Cooling Off, and July Climate Data

It's beginning to feel a lot like autumn already for much of Alaska, as temperatures have dipped below the declining seasonal normal in the past few days.  Sub-freezing temperatures occurred in many of the colder spots of the central and eastern interior this morning, including in the Fairbanks area: 27°F at Goldstream Creek and 31°F at the Creamers Field SNOTEL site.  The early chill will hasten the arrival of autumn colors in the next couple of weeks.

I've been too busy to post my usual monthly climate update in recent days, but better late than never - here's a look back at climate anomalies in the month of July.  It was a fairly warm month overall, and significantly drier than normal on a statewide basis, which marks a big contrast with last year's record wet July.  Warmth was widespread (except for Southeast), but the dryness was most significant along and north of the Gulf Coast from Cook Inlet to the far northern Panhandle.  Here are percentile rank maps from NCEI (top) and ERA5 reanalysis (bottom):

As usual, the NCEI and ERA5 maps differ significantly for precipitation, with ERA5 showing much wetter conditions from the western interior to the Alaska Peninsula and Kodiak Island; and ERA5 also highlights the unusually sunny and dry conditions across the North Slope.

One of the most significant events during the month was the heatwave focused on northwestern Alaska early in the month.  Rick Thoman comments a bit more on this in his blog:

https://alaskaclimate.substack.com/p/july-2025-arctic-and-alaska-climate

Wind was above normal in the zone of wet and cloudy weather across the southwest.  This region of poor weather seems to have been caused by a frontal zone along the eastern side of the (quasi-permanent) Bering Sea trough; as the second figure below illustrates, there was a subtle north-south ridge axis over Alaska, blocking the westerly flow.  The more significant upper-level feature was a ridge over the East Siberian and Alaskan Arctic Ocean, and that was a key player in the northern heat wave:

https://ak-wx.blogspot.com/2025/07/northern-heat.html

Regional lightning activity was not far from normal for the month overall, based on lightning strike counts that include northwestern Canada; but it was more active in parts of the Alaskan interior, and especially north-central areas.  As is typical, most of this activity occurred early in the month, including well over 10,000 strikes on the 7th.  It appears this is the first year (2012-present) with over 10,000 cloud-to-ground lightning strikes on 5 different days during summer, based on data collected by the Alaska Lightning Detection Network.  I'll have more to say about this summer's lightning and wildfire activity in a subsequent post.

June Climate Data

June climate data are in from NOAA/NCEI, so it's time for a recap.  As we all know, it was a very warm and dry June for the state as a whole: the sixth warmest and fifth driest since 1925, according to the NCEI data.  The only years that were both warmer and drier in June were 1936 and 1957, although June 2022 was very similar in temperature and was the driest on record in the NCEI dataset.

The warmth was most anomalous for the northeastern interior, and the ERA5 climate model (reanalysis) data backs this up:

Only June 2004 was warmer in the northeastern interior, and that was also the warmest June statewide, leading into the worst fire season in modern history.  This year's 300,000 or so acres that burned in June pales in comparison with the nearly 1 million acres that burned in June 2004 (followed by another 5 million in July and August).

ERA5 data confirms that unusual dryness was widespread from the Panhandle to the West Coast and across most, though not all, of the interior.

The circulation pattern that produced this outcome involved high pressure over the East Siberian Sea and low pressure in the Gulf of Alaska:

In winter this would be a cold pattern as cold air sinks into Alaska from the high Arctic, but in the height of summer a warm outcome is favored by ample sunshine heating up the continental interior (see below).  It's also worth noting that the exceptional warmth in the last third of June was driven by a trough in the Bering Sea and a big ridge over the interior, i.e. a more amplified pattern than the monthly mean suggests.

Wind was above normal in the Aleutians and western/southwestern Alaska, but mostly lighter than normal elsewhere.

But June is firmly in the rearview mirror now, as the pattern has been completely different in the last week.  McGrath tied a daily record low temperature yesterday, and CPC suggests the generally cool weather will continue for at least the next couple of weeks.  There have only been 4 years since 1925 when July was cooler than June on a statewide basis - will it happen again this year?  It's seems quite possible.

