ESRL Global Systems Division
NPN Alaska Profilers Help NWS Forecasters with Anchorage 100 Year Snow Event
A record setting snow event occurred over Anchorage during the weekend of March 16-17, 2002. Snow began Saturday evening and then ended late Sunday evening with snow intensities reaching 1.5" - 2.0" per hour and total accumulation at 28.7 official inches. According to the forecasters the storm was a very complex event attributed to a "one in a 100 year lineup" of the atmosphere associated with an arctic front whose boundary was located less than 100 miles to the southeast of Anchorage. Producing this record event was a combination of:
- just the right wind flow at the surface and aloft,
- just the right amount of moisture,
- just the right vertical temperature structure, and
- just the right time change of conditions.
In addition to satellite imagery from GOES and data from a radar located on the Kenai pennisula, the forecasters also said that "Tazlina (Glennallen) and Petersville Road (Talkeetna) profilers were of great help in monitoring changes in upper wind strength and direction....which played a key role in forecasting the end and intensity of the snow Sunday." As shown at left, the Talkeetna and Glennallen profiler locations are approximately 85 miles NNW and 170 miles NE of Anchorage, respectively.
Talkeetna and Glennallen data displays of the wind speed and direction from ground to 16.25km (top panel) are shown below from March 16, 00:00 UTC (3:00p on March 15, Friday, local time) on the right side of each display to March 18, 23:00 UTC (2:00p on March 18, Monday, local time) on the left side. The lower panels show the snow event as indicated by the red and yellow areas. Note that the ending of the snow is marked by a change of wind direction about 06:00p Sunday evening (03:00 UTC Monday).
Name: Margot H Ackley