Mammoth Weather Outlook

After a nice rain free Friday and Saturday, a chance of showers return to the Sierra Sunday with next week have a better chance…..


Please click on header above for better format


Finally some warmer temps this weekend….    However, the overall pattern is still one that shows a split flow pattern over the Eastern Pacific, as a strong high pressure system dominates Central Canada and the long wave trof  forcing creates an active pattern “For June”,  across from Southern CA through the southern states through next Sunday. Another comment of interest is that the next system off the Southen CA coast stalls over that area Monday near the dateline promoting this split. Additionally, the low pressure systems create a lot of unstable air aloft over the Sierra, which creates a better chance of showers and thunderstorms.

Monday through Wednesday looks to be the best days for precip of the Sierra next week. Again, as mentioned several times this Spring, the Sierra above 8500 to 9000 feet still has a lot of snow cover. That fact inhibits convection and precip along the crest during times, without upper level forcing.

Longer Range:

There are some signs that the upper air anomalies near the dateline; (Low pressure to the north and high pressure to the south) will progress eastward next week. This would end the split flow pattern later next week for the Eastern Pacific and especially CA and the Sierra, but keep it going for the Mid West and South over the CONUS.  The longer range pattern suggests that a West NW flow aloft pattern may develop by next weekend which would be drier for the Sierra if it develops. Additionally, stronger NW flow may develop the following week would bring dry, breezy cooler weather that following week,  Beyond that timeframe, there are some ensembles that suggest, that the continental high will begin to develop around the Summer Solstice.  Of interest to most weather geeks is where that Continental high will develop. Will it be close to CA for record heat and moisture, or too far east over the desert southwest that allows weak upper trofing to keep our weather especially breezy and dry in the afternoon and cool. This will all be worked out over the next few weeks! One thing is for sure, the pattern Spring into Summer is nearing and El Nino is strengthening.

See the EL Nino Maps below:




Strong Ridging just off the West Coast is forcing an elongated Trof in the upper levels over CA and Western NV with cooler showery WX Thursday and Friday….El Nino out over the EQ pacific will be perking up later this Summer…

The Strong off shore upper ridge has set up some strong upper troughing over CA and Western NV. Although Southern Mono Clounty should be spaired today from major rains….The upper forcing should shift south Thursday into Friday with better action for the Mammoth and June areas. Expect showers and Thunder with even the sierra crest getting some snowflakes during that time. There may be some areas that will get 1/2 inch of rain, especially Thursday afternoon into the night and Friday looks unsettled as well. By Friday night, a part of the trof shifts east and we get a break in the weather for the most part Saturday. Another chance to slight chance of showers returns Sunday and Monday. Temps will be in the 50s in Mammoth Thursday, Friday with low 60s returning over the weekend with 30s at night.  There is likely to be unsettled periods of WX during the month of June as well.


EL Nino From the CPC:

So far, the subsurface warming of ocean water below north of the Equator has been modest with some suggestion that a Modoki type El Nino may be in order as the Nino 3.4 area show modest warming.  The Modoki El Nino tends to provide most of the warming near the dateline and possibility the central american coast.  There is a strongwarm pool off the Central American Coast so this suggests the possibility of a Modoki event. Many Modoki El Ninos bring dryer winters to CA.

This discuession below suggests a stronger surge of sub surface warming is on the way this Summer, with the intensification of El Nino as it rises to the surface. The potential sub surface warmer surge would be due to a strong downwelling Kelvin Wave event.  If successful, this change would give better odds for a wetter winter than the typical Modoki event for California.


Last Updated – 05/23/23
Valid – 05/31/23 – 06/13/23
An active Madden-Julian Oscillation (MJO) signal remains apparent in various atmospheric fields, and continues to project well on the RMM-based and CPC upper-level velocity potential based MJO indices. Recent observations have indicated that other modes are interfering with this intraseasonal signal. Notably, the large circulation of Typhoon Mawar over the West Pacific, and persistent anomalously strong upper-level westerly winds over the East Pacific have caused a slowdown in the eastward propagation of the MJO, which had been on the fast end of the 30-60 day circumnavigational envelope throughout much of the Boreal Spring. The confluence of these modes has resulted in a very strong westerly wind burst (WWB) along the equatorial West Pacific, co-located with the warmest waters of the West Pacific warm pool. This WWB is likely to generate a strong and breaking downwelling oceanic Kelvin wave, which would serve to reinforce and increase the influx of warmer upper-ocean water across the equatorial Pacific. Therefore the MJO slowdown and tropical cyclone activity over the Pacific increases confidence in a transition towards El Nino conditions.



Warming Trend to continue through Saturday…..Southerly Flow and impulses from the SSE will increase chances of Showers this weekend then cooler drier air expected early to mid following week…

It was a beautiful morning in the Mammoth Lakes today. Still a deep snowpack at elevations at and above 8500 feet. This snowpack will inhibit surface convection, however, there will be an increase in mid to upper level forcing, in the high country this weekend, and a better chance of rainfall. Our freezing level is above 13000 feet so no snowfall expected. Our Sun angle is now about the same as July 25th and thus good surface heating will increase snow melt and stream flows as we go through the weekend. Those fishing the creeks and streams need to be mindfull about several potential hazards associated with our water ways, especially during mid afternoon and evenings during the peak diurnal water flow periods.

(Weather Medium Range)

High pressure aloft will continue to build, both along the coast of BC, Canada and over Central CA through this Saturday. Warmer weather with an increase of snow melt expected. In addition this weekend, an area of low pressure will spin up over Northern Baja and the Gulf of CA in a weak Rex Block Fashine. Moisture and some upper level forcing will contribute to an increase of showers and thunder this weekend, especially over areas with out snowpack. However, all areas have the threat of some rainfall. It should be noted that as long as a dense snowpack continues over the high country, there is going to be a persistant limitation on the usual high temps and afternoon convection until it is gone.

Next Week:

The upper level ridge will shift east early next week with the long wave ridge redeveloping near 140West. This will redevelop a mid latitude trof over the far west and Great Basin during the 2nd half of next week. Expect breezy and somewhat cooler weather for the high country, especially during the second half of next week. Temps will return to normal or even a bit cooler than normal into the following weekend. Upper 50s to low 60s?  Also, if a closed low or cutoff low develops off shore, there may be some showers.  Beyond that we get into June and its too far off to tell.

El Nino:

Continues to develop over the central to eastern pacific EQ region. It will be a long time for any expectation for mid latitude forcing, if we even get it!

Well see later in the Summer.

Remember, the high latitude response is a positive PNA or strong upper high over BC west to the Eastern Gulf of AK. That is in contrast or the opposite of the -PNA during La Nina.

El Ninos here in CA tend to affect our area later in the Winter and so it may be a very nice warm dry Fall! ?

The Dweeber……………………:-)