Powder Forecast — Tuesday January 10th, 2017

Tuesday January 10th, 2017

Ted Schlaepfer CCM  —- Mammoth Mountain WeatherGuy

Forecast Summary:

    Part three of the major storm cycle peaks tonight with blizzard conditions followed by one last smaller storm Thursday before the storm cycle ends Friday.  Dry weather is then expected through the MLK holiday weekend and into the middle part of next week.  The next chance for snow will then be late Wednesday or Thursday next week with a continued chance through the following weekend that could be a start to another storm cycle.  Longer range models are suggesting that storms could continue at times through the end of the month and into early February.

Next update Friday 1/13.

Snowfall forecast are for the Sesame snow course (Main Lodge)


**Snowfall forecast confidence ranges from very low (1) to very high (5)

Wed 1/11 = 27 – 30” (H20 = 3.00” – 3.25”) **3

Thu 1/12 = 7 – 9” (H20 = 0.65” – 0.85”) **3

Fri 1/13 = 5 – 7” (H20 = 0.45” – 0.55”) **3

Storm Total = 39 – 46” (H20 = 4.10” – 4.65”) **4

Sat 1/14 = 0”

Sun 1/15 = 0”

Mon 1/16 = 0”

Tue 1/17 = 0”

Wed – Fri 1/18 – 20 = 6 – 18”

January Snowfall = 91.5”

January Forecast = 160 -185”

Detailed 5-day Snowfall Forecast:

Tue 1/10 — Blizzard conditions continue tonight and continue overnight with snowfall rates tapering off toward dawn.  Accumulations 27 – 30” by Wednesday AM. 4 – 5 feet up top.

Wed 1/11 — Snow showers continue through the morning hours before tapering off PM and into the evening, then increase again toward dawn.   Accumulations 7 – 9” by Thursday AM;  Around a foot up top.

Thu 1/12 — Snow likely increases during the day before ending Thursday night.  Accumulations 5 – 7” by Friday AM.  Close to a foot up top.

Fri – Sat 1/13 – 14 — No snowfall expected either day.

Forecast Discussion:

Short Term:   

  Satellite imagery (below) shows the final strong storm in the series of storms dating back to last week is now moving ashore into central and northern CA with heavy rain and strong winds.  Heavy snow has already developed over parts of the Sierra and snowfall in Mammoth will increase further in intensity this afternoon with major blizzard conditions forecast for tonight.

   The latest model QPF for this storm is around 3-4” inches with the GFS model (below) showing about 3” for today and tomorrow.   The ECM model is slightly higher and around 4 inches and the Canadian is similar to the ECM.   Overall, the forecast follows the wettest guidance as these are ideal conditions for a Sierra snowstorm with a strong moist westerly jet slamming into the Sierra.

   Snowfall amounts should be around three feet at Main by tomorrow late morning when the snowfall mostly ends with 4-5 feet of snow up top.  This storms isn’t as warm as the last one with snow levels around 5K that will rise slightly this evening before falling tomorrow to near 4K.  Still, it will be Sierra cement type snow, just not as heavy as the last storm and fun to ski/ride.

   Wednesday will be a powder day on the mountain, hopefully with some terrain to take advantage of the new snowfall since the mountain has been mostly closed over the last few days due to extreme avalanche danger and stormy conditions.  With some snow showers expected to continue through the day and into the night, it is doubtful that the top will open.

   Models are showing one last smaller storm moving in early Thursday which is the remnant parent low pressure system that fueled all the storminess since Saturday.   Models are generally in agreement with the track of the storm down the coast (image below) and close enough to the Sierra for some jet energy to push a front into the range for snowfall on Thursday.

   It won’t be a big storm with probably around 6” at Main and maybe close to a foot up top and the snowfall will probably keep the top closed for another day.  Nonetheless, there will be fun skiing/riding Thursday as the storm will be the coldest of the cycle and the snowfall of a drier quality.

   The storm cycle finally ends Thursday night with dry weather returning Friday.  A high pressure ridge (image below) will then build into CA over the weekend and into next week for fair and dry weather.   Temps will remain seasonably cold through the weekend (awesome conditions) before warming up next week with freezing levels approaching 11 K by Tuesday.

Long Range:

  The dry weather likely lasts into the middle part of next week before the pattern may change back to stormy again by the end of the week and into the following weekend or longer.  The GFS model develops a strong zonal flow next week with the jet stream lowering in latitude toward the end of next week.   It moves the first storm into CA next Thursday (image below) with some ensembles showing it could move in as early as late Wednesday.

   The potential pattern for the end of next week is different than the current pattern.  The current pattern was the result of upper level blocking or ridging in the Gulf of Alaska and Aleutians that forced a southwesterly and now westerly jet stream underneath it into CA laden with sub-tropical moisture.

  The pattern end of next week does not show a block or ridge in that position, but a deep low pressure trough instead with a similar strength or even stronger westerly jet stream moving across the entire Pacific and into the West Coast.   That means that storms would still have good moisture from the ocean to produce snowfall, but also more cold air as the counter-clockwise circulation of the G.A. upper low allows for colder air to move into the back side of the circulation.   Bottom line, these potential storms would be all snow and not produce a large threat of high snow levels and rain.

    The GFS model has been rather bullish on a stronger storm for the end of next week (image below) and the ECM is only slightly weaker.   However, the Canadian shows continued weak ridging and is the odd model out, although some of the GEFS ensembles similar to the Canadian.  However, the 12Z run of the Canadian ensemble does show the jet lowering into CA, just later than the other models by a couple days.

   The potential pattern does have some support by the GFES ensemble mean (image below) that shows a lower latitude westerly jet (purple arrow) and the ECM ensemble is even more bullish.   The ECM mean shows a nice storm pattern continuing into the following week.  So after almost a week of dry weather, it looks like snowfall returns by Thursday or Friday next week, and it could be heavy at times again.

   The latest climate models are not in good agreement for the rest of the month.  The ECM model keeps the Gulf of Alaska low in the same general position through the end of the month and into early February.  The CFS has the low weaker, bit farther off the coast, and is generally drier.  Seems to me it is feast time after lots of famine.  I am favoring continued storms at times into early February, but probably not a big as of late.  WG

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