The last week of August should be pretty uneventful with warm sunny days….periods of haze and cooler nights….Meteorological Summer comes to an end….Heat returns to CA on September 3rd and builds through Labor Day weekend….100s in LA and Bishop….80s in Mammoth

 

The highlights of the last post was subtropical moisture that brought some thunder and brief heavy rain showers Monday afternoon.  Our highs have been in the low to mid 80s and have recently pulled back into the mid 70s. Yesterday Monday, we had southerly flow and that brought up smoke from the Sequoia Fire. Today’s SW flow effectively cut off that smoke train. However, particulates returned from the fires burning along the coast with smoke accumulating over the San Joaquin valley.   It is difficult to forecast future smoke outlooks as so much depends upon how effective fire suppression is. Today was a much better day for the fire fighters on the coast as onshore flow and a deeper marine layer helped much for the coastal range fires.   However, checking the air quality sites this afternoon, they were pretty awful over San Jose, north to the Bay Area, then ENE to Tahoe and Reno. So Air Quality has improved in Mono County and is worse to the north today.

Little change in the forecast is expected the next few days, with the bias of the denser smoke to our north.   The weekend outlook is fairly persistent.   Highs in the 70s with lows in the 40s.

 

Outlook:

The only change in the pattern that occurs is right around September 1st, when the eastern pacific high builds north into the Gulf of AK. This may pull down some cooler air from Canada. Will have to follow this as it represents a significant shift in wind direction. Hope it does not shift the smoke into Mammoth. Maybe the fires will be under control?

Of note, the westerlies really rev up across Canada next week. Significant snows fall in the Canadian Rockies, beginning this Sunday and continue next week… During the first week of September a chilly low pressure system sets up over Central Canada. Some of this cold air invades Montana and the Dakota’s by mid week next week and some Snows are possible for the Grand Tetons next week as well. Some models even pinch off some of that cold air into the Great Basin, but Climo-Support for that is not all that great, that time of the year.

The Dweebs still expect some good warm weather spells to occur in September.  The 2nd week of September shows promise for that…..of course the nights will become chilly….  Meteorological Fall Begins September 1st, next Tuesday.  Hope ya-all had a good Summer.  After all, it could have been worse.  We could have had long periods of dense smoke like a couple of summers ago.

 

Dr Howard and the Dweebs………………..:-)

 

Pattern Change initiates Dry SW flow aloft for drying trend into Friday…..Although little change in temps are expected for Mammoth Lakes…..Subtropical Moisture returns at weeks end…

RECAP:   Yes its been been very warm to hot across the State.  Down in Southern California, the protracted heat wave has caused misery for many. At resort levels at Mammoth Lakes, we actually had some very pleasant weather over the weekend with highs in the 70s.  That was because when we really moisten up, we loose a lot of in coming solar radiation and thus there was a lack of surface heating.  Mammoth did have some light showers, mainly in the late afternoon and early evening hours along with some thunder. Southwest flow was initiated yesterday. With more sunshine during the day, we got up to 84 degrees on Tuesday.  Nights in the 50s

Current Pattern:

The subtropical high at 500MB was centered over SW Utah this morning,  (597DM) and is progged to weaken through Friday over AZ to 591DM. So a 60 decameter drop.  This is in response to a trof of low pressure moving into Washington state today.  For Mammoth, although heights will fall the next few days, there will be more sunshine, as our airmass continues to dry from west to east. So the effects of airmass cooling will be negligible, with only a few degrees of cooling by Friday.  At night it will be a different story as the dry airmass  allows lows at night to pull back into the 40s.  Also, expect a resumption of  the Mono Zephyr, beginning today into Friday.   Another point to make is that there are a lot of fires burning to our west.  With the upper flow becoming more WSW. Expect smoke from the west to arrive later today or tonight….

For you folks in Southern Ca, there will be some 5 to 10 degrees of cooling which will begin today. By weeks end, coastal sections may be in the 70s, Coastal Plain in the 80s and Valleys in the 90s by the weekend.

Owens Valley:

Upper flow was still SSE this morning but becomes SW later today.  So today is the last of the Thunderstorms for a while. Drying continues in the Owens Valley through Friday..

Dew-points will come down a bit as well.

