Saturday, December 5, 2009

T-1 Day

Don't you feel like tomorrow can't come fast enough?

Cold front has moved through already this morning. This begins a week of very cold and snowy weather. We may see a snowshower or two today.

Low pressure coming down the coast tomorrow with even colder air. This storm is going to connect with a moist flow off the ocean to create heavy snowfall Sunday night through Monday night. Lows in the teens Sunday night and highs will be lucky to break 20 on Monday & Tuesday, and should stay in the low teens above 7000 ft. Lows Monday night could drop below zero in Truckee if the skies clear. Why is this so important? Models are in agreement on around .75 - 1 inch of liquid from the storm. A normal storm at 32 degrees the snow ratio is 10:1 so we would get 8-10 inches. This storm will average snow ratios of 20:1 at lake level, with up to 30:1 at the highest elevations. That puts us at 15-20 inches at the Village and over 2 ft. possible on top if current predictions hold. This will be similar to the snow we got on Christmas Eve last year. You can clear your driveway with an oscillating fan.

Getting a little break Tuesday but it will be cold. Next storm moves in sometime on Wed. and could last through Friday. It is going to have a good tap of moisture extending all the way across the Pacific. Still a disagreement on the models as to where the heaviest precip comes into CA. These storms are perfect examples of El Nino pattern storms where the bulk of the moisture goes into Central and Southern CA and we are on the Northern edge. Models have been pretty consistent the past couple of days with somewhere around 2-3 inches of liquid over Tahoe. Snow ratios with the warmer moister flow off the ocean will most likely be closer to 12:1. With that, current predictions would bring us 2-3 feet of additional snowfall. Will have to keep watching the exact track and where the moisture plume into CA sets up.

Still a chance at another storm on Sunday, but models in a bit of disagreement. This mornings GFS brings quite a big storm in for Sunday. MJO is fizzling out in phase 7. Forecasts have it circling back around to phase 5 this week and then heading East through the Pacific again. Our favorable area for the MJO to feed the jetstream is going from phase 5-7. We may have a little bit of a break in storm activity the week of the 14th before we start another round of storms. With a forecasted positive PNA promoting ridging in the Eastern Pacific we need help from the MJO to pump the jet under the ridge like we have this week. Eventually heading into January the effects from El Nino should do the job on its own. Thanks to the MJO we may get a head start here in December with snowfall before we have a big winter. Stay tuned......BA

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