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January 20-21 Snow/Sleet/Ice/Rain event OBS


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72403 IAD Sterling Observations at 00Z 21 Jan 2012

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PRES HGHT TEMP DWPT RELH MIXR DRCT SKNT THTA THTE THTV

hPa m C C % g/kg deg knot K K K

-----------------------------------------------------------------------------

1014.0 93 -0.9 -11.9 43 1.52 245 2 271.2 275.5 271.4

1013.0 101 -0.9 -15.9 31 1.10 243 2 271.2 274.5 271.4

1011.0 116 -1.3 -17.3 28 0.98 240 2 271.0 273.9 271.2

1000.0 199 -2.1 -15.1 36 1.19 220 3 271.1 274.5 271.2

997.0 223 -2.3 -15.3 36 1.17 209 3 271.1 274.5 271.3

986.7 305 -2.9 -15.2 38 1.19 170 5 271.3 274.8 271.5

949.3 610 -5.0 -15.0 45 1.26 150 12 272.2 275.9 272.4

933.0 746 -5.9 -14.9 49 1.30 190 9 272.6 276.4 272.8

926.0 806 -5.1 -10.1 68 1.92 208 7 274.0 279.5 274.3

925.0 814 -5.1 -10.1 68 1.93 210 7 274.1 279.6 274.4

913.3 914 -5.1 -8.4 77 2.23 215 13 275.1 281.4 275.5

909.0 951 -5.1 -7.8 81 2.35 217 14 275.5 282.1 275.9

893.0 1091 -5.1 -7.8 81 2.39 224 17 276.9 283.7 277.3

880.0 1206 -2.3 -4.7 84 3.08 229 20 280.9 289.8 281.4

878.6 1219 -2.4 -5.0 82 3.00 230 20 281.0 289.6 281.5

857.0 1416 -3.5 -10.5 58 2.01 249 18 281.8 287.8 282.1

850.0 1481 -3.7 -14.7 42 1.45 255 17 282.3 286.6 282.5

847.0 1509 -3.5 -16.5 36 1.25 256 17 282.8 286.6 283.0

841.0 1565 -2.9 -15.9 36 1.32 259 17 284.0 288.0 284.2

813.4 1829 -3.9 -16.2 38 1.33 270 19 285.6 289.7 285.8

804.0 1920 -4.3 -16.3 39 1.34 273 22 286.1 290.3 286.4

792.0 2039 -1.9 -14.9 36 1.53 277 27 289.9 294.7 290.2

782.6 2134 -1.5 -13.3 40 1.76 280 30 291.3 296.8 291.6

777.0 2191 -1.3 -12.3 43 1.92 281 31 292.2 298.1 292.5

765.0 2315 -2.3 -11.3 50 2.12 283 34 292.4 298.9 292.8

753.2 2438 -2.9 -7.3 72 2.95 285 37 293.0 301.9 293.5

750.0 2472 -3.1 -6.2 79 3.22 283 37 293.2 302.9 293.8

724.7 2743 -4.8 -7.7 80 2.96 265 41 294.2 303.3 294.8

717.0 2827 -5.3 -8.2 80 2.89 262 43 294.6 303.4 295.1

700.0 3015 -5.9 -9.7 75 2.63 255 48 295.9 304.1 296.4

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72403 IAD Sterling Observations at 00Z 21 Jan 2012

804.0 1920 -4.3 -16.3 39 1.34 273 22 286.1 290.3 286.4

792.0 2039 -1.9 -14.9 36 1.53 277 27 289.9 294.7 290.2

782.6 2134 -1.5 -13.3 40 1.76 280 30 291.3 296.8 291.6

777.0 2191 -1.3 -12.3 43 1.92 281 31 292.2 298.1 292.5

For comparison, 18z NAM sounding for 0z at IAD had:

825mb -0.5C

800mb -0.4C

775mb -3C

18Z GFS had:

850mb -1.3C

800mb -1.5C

Looks a bit colder than either in reality. Below that level, NAM looks like a pretty decent match.

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What is it with the bubble that develops around the city during a lot of winter storms? I can't count the number of times that ive seen it.

On the radar? That's an artefact. The radar beam is seeing virga and the clouds aloft at a distance because the beam finally intersects them at that range. The beam is not parallel to the ground, but starts at a low angle (e.g., 0.5deg) and then scans progressively higher angles. Above the radar is the "cone of silence". There could very well be virga and there are certainly clouds above our area, just the radar can't see them.

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On the radar? That's an artefact. The radar beam is seeing virga and the clouds aloft at a distance because the beam finally intersects them at that range. The beam is not parallel to the ground, but starts at a low angle (e.g., 0.5deg) and then scans progressively higher angles. Above the radar is the "cone of silence". There could very well be virga and there are certainly clouds above our area, just the radar can't see them.

Thanks for the explanation!

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Radar looks decent to the SW of here. Maybe some flakes knock on the front door here soon in LoCo

The intresting thing about that is that the precip is advancing towards the radar. GR2AE says the virga "deck" is around 1000ft and "falling". Probably snowing on the blue ridge pkway right now.

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The intresting thing about that is that the precip is advancing towards the radar. GR2AE says the virga "deck" is around 1000ft and "falling". Probally snowing on the blue ridge pkway right now.

I wouldnt be surprised JT if it is. Get out there at 1, 2, 3000 feet and i bet it is coming down.

they need to put webcams up so it can be used for night viewing as well.

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if you recall the Big Meadows ob I posted earlier today, S and SW of DCA never got into the arctic air

I know this is no comparison, but PDII EZF had a ton of sleet after a relatively few hours of snow+

Yep. We in Woodbridge had about 8-10 inches of snow, then sleet for the next 18 hrs or so, Piled another 5 inches of dreadfull iceballs at 14 degrees during the event. It was so frustrating.

Finally down below 30. Sitting at 29.6, Was at 30.8 about an hour ago, so I guess that's better news.

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