Outlook:

Hurricane Genevieve is nearing Cabo San Lucas. This tropical storm will move along the Baja Coast and weaken over time over the colder water.  Moisture will be released northeastward as the systems becomes a depression, with its remains exiting possibly over central or northern CA Monday Afternoon or night.  Although there may be some showers or thunderstorms from this system, main effect will be an increase of moisture for California, beginning Saturday over Southern Ca and Sunday and Monday for the rest of California.\

There is some suggestion from this mornings 12z GFS run that another Subtropical low will spin up, this time in the “COL”, and track toward CA mid week next week. That may be a good precip producer for the fires burning throughout Northern CA. This is a long shot at this point but worth watching…

We are getting close to the time when California may benefit from a dying Hurricane that could bring beneficial rains to the state. A Window is opening over the next few weeks….

Anyway…..It is worth noting that Meteorological Fall arrives on the first of September, so the days will become notably shorter in the next few weeks along with much cooler night

Dr Howard and the Dweebs……Covering the Eastern Sierra Weather for 40 years……:-)

 

 

 

 

After an overall mild Summer, Southern CA will experience its first long term heat and humidly wave this weekend into next week….

Saturday AM update:

The hottest dome of air of the Summer is expected to continue building today through Tuesday. A 600+DM at 500MB subtropical high builds into South Eastern Nevada with 600DM iso heights extending to the CA NV boarder Monday and Tuesday.  This is quite the heat pump. Upper Flow will be mainly SSE over Southern CA, so dew points will make it feel even warmer as compared to earlier in the Summer. And…the Circulation around the periphery of the anticyclone has the impulses well off shore, so no real trigger mechanism for any rain coming up from the south. in the medium range.

This is likely to be the peak of the Summer heat associated with the subtropical high. Later in the Summer and Fall Katabatic type systems with winds moving off shore could rival temps in the Fall, but with much less humidly. The Upper High peaks Monday and Tuesday so heat will build through then. Highs 105 to 110 in the Valleys of So-Cal are possible with an easing of the heat not expected until later next week.

In the high country of the Sierra and Mammoth Lakes, this particular pattern is associated with not only above normal temps, but in this case, atmospheric modification,  Moisture, now already in place, was aided by the remains from tropical storm Elida this past week. Recent afternoon convention has modified our air mass further with recent afternoon and evening thunderstorms. The high elevated heat source of the Sierra is notorious for this.  Often times, this is the Sierra’s natural cooler, as cloud cover will help keep those high temps confined to the low to mid 80s here. If this were early to mid July, we would be looking at low 90s.  However, without much of an afternoon Zephyr, lows at night will be mostly in the 70s through 9:00pm to 10:00pm, and may remain in the 60s through 1:00AM the following morning. . These mild temps are contingent upon no significant rain early in the evening.  As the Old Farmers Almanac says, these are the “Cat Nights” of the Summer!   😉

 

Dr Howard and the Dweebs……………………

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The weather has been mostly copacetic this Summer with only short term heat waves and little in the way of humid weather.  That looks to change in the short term as a strengthening subtropical high works in tandum with a low pressure circulation off shore, This is expect to channel subtropical moisture from the remains of tropical storm Elida some 1400 miles south of the Channel Islands, late Wednesday afternoon. Subtropical cloudiness like altocumulus castellanus, was observed Wednesday, a sign of subtropical moisture aloft moving into Southern CA. Dew points were in the low 60s west of the Coast Range, 40s in the east San Gabriel valley and 30s in the high deserts. That will change over the next few days…

Dewpoints will be increasing the next few days….

For Mono and Inyo counties, 500mb heights are expected to rise to the mid to upper 590s DM.  This will challenge some high temperatures records early next week. The upper flow for the most part is southerly but at times southeasterly. This may tap monsoonal flow and initiate precipitation if there is some triggering mechanism. Too soon to tell, so the forecast called for mainly isolated TSRWs,.  Stay tuned if the models indicate some kind of upper jet or wave rounding the periphery of the upper high that will build north into southern Utah, next week.

 

Although moderate zephyr winds will blow during the afternoon and evening hours for a few day, they will weaken as the Thermal trof jumps the sierra to the west this weekend….

 

High in Mammoth in upper 70s Friday then low to mid 80s this weekend…..possibly mid to upper 80s early next week….

 

Stay Tuned…………………

 

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