Change in Pattern in Process with Cooling, Windy Periods and Light Snowfall Likely through Tuesday……Further Retrogression Possible Toward Months End….

Monday Afternoon 4:15pm

It was a cold day today. I almost forgot how it feels when its cold!  Highs were in the mid to upper 20s.    Mammoth Mt reported 3 to 5 inches of cold dry powder this afternoon.  With a little luck maybe we’ll double that!  Yes, the upslope portion of the storm chatted about for tonight looks more likely for South Central Mono County as a Deformation Zone sets up, where the upper flow bends from the SW……then returns around the upper low off shore tonight.  The big question is,  where exactly will it set up? It could be north of Mammoth near June Lake/Conway Summit or….Mammoth Lakes to Crowley Lake. We’ll know where it set up by Tuesday morning as there will be people saying…….Where did all this snow come from?   😉

Longer range is looking colder with Modified Arctic on the way a week away and yet another shot of Arctic air around the 18th to the 20th.  With a little luck, if the upper ridge retrogrades enough, we’ll be touting a Platinum Powder Alert! for that time.   Platinum Powder Alert Criteria is 12 inches of snow or more at a snow to water ratio of at least 15:1 at 10,000 feet over a 12 hour period.

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Monday AM:

Forecast remains on track with light snow expected to continue today into tonight….Light accumulations expected…..

With 2 inches now on the ground now on Mammoth Mt, and another 2 to 3+ inches still possible into Tuesday morning…..The forecast appears to be on track….

The Eastern Pacific ridge remains amplified and positive tilt, allowing the formation of a closed low to develop over the Great Basin today with unstable air aloft. As the closed center passes over the top of us and moves off the South Central CA coast early Tuesday AM….. through the process, some upslope precip is certainly possible.

There is a slight chance that a weaker system may kick off some more snow showers Wednesday Night.

Highs today Monday will be in the upper 20s, and then up to the low 30s Tuesday, then upper 30s/Lower 40s by Mid week…….Lows at night will be in the single digits and teens through Thursday AM.  Expect teens and 20s Friday and Saturday…..

Expect moderating temperatures Friday into Saturday with highs in the upper 40s and lower 50s…..It will become windy again by late Saturday afternoon or night, then especially Sunday, as another cold Great Basin Low develops Sunday into the following Monday. More light snowfall is possible late Sunday Night or Monday a week away….It will be colder again next Monday after a mild upcoming Friday and Saturday.

This all is still considered a dry pattern for the State….

Longer Range Outlook hints at further retrogression of Long Wave Ridge, This in turn would pull the upper Trof off shore for over water trajectory. This is hinted at for the period toward the end of the month of February…..

More later this week……

 

Dr Howard and the Dweebs………………………:-)

 

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Sunday AM:  9:35AM

Forecast discussion below still on track…….

QPF amounts from the mornings updated Sunday 3KM 12z WRF NAM, show an inch or two of snow tonight Sunday from the 2nd wave and between 2 and 4 inches from the 3rd system between Monday afternoon and early Tuesday AM.  So snow totals seem on track, as forecasted in my earlier discussion below.   If by chance there is a 20 mile shift in the track of the Monday nights system, we could get a bit more….

One bright spot here is that the developing pattern is much colder over the next several days and so Mammoth Mt will be able to add to the natural snowfall with a bit of their own via snow making….

 

Dr Howard and the Dweebs………………………:-)

 

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Latest guidance including the Saturday 12Z NAM is showing several waves that will move through Mono County Through this Tuesday.  The first wave and front is expected to flush through Mono County Saturday by mid-afternoon with a wind shift from NW to N to eventually NE tonight.  Winds are not expected to be strong today even over the crest with strongest winds with possible gusts to 50mph holding off by late afternoon and tonight.  So breezes in the 15 to 30MPH range most likely over the higher elevations mid day.  This wave is dry with no precipitation expected today Saturday.  Just mainly breeze and cooling. Todays highs will range up to 50 degrees in the Town of Mammoth to only 30s and 40s on Mammoth Mt.  That is compared to the low 60s in town on Friday.

The following wave is stronger as it comes SE to the Oregon Coast then digs south down the Northern CA Coast before turning inland north of the Bay Area Sunday evening. This colder system has a little over water trajectory and may bring some flurries to light snowfall sometime Sunday afternoon or night especially over the higher elevations. Winds will also be stronger with this wave and will be quite noticeable, especially later in the afternoon Sunday then stronger yet Sunday night for a short period. This is even true for the lower elevations of Mono County where gusts to 50MPH through some of the Valleys are possible. Highs on Sunday will be down into the 40s at 8000 feet.

