1″/hr Snowfall Rates and Transition to Sleet as Observed by Time Lapse Photography and WSR-88D Data

Now that the much-awaited winter storm is unfolding across the region I thought I’d share a time lapse of today’s snow accumulation ending with a sudden changeover to sleet in Cary, NC (central Wake county).  The attached animated GIF contains 17 frames at 15-minute intervals between 12:15 pm and 4:15 pm EST (1715-2115Z) today (February 12, 2014).  Snowfall rates were around 1″/hr for roughly 4 hours.  The last 2 frames of the time lapse show a dramatic improvement in background visibility, an indication of the quick changeover to sleet that occurred between 3:45 pm and 4:15 pm EST (2045-2115Z).  You can also see my (relatively futile) attempts at shoveling the driveway.

I’ve also attached an animated GIF of KRAX 0.5 degree REF/CC from 3:45 to 4:15 pm EST (2045-2115Z).  My precise location is marked by the ‘red dot’ at the center of the range rings in central Wake county. You can clearly see the SN/PL transition occurring along a SW-NE line of reduced correlation coefficient values across Chatham/Lee/Wake/Franklin/Nash counties.  In this case, reduced CC values can be used as a reasonable proxy with regard to identifying the leading edge of the warm nose (~2+ C) advancing northwest across the Highway 1 corridor.

***Below Update at 4:00 pm (2100Z) February 13, 2014***
I’ve posted a more complete time lapse that captures virtually the entire event in central NC, from 1715Z on February 12 through 2045Z February 13.  The time lapse shows:

1) the initial round of heavy snow between 1715-2045Z (Feb 12)
2) the transition to sleet between 2045-2115Z (Feb 12)
3) the gradual transition from sleet to freezing rain between 0000-0300Z (Feb 13)
4)
the accumulation of ice as noted by the increasing ‘sag’ of trees between 0300-1000Z
5) the
melting of ice (as indicated by ‘rebounding trees’) associated with strengthening
insolation and above freezing temperatures after ~1600Z
6)
further melting and a transition from rain to snow after 1900Z in
association with the deformation band

Brandon Vincent
Meteorologist
WFO Raleigh, NC

Time Lapse of the February 12-13, 2014 Winter Storm (1715Z February 12 through 2045Z February 13)

Time Lapse of the February 12-13, 2014 Winter Storm (1715Z February 12 through 2045Z February 13)

 

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2 Responses to 1″/hr Snowfall Rates and Transition to Sleet as Observed by Time Lapse Photography and WSR-88D Data

  1. J. Halverson Prof Geography UMBC says:

    Nice use of CC to demonstrate a key phase transition. It’s also notable that there is a patch of enhanced dBZ along the western segment of the CC minimum.

  2. Jonathan Lamb says:

    Wow, neat writeup Brandon! Jonathan

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