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snow update: 1st major storm on track

By ccrossen | November 15, 2010

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Get ready for real winter starting this weekend. For those who have been getting the small fix and for those still waiting to get the legs going, the first major storm, a relatively early one at that, is on target for this coming Friday – Monday. If everything pans out, we could get multiple feet from this storm, which looks like it will hit in two waves, with the strongest part of the system striking Sunday – Monday. A strong, smaller portion moves in Friday, with cold temps, dropping the snow levels down to 3,000′ by Saturday. The system then backs off, and hits again on Sunday – Monday. We could see up to two feet in town, with up to five feet along the Crest, depending on how things hit. Winterize, get your errands done, stock up, and get ready to ski next week.


A number of resorts officially open this weekend. They’ve had favorable temps for blowing snow, and this storm will really setup a good base for skiing right away, especially during the Thanksgiving holiday.


See below for more details. Also, there’s a very positive reports from NWS, TWD, and Sheckter indicating that they believe we will see a wetter than average winter.


From NWS:

COLD FRONT WILL BE STRENGTHENING JUST NORTH OF THE AREA THURSDAY NIGHT AS COLD AIR DIGS ACROSS THE EAST PACIFIC AND STRONG PACIFIC JET (160KT+) MOVES THROUGH THE PACNW AND INTO THE NORTHERN ROCKIES. FRONTOGENESIS AND UPPER LEVEL FORCING FROM JET FEATURES WILL HELP BAND OF PRECIPITATION INTENSIFY ALONG FRONT WHICH WILL THEN BEGIN TO SAG SOUTHWARD FRIDAY. BOTH MODELS PUSH THE FRONT TO AROUND I-80 MIDDAY FRIDAY AND THEN THERE IS A NOTABLE ACCELERATION IN THE ECMWF. DECIDED TO WARM TEMPERATURES A BIT OVER THE SOUTHERN HALF OF THE FORECAST AREA AS TEMPERATURES COULD BE WARMER IN THESE AREAS PRIOR TO FRONTAL PASSAGE. OTHERWISE A VERY SHARP TEMPERATURE GRADIENT BEHIND THIS FRONT BRINGING SNOW LEVELS DOWN IMMEDIATELY TO THE VALLEY FLOOR. FRONTAL DYNAMICS WEAKEN AS THE FRONT SAGS SOUTH OF HIGHWAY 50. SO THE BEST QPF WITH THIS INITIAL FEATURE IS GOING TO OCCUR NORTH OF I-80 WHERE SEVERAL INCHES OF SNOW WILL BE POSSIBLE BY THE END OF THE DAY FRIDAY. TRAVEL THROUGH THE TAHOE BASIN AND ACROSS NORTHEAST CA WILL LIKELY BE IMPACTED.


MAIN UPPER LOW THEN MOVES SLOWLY SOUTHWARD ALONG PACNW COAST SAT-SUN WITH DECENT OVER WATER TRAJECTORY. VERY COLD AND UNSTABLE CONDITIONS SHOWN IN SOUNDING PROFILES SUGGEST SYSTEM WILL BE QUITE CAPABLE OF PRODUCING ITS OWN MOISTURE SOURCE AS ASSOCIATED CONVECTION IN THE PACIFIC GENERATES DEEP MOISTURE PROFILE. MODEL QPF SHOWS SEVERAL PERIODS OF PERSISTENT QPF ACROSS THE NORTHERN SIERRA INTO WESTERN NV. THERE IS A GOOD POTENTIAL FOR SEVERAL FEET OF SNOW TO FALL IN THE TAHOE BASIN WITH SEVERAL INCHES OR MORE POSSIBLE IN LOWER VALLEY AREAS. THERE IS STILL SOME UNCERTAINTY TO EXACT LOCATION OF HEAVIEST SPILLOVER AND BANDING. THE GFS CURRENTLY FAVORS THE HIGHWAY 50 AND I-80 ZONE WHILE THE ECMWF IS A BIT FURTHER NORTH. ANYONE WITH INTERESTS IN THE SIERRA OR WESTERN NV (ESPECIALLY TRAVEL RELATED) SHOULD CONTINUE TO MONITOR THE LATEST FORECASTS AS THIS STORM HAS THE POTENTIAL TO PRODUCE WIDESPREAD IMPACTS FROM ACCUMULATING SNOWS. TEMPERATURES WILL ALSO BE WELL BELOW NORMAL WITH DAYTIME READINGS NOT GETTING OUT OF THE 30S IN MANY LOCATIONS.


From TWD:

The storm will move in on Friday with the initial cold front bringing a round of heavy snow. The snow should then lighten up on Saturday before the main low moves down the coast tapping Pacific moisture and brings another round of heavy snow Sunday and into Monday. So let’s talk about potential snow totals. Instead of being conservative let’s look at lowest amounts and highest amounts possible based on the the latest model runs. Models are consistent on 2-3 inches of liquid over Tahoe for 2 days now, so that will be the basis for multiplying snow ratios. At lake lake level and in Truckee the temps will be 25-30 degrees. That is snow ratios of 12-15:1. I would say lowest end would be 18 inches with up to 3 feet possible. Above 7500 ft. the temps will only be 15-20 degrees which is snow ratios of 20-25:1. I would say that means lowest end 3 feet with up to 5 feet possible on top of the mountains. On the crest the potential is there to break 5 feet. We will even see several inches in Reno.


Since storms like this aren’t that common I looked back through the records of the NWS reporting station that is on top of Squaw. You have to go back 8 years to find a big multi-day storm in November to 2002. Nov. 7th-10th that year 44 inches fell at the reporting station which is a good estimate for the entire Sierra crest. This storm will be in that ballpark. The last big November as whole was the year before that with 88 inches in the month. So far this November we are at 17?. So it’s looking like we may be in store for the biggest November storm in at least 8 years and biggest Nov. for snow in at least 9 years.


From Sheckter:

Dweebs are now on board with the first major storm of the season. It appears that snowfall may begin as early as Friday morning……however a lot of the moisture with this system will remain off shore until a secondary short wave reloads the upper trof later Sunday. So the main thrust “is currently” expected into the Sierra , Sunday night and Monday a week a way.


The good news is that if these models are correct….and that is a big if beyond next weekend, the longest range looks dry for the Thanksgiving holiday, with the next large trof rolling in the end of the holiday weekend. (Wishful thinking?).


Just a quick note that that Dweebs believe that this will now be a wet La Nina winter for the Sierra. 100% to 120% of normal. It is mid November and so far the biggest observations to me are that:


1. The Upper jet across the pacific has been much stronger then normal. This will have the effect of limiting blocking patterns. So far there has been insignificant blocking over the western and central Atlantic.


2. This La Nina is associated with one of the strongest negative phase PDOs since the 1950s. This is highlighted by a lot of anomalously cold water over the far eastern pacific. This tends to perpetrate west coast troughing and should lead to wetter than normal conditions, extending well south into the central sierra this winter. Temperatures will average below normal through early 2011. As a note, the odds still favor a drier then normal winter for Southern Ca.


Having a negative phase PDO strongly correlates to having more persistent troughing in the Jet stream over/or along the West Coast…..and this supports an active, stormy pattern for the West coast and above normal temps over most of the Central and Eastern US.


Many of the Arctic out-breaks will be displaced west of the Continental divide early this winter and although it will get plenty cold over the northern tier states…cold air penetration will not be nearly as far south as it was last winter. That is because the pattern will be quite progressive as a result of the strong pacific upper jet.

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