Precip Data

With some help from Rick Thoman, I've managed to get hold of the NWS daily Alaska precipitation analysis data, i.e. the precipitation estimates that are displayed by the Alaska-Pacific River Forecast Center at:

https://www.weather.gov/aprfc/qpe_qpfViewer

Here's how the last 30 days stack up against normal for the time of year (using PRISM 1981-2010 normals):

That's a lot of dry.  Fairbanks picked up its first measurable rain in over a month yesterday, amounting to 0.35", but most locations around the area didn't see that much.  Here are estimated totals from the last 7 days:

A couple of cautionary notes about the data: first, obviously, there are very large areas with little or no data, so don't be impressed by the level of detail on the maps.  The analysis method takes the often-scarce observations and uses the high-resolution PRISM normals to create a best guess of how the precipitation may have varied depending on elevation, terrain orientation, and so forth.

The other note is that the analysis uses only automated observations, because the daily analysis is valid for 1200-1200 UTC, or 3am-3am AKST.  Manual observations like co-op or CoCoRaHS are not included.

The 90-day maps show less than 0.75" of liquid-equivalent precipitation in the Y-K delta region, and less than 20% of normal near Bethel and a few other spots around the state.

Cold and Dry

The past few days have brought a fairly notable cold spell to the eastern and northeastern interior, with the first sub-minus 50°F temperatures of the season emerging at the usual cold spots.  Today is the fifth consecutive day with a daily minimum of -50°F or lower at the Chalkyitsik RAWS site near Fort Yukon, and this appears to be the most since January 2010 for that particular site (although there's a lot of missing data from 2012-2015).

It's been pretty chilly in Fairbanks too, with daily low temperatures below -30°F for three days, and a high temperature of -30°F on Saturday.  Of course solar heating is essentially zero at the winter solstice.  As an aside, here's a link to a very attractive solstice video from the other day.

Here's a time-lapse taken yesterday of the short daylight hours around the winter solstice in Fairbanks. Today, Fairbanks will only see 3 hours and 41 minutes of daylight, and the sun will only rise 2° above the horizon. #akwx pic.twitter.com/mCBQH8DKC1

— NWS Fairbanks (@NWSFairbanks) December 22, 2019

It has been a little unusual to see cold like this at valley level without colder conditions aloft.  According to the Fairbanks balloon soundings, the 850mb temperature did not drop below zero Fahrenheit; this temperature is colder than normal at 850mb, but not dramatically so - a colder air mass prevails about a quarter of the time in deep winter (per data since 1981).  In contrast, only about 5% of days see a high temperature of -30°F or lower in Fairbanks at this time of year.

This means, of course, that the surface-based temperature inversion has been strong; see Saturday morning's sounding below.  The surface-850mb temperature difference has been about 20°C in recent days, and this is exceeded on only about 7% of days in December and January - and more often than not it happens when conditions are warmer than normal aloft.  Big inversions tend to occur under high pressure, when clear skies and calm winds allow for strong radiational cooling, and at the same time subsidence aloft produces relatively warm, dry air above the inversion.  In contrast, cold air aloft tends to occur in association with a trough, which also typically brings cloudier and less calm conditions that don't promote a strong inversion.

So the unusual aspect of recent days has been the juxtaposition of relatively clear and calm conditions with a cool air mass, allowing surface cold to "outperform" over the northeastern interior.  One important reason for the absence of cloud is that the air aloft has been very dry indeed; the total column water vapor ("precipitable water") dropped to about 1mm late last week, which is down in the extreme lower tail of the historical distribution.  Less than 2% of soundings are this dry in Fairbanks in December and January.  The dryness of the air probably has to do with its origin in the high Arctic, as it seems to have been transported southward on the west side of a persistent and intense "polar vortex" near Canada's Banks Island.  This is illustrated below by the 500mb charts from last Friday morning and this morning respectively, courtesy of Environment Canada:

If we look at the history of precipitable water and surface-850mb inversion strength in Fairbanks, there is an inverse relationship, and this stands out particularly clearly when cold air is in place - see the figure below.  The blue markers show precipitable water versus inversion strength for the lowest 10% of 850mb temperatures in December and January; notice the uniformly low water content when the air is cold both aloft and at the surface (i.e. blue markers and strong inversion).

In conclusion, the combination of very cold and very dry air aloft is a recipe for extreme cold at the surface in Alaska's interior, and the last few days fulfilled the dry aspect of this.  There's a chance the "very cold" part may show up too in the near future; and this would be quite a shock to the system after all the warmth of recent years.   At the very least, the coming weekend looks to bring the coldest weather of the season so far.

