9 DEGREES WAS 4.4 DEGREES ABOVE NORMAL. IT ENDED UP AS THE 13TH WARMEST APRIL ON RECORD AT FAIRBANKS. THIS CONTINUED A RECENT TREND OF WARM APRILS. SIX OF THE WARMEST 10 APRILS HAVE BEEN OBSERVED SINCE 1990. FOR THE MONTH...THE AVERAGE HIGH TEMPERATURE AT THE AIRPORT WAS 50 AND THE AVERAGE LOW WAS 24. THE HIGH TEMPERATURE FOR THE MONTH OF 61 DEGREES WAS OBSERVED ON THE 16TH AND THE LOW FOR THE MONTH OF 8 BELOW OCCURRED ON THE MORNING OF THE 4TH. TWENTY-SIX OUT OF 30 DAYS THIS PAST APRIL HAD TEMPERATURES THAT WERE ABOVE NORMAL...WITH THE ONLY COLDER THAN NORMAL WEATHER FROM APRIL 2ND TO 4TH AND ON THE 30TH. THE WARMEST TEMPERATURE DEPARTURES FROM NORMAL OCCURRED AROUND MID MONTH...AND ON THE 16TH THE HIGH OF 61 DEGREES ESTABLISHED A NEW RECORD HIGH FOR THE DATE SURPASSING THE OLD RECORD OF 59 SET IN 1993. IT WAS ALSO THE EARLIEST 60 DEGREE TEMPERATURE AT THE AIRPORT SINCE 1997. THERE WERE 19 DAYS WITH A HIGH TEMPERATURE OF 50 DEGREES OR WARMER...WHICH WAS WELL ABOVE THE AVERAGE OF 11 DAYS. THE PERSISTENTLY MILD WEATHER COMBINED WITH PLENTY OF SUNSHINE TO MELT OUT THE SNOW PACK QUITE RAPIDLY. THERE WAS 20 INCHES OF SNOW ON THE GROUND ON THE MORNING OF THE 9TH THAT ALL MELTED AWAY BY THE 20TH. THE LAST DAY WITH AN INCH OR MORE OF SNOW ON THE GROUND WAS THE 19TH...WHICH WAS JUST 3 DAYS SHY OF THE AVERAGE DATE FOR THE LOSS OF THE WINTER SNOW PACK...WHICH IS APRIL 22ND. THERE WAS AN INCH OR MORE OF SNOW ON THE GROUND FOR A TOTAL OF 184 DAYS THIS WINTER...WHICH WAS ONLY 2 DAYS SHY OF THE LONG TERM AVERAGE. THIS PAST APRIL WAS DRY WITH ONLY 7 HUNDREDTHS OF AN INCH OF RAIN WHICH INCLUDED A TRACE OF SNOW AT THE AIRPORT. THE 7 HUNDREDTHS OF AN INCH OF RAIN WAS NEARLY A QUARTER INCH BELOW NORMAL...BUT DID NOT RANK AS ONE OF THE DRIEST APRILS ON RECORD. THERE HAVE BEEN MORE THAN 20 APRILS OVER THE YEARS WITH 5 HUNDREDTHS OF AN INCH OF LESS OF RAIN (AND MELTED SNOW). THE LACK OF PRECIPITATION WAS NOT LIMITED TO THE VALLEY AS MOST HIGH ELEVATION SITES AROUND FAIRBANKS ONLY HAD AROUND AN INCH OF SNOW THIS PAST APRIL. HIGHER ELEVATION SITES STILL HAD SIGNIFICANT SNOW ON THE GROUND AT MONTHS END...WITH 8 INCHES AT KEYSTONE RIDGE ON MURPHY DOME...AND 22 INCHES AT MUNSON RIDGE SOUTH OF CHENA HOT SPRINGS AT AN ELEVATION OF 3100 FEET. LOOKING AHEAD TO MAY...NORMAL HIGH TEMPERATURES RISE FROM 54 DEGREES ON THE FIRST TO 67 DEGREES ON THE 31ST. NORMAL LOW TEMPERATURES RISE FROM 31 ON THE 1ST TO 44 ON THE 31ST. MAY TENDS TO BE A FAIRLY DRY MONTH WITH THE LIKELIHOOD OF SHOWERS TYPICALLY INCREASING LATE IN THE MONTH. ON AVERAGE ONLY 6 TENTHS OF AN INCH OF RAIN IS OBSERVED. MOST YEARS THERE IS LITTLE OR NO SNOWFALL IN TOWN DURING THE MONTH OF MAY...BUT TWICE IN THE LAST 30 YEARS THERE HAS BEEN MORE THAN 6 INCHES OF SNOW...MOST MEMORABLE FOR LONG TIME RESIDENTS IN 1992 WHEN THERE WAS 14.1 INCHES OF SNOW. HIGHER ELEVATION SNOW ON THE HILLS AROUND FAIRBANKS IS NOT ALL THAT UNUSUAL IN MAY ABOVE 1500 FEET...ESPECIALLY DURING THE FIRST HALF OF THE MONTH. THE LAST FREEZING TEMPERATURES OF THE SPRING ON AVERAGE ARE OBSERVED AT THE AIRPORT AROUND MID-MONTH...BUT RURAL VALLEYS WILL TYPICALLY HAVE FROST ON CLEAR NIGHTS EVEN LATE IN THE MONTH. POSSIBLE SUNSHINE INCREASES FROM JUST OVER 17 HOURS ON THE 1ST TO 20 HOURS AND 29 MINUTES ON THE 31ST. SOME TWILIGHT IS VISIBLE ALONG THE NORTHERN HORIZON AT THE START OF THE MONTH...AND BY MID- MONTH THERE IS 24 HOURS OF USABLE DAYLIGHT. THE FORECAST FOR MAY FROM THE CLIMATE PREDICATION CENTER INDICATES THAT THERE ARE NO STRONG CLIMATE SIGNALS THAT WOULD INDICATE AN INCREASED CHANCE OF EITHER SIGNIFICANTLY ABOVE OR BELOW NORMAL TEMPERATURES OR PRECIPITATION. ...MONTHLY WEATHER SUMMARY FOR FAIRBANKS ALASKA... OBSERVED LAST MONTH...04/2012 OBSERVED RANK AVG MAX TEMP (F) 49.7 9TH WARMEST OF 107 YEARS AVG MIN TEMP (F) 24.1 22ND WARMEST OF 108 YEARS AVG TEMP (F) 36.9 13TH WARMEST OF 107 YEARS TOTAL PRECIP (IN) 0.07 26TH DRIEST OF 99 YEARS TOTAL SNOW (IN) T 81ST SNOWIEST OF 97 YEARS $$ CB/RT

