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A Quick Look at NAM – Who Will Have a White Christmas?

23 Dec 2008, 8:48 am
Forecast Snowdepth Animation - Click for Full Size
Forecast Snowdepth Animation - Click for Full Size
Forecast Snowdepth Christmas Day Valid 21z, 12/25/08
Forecast Snowdepth Christmas Day - Click for Full Size

To NAM, or not to NAM: that is the question… Weather ’tis nobler in the mind to suffer the slings and arrows of outrageous fortune, or take arms against a sea of troubles, and by opposing end them? To die.. to sleep.

Could Hamlet have been trying to determine the track of snow and rain this morning? After viewing the 06z NAM run this morning I decided to share with you the forecast snowdepth product that you have seen from time to time. Recall from previous posts (our search feature above right is an excellent tool for just such a purpose), that forecast snowdepth is essentially if new snow were to fall in some area within a forecast cycle, how much snow is likely to be left on the ground at the end of each interval within that forecast period, above that which is already existing at ground level.

The interesting part for this forecast (recall again that our WRF/NAM product contains forecast intervals of three hours out to 84 hours or 3.5 days from initialization), is the snowdepth forecast to exist along the surface low that we discussed yesterday, in addition to new snowfall from the Central Rockies to the Pacific Northwest.

Note in the animation (click here for full size or the graphic at top left) the swath of snow forecast to remain beginning in northeastern Texas on a track northeasterly through the Ohio valley. This is similar in thinking to yesterday’s outlook, but more on a line south and east to what the models were thinking. There certainly is some more hefty snow in the works for many areas!

Additionally, note how the snow ‘disappears’ as the animation progresses due to the warmer temperatures we discussed will advect into the region. I have the loop speed for the graphic a little faster than normal so you can appreciation the propagation of this system.

Because so much snow is already existing from the central Rockies to the Pacific Northwest, it may be slightly more difficult for you to discern new snowdepth patterns in the animation. This is actually a normal thing, especially for the Cascades this time of year, however new snowfall can be discerned within the region, especially along Northern California northward, and east into Wyoming.

That’s all for now, just wanted to give you a quick look at what NAM was thinking this morning. Oh, I almost forgot! You can see it in the animation, but I also saved a forecast snowdepth image for Christmas Day, valid 21z, December 25 (top right). So if you want to know who NAM thinks will have a white Christmas, just give it a click! =)

Please be sure to view our Advisory and Radar Centers for the latest updates and developments.

As always stay tuned to your favorite weather outlet, stay informed, and stay safe!



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