Objective Comments and Analysis - All Science, No Politics
Primary Author Richard James
2010-2013 Author Rick Thoman
Saturday, May 18, 2024
Strong Bering Sea Storm
Monday, May 13, 2024
April Climate Data
Friday, May 10, 2024
Cold and Snow
Here's a bit of follow-up on the unusually late cold and snow. According to Rick Thoman (and relayed via Brian Brettschneider on Twitter), Monday's half-inch of snow in Fairbanks was the first time since 1978 that measurable snow occurred after green-up.
The late snow in 1978 was much later - May 27 - but it was also more marginal, with mixed rain and snow reported, and officially-measured accumulation of only 0.1". A more legitimate late snowfall occurred in 1966 in Fairbanks, with 1.6" measured on May 15-16; that was 8 days after breakup at Nenana, and almost certainly after green-up too (although the NWS green-up history only goes back to 1974).
Not to be left out, Anchorage also saw accumulating snow on Wednesday night. This is a top-10 latest date for snow, and it's actually the latest on record with measurable snow on the ground at the daily observation (data back to 1953). The previous record was May 6, 1955. Interestingly last year there was snow on the ground on May 4.
The cold hasn't stopped breakup from proceeding, however. The ice went out on the Yukon River at Tanana on Wednesday, and the Kuskokwim tripod at Bethel stopped the clock on Wednesday morning, despite a temperature of 25°F with snow falling. Unfortunately significant flooding is now occurring in Bethel and elsewhere on the lower river, as the ice is jammed up downstream.
On the other side of the Arctic, very unusual cold is also affecting western Russia; it was snowing in Moscow yesterday for their big parade. Severe freezes have also occurred in the Baltic states in recent days - a rare event for this late in the season. As I commented in my last post, I think the "perturbed" flow pattern can be traced back to the lingering circumpolar disruption caused by the March stratospheric warming event.
Monday, May 6, 2024
Late Snowfall
Friday, May 3, 2024
April Snow and Temperature
Tuesday, April 30, 2024
Winter Lives
Breakup and snow melt are well advanced for parts of the Alaskan interior, but winter isn't quite ready to relinquish its grip in the far north. Temperatures dropped below 0°F this morning across much of the western and interior North Slope, and a strong northerly wind event developed at Howard Pass, with brisk wind chills below -30°F.
This morning's low temperatures:
Monday, April 22, 2024
Warming Up Fast
A very strong upper-level ridge over Southeast Alaska and northwestern Canada has produced a big warm-up for eastern and southern Alaska in the last week, with temperatures reaching record levels for the time of year in some spots. Yakutat reached 64°F on Friday, which would be the warmest on record this early in the season if it were not for a similar warm-up in 2021. Numerous locations set daily record highs on Friday and/or Saturday, from Ketchikan (65°F) in the far south to Bettles in the northern interior (56°F).
Here's the 500mb analysis from 4pm AKDT on Thursday, courtesy of Environment Canada:
The most unusual warmth I spotted was at Cordova, where the daily minimum temperature of 47°F on Thursday was the highest overnight minimum this early in the season by a full 3 weeks. Bettles also saw a record warm night for this early, with a low temperature of 39°F on Thursday despite having 29" of snow on the ground at that time.
As of the last daily report, Fairbanks snow depth is down to 3", so the official meltout date may well be today. The ice at Nenana is looking very rotten, and the accumulation of thawing heat units is now in the historical range for breakup. However, with unusually thick ice this year - measured at 50" a couple of weeks ago - perhaps it will be a few more days before the tripod goes out.
