Powder Forecast — Friday December 30th, 2016

Powder Forecast — Friday December 30th, 2016

Ted Schlaepfer CCM  —- Mammoth Mountain WeatherGuy

Forecast Summary:

    Partly to mostly cloudy Saturday with just a chance for light snow showers during the afternoon/evening followed by dry weather through Sunday during the day with increasing wind and clouds during the afternoon.  Snowfall develops Sunday evening and continues Monday with much colder temperatures with snowfall tapering off Monday night.  Snowfall picks up again Tuesday and become heavy overnight into Wednesday with a continue chance for snow through Wednesday before ending by Thursday.  Friday and Saturday should be dry and cold followed by a chance for a significant storm Sunday and through early the following week with a continued chance for snow at times into mid-January before storms may become less frequent second half of the month.

Next update Tuesday 1/2.

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


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

Sat 12/31 = 0”

Sun 1/1 = 0 – 1”

Mon 1/2 = 3 – 5” (H20 = 0.15” – 0.30”) **3

Tue 1/3 = 8 – 11” (H20 = 0.40” – 0.55”) **3

Wed 1/4 = 12 – 18” (H20 = 0.75” – 1.25”) **3

Thu 1/5 = 5 – 8” (H20 = 0.35” – 0.55”) **2

Storm Total = 28 – 42” (H20 = 1.65” – 2.65”) **3

Fri 1/6 = 0”

Sat – Mon 1/7 – 9 = 12 – 36”

December Snowfall = 73”

December Forecast = 73”

Detailed 5-day Snowfall Forecast:

Sat 12/31 — There is chance for light snow showers Saturday afternoon and into the evening.   No accumulation expected other than possibly an inch.

New Years’ Day 1/1 — Dry with increasing clouds and wind during the day, then snow develops during the evening and increases overnight.  Accumulations up to 6” by Monday AM when lifts open.

Mon 1/2 — Snow and colder temps continues during the day and into Monday night, tapering by Tuesday morning. Accumulations 7 – 11” by Tuesday  AM.

Tue 1/3 — Chance for snow during the morning, then snow increases again Tuesday afternoon and night when it becomes heavier into Wednesday.  Accumulations 12 – 18” by Wednesday  AM.

Forecast Discussion:

Short Term:   

  Satellite imagery (below) shows an area of low pressure is currently sliding into SoCal this afternoon with rain showers and some clouds into Mammoth, but no snowfall.   The low will move eastward too far south for any snow for Mammoth.   There is two more low pressure systems upstream that will move through into/through CA through early next week as strong high pressure has formed in the Gulf of Alaska as part of the Rex Block (high pressure sitting north of a cut-off low pressure) in the E. Pacific and strong meridonal flow is established along the West Coast.

   The models (GFS below) move the next upper level low pressure system on Saturday too far westward on its track southward into SoCal to produce any meaningful snowfall in Mammoth during its passage.   Nonetheless, there could be light snow showers during the afternoon and evening while the SoCal mountains take the brunt of the storm where more than a foot of snowfall could fall by Sunday.

   The third upper level high latitude type low pressure system then moves into NorCal on Sunday with the front moving southward into Mammoth by Sunday night.  The increasing winds and clouds during the day will be the indicator of the snowfall that should develop Sunday night and continue at times through Monday.

   The models all agree that it will be a very cold weather system with snow levels getting down to 1000-2000 feet by Monday and should remain low into Tuesday. The models don’t agree about how much moisture the system will contain with the ECM model much wetter than the GFS. The Canadian is in between the two.  The orographic effects should be good under the stronger jet stream so there is certainly a chance for the ECM to verify, although I am skeptical of liquid amounts over 1” under such a cold air mass.

   Regardless, the snow ratios should be in the 20:1 range and the powder extremely dry and fluffy.  Good luck trying to make a snowball.   I suspect there will be more than a foot at Main by Tuesday AM with a decent shot at close to 18” and 24” up top.   It should also be a great riders of the storm day Monday under the snowfall, but bundle up, it will be crazy cold.  It will probably be single digits to low teens on the mountain Monday and Tuesday.

   The models are now in agreement that the main upper level low pressure system will remain along the West Coast into mid-week with the western flank moving back west over the ocean (image below).   That will allow the trough to entrain Pacific moisture before it finally moves ashore Wednesday.  While the snow levels will rise a bit late Tuesday ahead of the front, the increased moisture also means more total liquid to produce snowfall, even if ratios are 15:1 instead of 20:1.

   The models are, of course, not in agreement with how much entrainment of moisture will occur with the ECM the wettest again.   The GFS model (image below) has about three quarters of an inch while the ECM has over an inch.  The Canadian is similar to the ECM.  So it appears that snowfall will pick up again Tuesday during the day and become heavier overnight into Wednesday with snow probably continuing through at least Wednesday morning before ending Wednesday night.

   It will still be a cold storm and the powder dry/fluffy. Looks like another 18-24” is possible from Tuesday afternoon through Wednesday morning with maybe 3 feet up top.  Interestingly, the ECM ensemble mean is the wettest and shows over 1.5” liquid for the event, so there are likely more than a few ensemble members that entrain even more moisture, meaning that there is a chance for an even bigger storm.

   Looks like there will be a break Thursday and into Saturday under dry and cold NW flow.   The skiing and riding should pretty much be epic under the cold conditions and new snowfall.  The top and backside might not open until Thursday after being closed since Sunday, should be epic.

Long Range:

  Longer range models are showing another potentially significant storm moving into Mammoth by Sunday the 8th.   The ECM model (image below) has a deep trough moving ashore with a strong southwest oriented jet stream into central CA.   The model shows a significant snowfall event with over 3” liquid with the backside of the trough still offshore.

   The 12Z Canadian model (image below) shows historic amounts of QPF with around 10” for Mammoth in 24 hours.   That would be 80-100 inches of snow.   That is most certainly way overdone, but there is a signal for a stronger storm around that time frame with good support in the ensemble suites.

   However, caution should still be taken as the GFS model, which showed it in the 12-14 day fantasy range, has now been trending differently as it does not take a final upper low level pressure system far enough southward to phase properly with the subtropical moisture situated in the eastern Pacific.   As a matter of fact, the latest 18Z GFS model went completely dry after showing 10” in the 18z run yesterday.  Hopefully it is out to lunch and not onto something.

   Farther down the road, the ensemble (GEFS below) show another low pressure trough moving ashore mid-week for another chance for snowfall.   That would be followed by another chance end of week according to the 12Z ensemble.

   The generally stormy pattern could continue through mid-month per the climate models.   The CFS (image below) and the ECM weekly climate model both have a trough along the coast through mid-January for storm chance before weakening it over the second half of the month for decreased storm frequency.    Overall, January could be a very big month, unless that 18Z GFS is right  WG

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