Extremely Dry October

Last week I noted the very unusual lack of cloudiness in Fairbanks since the beginning of October, and now that the month's climate data is complete, the magnitude of the anomaly stands out more clearly.

First, it's remarkable to observe that the airport's ASOS instrument reported less than 50% cloud cover on 23 of 31 days, which ties a record for any month of the year: only March of 2002 and March of 2011 had this many mostly-clear days (based on ASOS data since 1998).  Of course, March is usually much less cloudy, with an average of 14 mostly-clear days compared to October's normal of 5 days.  The next closest October for mostly-clear days was 2009, with only 10 days.

The normal seasonal variation of cloudiness in Fairbanks is approximated by the normal relative humidity at 850mb, as measured by balloon soundings - see the chart below.  Based on soundings since 1958, October has the highest normal 850mb relative humidity of any month of the year.  Consider how remarkable it is, then, that October 2016 had the lowest 850mb relative humidity of any month in the historical record (1948-present).

Compared to past Octobers in Fairbanks, the low humidity aloft was really extreme: the monthly mean 850mb relative humidity was 4.9 standard deviations below the 1981-2010 normal.

As noted in the previous post, the clear weather has been caused by a very persistent high pressure ridge over the state, leading to subsidence and drying aloft together with blocking of normal moist westerly winds.  Despite a lack of snow cover for most of the month and windy conditions at times, the clear skies allowed surface temperatures to drop relatively low compared to the pronounced warmth aloft: the month's mean surface-850mb inversion was the strongest on record for October.

October's "blocking" circulation pattern was pronounced around the Northern Hemisphere, with high pressure across the Arctic Ocean and a strongly negative Arctic Oscillation.  It's interesting to note that the Arctic Oscillation and its cousin the North Atlantic Oscillation have tended to be negative during October in the past 15 years, and this seems likely to be related to the loss of Arctic sea ice at this time of year.

With clouds in short supply over Fairbanks in the past month, precipitation was nearly zero; the October total liquid equivalent was 0.02", the lowest for the month since 1914.  The meager snow cover from the 20th has mostly sublimated or melted away, and the airport's snow depth measurement has been down to only a trace for several days.  However, there's variation from place to place; a downtown webcam showed a thin snow cover today, but the ground is basically bare on UAF's West Ridge and up at Cleary Summit.

Clear and Colder

With a little snow now on the ground and nights continuing to lengthen rapidly, temperatures have dropped sharply under clear skies in the past few nights.  Last night was the coldest yet, with temperatures below -15°F in quite a number of locations in the eastern interior.  Here are a few of the coldest measurements so far:

-24°F  Bolio RAWS at Fort Greely
-22°F  Chicken COOP
-20°F  Tok #2 COOP
-17°F  Circle Hot Springs COOP
-16°F  Salcha RAWS
-12°F  Northway AP

The coldest spot around Fairbanks seems to have been the sensor near Smith Lake on UAF's North Campus, which reached -13°F yesterday and -12°F today.  Fairbanks airport dropped below 0°F for the first time yesterday; this is just slightly earlier than normal.

The cold is not particularly unusual for the time of year, but the persistence of clear skies this month certainly is very unusual.  In just the past 2 weeks, Fairbanks has seen sunny and very warm weather (55°F on the 12th), sunny and windy weather, and now sunny and calm, cold weather.  The absence of cloud is remarkable, because this is normally one of the cloudiest times of year in Fairbanks (only early August is comparable).  Including today, 19 of 24 days so far in October have had less than 50% cloud cover on average, and this is easily a record for the entire month - the previous highest total was 10 of 31 days in 2009 (based on ASOS data since 1998).

The reason for the clear skies is plain to see in a reanalysis estimate of 500mb heights so far this month: an axis of high pressure has extended from the northeastern Pacific to northwestern Alaska and the Chukchi Sea.

Compared to normal, upper-level pressure has been well above normal to the northwest, and so the usual westerly flow across interior Alaska has been blocked.  Obviously this also explains the lack of precipitation; the light snowfall last week produced a mere 0.02" of liquid equivalent precipitation - the month's only precipitation.  The driest October on record in Fairbanks was 1954, with 0.08".

Here's the October 1-22 average relative humidity at 850mb, according to the NCEP/NCAR reanalysis: there's a large zone of sub-45% values across the interior.

