Powder Forecast — Tuesday January 17th, 2017

Tuesday January 17th, 2017

Ted Schlaepfer CCM  —- Mammoth Mountain WeatherGuy

Forecast Summary:

   Another borderline major storm cycle starts tomorrow and lasts through the weekend with three storms and multiple waves of snowfall affecting Mammoth into next Monday.  The heaviest periods of snowfall are expected early Thursday, Friday during the day, and Sunday during the day and Sunday night with breaks between storms.  Dry weather likely returns next Tuesday and probably lasts for the rest of the month and into early February.  Longer range models are suggesting that storms could then return by late in the first week of February or over the second week and could linger into mid-February.

Next update Friday 1/20.

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

http://patrol.mammothmountain.com:83/Home.aspx

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

Wed 1/18 = 0”

Thu 1/19 = 10 – 12” (H20 = 1.00” – 1.25”) **4

Fri 1/20 = 2 – 4” (H20 = 0.20” – 0.35”) **3

Sat 1/21 = 16 – 20” (H20 = 1.25” – 1.50”) **4

Sun 1/22 = 3 – 5” (H20 = 0.25” – 0.50”) **3

Mon 1/23 = 30 – 36” (H20 = 3.50” – 4.0”) **3

Tue 1/24 = 2 – 4” (H20 = 0.20” – 0.40”) **3

Storm Series Total = 63” – 81” (H20 = 6.40” – 8.0”) **3

Wed – Fri 1/25 – 27 = 0”

January Snowfall = 141.5”

January Forecast = 200 – 215”

Detailed 5-day Snowfall Forecast:

Wed 1/18 — Snow flurries in the morning turns to steady snow by the late afternoon with a period of heavier snow overnight.  Accumulations 10 – 12” by Thursday AM, ~18” up top.

Thu 1/19 — Snow showers taper off during the day, end by evening, not much accumulation or storminess during operations. Snow begins again late at night.  Accumulations 2 – 4” by Friday AM, ~6” up top.

Fri 1/20 — Snow, heavy at times, during operations with continued snow at times overnight and into Saturday.  Riders of the storm day.  Accumulations 15 – 18” by Saturday AM, 24”+ up top.

Sat 1/21 — Snow showers taper off during the day, end by evening, storminess during morning operations mostly with a few inches accumulation. Snow begins again overnight.  Accumulations 3 – 5” by Sunday AM, ~9” up top.

Forecast Discussion:

Short Term:   

    The dry period of weather that started last weekend will come to an end tomorrow as the next storm cycle begins with three storms over the weekend and into Monday next week.  Not as much precipitation is expected this time, but it will also be an all snow event for the mountain and town as snow levels will stay below 7000 feet for the entire period.  Current projects are showing about 5-7 feet at Main and possibly close to 10 feet up top for the entire storm period.

   Models are showing the first upper level low pressure system (image below) splitting from the jet stream tomorrow afternoon with energy in the southern split moving into the Sierra tomorrow night.   This storm will be the primer for the subsequent storms to follow.

   Snow flurries will probably begin tomorrow morning with snowfall increasing late afternoon and evening before a period of heavier snowfall occurs late at night and turns to showers around dawn Thursday, ending Thursday PM.  GFS (image below) and ECM models are similar with around 1.25”-1.50” liquid precipitation expected from the relatively fast moving front.  Snow levels start around 7K Wednesday morning and lower to around 5.5K when the front moves in, and then down to 4.5K Thursday AM.  It will be typical Mammoth snow and not cement.

   There will likely brief break Thursday evening and into the night before snowfall redevelops by dawn Friday.   Snow, heavy at times, is then expected during the day and through Friday night.  The upper level low pressure system (image below) is being driven by the polar jet (blue arrow) and is very dynamic. It is an usual pattern in that the 500-mb heights will get unusually low for CA with a geopotential height of 534-dm expected in Mammoth Friday PM.

