Powder Forecast — Friday February 17th, 2017

Friday February 17th, 2017

Ted Schlaepfer CCM  —- Mammoth Mountain WeatherGuy

Forecast Summary:

  Snow continues for the rest of today and tonight before tapering off tomorrow for the most part.   After a brief break Sunday during the day, heavy snow returns Sunday night along with strong winds with continued heavy snow at times Presidents’ Day and into next Tuesday.  One last round of drier snowfall is expected Tuesday night and Wednesday before dry weather may return for a few day.  Storms may then return near the end of the month or early March with longer range models suggesting dry weather could return by end of the first week of March.

Next update Tuesday 2/21

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


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

Sat 2/18 = 20 – 22” (H20 = 1.85” – 2.00”) **4

Sun 2/19= 2 – 4” (H20 = 0.25” – 0.35”) **4

Mon 2/20 = 10 – 12” (H20 = 1.00” – 1.25”) **3

Tue 2/21 = 28 – 32” (H20 = 3.00” – 3.50”) **3

Wed 2/22 = 10 – 12” (H20 = 1.00” – 1.25”) **3

Thu 2/23 = 4 – 8” (H20 = 0.35” – 0.75”) **3

Storm Total = 64 – 78” (H20 = 7.45” – 9.10”) **3

Fri 2/24 = 0”

Sat – Mon 2/25 – 27 = 0 – 12”

February Snowfall = 77.5”
February Forecast = 130 – 150”

Seasonal Snowfall = 411”
Seasonal Forecast = 575”- 625”

Detailed 5-day Snowfall Forecast:

Sat 2/18 — Snowfall tapers off during the day, ends Saturday PM/night.  Accumulations 2 – 4” by Sunday AM.  ~6” up top.

Sun 2/19 — Likely dry during the day, then snowfall develops overnight Sunday and become heavy by dawn.   Accumulations 10 – 12” by Monday AM.  12”+ up top.

Mon 2/20 — Snow, heavy at times along with strong winds, expected during the day and overnight into Tuesday.   Accumulations  28 – 32” by Tuesday AM.  Close to 48”+ up top.

Tue 2/21 — Snowfall likely tapers off during the day before increasing again Tuesday night and into Wednesday.   Accumulations  10 – 12”  by Wednesday AM.  12”+ up top.

Forecast Discussion:

Short Term:   

    Satellite imagery below shows a strong area of low pressure and associated fronts moving into central and southern California with stormy conditions.  Enough energy has moved eastward into the Sierra today for steady snowfall in Mammoth and that should continue through tonight and into tomorrow morning as the upper level trough slides eastward.

  The main upper level low pressure system  well off the coast is moving southeastward into Baja (image below) over the next 24-36 hours so the heaviest snowfall should end this afternoon as the energy from the low is displaced southward.

  One good thing about have the low and related strong jet stream move south is that the winds are relatively light today resulting in less fracturing of the snow crystals and thus higher liquid to snow ratios than what would be expected from this storm that is not that cold.   And of course, the lifts stayed open.   Over 10” has fallen as of this writing and I can imagine great turns on 22 this afternoon. GFS is showing over 2” of liquid today and tomorrow (images below), so total amounts could be close to 2 feet.

   There should be a break early Sunday and at least through the morning hours before snowfall likely returns Sunday night ahead of the main event.   The models, per the ECM below, are still advertising the passage of a strong upper level low pressure system Monday and into Tuesday with will contain a weak/moderate Atmospheric River (AR).   The warm front moves into the area Sunday night followed by the cold front passage Monday.

    This AR is not as warm as the previous event last week and snow levels will stay near 7K or lower when the heaviest precipitation occurs Monday.   Those levels will come down to near 5.5K by Tuesday morning.   The snow quality will be Sierra cement, but not the super wet type, just slightly heavy.   GFS model (image below) is showing around 4” liquid Monday, ECM not as much (2”+) as it has the focus of the AR farther north.

   The forecast leans toward the GFS solution as that makes more sense based on the upper level pattern.  Not quite sure 4” will fall, but I can easily see 3”+ for the whole day and night.  Expect at least two feet of snow and possibly close to 3 feet at Main with around 4 feet up top for Tuesday AM.  Not sure many lifts will be open on Presidents’ Day due to strong winds with continued snow showers Tuesday under lighter winds.