The third and final wave has initially less over water trajectory than Sundays wave but makes up for it later. The System depicted by the 12Z -12KM NAM has a closed 500MB center located over Alpine County south of Tahoe at 4:00PM Monday  where it continues to spin up that night as its center digs off the South Central CA coast.  At the moment this track favors the potential for a good period of upslope snowfall for Southern Mono County southward, especially Monday night into Tuesday AM. However, the 3KM 12Z Saturday NAM, shows some very light snowfall developing Sunday Night from the 2nd wave, before the 3rd wave generates upslope snowfall, mainly Monday night into Tuesday Morning. The QPF from the 3KM NAM shows totals of 2 to 4 inches by Tuesday AM with isolated areas getting up to 6 inches of snow, mainly from Upslope Monday overnight.

 

High temperatures will be in the 30s Monday and Tuesday…More seasonal for February!  🙂

Changes are beginning to occur in the long wave pattern now with first of several North-South Slider’s over CA and Great Basin beginning Monday…..This is a colder pattern with Light Precipitation Possibilities in our future…

Friday 11:00AM:

No surprise’s this morning…  Models are consistent with dry cold front Saturday highlighted by wind and cooling. The following “Inside slider’ will dig back over the Sierra Monday and spin up off shore. Snow showers with light accumulations are expected Monday into Tuesday with 2 to as much as 6 inches possible over the crest.

Prind. point here is that the Eastern Pacific Ridge is retrograding by some 1000 miles to the west. This adjustment may continue slightly over the next few weeks or may adjust a bit back. Last nights EURO’s 5 days means are projecting a bit more westward movement, enough to drop a closed low down the coast sometime during the 3rd week of February. It’s ensemble’s retrograde the ridge to 150west or another 10 degrees west of where it will be by Sunday. The Ensemble Control is even more encouraging in that its 5 day means retrogrades the upper ridge to about 155 west by the period between the 18th and the 23rd. That is far enough west to set up a partial latitude trof off the central west coast for over water trajectory.

Now before you get too excited, this is the Ensemble Control and not the ensemble itself.  I guess you could gather from all this that “Things are moving in the right direction!”  😉

 

Dr Howard and the Dweebs……………………..:-)

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If you were in Mammoth today driving around town this afternoon and your car thermometer read 60 or 61 degrees, that was no error. It looks like we have one more day of that before our ridge begins to retrograde westward and chilly air moves south over the far west instead of all of it spilling east of the divide.

Although I still do not see as of yet as storm track from the West, there are some changes now occurring in the long wave pattern that are encouraging at the least. Looking at several global models the past few days there is a trend now of retrogression in the long wave ridge that has been mostly east of 130 W for most of the winter to shift westward to 140W.  This is always a location that will allow systems bringing chilly air from BC, Canada to drop south via the Pacific NW into either California or the Great Basin, depending upon the amplitude of the up-stream ridge.

In looking at the guidance yesterday from the European models Day+11, The Eastern Pacific Ridge is located along 140W. So expect a series of short waves to come south the next 10 days beginning this Saturday, bringing shots of Cooling and wind over the crest, and even the chance of some light snowfall. Another twist in the nature of this pattern is that these little short waves of energy can back up over the Sierra to the west coast, and spin up over water.  Depending upon the location of the spin up, there is always the possibility for one of them to draw in some subtropical moisture and then give us a very nice surprise!  I like surprises like the one that “may occur” early next week from a Cut Off low that may develop just west of between Paso Robles and Monterrey Bay. The Dweebs will keep a wary eye on that little bugger. Should it develop further south, it would mainly favor the Owens Valley and Southern Sierra, south to parts of Southern CA. These cut offs can be both unpredictable and unstable at times. They can produce some moderate to even strong convective thunderstorms on the west side of the Sierra and especially coastal communities with a lesser chance of some of them making it through into the Sierra. At this time, the models do not want to move this system once over water,  back inland anytime soon.  So well wait and see….

 

 

Mid Winter Blues to Continue this Week with Above Normal Temperatues and Light Winds….Slider Type System the end of the week may bring some Cooling and Breeze to the upper elevations….The Dry Stretch is likely to continue though Mid Month….

Wednesday AM:

This is just a quick update on some of the models and the handling of the Sunday night/Monday system. This morning, the GFS has come into line with yesterday mornings Canadian in taking the short wave west more over CA Monday AM.  However, The new Canadian is now further East. Obviously more time is needs for the Models to sync. BTW…the ECMWF is somewhere in-between….