With meltout occurring earlier this year than the last two seasons (both in early May), green-up and fire season in the eastern interior will probably come to life a bit earlier as well. Here's an article discussing this, with a few comments from Rick Thoman:
https://www.webcenterfairbanks.com/2024/04/17/fires-floods-risk-with-early-may-green-up/
It makes sense that there would be a connection between early snowpack loss and increased early-season fire activity, so I had a quick look to see if this shows up in the data. The chart below shows June 1 fire acreage statewide versus the snowpack meltout date in Fairbanks:
There does seem to be something of a relationship, although it's marginal and the sample size is small (I only have daily fire data back to 1995). If we step forward to July 1, the relationship seems to disappear:
The highest July 1 acreage on the chart was in 2022, when the Yukon-Kuskokwim region saw unprecedented early fire activity owing to a very dry spring; there's a lot more to the puzzle than just the timing of meltout.
https://ak-wx.blogspot.com/2022/06/early-fire-and-may-climate-data.html
Tuesday, April 16, 2024
Breakup Outlook
Thursday, April 11, 2024
March Climate Data
I'm not quite back to a normal posting schedule, but here's a quick look back at the March climate anomalies across Alaska. It was another wetter-than-normal month for the state as a whole, the 5th in a row according to NOAA/NCEI, and indeed only October was drier than normal in the last year. It was also the 6th consecutive March with above-normal statewide precipitation; the last significantly dry March was way back in 2017.
As in February, the wet weather was focused in western Alaska owing to a Bering Sea trough:
According to ERA5 data, March was also an exceptionally cloudy month, except in the Panhandle.
Monthly mean temperatures were significantly above normal in the southeastern interior and near the coastline from Anchorage eastward, although not approaching record levels.
ERA5 snowpack data shows a significant excess for most of western and northern Alaska, as well as south-central, but low snow in the southern interior and the Panhandle.
The April 1 NRCS snow survey has some very interesting comments:
"The most exceptional April 1 snowpack in Alaska exists around Valdez. This is a place known for massive snowfall and this year’s snowfall has not disappointed. NRCS Snow Survey uses software to quality control station data based on previous values recorded at a site. The first time our quality control software had to be adjusted for the Upper Tsaina SNOTEL, near Thompson Pass, was in November, when a massive snowstorm eclipsed the amount of snow that had ever been recorded at this site for the date and flagged the data as erroneous. The same thing had to be done in December, and then again in January before we finally set the snow depth higher than the value the station is capable of measuring, which it is currently at. This station was installed in 2002 and has been reading its period-of-record maximum value for most of the year. Right down the road, the Lowe River Snow Course has a much more robust history, and on April 1 it was measured as the highest value in fifty-three years of observation.
Exceptional snowpack continues north from Thompson Pass into the Copper River Basin. Several April 1 measurements in the Copper River lowlands were made as the second highest on record. This basin snowpack has been hearty all year but is not as outstanding as it was last year at this time, when most of the measurements were period-of-record maximums. The other record snow measurements in this report were taken from our partners in Canada, where there are two April 1 records in the upper Porcupine.
The snowpack around Anchorage has been making headlines this year. This highlights a difference in how snow measurements are taken. The Anchorage National Weather Service office at Sand Lake uses a snow board and records the amount of snowfall that falls on the board several times a day throughout the winter. The amount of snow that has been measured is currently the third highest on record and will crown 2024 as the snowiest if a few more inches of snow falls this spring. Snow Survey measures snowpack as an quantity of snow water equivalent (SWE) a site has at a given date. The Kincaid snow course is very close to the Sand Lake office and recorded its sixth highest April 1 reading in its much less robust thirty-three-year period-ofrecord. This is most likely a function of melting during periods of above Normal temperature in February and March.
There are a few places in Alaska with below Normal snowpack on April 1. The measurements taken on islands in Southeast Alaska are below Normal. Several stations are also reporting below Normal snowpack in the interior, where slightly below Normal snowfall combined with warmer than Normal temperatures. In Northwest Alaska Kelly Station SNOTEL has reported below Normal SWE for all of 2024 and is reporting less than half of Normal snowpack on April 1.
In Western Alaska and on the North Slope above Normal precipitation through the winter months hints at above Normal snowpack. Bethel, Aniak and McGrath have had considerably wetter than Normal monthly precipitation totals in February and March. In an effort to understand snowpack in the Kuskokwim basin, the McGrath SNOTEL was installed in 2019. This station is proximal to the no longer measured McGrath Snow Course. The 7.6 inches of SWE reported at the SNOTEL would be considerably higher than the 5.6 inches that is the period-of-record April 1 median for the snow course. Interestingly the reported SWE is the lowest in the McGrath’s five-year history, a testament to how snowy the last five years have been in this region."