I’ve complained about the Palmer Drought Index for a few years now. I’m still doing it… First off, it doesn’t recognize that anything inside of one standard deviation of average precipitation is normal. That includes one standard deviation to the low side. If you are at 99.999% of normal rainfall, that is not a drought. But worse, it adjusts the precipitation value based on the temperatures, which we know are not being correctly represented by the NOAA folks as they are claiming horrendous record heat when we’re cold and lighting the fireplace…
The Palmer drought index, sometimes called the Palmer drought severity index and often abbreviated PDSI, is a measurement of dryness based on recent precipitation and temperature. It was developed by meteorologist Wayne Palmer, who first published his method in the 1965 paper Meteorological Drought for the Office of Climatology of the U.S. Weather Bureau.
The Palmer Drought Index is based on a supply-and-demand model of soil moisture. Supply is comparatively straightforward to calculate, but demand is more complicated as it depends on many factors, not just temperature and the amount of moisture in the soil but also hard-to-calibrate factors including evapotranspiration and recharge rates. Palmer tried to overcome these difficulties by developing an algorithm that approximated them based on the most readily available data, precipitation and temperature.
The index has proven most effective in determining long-term drought, a matter of several months, but it is not as good with conditions over a matter of weeks. It uses a 0 as normal, and drought is shown in terms of negative numbers; for example, negative 2 is moderate drought, negative 3 is severe drought, and negative 4 is extreme drought. Palmer’s algorithm also is used to describe wet spells, using corresponding positive numbers. Palmer also developed a formula for standardizing drought calculations for each individual location based on the variability of precipitation and temperature at that location. The Palmer index can therefore be applied to any site for which sufficient precipitation and temperature data is available.
Critics have complained that the utility of the Palmer index is weakened by the arbitrary nature of Palmer’s algorithms, including the technique used for standardization. The Palmer index’s inability to account for snow and frozen ground also is cited as a weakness.
So if you have 20 feet of snow, you are in a drought. If you have 2 real drought years in a row, and then absolutely normal, or even well above normal, rainfall, you are in a drought (since it hasn’t filled up the ground yet, per the model). If the folks at NOAA cook the temperature normals and you have average rain, you are in a drought. Etc. etc.
This leads to such absurdities as last year in San Jose California having a bit above normal rainfall, yet staying a ‘drought’, and this year we’re well above normal rainfall, so we are having a Flooding Drought. Again.
Here’s the watches and warnings map for today:
Since they produce this color map independent of the legend, I would need to do a screen capture / edit to pick that up. Instead, being lazy at the moment, you can just hit the link to see the legend in detail:
The only part I’m interested in at the moment is that large patch of green in the middle of California. That’s the flood area. Light green is a warning, dark green a watch.
(Oddly, the legend does not show some of the colors on the map, like the bright red in Montana or the pink / fuchsia in the Sierra Nevada Mountains of California that will be under heaving winter snows and avalanche conditions, so “go figure” on how they make their legend and the wisdom of using a dozen hard to distinguish colors when the monitors displaying it vary widely in bit depth).
But the key bit is just that the center of California, all of it, is under some kind of flood watch or warning, and I’ve had rain persistently over the last weeks, on and off. There’s a LOT of water in California right now. So, about that drought…
Oh, look, at least 1/2 of California in a drought… Now the bottom 1/3 of the State is a functional desert, so good luck explaining to me how you have a drought in the Mojave Desert and notice… Then there’s those snow covered Sierra Nevada. I guess it is a drought due to being under snow. Finally, that middle 1/3 that is under flood watches and warnings: Drought because?… How many years of above average rainfall and flooding does it take for the “model” to “refill” the ground?