This means that there will be at least some cooling, sierra crest winds will increase and there will be a slight chance of snow showers. Should the GFS this AM verify, there may be a few inches of snow Monday. as well as highs in the 30s

 

The Dweeber…..

 

Tuesday AM:

The is a slight change in the pattern coming as stronger short waves come out of the North Pacific and dive SE over the Pacific Northwest, Northern Great Basin and Rockies, the next 7  to 10 days. Although this pattern continues the trend of dryer than normal conditions for the Eastern Sierra, at least there will be periods of cooling and upper elevation wind. This will begin later this weekend and into next week. Both ECMWF, GFS and Canadian show a couple of chilly waves coming SE through in the Great Basin beginning the end of this weekend into next week. They handle the waves a little differently and so this will have to be watched over the next few days.  Odds are best that this will only bring wind to the upper elevations and cooling.  It is the 2nd wave that is of interest this morning. The EC and GFS take this wave over the Northern Great Basin and Rockies, so far enough east that they are moisture starved.  However, the new 12Z Canadian model this morning is spinning the wave up over the Pacific Northwest Sunday night and dropping it south over California Monday. It shows the upper ridge off shore sharpening up and backing to near 140 west.  This would be a cold showery pattern for Monday.  I think that for the time being, the forecast should stay dry for CA as there is the most consistency in both the GFS and EC.  However, at the same time, keeping an eye on those two models to see if there are any changes in the handling of that wave over the next two days.

 

Longer Range:

Per CPC discussion, although the MJO will be going into the colder phases for the Eastern US, the feeling was that there will be enough westerly flow across Canada to keep most of Arctic Air well to the north. However, it still maintains the Far Eastern Pacific Ridge, East Central Trof-Pattern across the CONUS. Looking at the Day Plus 11 means, the upper west coast ridge does retrograde a bit to about 140 west. This should be enough to allow periodic shots of energy over the Great Basin allowing cooler weather at times the following week. If the Ridge retrogrades to 140west, this would be a colder pattern for our area.

This is in itself is still a dry pattern. ( you can get light snow in a dry pattern)  If the MJO continues its march eastward from phase 8 to 1 to 2 then 3 and remains coherent,  it is conceivable that by week 4  (End of February and early March) snows will move back into the Sierra, based upon the MJO alone.

Last but not least, it appears that there will be a subtropical jet that develops over the Subtropical Eastern Pacific that may effect Southern CA…..Later this month.

Dr Howard and the Dweebs…………………:-)

 

 

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Monday 2/5/18 3:00pm

 

FYI Global models are trying brings us a cold inside slider type system around the 12th;  Possibly a little before or a little after.  ECMWF has the most over water trajectory. I only mention this as it is interesting to see that both the GFS and ECMWF are showing it to some degree.  This is a pretty cold system and would be good for some light snow showers at the least, if it comes though at all.   Stay Tuned…..

 

ECMWF EPS just started to Run…Will be interesting to see what it shows….

 

 

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A negative tilt, upper ridge will remain parked off the west coast with dry weather and unseasonably warm temperatures continuing for the Eastern Sierra. Light breezes, night-time temperature inversions will keep over night lows in the teens along the highway 395 corridor and lows between 25 and 30 in the Town of Mammoth. The only change expected in the pattern in the medium range,  will be a small slider type system over the weekend. This may increase breezes over the ridges and bring between 5 and 10 degrees of cooling by weeks end. The system will be moisture starved as its track is over land and not over the water.  Although there are some variable solutions in the week 2 progs of the ECMWF and GFS, the vast majority of their ensembles continue the trend of dry weather through mid month.  It is only during the second half of February that a meaningful change is expected in the pattern, the details of which are unclear.

For those wondering how the winter is faring water wise up on Mammoth Pass. DWP came in with their manual measurements a few days ago which determined that Mammoth Pass has 14.1 inches of water and is 51% of normal for February 1 and 33% of Normal for April 1st. The Town of Mammoth has 1.1 inches of water which is 8% of normal to date and 5% of normal for April 1st. (Huge Difference!)

When you check with the CA Department of Water Resources, you find that for the Central Sierra from Huntington Lake North to Calaveras’ Big Trees, that as of today, is in a dead heat with the Winter of 2014/2015 which was one of the driest years. However, that winter turned wetter that year during the first week of February where a storm brought between 2 to 3 inches of water between this week and next.  So more than likely we will be behind the winter of 2015 this week.  That puts the Central Sierra in a class between the Winter of 1977 and 2015. By the end of February, with a dry spell like this one, even with a wet March, it becomes increasingly difficult to have a meaningfully good water year….

 

Dr Howard and the Dweebs…………………:-)