   That means it will be the colder storm with snow levels likely near or below 3000 feet and that the snow will be cold, dry powder.   Not super dry like Utah, but certainly dry enough for easy turns with Friday a “riders of the storm” day and this storm might not be too windy to cause a shut-down of lift operations.   There could be epic skiing/riding around Ch. 22 by midday with refills all afternoon.

   The GFS and ECM are similar again with QPF and are showing about 1.25” liquid and up to 1.75”.   Expect more than a foot of snow at Main with probably around 18” and an outside shot at a two foot dump with at least two feet of powder up top by Saturday morning when the snow tapers off and ends Saturday night.

   That break will also be brief as the third and final storm develops off the coast early Sunday with moist up-slope flow increasing Saturday night and snow developing by dawn Sunday.    The upper level jet aligns into a southwest flow (image below, purple arrow) which is the ideal flow for orographic enhancement over the Sierra and particularly the San Joaquin drainage basin in which Mammoth lies on the eastern side.

   That means that the third storm will be the wettest of the three with model QPF in the 3.50-4.50” range. The GFS model (image below) is slightly wetter than the ECM and shows about 4” for Sunday with additional precipitation into Monday when the upper low moves through the Sierra.  Snow showers should continue through Monday and into early Tuesday.

   Snow levels will start out low tand around 4K Sunday with the cold air in place from the previous storm.   Levels will rise to near 6K Sunday evening before lowering again overnight back down to below 3000 feet early Monday.   The snow will not be cement even though it has a subtropical tap and will be typical Mammoth powder with drier powder moving into the Sierra at the back end of the storm Monday morning.

  Overall, this last storm may dump around 3 feet at Main and up to 5 feet up top by the time the snow ends Tuesday morning.    It could be a riders storm Sunday, although this storm may be the windiest storm and lift operations could be severely affected since the brunt of the storm and wind moves through during the day Sunday.

Long Range:

     All the models are showing a ridge of high pressure (image below) building into California by the middle part of next week and holding for the rest of the week and into the following weekend for fair and dry weather.

   Longer range ensembles (image below) are also favoring that the ridge along the West Coast will hold into early February as the global pattern shifts and a deep trough develops in the East Coast, something that has not occurred too often this winter and was common during the height of the drought.

   So it looks like the upcoming stormy period will be the last storms for January which could be a record setting month.  January 2017 will likely break the January record for most snow (182″ Jan 1995) and could break the all-time monthly snowfall record of 209 inches from December 2010, the last big snowfall season.

  The ECM and CFS (image below) climate models are saying that the global pattern shift will be short-lived and that storms could return by end of the first week of February and then could last into the middle part of the month.    That is a long ways out, but it seems like the global patterns are favoring the West Coast this season and I would not be surprised that the models may be right.  WG

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Powder Forecast — Friday January 13th, 2017

Friday January 13th, 2017

Ted Schlaepfer CCM  —- Mammoth Mountain WeatherGuy

Forecast Summary:

   The storm cycle has ended and dry weather will return over the weekend under seasonably cold temperatures with just a chance for flurries Sunday.  Dry and warmer weather is expected early next week before snowfall returns on Wednesday. Heavy snowfall is expected again early Thursday followed by another storm Friday that will have dry powder for Saturday.  Snow showers probably continue over the early part of the weekend before more snowfall likely returns by early the next week.  There could then be another break toward the last part of the month with a chance for storms to return by the end of the month and early February.  Longer range models are suggesting that drier weather could return over the first week of February and last into mid-February.

Next update Tuesday 1/17.