The departure from normal shows where the dry conditions aloft have been most unusual:

Colville Delta Dryness

Reader Tracy recently asked about conditions around the Colville River delta of the North Slope this summer in light of very dry ground conditions that she observed there during July.  How is this best explained - dry weather, warm weather, lack of winter snowfall, or something else?

The first thing to note is that precipitation has not been unusually low this summer; the Colville Village COOP reported 1.81" of precipitation in June and July, compared to a 19-year median of 1.44".  Similarly, the Kuparuk COOP observer measured 1.91" of precipitation compared to a 31-year median of 1.20" for the June-July period.  Nuiqsut airport reported 1.84", their second highest June-July total on record (17-year median of 0.88").

Looking at temperatures, the June-July period was slightly but not dramatically warmer than normal, except for the heat wave in mid-July.  Overall Colville Village was 1.5°F above normal for the two months, and Kuparuk was 1.3°F above normal; three of the last four years were warmer than 2016 over this period at Colville Village.  However, if we look back to May we find very unusual warmth, which contributed to a very early melt-off of the winter snow cover.  Colville Village reported zero snow depth (i.e. no snow over more than 50% of the ground area) on May 14, the earliest date on record (data from 1997-present).  Kuparuk reported melt-off on May 12, also very much earlier than normal (but not a record).  For the rest of May after melt-off, temperatures were persistently above normal in both locations.

The chart below shows that melt-off typically occurred in early June prior to last year at Colville Village (at least since 1997), so this year's early melt added 2-3 weeks of warming and drying of the ground surface in early summer.

At first blush the early melt-off seems to be significant relative to a short summer season: by July 15 this year the area had been snow-free for 9 weeks, compared to around 6 weeks in a normal year.  With evaporation taking place for 50% longer, and with the potential for 24-hour sunshine at this time of year, ground moisture levels might be expected to take a hit relative to normal.  However, temperatures were still low in absolute terms in the second half of May, and it is a cloudy time of year, so total evaporation may have been only slightly enhanced compared to a normal summer.

I was hoping to dig into the detailed evaporation calculation using data from Barrow's CRN site, but unfortunately the NCEI website is not working at present.  In lieu of a full calculation for Barrow, I computed the daily average vapor pressure deficit from Nuiqsut airport, which in any case is much closer to the Colville delta.  The chart below shows the sum of daily average vapor pressure deficit values from the date of melt-off to July 31 in each year since 1999.  Recall that the vapor pressure deficit is directly proportional to the evaporation rate, all else being equal (e.g. wind and solar radiation).  The results indicate that evaporation this year was probably higher than the long-term average but may have been no higher than 2015, and was perhaps lower than 2015.  It's clear that the evaporation is more closely tied to summer temperatures and humidity (and no doubt cloudiness and wind) than to melt-off date, because it's just too cool in May to accomplish much evaporation regardless of whether the ground is snow covered or not.

Looking again at the melt-off chart, another point of interest is that the peak snow depth in winter 2015-2016 was only 9" at Colville Village, which is the lowest in the 20-year history.  It's not a large difference in terms of absolute water content of the snowpack, but the small snow deficit may have contributed to reduced ground moisture levels this summer.  In conclusion, I'd say the dry ground conditions observed by Tracy were caused by a combination of factors, including at least: a slight lack of snowpack last winter, an early melt-off allowing for early warming and drying of the ground, and slightly unusual warmth (and one heat wave) this summer.  It would be interesting to hear others' perspectives; and the faithful climate observers at Colville Village would probably have some useful insight as well.

Here is a parallel melt-off chart for Kuparuk with its longer observing history.  Last winter's snow depth was low there too compared to recent years, although there is a pronounced long-term trend towards rising winter snow depth; this may or may not be real, as it could be related to changing measurement practices or variations in measurement location.

A Most Unusual Winter

In standard meteorological terms, the Northern Hemisphere winter season is defined as December through February, and now that it's in the books it is worth looking at how Fairbanks fared for various aspects of the climate.

