Major Change in Hemisipheric Pattern to effect Eastern California with Cooler more Unsettled Weather more on than off through the end of May……However, this weekend looks fair and mild, then warm the beginning of next week….

Models are trending a bit slower and stronger with the Thursday Trof, now lingering it into Friday. Although yesterdays guidance showed about 8 to 10 degrees of cooling, it now looks more like between 10 to 15 degrees total. With the deeper scenario, heights will be lower and thus along with the stronger breezes Thursday, snow showers will likely develop over Mammoth.  Additionally, it may stay showery on and off through Friday night. The weekend looks Fair and warmer with highs back to near 60 Saturday and mid to upper 60s Sunday and Monday.

As indicated yesterday, there is a fundamental change in the Western Hemispheric Pattern Taking place. Whether it is MJO initiated or the fact that the QBO is now stronger in its positive mode. Blocking that has been so strong over Eastern Canada, east to Greenland this past Winter/Spring has totally broken down, with that upper height anomaly NNE on the other side of the NP. The main PV is now located north of the Bering Sea. A high latitude blocking High is setting up over west-central Canada. That combined with changes over the western Pacific, possibly initiated by the MJO, teleconnects to an incipient long wave trof that may prove to be stronger and more persistent over time. Once set up….The Climate Forecast System Vs.2 does not break down the west coast long wave until the first week of June.  Sensibly, we will begin to experience unsettled weather tomorrow into Friday with a break over the weekend into early next week. That may prove out to be the last of the warm weather as the long wave begins to extend SSW along the California coast the middle of next week into that following weekend.

Memorial Weekend weather may be much cooler than normal with snow showers possible or ????  ;-)

 

Next update Monday or Tuesday as the Dweebs will be traveling again…….:-)

Temperatures to trend slowly toward more seasonal norms the next week to 10 days as a series of weak trofs effect the central west coast

Tuesday Morning Update:

Latest guidance points to a Vort max that has recently moved on shore just south of Monterrey Bay at 15Z. You can see the dark area of that Vort center plainly on shore in the water vapor loop. Although the timing of the dynamic forcing will not be perfect as the dynamic lift for the Sierra will come too early for the diurnal heating…..there will nevertheless be some buildups and some Thunder/RWs over Eastern Ca. No cooling is expected now from this system. A stronger trof will move into our region Thursday, bringing about 8 degrees of cooling along with gusty SW breezes during the PM hours.  A few showers are possible Thursday Evening. 

A NW flow aloft with higher heights at 500MB will finish off the weekend promoting high temps back into the upper 60s and low 70s Sunday and Monday.  The next note worthy weather system will develop the 2nd half of next week. It is a colder trof bringing the chance of showers. Stay tuned on that one. A long wave trof may develop and hang around for quite a while there after.

_______________________________________________________________________________________________________________________________________________________________________________

Its springtime in the Sierra!….and the Maps show it!

If you think that it has been warmer then normal the past several days…you are correct.  Seasonal highs at the 8000 foot level should be more in the low 60s this time of the year while lows are expected in the low 30s. The past week, mammoth experienced highs in the low 70s and lows in the 40s.  With the positive height anomaly shifting to the east, a slow cool down will take place the next few days along with an increase of afternoon breeze.  However, with all said, highs will still average some 5 to 8 degrees above normal until stronger trofing develops later next week. Daytime Highs may then return to the low 60s or possibly lower.

North American height anomalies in the 6 to 10 day outlook show positive height anomalies over North Central Canada and Southern Ca with lower heights north of AK and the pacific NW.  The polar vortex is set up north of AK.  So a split in the westerly’s and a southern branch will develop off the west coast pushing marine air into the coastal areas beginning Thursday. The longer range shows even lower height anomalies later next week.  All in all its still spring. The Dweebs would not be surprised to see another dusting over the higher elevations by the following weekend.

 

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

 

Mid Springtime Showers And Thunder still On for the High Country this Weekend with Showers, Thunder and even some snowfall Monday-Tuesday over Upper Elevations….Fair Weather Returning by….Or Just after Mid Week…….

The GFS has done an excellent job so far in forecasting the coupling of a short wave now over the Northern Rockies that will ultimately diverge to the Rt and pick up the old cut-off low, now located at about 139W and just north of the Tropic of Cancer. All models have this scenario now over the next 48 hours.

Current Weather as of 5-3-2013: From the 12Z Friday WRF Model

The Subject short wave is located From Coeur D’Alene, SW to the CA/OR border. As the upper ridge off the NW coast builds north due to upstream amplification, it becomes positive tilt allowing the short wave to diverge to the Rt, forcing it to spin up a closed center over Northern Ca Saturday afternoon. Saturday PM will be the first opportunity for showers over the Sierra from the northern system only. At the same time, all this SW digging has picked up the Old Cut off as it begins to move toward the Southern Ca coast Saturday. This old cut off is the system that carries the moisture. By Saturday/night,  the cut off opens up and spins up a 70….then 90knot upper jet that transports moisture into Southern Ca. During the day Sunday…..Moisture and UVV increase for Southern Ca and so does the rain and possible thunder, especially Sunday afternoon and night.

Mammoth WX:

By Sunday evening, the cooler system to the north is well off the San Fran Coast and the short wave that was once the old cut off is moving on shore early Sunday evening. Rain should be in progress by Sunday afternoon and this is great news for the fire fighters that are battling fires in the mountains NE of LA.  As the upper low at 500mb continues to spin up off San Fran coast, subtropical moisture gets pulled up through the Owens Valley, Southern Sierra, reaching the Mammoth Area then late Sunday night into Monday morning. The moisture then continues to flow up into the Northern Sierra and remains until the offshore cut off low makes its move inland….Monday night into Tuesday.  

 

QPF: The GFS put more precipitation in the Sierra then LA…the WRF has more in the LA area.  WRF has .75 inches over next 72 hours with the Sierra .50 

The GFS has a lot more in the Sierra. At this time, the Dweebs are looking at light snowfall for the Mammoth area with any where from 1 to 6 inches over the higher elevations above 9000 feet.  The snow level will be as low as 8000 during the Monday/Tuesday time frame.  As the upper low ejects east between Tuesday and Wednesday…..Shower chances diminish mid week, lending to a fair warm following weekend with above normal temps….

 

This is the Dweebs last update until Mothers Day…….Adios!!!

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