Saturday, February 24, 2018

Snow and Wind

The weather of the past couple of weeks has been very unsettled across western and interior Alaska, with multiple stormy episodes, and the contrast to the first 10 days of the month could hardly be greater.  Fairbanks has seen accumulating snow on 12 of the past 14 days, which is the most for this late in the season since 1971; snowfall normally becomes less frequent and lighter as winter advances.

The recent snow has brought the seasonal total to 67.1 inches, or 20" above the long-term median for the date (see below, click to enlarge).  This is marginally more than last winter for the same date, and it's the most since 2000.  A few more inches in the next few days could push February into the top 10 for snowfall, but we probably won't catch last February's total of 23.3" (see here for last year's blog post).



Another symptom of the stormy pattern has been the recurrence of relatively high winds of late in Fairbanks.  Conditions have been notably breezy in 5 separate events of the past 2 weeks, and 5 calendar days have seen peak 2-minute wind speeds above 20 mph (an unusual occurrence in Fairbanks).

The history of 2-minute wind speeds in Fairbanks only goes back to 1996 (the beginning of the ASOS era), but 5 windy days in 2 weeks ties the winter-time record from both March 2003 and December 2013.  In both of those previous cases most of the wind was in one prolonged multi-day event (see here for a blog post on the December 2013 wind); whereas this month we've had repetitive events, and this is really unusual.

The 500mb and 850mb height maps from the past 2 weeks show a pattern that is quite typical for warm and snowy conditions in Fairbanks, with a long fetch of southwesterly flow entering western Alaska.  Westerly flow aloft is easily the most favorable wind direction for heavy precipitation in the cool season, as we saw here.  It's also most common for strong breezes in Fairbanks to come from the west, as they have this month; the last figure below shows that the vast majority of windy days occur with westerly flow in deep winter.  (But note that this is not true in March, when winds are typically stronger and much more often come from the northeast.)






4 comments:

  1. Seasonal occlusions frequent our area pre-March as noted. The trailing cold front brings the surface breeze. Two cold fronts in succession topple trees and create problems. If March coming is typical the prevailing winds will shift to NE to SE with the Tanana valley jet quite active.

    Flocks of Ravens will soon gather to court and breed and can be seen over rising terrain near the University of Alaska Fairbanks or other nearby hills on windy days.

    Gary

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    1. Monday...Orographic lifting of W to SW flow is producing heavy snow N and W of Fairbanks again. Forecast of 6-12" depending on location. Winds will pick up this eve 15-30 again moving it about.

      Repetitive weather and well forecast by the NWS. Might beat last year?

      Gary

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    2. It's really remarkable, Gary. I will be in Fairbanks mid-March and am looking forward to the very snowy scene.

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