First, and obviously, it was very warm and very dry.  The mean temperature of +3.0°F was the 6th highest on record (1930-present), with January and February being somewhat warmer than December; but none of the 3 months was in the top 5 for mean temperature.  More remarkable was the near complete absence of unusual cold; only 3 days (December 5, 6, and 25) had a daily mean temperature more than 10°F below normal.  In contrast, 34 days were more than 10°F warmer than normal.  The lowest daily high temperature (including November) was a mere -9°F, so there was not a single day that remained at or below -10°F from midnight to midnight; this is unprecedented for a whole winter season.  The last such day was February 9 of last year.

Snowfall and liquid-equivalent precipitation were incredibly meager and both were easily the lowest on record.  The totals (0.13" and 2.5" respectively) were less than 10% of normal, which is astounding for a three-month season.  The snow depth remained nearly constant at either 12 or 13" since December 1, which is the least amount of variation ever seen in Fairbanks for the winter season.

Looking at some other variables that are reported by the airport's ASOS platform, the average visibility was the highest on record since the ASOS was introduced in 1997.  That's not a surprise because it hardly snowed at all; there were only 4 days on which visibility of 1 mile or less was observed, and this is a record for 1950-present.  However, cloud cover was only modestly below normal (7th lowest of 19 years).  As Brian showed in a blog post yesterday, the sea-level pressure for December-February was at record low levels across most of the Bering Sea and western Alaska, so ironically it was a very stormy pattern farther to the west and southwest; it was the persistent southerly flow and downsloping that kept Fairbanks so warm and dry.

Speaking of wind speed, the average daily wind speed in Fairbanks was well above normal and appears to be a record for the ASOS era (excluding 2010-2011, which seems to have a lot of missing data).  Only 53% of the ASOS observations reported calm winds in December through February, compared to about 65% in a normal winter and as high as 81% in 1998-1999.

I've discussed previously the low variance of temperature since the beginning of this year, and it's worth noting again here that the December-February variance of daily temperature anomalies was extremely low.  Only 1997-98 had a lower variance - and that was the last big El Niño winter.  This winter's standard deviation of 10.6°F compares to a long-term normal of 16°F.

Of course with the astonishing lack of snowfall the variance in snow depth was also extremely low (all-time record), as noted above; so one might be tempted to say this was the most boring winter on record.  It's interesting to look at the long-term trend in winter variance of temperature and snow depth - see the chart below.  Both have decreased in the past few decades, and the decrease in snow depth variance is particularly notable.  In fact the snow depth variance seems to be in a well-established long-term downward trend; every one of the past 16 winters has seen snow depth vary by less than what was normal in the 1930-1970 period.  There might be some influence here from changing measuring practices, but I doubt that would explain the bulk of the change.  It's certainly a topic for further investigation.

For the sake of completeness, here's the NWS summary for February.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1053 AM AKST TUE MAR 1 2016

...MONTHLY WEATHER SUMMARY FOR FEBRUARY FOR FAIRBANKS ALASKA...

THE REMARKABLY WARM AND DRY WEATHER PATTERN FOR FAIRBANKS CONTINUES.
FEBRUARY 2016 MUCH LIKE JANUARY 2016 AND DECEMBER 2015 WAS WARMER
THAN NORMAL AND EXCEPTIONALLY DRY. ONLY 0.6 INCHES OF SNOW FELL
DURING THE MONTH OF FEBRUARY AT THE FAIRBANKS AIRPORT WHICH
RANKED AS THE 99TH SNOWIEST OF 105 YEARS OF RECORD. NORMAL SNOWFALL
AT THE FAIRBANKS AIRPORT DURING THE MONTH OF FEBRUARY IS 8.1
INCHES. ALL OF THE 0.6 INCHES OF SNOW FELL ON THE 6TH WHICH WAS
THE HEAVIEST 24 HOUR SNOWFALL FOR THE MONTH. TRACE AMOUNTS OF SNOW
FELL ON 3 OTHER DAYS.

ONLY 0.05 INCHES OF PRECIPITATION FELL AT THE FAIRBANKS AIRPORT IN
FEBRUARY WHICH WAS 0.37 INCHES BELOW THE NORMAL PRECIPITATION OF
0.42 INCHES. THIS RANKS AS THE 8TH DRIEST FEBRUARY OF 105 YEARS OF
RECORD.