   The main upper level low pressure system then moves ashore Tuesday night and next Wednesday per the GFS (image below).   Snow levels will be lower with this last storm, but so will liquid amounts.

   Nonetheless, the models (image below) are showing at least 1” of more snow water equivalent for at least another foot of snow.  Snow levels could get down to 4000 feet by early Wednesday and the snow quality will be much drier.    It looks like Wednesday could be an epic powder day with snowfall tapering off during the day along with decreasing winds.

 Long Range:

   The storm cycle ends Wednesday night/Thursday followed by at least a few days of dry weather into the following weekend. The longer range pattern is not in agreement with some models dry and others showing a chance for storms to return end of the month.

   The GFS model is the dry one with high pressure ridge in the Gulf of Alaska and a trough across the interior west with short waves staying east of CA.  The ECM model (image below) has a blocking ridge in the Gulf of Alaska too, but it has short waves moving southward farther westward including hints of a westerly breakthrough under the ridge.

   The Canadian is the most bullish (image below).   It moves the upper low around the Gulf of Alaska ridge faster and deepens it off the coast quicker along with tapping subtropical moisture.   It develops strong southwest flow into the Sierra along with a strong surface low for heavy snowfall for Mammoth.

   The forecast right now just calls for a chance for storminess by the end of the month and early March under low confidence.  The ensembles are all over the place right now with a huge spread.  Using the mean, the Canadian ensemble looks like the GFS pattern and the ECM favors weak ridging.

    The longer range climate models are saying that any dry weather in early March could end by the second week of March as both the CFS and ECM are favoring normal precipitation for that week (image below).   So winter could continue in March, but maybe not as intense.  WG

Posted in Mammoth Lakes Weather Forecast, Mammoth Mountain Weather Discussion, Mammoth Weather | Tagged | Comments Off on Powder Forecast — Friday February 17th, 2017

Powder Forecast — Tuesday February 14th, 2017

Tuesday February 14th, 2017

Ted Schlaepfer CCM  —- Mammoth Mountain WeatherGuy

Forecast Summary:

  Dry weather continues through Wednesday before a storm cycle starts Thursday. Snow develops during the day Thursday and ends quickly Thursday evening.  Snow likely develops again by Friday afternoon and continues at times through Saturday and into Sunday.  After a brief break Sunday, heavy snow develops Presidents’ Day and into next Tuesday with continued snow at times possible for the rest of next week.   Dry weather is then expected to return over the last weekend in February with a chance for storms to return over the first week of March.

Next update Friday 2/17

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


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

Wed 2/15 = 0”

Thu 2/16 = 0”

Fri 2/17 = 4 – 6” (H20 = 0.45” – 0.65”) **4

Sat 2/18 = 8 – 10” (H20 = 0.85” – 1.10”) **2

Sun 2/19= 5 – 7” (H20 = 0.50” – 0.70”) **2

Mon 2/20 = 2 – 4” (H20 = 0.25” – 0.45”) **2

Tue 2/21 = 18 – 24”

Wed – Fri 2/22 – 24 = 12 – 24”

February Snowfall = 74.5”

February Forecast = 130 – 150”

Seasonal Snowfall = 408”

Seasonal Forecast = 575”- 625”

Detailed 5-day Snowfall Forecast:

Wed 2/15 — No snowfall expected.

Thu 2/16 — Snow develops during the morning and becomes moderate during the afternoon, ending evening.   Accumulations 4 – 6” by Friday AM.  6”+ up top.

Fri 2/17 — Snow develops during the afternoon and continues at times overnight.   Accumulations  8 – 10” by Saturday AM.  12”+ up top.

Sat 2/18 — Snow showers continue during the day and overnight.   Accumulations  5 – 7”  by Sunday AM.  ~10” up top.

Forecast Discussion:

Short Term:   

    High pressure will hold over the Mammoth area for one more day Wednesday before storminess returns Thursday and over the weekend as a borderline major storm cycle develops for CA.   It looks like snow could fall at times for about 8-10 days or through most of next week.

   The models per the ECM below bring the first storm system to the coast on Thursday morning with a front moving southward through CA during the day.   Snow should develop during the morning hours and become moderate for a bit during the afternoon before ending Thursday evening.