I have a hard time with the hype over the “persistent drought” in California and attributing it to Global Warming when under a Flood Watch / Warning / precipitation that doesn’t stop for days on end… I’ve got 2 fences to fix and the weather hasn’t let up long enough to mend them. It looks like I’ll be building fence in the rain this weekend, that is, if the drought doesn’t wash away my yard…
Here’s our percent of normal rainfall in the fourth column, or third column of numbers:
Printer Version Climate Station Precipitation Summary SRUS56 KRSA 090200 RR4RSA CLIMATE STATION PRECIPITATION SUMMARY NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA 600 PM PST WED FEB 08 2017 WARNING!! THIS PRODUCT IS AUTOMATED AND UPDATED ONCE PER DAY THIS PRODUCT CONTAINS PRELIMINARY CLIMATE DATA DATA REPRESENT PRECIPITATION ENDING AT 400 PM PST ON 02/08/2017 SINCE OCT 01- OCT 01- OCT 01- OCT 01- MIDNITE FEB 08 FEB 08 FEB 08 SEP 30 CLIMATE STATION TOTAL 2017 PON 2016 PON NORMAL NORMAL ------------------------- ------- ------------ ------------ ------- ------- ...NORTHERN CALIFORNIA... MEDFORD OR 0.14 17.58 165 14.23 134 10.64 18.35 KLAMATH FALLS OR T 6.80 96 6.79 96 7.06 14.96 CRESCENT CITY 0.51 61.17 159 49.77 130 38.37 64.03 EUREKA 0.33 39.26 163 33.16 138 24.09 40.33 UKIAH 0.95 37.12 169 23.28 106 22.01 37.35 MONTAGUE / SISKIYOU 0.15 10.92 114 8.67 91 9.54 18.47 ALTURAS 0.03 8.20 125 8.07 123 6.54 14.17 MOUNT SHASTA CITY 0.31 36.31 150 22.62 93 24.22 43.21 REDDING 0.34 33.56 164 22.63 111 20.43 34.62 SACRAMENTO EXEC AIRPORT 0.38 23.21 212 8.92 82 10.94 18.52 SACRAMENTO - CSUS 0.39 23.25 194 M M 12.01 20.27 BLUE CANYON AIRPORT* 3.08 82.92 228 42.32 116 36.42 64.62 SANTA ROSA 1.20 44.79 199 19.48 87 22.47 36.28 SAN FRANCISCO 0.34 21.09 144 13.79 94 14.67 23.65 SFO INT'L AIRPORT 0.26 20.90 164 10.55 83 12.75 20.65 OAKLAND AIRPORT 0.33 18.41 150 10.44 85 12.26 20.81 LIVERMORE 0.22 16.82 180 8.98 96 9.32 15.71 MOUNTAIN VIEW - MOFFETT 0.04 11.09 132 8.04 96 8.41 14.68 SAN JOSE 0.06 11.23 124 8.84 98 9.06 14.90 ...CENTRAL CALIFORNIA... STOCKTON 0.37 14.35 174 9.48 115 8.24 14.06 MODESTO 0.10 11.64 157 9.44 127 7.41 13.11 MERCED 0.03 11.38 169 8.21 122 6.73 12.50 MADERA T 10.15 152 8.19 123 6.68 12.02 FRESNO T 10.53 168 9.62 154 6.25 11.50 HANFORD T 7.38 132 5.47 98 5.58 10.10 BAKERSFIELD 0.00 6.14 177 3.28 95 3.47 6.47 BISHOP 0.00 6.57 227 1.87 64 2.90 5.18 SALINAS 0.00 10.43 144 8.95 124 7.24 12.83 PASO ROBLES T 12.29 172 5.55 78 7.14 12.78 SANTA MARIA 0.02 12.22 160 4.81 63 7.63 13.95 ...SOUTHERN CALIFORNIA... SANDBERG 0.00 7.29 109 4.72 71 6.67 12.33 PALMDALE 0.00 4.13 93 3.17 71 4.44 8.30 LANCASTER 0.00 4.46 108 3.02 73 4.12 7.38 SANTA BARBARA 0.04 16.63 168 6.67 67 9.90 17.76 CAMARILLO 0.10 14.50 175 3.19 39 8.27 15.22 BURBANK - BOB HOPE 0.02 10.59 116 4.84 53 9.14 17.31 LAX INT'L AIRPORT 0.03 13.41 184 4.18 57 7.30 12.82 LOS ANGELES / USC 0.03 15.74 193 4.20 52 8.14 14.93 LONG BEACH 0.03 16.06 230 3.29 47 6.97 12.26 FULLERTON 0.03 14.11 184 3.71 48 7.65 13.88 IRVINE - JOHN WAYNE 0.02 13.49 179 3.26 43 7.52 13.33 OCEANSIDE 0.00 10.38 147 4.80 68 7.07 13.66 RAMONA 0.00 14.85 184 10.08 125 8.07 16.04 SAN DIEGO - LINDBERGH 0.00 8.04 142 6.06 107 5.67 10.34 ONTARIO T 12.70 155 4.31 52 8.21 15.04 RIVERSIDE 0.01 11.09 176 3.76 60 6.30 12.40 PALM SPRINGS 0.00 5.32 176 2.45 81 3.02 5.74 THERMAL 0.00 2.99 182 1.63 99 1.64 3.20 CAMPO 0.00 12.47 155 6.75 84 8.03 15.73 BARSTOW - DAGGETT 0.00 3.87 210 1.29 70 1.84 4.06 NEEDLES 0.00 2.00 95 1.37 65 2.10 4.62
Gee Barstow, down in that southern desert, at over 200% of normal rainfall. That’s quite a drought! Long Beach in the LA Basin drought area at 230% of normal. More drought like that the beach will wash away… Sacramento Exec Airport (inland about 60 miles / 100 km from San Francisco Bay) 212% of normal. Santa Barbara, where that dark red spot is on the coast above Los Angeles, at 168% of normal.
