Old Closed low is drifting north now and will shift east Tuesday through Wednesday Night….Expect an increase of showers and thunderstorms Tuesday afternoon into Wednesday night….Current pattern to transition toward Fall….

A closed low that has been off shore now for over a week is currently making its way northward toward the Central CA coast. A pattern shift with a fall like trof dropping out of BC, Canada is drawing it northward. This closed low will have plenty of upper divergence and surface deformation for showers and Thunderstorm’s anytime between Tuesday and Wednesday night. The showers that developed this afternoon was the first wave coming through. It has pretty much come and gone. However, there is some convection reforming to our south and so can not rule out some showers later this evening.

The closed low off to our south will be moving north the next 24 to 36 hours. Mono county will becoming under the influence of the NE quad with upper divergence and deformation at the surface. No doubt that there will be thunderstorms over the sierra and that some areas will get some pretty heavy rains within the deformation zone, but at the moment, it is unknown where that will set up for Tuesday afternoon and especially Wednesday.

This weather pattern appears to be part of a significant pattern change. A shift from Summer to Fall like weather. What the Dweebs are looking at on a larger scale is a pattern change that will switch the mean upper ridge currently over the Great Basin to Long Wave Troughing over the northern portion of that region. The Transition will not happen over night through but soon enough.

The first trough coming in this Thursday is part the process that is ejecting the cut off through California Wednesday. That trof will spread breezy conditions and cooler air over our region Friday into Saturday. That trof will be followed by an even stronger Trof the following week if the Euro model is correct. So far any showers directly associated with both systems will remain well to our north. However, the nights will really be cooling down this weekend with low 30s in some areas. Further cooling may occur by the middle of next week. Daytime highs in the low to mid 60s Friday.

Tuesday12:00 PM update shows GFS is coming in deeper and so confidence is increasing for the first dusting of snow next week with the “Equinox Storm”

The first blast of Fall Weather is always exciting here in Mammoth. However, it usually is followed by warmer weather into October.

Dr Howard and the Dweebs………………….:-)

First day of meteorological fall will continue with the trend of above normal temperature’s…..High Humidity to our south will work northward for better chance of warm rains next week….Winter of 2018 looks likely to be very different than 2017

Sky conditions cleared out nicely over night and as a result, lows dropped down into the 40s this morning.  Upper level winds have become easterly as an egg shaped upper high is currently progressing east over Northern CA.  This upper high will become northwest-southeast orientated and allow moisture that is currently over Baja from TS Lidia, to move up through Southern CA. Eventually making its way into the Southern Sierra and north.  Both the southern and central sierra may benefit from wetting rains early next week. The Dweebs expect an out break of thunderstorms at some point. The call for wet storms will be tied into the timing of impulses of upper divergence that would move up from the SSE.  More on that later….

Temperatures will remain both above normal and will be dependent upon cloud cover into next week. Highs this weekend are likely to be in the low 80s with lows in the 40s then low 50s as the moisture increases. Longer range charts for Tuesday and Wednesday show a strong easterly wave over AZ that may pivot into CA then north into the Southern Sierra by Mid-week.  Of note, with the increase of thunderstorms, will bring the increase of lightning and possibly fire starts in the forest.  Lets hope the rains are wet enough to prevent that next week.

Climate:

The Dweebs are starting to look at some of the teleconnections that can effect the weather on a climate scale of time. This is the time frame of 30 days and beyond.  September will likely remain above normal in temperature. However., I do see the possibility of that elusive equinox cool down or trough followed by warming.

The key teleconnections are quite a bit different as compared with last winter.  There is cooler than normal water in the Bering Sea, VS last years warmer them normal SSTA.  The QBO has become East to West arguing for a deeper Hudson bay Low and the Pacific Decadal Oscillation is now neutral trending Cold for the west coast.   This all argues for more meridian flow for the eastern pacific and across the CONUS vs zonal flow from the pacific last winter.  It appears that from a temperature point of view, the Fall will become quite cold (November) with periods of Continental Air backing into the Great Basin at times this Winter. As far as precip, it is still too early for a call, but at the least, not nearly as wet as last winter.  Colder storms will higher snow to water ratios seem more likely. AR events, although still quite possible in an ENSO neutral trending Cold, will be far fewer in numbers. Last winter we has some 15 AR events. Normal is about 5.

 

Dr Howard and the Dweebs…………….:-)

As subtropical moisture moves out….The heat is on this weekend with record highs in jeopardy by early next week…..Long period of above normal temperatures expected with the chance of some thunder developing over the Labor Day Holiday…

Our weather pattern will transit to more of a late July and early August weather pattern with 500MB heights becoming quite high over the Great Basin and California. 500mb-1000mb thicknesses are expected by the GFS to reach low 580s over Eastern CA by late this weekend into the early part of next week. This will be good enough to tie high temperature records for the Bishop AP and Mammoth Lakes with low 80s in Mammoth and between 100 to 105 temperatures for the Owens Valley, early next week. Through the middle of next week, it is expected to be a dry pattern. However, isolated thunderstorms may begin to develop my mid week. Expect some of the best back country travel this summer this weekend into next week as the high elevation snow pack is nearing normal for this time of the year. Of course the Mosquitos are probably still active in the usual areas.  Once over night lows drop below freezing they will be gone too.

The high temperature records for Bishop Monday and Tuesday of next week the 28th and 29th are 103 and 105, set back in 2001 and 1950. It is reasonable to expect similar highs then. A anomalously strong continental high will be responsible for the heat this weekend, well into next week. Some changes are in store for the holiday weekend as moisture moves up from a dying tropical storm over the Gulf of CA. This may bring the return of mainly afternoon and early evening thunderstorm’s over the sierra that weekend,  As we all know, Mammoth is usually one of the last areas to get rain from summer type afternoon and early evening storms. I will have an update later next week on the progress of such a pattern developing.

 

Dr Howard and the Dweebs…………………:-)