Persistence

Here is a an updated plot of standardized daily temperature departures for Fairbanks thus far this year. Recall that standardized departures are simply a way of scaling the absolute departure from normal to reflect the typical variability for a given time of year Technically, it's the departure from normal divided by the standard deviation. In this case, the daily normal and the standard deviation are taken from the 1981-2010 NCDC normals. This month, the outstanding feature is the nearly unbroken persistence of the warm anomalies rather than any major daily extremes.

Tanana River at Nenana goes out

The ice broke on the Tanana River at Nenana Monday evening, tipping the tripod on the Nenana Ice Classic at 839pm ADT. This is the fourth earliest break-up of the ice on the Tanana since the Nenana Ice Classic started in 1917. Here is a plot of break-up dates since 1917. The black lines represent simple linear regression. From 1917 through 1976 there is no trend at all. Since 1977 (corresponding to the shift of the phase of the PDO from negative to positive), the trend is not (yet) statistically significant, due to the comparative small sample size since then. However, for the entire 96 years of record, the trend toward earlier break-up dates, by more than a week is significant.

Seasonal Snowfall Comparison

The snow season is not necessarily done with yet, but with mild weather here and the snow melted out in town, here is a comparison of total seasonal snowfall between the Fairbanks Airport and here on Keystone Ridge. The percentage of snowfall on the ridge compared to the airport is plotted by the orange line. As Keystone Ridge is more than 1000 feet higher elevation than the airport, it's no surprise that every year there is more snow on the ridge than the airport, and the 16 season average is 39 percent more on the ridge than the Airport. It is somewhat surprising that in some seasons the difference is not very great: in three of sixteen winters the difference is less than 20 percent. This reflects the fact that the transition season from rain to snow in the autumn is often abrupt, and that spring is usually quite dry, so contributes little to the seasonal total. The winters with the biggest percentage difference, this past winter and 2009-10, both resulted from Keystone Ridge receiving much more snow in one or more events when winds aloft were west to southwest, a favored direction for copious precipitation.

Snowpack Meltout

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
257 AM AKDT FRI APR 20 2012

...FAIRBANKS WINTER SNOW PACK MELTS OUT...
...RIGHT ON SCHEDULE...