  Models are suggesting the front will weaken significantly when it moves into the S. Sierra and liquid QPF amounts are only around half an inch.  Snow levels will start out around 7K before lowering to 6.5K during the afternoon.   Overall, looks like close to 6” is possible at Main with 6”+ up top.   Snow should be similar in quality to what fell last Friday, not too heavy, but not blower powder either.

   A second system will quickly move to the coast Friday before splitting from the jet and diving into Baja by Saturday morning (image below).    Looks like most of the energy with the storm will move into SoCal where they could get hammered with the frontal system edging into the Sierra Friday afternoon.

   Based on this pattern, there could be limited moisture/dynamics making it to the eastern side of the Sierra with the discerning factor being where the upper low tracks as it splits from the jet Friday.   A bit farther east and more snow could fall, a bit farther west and Mammoth could get skunked.

  Model QPF varies from about an inch with the GFS (image below) to around half an inch with the latest ECM model. The forecast follows the ECM ensemble mean that shows around 0.75” Friday with the confidence level rather low due to the uncertainty.

   Nonetheless, light to moderate snow showers could continue at times through Saturday as the trough shifts eastward, but a major snow storm is not anticipated over the first part of the weekend.    The ECM keeps snow showers going through Saturday night and into Sunday morning in the wrap-around flow of the surface low pressure system and the GFS is similar.   Overall, looks like close to 2 feet will fall starting Thursday morning and into Sunday before a brief break is expected Sunday during the day.

Long Range:

   The models are in general agreement that the strongest storm in this series of storms will hit the Sierra and Mammoth on Monday and into next Tuesday.   The ECM model (image below) deepens an upper level trough off the coast early Monday and significantly increases the southwest flow into CA (purple arrow).  The GFS and Canadian are similar or stronger.

  Not only will this entrain moisture into the flow and possible a weak AR, but the southwest oriented jet stream is perfect for orographic enhancement of the precipitation by the blocking terrain of the Sierra.   And southwest flow aligns perfectly with the San Joaquin River basin that extends southeastward from the top of Mammoth.

   This means that if the models are right heavy snowfall will develop Monday during the day and continue into Tuesday as the low pressure system moves ashore.   It will also probably be quite windy too with limited lift operations on Presidents’ Day.   Right now, looks like around 2 feet could fall Monday and into Tuesday with snow levels falling from around 6K Monday to near 5K Tuesday.  It won’t be cement, but not dry powder either.

    The ECM model slowly moves the upper trough to the coast through next Friday (image below) for continued snow at times under lowering snow levels with snow levels possibly below 4K by the middle/end of next week.   That means continued snow at times and also the chance that blower powder or drier quality snow could fall when the colder air arrives.   Still too far out for those details, but there certainly is a chance.

   Overall, the models are suggesting that storms could continue at times through the end of next week.   The latest ECM and GFS models have 6-8” of liquid over the 10 day period while the Canadian model is the wettest (image below) and has the precipitation bulls-eye right over Mammoth with 12”+ liquid inches or about 100” of snowfall.   Current forecast doesn’t favor that much, but certainly 5-7 feet is possible with 4-5 feet in town.

   The longer range climate models are mixed about what happens late this month and early March.   I suspect there will be another dry period of at least a few days before any storminess makes yet another return to CA.

   The climate models are showing that the winter pattern might repeat again in March.  Remember, what has occurred in January and again February was a blocking high formed early in the month near Alaska and the westerly jet undercut the ridge for storminess including periods of rain in town and lower down on the hill.   Then just after mid-month January, a trough of low pressure developed from the Gulf of Alaska southward along the West Coast for periods of heavy snowfall with the next event representing the February repeat.

    Both the CFS (image below) and ECM are now showing a ridge developing near Alaska again in early March.   The CFS model does not show much energy moving eastward under the ridge for a breakthrough of the westerlies, but the ECM model shows a weak breakthrough and storms moving onto the coast.

     Models have generally underestimated the strength of the westerly jet this winter season and that could certainly be in the cards again.   Week 3 climate model forecasts show only a little better skill than climatology, so we will just have to keep an eye on the situation moving forward to see if March will be a big month too.  WG

Posted in Mammoth Lakes Weather Forecast, Mammoth Mountain Weather Discussion, Mammoth Weather | Comments Off on Powder Forecast — Tuesday February 14th, 2017