East Coast Storm to Move Off Shore Opening Up The Wave Length A Bit….Snow Showers Possible Sunday…..Retrogression Now In The Cards…..

There is the beginnings of a possible change in the pattern this morning…. One that won’t immediately bring us significant snow, but one that, at the least, begins the process with retrogression of the longer range.

In the short term….. The big east coast storm is now moving out to sea and the wave length is opening up across the CONUS, thus the west coast ridge will temporarily weaken.  The ECMWF has the 2nd weak upper low sliding down the west coast rather then moving into the pacific northwest diving toward the Rockies. This is a major change in the way the EC handles that weak system. The importance of this, is that now, it is at least closer to the thinking of the 06z and 12z GFS and this mornings 12z NAM. Now all the models generate at least a little light snowfall over Mammoth Sunday. It is not expected to be much…..possibly a dusting to an inch or two, but at least something.  Of more importance is the notion that in back of this weak short wave is the sharpening of the west coast upper ridge back out to 135 west, next week. This may be more significant as we go into the month of February as some sort of retrogression in the long wave is the most likely scenario prior to either a storm coming into the Sierra from the Gulf of AK or some undercutting of the westerlies. However with that said the deterministic 12z run of the GFS progresses the long wave back to the west coast again next week. However, a significant number of both the ECMWF and GFS ensembles create retrogression to 140W.

Additionally toward the end of week 2, the GFS REXes up over the Aleutians at 160w by the 8th.  This is some thing new and will have to be watched……as if it is persistent and strong enough, the down stream effects would be profound.  All the models are saying, is that a change is coming in the next couple of weeks. However, it does not mean significant snowfall for Mammoth yet.

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.

No Change In The Current +Phase PNA Pattern Across The Western Hemisphere….Small Feature May Give The Sierra Some Snow Showers Weeks End

+Phase PNA all the way….That is about all that I can say…..Today.

Actually;

Not a lot of excitement out over the far west. The little feature coming in Saturday night into Sunday would be regarded as nuisance weather a few weeks ago. Today it is big news, as if it comes in like like last nights 06z GFS and this mornings 12z ….it might bring in some snow showers Sunday afternoon and night……Wow!  However, the ECMWF model has it well east of here. Officially, there is nothing in the forecast from NWS precip wise for this weekend.

High temps in the Town of Mammoth will be the  low to mid 50s through Friday, then mid 40s Saturday and then upper 30s to low 40s Sunday and Monday.  Over night low will remain in the 20s until the end of the week when they will cool to the teens into Monday. Sierra Crest winds will be pretty light after today/Ngt until the weekend.

Unfortunately, the current pattern is really entrenched with a very cold and deep Hudson Bay Low well anchored and effecting the eastern CONUS with the other anchoring upper low south of the Bering Sea. This may end up being one of the coldest eastern winters since the mid  70s!

When will winter come back?  Well….its hard to say when. However, it will come back.  The second half of February is a good guess. A better guess is March when the Sun is higher in the sky which will eventually break up the thermal anchoring  Hudson Bay Upper Low.  

We’ve been here before….

The good news is that the Sierra still has a tremendous snow pack!

Interesting recent note from Jan Null past lead forecaster from WSFO SFO:

“Second, through the end of December, San Francisco had 11.65 inches of rain.  Looking at the long term history for San Francisco, this would be the 36th wettest first 6 months of the rainfall season.  What has happened in the past with these wet starts?” 

There have been 40 years when the July through December rainfall in San Francisco was at least 11.00 inches. Of these only 6 ended up with below the 160-year seasonal average of 21.89 inches.  

The Dweebs Comment:

So there is still a lot of good odds that this winter will come back or…….about a 15% chance that it will be dryer then normal….(for the bay Area)

The Dweeber…………………:-)

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.

Hemispheric Pattern To Remain Very Stable 4 Wave….No Significant Change This Week

The Western Hemispheric Weather Pattern will remain stable this week as a 4 wave stationary pattern is locked in. Key anchors are the deep Hudson Bay Low over east central Canada keeping the frigid WX over the Eastern CONUS and another deep stationary trough south of the Bering Sea. Teleconnections favor a continuation of strong west coast upper ridge for another week or two.

Even though this pattern will continue, the below normal precipitation pattern of the past will go through periods of weakness or slight retrogression to allow shots of cooling or even some light snow or snow showers.  By the end of this week a system may move through the west coast ridge and provide some light snow or showers.

In the meantime, daytime highs in Mammoth will continues in the mid to upper 40s with lows in the teens and twenties. Winds will continue to be light in town and gusty over the sierra crest.

For the upcoming week….there will be a couple of weak short wave impulses that will be associated with some convergence aloft moving through the Rockies that will build surface pressures and thus increase the NE surface gradient Tuesday into Wednesday. So a period of East or Northeast wind will kick up over the Sierra Crest later Tuesday through Wednesday. Although this is a dry system, it will bring an increase of wind along with slight cooling for the Mammoth area by mid-week. Thereafter, the upper west coast ridge strengthens Thursday into Friday for warmer WX, then weakens Saturday into Monday as a short wave trof moves into California bringing the chance of some light snow or showers to the Mammoth Sunday/Monday along with cooler WX.

It is important to note that the possibility of some light snow for the Mammoth area the end of the week is not a pattern change. Rather just a weakness in the current ridge-trof set up hemispherically.

The next real change when ever it happens will be associated with a break down of the west coast ridge or retrogression of the same. A portion of the Hudson Bay Low will need to move far enough east for the wave length to become excessive, then amplification and retrogression of the west coast ridge to taking place.  Timing wise…..this is not likely until sometime during the latter part of the first week of February.    Additionally, The MJO is still very active and in the favorable teleconnecting area. (El Nino like)  This may actually have been the stimulis in the creation of our current Ridge-Trof pattern as MJO does build a west coast ridge and favors the cold scenario in the east. (Very El Nino Like) Unfortunately for us, and which for whatever reason, the westerlies have not been strong enough without the necessary amplification for under cutting.


Mammoth Mountain continues to groom the excellent snow pack in the high country.


Dr Howard and the Dweebs…………………………………..:-)

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.