PERSISTENTLY MILD WEATHER AND PLENTY OF SUNSHINE THE PAST TWO
WEEKS HAVE NOW MELTED AWAY THE WINTER SNOW PACK IN FAIRBANKS. THE
LAST DAY WITH MEASURABLE SNOW ON THE GROUND AT THE FAIRBANKS
AIRPORT WAS APRIL 19TH. THIS IS VERY CLOSE TO THE LONG TERM AVERAGE
DATE FOR LOSS OF THE WINTER SNOW PACK...WHICH IS APRIL 22ND.

FAIRBANKS HAS HAD AN INCH OR MORE OF SNOW ON THE GROUND SINCE OCT
18TH...RESULTING IN 184 CONSECUTIVE DAYS WITH SNOW ON THE GROUND.
THIS IS AGAIN VERY CLOSE TO THE LONG TERM AVERAGE OF 186 DAYS.

SNOW COVER REMAINS AT HIGHER ELEVATIONS AND IN SHADED AND WOODED AREAS
EVEN AT VALLEY LEVEL. SNOW DEPTHS THURSDAY EVENING INCLUDED
19 INCHES AT KEYSTONE RIDGE...SOUTH OF MURPHY DOME AT 1600 FEET
ELEVATION...AND 29 INCHES AT MUNSON RIDGE...SOUTH OF CHENA HOT
SPRINGS AT 3200 FEET ELEVATION.

$$
RT APR 12

Chena Slush Out

Here's a somewhat fuzzy webcam photo looking south across the Chena River just before 8pm ADT Thursday from Front Street (image courtesy of Pro Music). There are some open areas but most of the water visible is water on top of ice.

AO and Alaska Temperatures

A reader asked if the yo-yo temperatures since last autumn are related to the Arctic Oscillation. Short answer, no.

Long answer:

For starters, the Arctic Oscillation Index is a way to describe (near) surface pressure patterns in the Northern Hemisphere at mid and high latitudes. However, as the plot below illustrates, the long term (1949-2012) correlation with surface temperatures in the cold season (Oct-Mar) are not very high over western North America and most of Alaska (the correlation is marginally significant over a small area over south-central Alaska).



For this past cold season, below is a plot of the daily AO index and the standardized daily mean temperature anomaly for Fairbanks (through April 13). As you can see, there was no patterning of the AO Index with how much above or below normal the temperature was in Fairbanks. Notice that the very cold weather in mid-November occurred with a somewhat positive AO, while the cold weather at the end of January occurred when the AO was at largest negative value of the whole winter. Similarly, the very mild weather in early December occurred with a strongly positive AO, while at the end of December the AO was again strongly positive but Fairbanks was considerably colder than normal. For the whole period (Oct 1-Apr 13), the correlation was functionally zero (0.02).

New Webcam

Yahoo! The FAA's webcam high atop Ester Dome, northwest of UAF, is finally online. Here's the southeast view from 418pm ADT Wednesday. There are also views looking north, southwest and west. You can plainly see Chena Ridge and the Tanana River.

Snowpack Meltout

With record heat in progress, and the snow depth down to 7 inches and going fast, here's a look at the winter snowpack meltout date since 1930. For this exercise, meltout date is the latest date with 1 inch or more snow on the ground which was preceded by a week of days with an inch or more of snow on the ground. This last bit is there to exclude the few years like, say, 2001, when the winter snowpack was gone by April 22nd, but there were two consecutive days with accumlating snow in early May that resulted in an inch on the ground on the morning of May 5th. For most of the period of record, this is the depth of snow on the ground early in the morning. The plot on the right shows this date for each year through 2011; the black line is the 5-year running mean. As you can see, since 1972 the winter snowpack has lasted into May only four times, though since the early 1970s there is no trend at all in meltout dates.

Meltout date this year will be April 17-19, so just a touch earlier than the long term average.

Hot April Heads-Up

The average temp the first half of April in Fairbanks was 30.1F, which is 3.0F above normal. Left is the updated plot of standardized daily mean temp departures for 2012, with the current warmth falling right in with yo-yo pattern we had all winter.

The 90% percentile April mean temps for Fairbanks (1905-2011 data) is 36.9F. In order for this month to make the top 10% warmest Aprils, the second half of the month would have to have a mean temp of 43.7F, which is 5.7F above normal for April 16-30th.

That's a tall order, but with the valley snowpack now going fast and the CFS and CPC weeks 1 and 2 guidance showing no end to the warmth, it looks to be within reach. Of course, six of the ten warmest Aprils of record have occurred since 1990.

