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Jan 11 CWG snow threats discussion


usedtobe

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I'm liking the NAM look of the early Friday AM system.

Annimating the freezing level on the 850 mb temperature charts

shows the strong west to east CAA and it is outracing

the precipitation for once.

The precipitation shuts off from west to east and reaches the Chesapeake

Bay by 10Z. (5 am Friday).

The 850 temps zero line is faster than the o line at the surface. The temp at DCA at the ground is 9.2C at 06Z and 3C at 09Z. The precip by then has shut off and we get no precip at 09Z so I don't see this run as being that different than the old one, maybe a little colder but in terms of snow, not much different than the last run. We might see a few flakes right at the end but most of the precip will fall as rain and I don't see much chance for accumulating snow.

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Wes, thank you for the frequent understandable lessons. For understanding,

I attached the NAM forecast soundings; the latest available being 12Z. The

boundary layer changes dramatically from one image to the other.

By 12Z the precip is long gone. note how much separation there is between the temperature lines and dewpoints. It gets pretty dry.

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By 12Z the precip is long gone. note how much separation there is between the temperature lines and dewpoints. It gets pretty dry.

The SREF depicts that the boundary layers support frozen precipitation just as the 6-hour precipitation

shuts off.

Someone west of the Bay could get light snow/sleet/rain showers just as the road surfaces near freezing

north and west of DC/Baltimore during Friday morning rush hour.

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The SREF depicts that the boundary layers support frozen precipitation just as the 6-hour precipitation

shuts off.

Someone west of the Bay could get light snow/sleet/rain showers just as the road surfaces near freezing

north and west of DC/Baltimore during Friday morning rush hour.

I looked at the sref probabilities for snow and it puts it at 09Z at 20%. For snow lovers who will settle for any amounts the 06Z gfs is the model of choice as it predicts .04" liquid equivalent as snow for DCA and 0.025 for IAD. The nam has something like .004 or so for both places, essentially a trace at the end of the event. I guess either is a possibility though accumulating snow from frontal systems with no real low to speak of in the face of cold advection is pretty rare. Could happen but I'd go with a forecast of showers possibly changing to snow before ending.

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Katie,

That picture scares me. The 12Z nam doesn't look very encouraging to snow lovers. The freezing line is still west of us at 09Z suggesting even if it did change to snow it would not be much and would have a tough time sticking on roads.

I was just checking the NAM on e wall (they have those high res images now) and yeah, its not good for snow At. All.

Oh well.

You still rock though :)

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Katie,

That picture scares me. The 12Z nam doesn't look very encouraging to snow lovers. The freezing line is still west of us at 09Z suggesting even if it did change to snow it would not be much and would have a tough time sticking on roads.

I got .5" on Monday when temps were forecast to be too warm for all snow. I can live with a T again on grassy areas.

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I got .5" on Monday when temps were forecast to be too warm for all snow. I can live with a T again on grassy areas.

Maybe the gfs will look better though cold fronts usually are not great producers because behind the front the cold advection fights the lifting from the vorticity advection.

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Maybe the gfs will look better though cold fronts usually are not great producers because behind the front the cold advection fights the lifting from the vorticity advection.

how is your 1-3 inch clipper coming along that you encouraged zwyts about?

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