THE VERY DRY MONTH OF DECEMBER 2015 COMBINED WITH THE EXCEPTIONALLY
DRY MONTHS OF JANUARY AND FEBRUARY 2016 RANKED AS THE LEAST SNOWY
DECEMBER...JANUARY...FEBRUARY PERIOD ON RECORD WITH ONLY 2.5
INCHES OF SNOW FALLING DURING THOSE THREE MONTHS AT FAIRBANKS.
THE SECOND LEAST SNOWY DECEMBER TO FEBRUARY PERIOD OCCURRED DURING
THE WINTER OF 1918 TO 1919 WHERE 4.9 INCHES OF SNOW FELL...NEARLY
DOUBLE WHAT FELL DURING DECEMBER 2015 TO FEBRUARY 2016. DURING THE
DECEMBER 2015 TO FEBRUARY 2016 PERIOD ONLY 0.13 INCHES OF
PRECIPITATION FELL AT THE FAIRBANKS AIRPORT WHICH ALSO RANKS AS
THE DRIEST DECEMBER TO FEBRUARY PERIOD ON RECORD. THIS IS ONLY ONE
THIRD OF THE PRECIPITATION THAT FELL DURING THE SECOND DRIEST
DECEMBER TO FEBRUARY PERIOD DURING THE WINTER OF 1935 TO 1936 WHEN
0.35 INCHES OF PRECIPITATION FELL. DESPITE NEAR RECORD SNOWFALL
IN BOTH SEPTEMBER AND NOVEMBER OF THIS WINTER SEASON...SEASON TO
DATE SNOWFALL CURRENTLY 52.6 INCHES IS NOW 3.7 INCHES BELOW THE
NORMAL SEASON TO DATE SNOWFALL ON THE 1ST OF MARCH OF 56.3 INCHES.

FEBRUARY 2016 WAS ALSO VERY WARM WITH NO SEVERE COLD PERIODS. THE
AVERAGE MAXIMUM TEMPERATURE WAS 20.0 DEGREES ABOVE WHICH WAS 10.0
DEGREES ABOVE THE NORMAL MAXIMUM TEMPERATURE OF 10 ABOVE. THIS
RANKED AS THE 11TH WARMEST OF 108 YEARS OR RECORD. THE AVERAGE
MINIMUM TEMPERATURE WAS 4.2 BELOW WHICH WAS 8.5 DEGREES ABOVE THE
NORMAL MINIMUM TEMPERATURE OF 12.7 BELOW. THIS RANKED AS THE 19TH
WARMEST OF 109 YEARS OF RECORD. THE MEAN TEMPERATURE WAS 7.9 ABOVE
WHICH WAS 9.2 DEGREES ABOVE THE NORMAL MEAN TEMPERATURE OF 1.3
DEGREES BELOW. THIS RANKS AS THE 14TH WARMEST OF 108 YEARS OF
RECORD. THE WARMEST TEMPERATURE DURING THE MONTH OF FEBRUARY WAS
42 DEGREES WHICH OCCURRED ON THE 25TH. THE COLDEST TEMPERATURE WAS
21 BELOW WHICH OCCURRED ON THE 19TH.

THE AVERAGE TEMPERATURE FOR THE DECEMBER 2015 TO FEBRUARY 2016 WAS
3.0 DEGREES WHICH RANKS AS THE 8TH WARMEST DECEMBER TO FEBRUARY
PERIOD ON RECORD. 

THE COLDEST TEMPERATURE OF THIS WINTER SEASON REMAINS 29 BELOW
WHICH OCCURRED ON CHRISTMAS 2015. THERE HAS NOT BEEN A 30 BELOW OR
COLDER DAY TO DATE THIS COLD SEASON. THERE HAS ONLY BEEN ONE COLD
SEASON 1976 TO 1977 IN THE CLIMATIC RECORD THAT THE TEMPERATURE
DID NOT REACH 30 BELOW OR COLDER AT FAIRBANKS. THE LATEST FIRST
OCCURRENCE OF 30 BELOW OR COLDER OCCURRED ON THE 27TH OF FEBRUARY
IN 1986 HOWEVER THE LATEST 30 BELOW OR COLDER IN FAIRBANKS OCCURRED
ON THE 3RD OF APRIL IN 1944. THE AVERAGE COLDEST MINIMUM TEMPERATURE
FOR THE MONTH OF MARCH IS 28 BELOW. ON AVERAGE THE TEMPERATURE
FALLS TO 30 BELOW OR COLDER ON TWO DAYS IN MARCH. THE AVERAGE
NUMBER OF 30 BELOW DAYS OR COLDER IN FAIRBANKS FOR A COLD SEASON
IS 25.