Temperature Differences

Measuring the temperature of the air seems like a simple thing, but in fact getting an accurate measure is actually not so trivial. For meteorological/cimatological purposes we of course want to keep the sensor out of the sun (because we're interested in the temperature of the air, not the temperature of the thermometer). This is done by enclosing the thermometer (or temperature sensor) in some kind of enclosure. But you want to keep the air moving through the enclosure, otherwise the mere fact that there is an enclosure will impact the temperature of the air inside.

So, there are basically two approaches used. First, have a fan move air from outside the enclosure across the thermometer and then out, or design you enclosure so that air can move freely through. The fan approach is termed aspirated, the second is termed passive. Usually there is not not much difference, but conditions this week, with brilliant sunshine, a still solid snow cover and not much wind are producing small but consistent differences. The graphic above shows the high temperatures on Wednesday. As you would expect, aspirated sensors run a little bit cooler.

First 50F of the Year

Updated: The high temperature at the airport was 51F.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
426 PM AKDT TUE APR 10 2012

...HIGH TEMPERATURE HITS 50 DEGREES IN FAIRBANKS....
...FIRST 50 DEGREE DAY OF THE YEAR...

THE TEMPERATURE AT THE FAIRBANKS INTERNATIONAL AIRPORT ROSE TO 50
DEGREES AT 330PM TUESDAY AFTERNOON. THIS IS THE WARMEST IT HAS BEEN
THIS YEAR AND IS FIRST TIME THE TEMPERATURE HAS BEEN AS HIGH AS 50
DEGREES SINCE OCTOBER 14TH.

OVER THE PAST 80 YEARS...THE AVERAGE DATE OF THE FIRST 50 DEGREE
OR HIGHER TEMPERATURE IN THE SPRING IN FAIRBANKS IS APRIL 10TH.

$$
RT APR 12

Spring time Inversion

Clear skies overnight and a still solid snowpack helped a reasonably strong inversion to form overnight. Valley min temperatures were in the lower teens while higher elevations barely got below freezing. Some specific low temperatures include:

Goldstream Creek: 10F
Chena Hot Springs: 11F
Woodsmoke PWS: 13F (near North Pole)
Fairbanks Airport: 14F

Keystone Ridge: 29F
Nenana Hills RWIS: 31F
Cleary Summit RWIS: 32F

Sunny Sunday

View from the Keystone Ridge weather station on Sunday, looking east. Snow depth is at 28 inches. We've not completely lost the snow cover in April any time snow depth has been two feet or more on April 8th.

Anchorage Sets Snowfall Record

After much adieu…


PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
740 PM AKDT SAT APR 7 2012

UPDATED WITH LATEST SNOW TOTAL

...ANCHORAGE SETS NEW SEASONAL SNOWFALL RECORD...

SNOW HAS TAPERED OFF TO FLURRIES AT THE NATIONAL WEATHER SERVICE
FORECAST OFFICE AND NO ADDITIONAL ACCUMULATION IS EXPECTED FROM
THIS STORM. AN ADDITIONAL 0.9 INCHES OF SNOW FELL BETWEEN 4 PM
AND 7 PM WHICH BRINGS THE TOTAL FOR THE DAY TO 4.3 INCHES.

THIS MAKES THE 2011-2012 WINTER SEASON THE SNOWIEST EVER WITH
A TOTAL OF 134.5 INCHES. THE PREVIOUS SEASONAL SNOWFALL RECORD
WAS 132.6 INCHES SET IN 1954-1955.

$$

SEB/CC

it's a Hot One

Yesterday was the warmest day since early October in Fairbanks-land. Some high temperatures included:

Woodsmoke: 50F (near North Pole)
Fairbanks Airport: 49F
Fort Wainwright: 49F
Goldstream Creek: 49F
Eielson AFB: 48F
Keystone Ridge: 45F

Fairbanks March Summary

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
244 PM AKDT SUN APR 1 2012

...MARCH WEATHER SUMMARY FOR FAIRBANKS...
...COLD AND SNOWY...

FOLLOWING A VERY MILD FEBRUARY...THE WEATHER PATTERN OVER NEARLY
ALL OF ALASKA FLIPPED...AND MOST AREAS HAD WELL BELOW NORMAL
TEMPERATURES FOR MOST OF MARCH. FAIRBANKS WAS NO EXCEPTION.

