North Slope Meltout

Spring has arrived in earnest on the North Slope in the past week, and the NWS noted today that breakup is underway:

209 PM AKDT WED MAY 27 2020

...BREAK-UP UNDER WAY ACROSS THE NORTH SLOPE...

WARM TEMPERATURES IN THE BROOKS RANGE ARE CAUSING RAPID SNOW MELT
THAT WILL CONTINUE THROUGH THIS WEEKEND. RIVERS DRAINING TO THE NORTH
SUCH AS THE COLVILLE, KUPARUK AND SAGAVANIRKTOK RIVERS ALL HAVE 
ICE REMAINING NEAR THE COAST, AND COULD HAVE ICE JAM ISSUES THIS 
WEEK AND WEEKEND AS RISING WATER LEVELS MOVE DOWNSTREAM. 

RIVERS NEAR THE ARCTIC COAST SHOULD BE MONITORED CLOSELY FOR ICE 
JAMS AND POTENTIAL FLOODING THROUGH THIS WEEKEND.

Here's the latest NWS breakup map (click to enlarge).

The average date for breakup at the Colville River delta is June 3, based on reports since 1996, so this year will not be far from normal.  The historical chart - see below - suggests a trend towards later breakup, but this is entirely because of two early years at the beginning of the series.  The long-term trend in temperature during May is most decidedly up.

Here are a couple of satellite images that illustrate the extent of snow cover remaining; the first image below is from Monday afternoon, and the second image is from today (click to enlarge).  Patchy cloud cover obscures the situation slightly, but there's no doubt the snow is disappearing.

[Update Friday pm: here's a great view from today, courtesy of and annotated by Rick Thoman.]

The Umiat webcams confirm that snow is gone on the middle Colville River (289' elevation), and even up at Toolik Lake (2460') there's a lot of bare ground now.  Both of these sites have exceeded 60°F already; summer's here.