LOOKING FORWARD TO MARCH THE TEMPERATURES CLIMB SHARPLY AS THE
SUN ANGLE AND LENGTH OF DAY INCREASES. THE AVERAGE DAILY HIGH
TEMPERATURE INCREASES FROM 18 DEGREES ABOVE ON THE 1ST TO 34
DEGREES ON THE 31ST. THE AVERAGE DAILY LOW TEMPERATURE INCREASES
FROM 9 BELOW ON THE 1ST TO 8 ABOVE ON THE 31ST. OVER THE PAST 108
YEARS THE TEMPERATURES HAVE RANGED FROM 56 ABOVE IN 1994 TO 56
BELOW IN 1911. MARCH IS ON AVERAGE THE DRIEST MONTH IN FAIRBANKS.
NORMAL PRECIPITATION IS 0.25 INCHES WHILE NORMAL SNOW FALL IS 4.9
INCHES. IN SOME YEARS THE SNOW PACK BEGINS TO MELT BY LATE MARCH
ESPECIALLY IN THE URBAN AREAS.

POSSIBLE SUNSHINE INCREASES BY NEARLY 7 MINUTES PER DAY DURING
MARCH INCREASING FROM 10 HOURS AND 12 MINUTES ON THE 1ST TO 13
HOURS AND 35 MINUTES ON THE 31ST.

THE FORECAST FOR MARCH FROM THE CLIMATE PREDICTION CENTER CALLS
FOR INCREASED CHANCES FOR ABOVE NORMAL TEMPERATURES AND INCREASED
CHANCES OF BELOW NORMAL PRECIPITATION. 


OBSERVED LAST MONTH...02/2016

                         OBSERVED   RANK
AVG MAX TEMP (F)             20.0   11TH WARMEST OF 108 YEARS
AVG MIN TEMP (F)             -4.2   19TH WARMEST OF 109 YEARS
AVG TEMP (F)                  7.9   14TH WARMEST OF 108 YEARS
TOTAL PRECIP (IN)            0.05   8TH DRIEST OF 105 YEARS
TOTAL SNOW (IN)              0.60   99TH SNOWIEST OF 105 YEARS

Exceptionally Dry

Ever since the persistent snows of November ended about 2 months ago, the weather has been very dry indeed in Fairbanks.  Through yesterday with its meager 0.2" of snow, the December-January period has seen only 1.9" of snowfall and 0.08" of liquid-equivalent precipitation.  If this stands, it will be the driest December-January period on record (1930-present); normal snowfall and precipitation are 19.3" and 0.98" respectively for this period.  For comparison, the last 2 winters saw 16.8" and 19.8" of snow in December through January.

However, if we look beyond just calendar months, there have been a couple of occasions when even less snow fell over the same length of time during winter; mid-winter 1952-1953 and early winter 1953-1954 both had 62-day spells with only 1.4" of snow.

I thought it would be interesting to look at the upper-level flow patterns that typically accompany very dry or very wet conditions on a monthly time scale in Fairbanks.  This is a similar analysis to the one I did for extreme daily temperature anomalies, see here.

The maps below show the average 500mb height anomalies that accompanied the 8 driest (left) and wettest (right) instances of each calendar month in Fairbanks since 1950.  In winter the driest conditions in Fairbanks tend to be associated with unusually low pressure to the south of Alaska, which reduces the strength of the westerly flow aloft and prevents weather disturbances (fronts and lows) from reaching the interior.  But it's very interesting to note that the height anomalies accompanying dry weather are less consistent and less pronounced than those accompanying wet weather.  My interpretation of this is that there is more than one way to get dry weather: very warm weather, with chinook flow, is dry, but very cold weather is dry as well.  Higher precipitation amounts tend to occur with near-normal temperatures, as we saw in this post.  Very wet weather, in contrast, tends to occur only one way in winter: when westerly flow is enhanced around an anomalous ridge to the southwest.


So does the flow pattern in the past 2 months match the historical pattern for dry weather?  The map below shows the 500mb height anomaly since December 1; it closely resembles the dry weather pattern for December.

Unsurprisingly, the dry weather pattern is also quite similar to the typical pattern associated with El Niño.  The map below shows the mean height anomaly during 10 significant El Niño's, indicating that low pressure aloft in the Gulf of Alaska is the preferred circulation state.