THE AVERAGE TEMPERATURE OF 4.5 ABOVE WAS NEARLY SEVEN DEGREES
COLDER THAN NORMAL AND RESULTED IN MARCH...QUITE UNUSUALLY...BEING
COLDER THAN FEBRUARY. AS WAS THE CASE IN JANUARY...DAILY
TEMPERATURES WERE NOT EXCESSIVELY LOW...AS THERE WERE NO
TEMPERATURES EVEN CLOSE TO RECORD LEVELS. RATHER...THE PERSISTENCE
OF CHILLY TEMPERATURES WAS MOST NOTABLE. EVERY DAY BUT ONE FROM
THE 10TH THROUGH THE 23RD WAS TEN OR MORE DEGREES COLDER THAN
NORMAL.

FOR THE MONTH...THE AVERAGE HIGH TEMPERATURE AT THE AIRPORT WAS
18 ABOVE AND THE AVERAGE LOW WAS 9 BELOW. THE TEMPERATURE ROSE
ABOVE FREEZING FOR THE FIRST TIME SINCE BEFORE CHRISTMAS ON THE
27TH...AND THE HIGH FOR THE MONTH WAS 44 DEGREES ON THE 28TH. THE
LOW TEMPERATURE IN MARCH WAS 30 BELOW ON THE 5TH...WHICH IS VERY CLOSE
TO THE LONG TERM AVERAGE LOWEST TEMPERATURE IN MARCH. THERE WERE
EIGHT DAYS WITH LOWS OF 20 BELOW OR LOWER...A BIT MORE THAN IN AN
AVERAGE MARCH.

MARCH IS TYPICALLY A DRY MONTH IN FAIRBANKS...BUT NOT THIS YEAR.
TOTAL SNOW OF 14.7 INCHES AT THE AIRPORT MADE THIS THE THIRD
SNOWIEST MARCH IN THE PAST 45 YEARS. MOST OF THE SNOW CAME ON THE
5TH THROUGH 7TH...WHEN SOME PLACES NORTH AND EAST OF TOWN RECEIVED
MORE THAN 18 INCHES OF SNOW. THE SNOW WAS QUITE POWDERY...WHICH IS
USUAL FOR THIS TIME OF YEAR. THIS BROUGHT THE SEASONAL TOTAL
SNOWFALL UP TO 57.4 INCHES...ABOUT 4 INCHES BELOW NORMAL. THE SNOW
DEPTH REACHED 29 INCHES ON THE 8TH...THEN COMPACTED TO 22 INCHES
BY THE 31ST.

SOME PRECIPITATION FELL ON MORE THAN HALF THE DAYS IN MARCH. THE
SNOW MELTED DOWN TO 0.74 INCHES OF WATER...NEARLY THREE TIMES
NORMAL.

LOOKING AHEAD TO APRIL...NORMAL TEMPERATURES CONTINUE TO INCREASE
RAPIDLY. AVERAGE HIGH TEMPERATURES RISE FROM 35 DEGREES ON THE FIRST
TO 54 DEGREES IN THE 30TH. APRIL IS OFTEN QUITE DRY. IN THE PAST
20 YEARS...HALF THE APRILS HAD LESS THAN ONE TENTH OF INCH OF
PRECIPITATION. MOST OF WHAT DOES FALLS TYPICALLY FALLS AS
SNOW...THOUGH RAIN SHOWERS SOMETIMES OCCUR...ESPECIALLY THE SECOND
HALF OF THE MONTH. ON RARE OCCASIONS SIGNIFICANT SNOWFALL OCCURS
IN APRIL...THOUGH ONLY FIVE APRILS IN THE PAST 60 YEARS HAVE
RECEIVED MORE THAN 10 INCHES OF SNOW. THE WINTER SNOWPACK USUALLY
MELTS OUT IN TOWN DURING APRIL. THE AVERAGE DATE FOR LAST DAY WITH
AN INCH OR MORE OF SNOW ON THE GROUND IS APRIL 22ND.

APRIL IS OFTEN A SUNNY MONTH...AS POSSIBLE SUNSHINE INCREASES FROM
13 HOURS AND 41 MINUTES ON THE FIRST TO 17 HOURS ON 30TH. DURING
THE LAST WEEK OF APRIL...SOME TWILIGHT REMAINS VISIBLE IN NORTHERN
SKY ALL NIGHT LONG.

$$
RT APR 12

Springtime in Alaska

A lovely April 1st at Denali National Park. Headquarters has a snow depth of 25 inches...which is pretty close to normal. Webcam photo from the FAA.