Friday, October 9, 2009

Imagine If It Were Cold......

Typhoon Melor moved away from Japan yesterday & is now beginning the process of being drawn into the jet stream.  Meanwhile the ridge this weekend over CA that will bring beautiful weather will kick East on Monday.  The ridge in the Central Pacific will simultaneously flatten forming a flat jetstream from one side of the Pacific to the other, almost exactly following zonally the warming area of water across the Pacific North of Hawaii.  It is rare to see a connection this far across the Pacific especially in the middle of October.  This will create a very strong & moist jetstream coming under a storm off the PacNW coast on Monday night, aimed directly at CA!

The precip should begin to fall by Tuesday morning over most of the area.  The storm could last a few days with the heaviest precip Tuesday night into Wednesday & then possibly some leftovers for Thursday.  Because of the direct West-East orientation of the incoming moisture there should be a lot of shadowing to the East of the crests, but still plenty of rain for everyone.  The models are a little back & forth on who gets the most, with the Central Sierra looking more likely with the latest model runs, but we can fine tune that later.  Either way it looks as if we will get at least a couple inches of rain possibly more.

The excitement with the storm will not be the snow but the strength of a storm so early in the season & the great start to the water year after dry falls the past few years.  The snow levels may begin just above 7000ft. especially with evaporational cooling that happens when a storm first starts & the precip falls into dry air.  As the bulk of the moisture comes in the snow levels rise to over 8000ft. so if you want to see snow you will have to hike high to see it.  The snow levels may come back a little below 8000ft. later Wed. before the storm ends.  A little trick for judging snow levels if you are running the models.  Usually the default mode of the models will have thickness lines as well as pressure lines & precip.  The 1000-500 thickness lines are the dashed lines running West to East with numbers in the 500's like 540, 546, 552, 558, etc.  For a snow level of around 6,000ft. you generally want the 552 line to be below us, for around 8,000ft. you want the 558 line below us.  You'll see with this storm the 558 line starts below us then goes above us which would suggest the snow level below 8,000 then rising above 8,000ft.

Imagine if this storm was all snow, we would have all the resorts able to open by the end of next week with several feet of snow.  We need the moisture either way.  Looking long term it looks as a ridge will form behind the storm will sun & mild temps for next weekend & the following week.  Next chance at storm activity looks to be the last week of the month, but of course that is subject to change.  Get all your stuff that can't get wet covered & tie things down this weekend.  Strong winds will also be a part of the storm, up to 100mph. on the ridges.  BA

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