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Posted at 12:00 PM ET, 01/11/2009

Our Microclimate Ice Storm

By Kevin Ambrose

* Biting Cold Looms: Express & Detailed Forecast | InaugurationCast *

An icicle melts late Wednesday morning near Fairfax, Va. By Capital Weather Gang photographer Kevin Ambrose. Click here for enlarged image.

I read the comments on CWG (here and here) and on about scattered ice accumulations across the D.C. area Tuesday night, including in Arlington and Reston. Meanwhile, some readers well to the west -- in the normally colder outer suburbs -- noted they were above freezing with no ice accumulation. At my house near Oakton, Va., the ice also did not accumulate.

It seemed odd there were isolated pockets of sub-freezing temperatures and accumulating ice near D.C. while many other areas were above freezing with plain rain. The next morning I think I may have solved the mystery of why we had some colder "microclimates" around the area that allowed ice to accumulate in some places but not others.

Keep reading for the explanation and more icy photos...

Ice accumulation on pine needles Wednesday morning near Fairfax, Va. By Capital Weather Gang photographer Kevin Ambrose.

As I drove to a meeting Wednesday morning, I crossed over a high hill located west of Fairfax, near Fair Lakes. As I drove up the hill there was a point where the trees suddenly had ice. All of the trees on the hilltop were frosted white, everything below was just wet. Thus, it appears the ice in our area was elevation related, where perhaps the highest hills were sub-freezing while most of the lower-lying areas were slightly above freezing.

I researched the hill with the ice and it is almost 500 ft. in elevation. The freezing line was between 450 and 475 ft.

I'd be interested to hear about other areas that did or did not experience ice.

Ice accumulation on trees Wednesday morning near Fairfax, Va. By Capital Weather Gang photographer Kevin Ambrose.

Frosted trees at the top of Ox Hill on Wednesday morning near Fairfax, Va. By Capital Weather Gang photographer Kevin Ambrose.

By Kevin Ambrose  | January 11, 2009; 12:00 PM ET
Categories:  Photography  
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Here in Burke,VA, I had no ice accumulation, just plain rain. Burke is about 8 miles southeast of Fair Lakes. The elevation here is 266 ft. So we were way below the freezing line.

Posted by: Yellowboy | January 11, 2009 12:40 PM | Report abuse

Kevin, great research and stunning pictures. In Silver Spring I can also concur that only the top of trees near high rises had any ice on them. It was quite notable that downstairs at entrance to same highrises, the walks and plants were all clear!

Posted by: Camden-CapitalWeatherGang | January 11, 2009 1:30 PM | Report abuse

Getting mighty sick of "plain rain" and even the outlook for my 62nd birthday on Thursday is starting to "dry up" so to speak. The extended charts show a pretty good frontal shortwave, but it is (a) tending towards the "clipper" genre [read: insufficient moisture] (b) tending to track slightly NORTH of us [read: just another #@&$ WINTRY MIX setup if there IS any moisture!]. Looks like I have to wait a while longer for the next "Knickerbocker".

Posted by: Bombo47jea | January 11, 2009 3:25 PM | Report abuse

There is still ice on the trees on top of the small mountains near Harpers Ferry.

Posted by: MKadyman | January 11, 2009 4:27 PM | Report abuse

Cascades/Sterling (behind the Costco) had some ice on the trees up on the hill. It's a higher elevation in that small area.
The sight caught me by surprise....

Posted by: bodyiq | January 11, 2009 5:29 PM | Report abuse

cool story. I'm curious about ice in Arlington, though...I didn't see any at all near my home or school. Whereabouts was the ice reported, anyone know?

Posted by: dinergirl | January 11, 2009 6:14 PM | Report abuse

No ice in Manassas.

Posted by: manassasmissy | January 11, 2009 7:19 PM | Report abuse

Western loudoun had ice - it actually lasted well into wednesday. Come on summer...

Posted by: rumbly45 | January 11, 2009 7:29 PM | Report abuse

dinergirl, I don't know where in Arlington received ice, but the person who posted the Arlington ice observation gave his elevation at 482 feet.

Posted by: Kevin-CapitalWeatherGang | January 11, 2009 8:14 PM | Report abuse

have i missed years past weather statements about this? but this is the first season nws talks about the elevation factor along with the normal 2000ft above sea level forecast. they have mentioned several times this season already about 500 ft icing?

Posted by: deveinmadisonva | January 11, 2009 8:19 PM | Report abuse

Early Wednesday morning, traveling to Tyson's Corner, I saw ice on tree branches as I hit the top of Idlewood Road; I turned left on Route 7 and saw a little less ice at first, but as I moved further west and back up the hill, I again saw ice on the tops of trees near the intersection with the Beltway. A definite difference in ice placement tracking to elevation, now that you mention it.

Posted by: --sg | January 11, 2009 8:50 PM | Report abuse

sg, Thanks, I was wondering if Tysons Corner had ice. The highest natural hill in Fairfax County is located in Tysons Corner, near the beltway. The hill is 515 feet in elevation. As an FYI, the highest man-made hill in Fairfax County (the old landfill) is near where I photographed, on Ox Hill, near Fairlakes. It is 567 feet in elevation.

Posted by: Kevin-CapitalWeatherGang | January 11, 2009 9:44 PM | Report abuse

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