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

http://patrol.mammothmountain.com:83/Home.aspx

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

Sat 1/14 = 0”

Sun 1/15 = 0”

Mon 1/16 = 0”

Tue 1/17 = 0”

Wed 1/18 = 1 – 3” (H20 = 0.15 – 0.25”) **3

Thu 1/19 = 21 – 26” (H20 = 2.10 -2.50”) **3

Fri 1/20 = 6 – 9” (H20 = 0.50 -0.75”) **3

Storm Total = 24” – 36” (H20 = 2.75 – 3.50”) **3

Sat – Mon 1/21 – 23 = 20 – 30”

January Snowfall = 141.5”

January Forecast = 175 – 200”

Detailed 5-day Snowfall Forecast:

Sat – Tue 1/14 – 17 — No snowfall expected all days except chance flurries Sunday.

Forecast Discussion:

Short Term:   

   The low pressure system that produced over two feet of cold, dry powder at Main has now mostly exited the area with some wrap-around flow today keeping skies cloudy.   Those clouds will clear out tonight for a blue bird morning with the top likely to open with continued seasonably cold temperatures.

   The weather will mostly be dry for the next few days. A weak short-wave (image below) moving southward along the western periphery of the long-wave trough situated over the Southwest under generally split jet stream flow will likely to be too far west to produce much more than clouds and flurries Sunday PM.   High pressure will then build into the region Monday and into next week for fair and warmer weather.

   Long Range:

     All the models, including the Canadian now (although it is slower and weaker), move a full latitude trough (image below) southward into the West Coast with the trough splitting when it moves into CA and plenty of energy in the southern split.   The system will contain a remnant AR and will have plenty of moisture to produce hefty snowfall and there is also cold air and snow levels will be low enough at the start at 7K for it to be all snow on the mountain and town.

  As the trough digs southward, moist upslope flow will against the Sierra will produce snowfall early Wednesday with snowfall increasing during the day and into Wednesday night.  There could be six inches on the ground by Wednesday afternoon with winds also increasing during the day.

    Heavy and strong winds are expected again Thursday during the day (riders of the storm, although winds may limit lift operations) with snow forecast to taper off Thursday night.   Model QPF is generally between 2.5 – 3.5” liquid with the majority falling Thursday early morning and into midday.   The GFS model below is showing around 2” for Thursday with the ECM around 2.5”.  Thinking that about 2-3 feet will fall at Main and 4 feet plus up top.

    Friday will be a powder day with more snowfall expected by midday or early afternoon.  A trailing short-wave trough (image below) will move southward in the flow into CA Friday and into Saturday for another round of snowfall.  This upper low is colder and will produce another dose of cold, dry powder as snow levels will get down to near 3000 feet.

   The ECM shows almost two inches liquid with this system with snowfall continuing at times Saturday before ending Sunday morning with possibly up to 30” new.  The GFS only shows about 1” liquid or around 15”.   The ECM mean is closer to the operational model and shows enough liquid precipitation for at least two feet at Main.  The forecast generally follows that guidance, but it is still a ways out and that will likely change.

   Models then diverge for early the following week.   The GFS model (image below) moves the ridge northward from off the SoCal coast and pushes the jet stream track into Oregon.

   The ECM operational model is completely different.   It has a deep trough off the coast and the moist jet (purple arrow) pointing into the Sierra with a front moving ashore into the Bay Area Monday morning.   The models also differ in the East Coast with the ECM showing a ridge in E. Canada while the GFS has a weak trough.

   The ECM ensemble mean is showing a trough as is most of the ensembles and the GEFS, unlike the operational model, is showing zonal flow much farther southward (image below) with the moist jet pointing into the Sierra.   Thus, the forecast right now favors more snowfall early over the following week, and it could be significant.   Looks like there will be another storm cycle starting middle of next week, although probably not as strong as this last one when 21″ liquid and over 140″ of snow fell at Main over 10 days.

   Longer range guidance favors ridging and dry weather to return by the end of that week (image below), although there is a good amount of spread in the ensembles and there is a chance for more storms.  The climate models shows a chance for storminess to return end of January and early February before hinting at a longer dry spell possibly heading into mid-February.  Overall, looks like the feast of new snowfall will continue for a while. WG

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