Man, that’s a heck of a drought… Oh, and do note these numbers are from BEFORE the present storm hits, the one causing the flood watches and warnings to be issued, so they will be rising over the next few days.
Here in UK our ‘droughts’ are largely caused by loss of soil humus/compaction causing restricted infiltration of rainfall to aquifers and increased run-off/flood. All attributed to Climate Change of course – though it is a ‘carbon’ issue it has little to do with CO2 in atmosphere rather more soil carbon loss.
Ummm… all of the cactus dies? ;o)
In the desert, the only time they notice is when it DOES rain. They hate it. In a normal year, in the southern desert, they get less than 3″ per year. They plan outside events YEARS in advance, knowing it will be sunny. Except when it rains. They are not happy about it.
Rather than allowing fear of disaster from the tiny, reptilian part of the mind control me, the greatest day of my life came on allowing the more rational part of my mind awaken to the benevolent higher power that sustains my life:
Off Topic, have you noticed this guy from Dutchsinse predicting one earthquake after another:
I’d not noticed. Do you know what is his method?
Too bad you still have such serious drought conditions out there in CA.
DRUDGE REPORT @DRUDGE_REPORT 3 minutes ago
California Lake Oroville flowing over emergency spillway first time in dam history
@ Larry; More FAKE NEWS.
I have seen this overflow at least twice before. This time the spillway was damaged by the flow and was shut off. The water & power outlets have been opened up to relieve the excess flows while the damage is being surveyed and repairs considered. Looked to me that the damage to the spillway was major…pg
Hmmm interesting apparently they either don’t have much historical knowledge or simply don’t care to do any fact checking with the dam owner.
Here is the article, the do mention the fact that this is the emergency spillway and it was the primary spillway which was damaged.
This is the first time for the Emergency spillway to be used. The regular spillway has been used a few times before ( I’ve been there and watched it – impressive).
What has happened is that the main (regular) spillway has had a sinkhole open under it likely from water leakage at a construction joint. This let hydraulic pressure start lifting that slab, and the spiral begins. The bending motion also breaks the thin sidewall, and then erosion out that side causes even more base erosion. Repeat until trashed, which is what it now is.
They have cut the main spillway back to something like 55,000 CFS due to too much erosion, and the lake level has risen to above the 901 ft of the concrete overflow that is the “emergency spillway” and about 15,000 CFS is overtopping it. (Inflow is about 100,000 CFS so lake level still rising and any excess is going to go over that emergency spillway).
The erosion at the main spillway was into the shoulder where the main dam is anchored, so “not good” and that puts a fundamental limit on what can be done.
Basically, at this point, we are hoping that the engineering done 1/2 century ago on that emergency spillway was really good. The lake is full, the dam is wide open on the drains, and the regular spillway is at max possible without disaster (and likely will need to be dialed back from there). It will be “what comes in goes out over the top of the Emergency Spillway” until we have a decent length of low rain and low snowmelt. Oh, and we have lots of snow to melt…
The potential catastrophe scenario is a big warm wet heavy storm that melts high snow loads. That rate of inflow can’t be moderated in the outflow, will erode the emergency spillway (that is just dirt over whatever basement rock exists) and will cause downstream flooding.
There is film from KCRA in Sacramento showing DWP taking down trees in the emergency spillway and removing power lines and such over the last 3 or so days preparing for this moment.
FWIW, I watched this all be built some 50 years ago, and was out at the Feather River a few years before when it was 2 feet from the top of the levee and we were trying to decide when to bug out and if it was going to flood. So I’ve been paying attention to this a long time… I was at the dedication and got Ronald Reagan’s autograph on the dedication handout…
This is very much “not good” and is not an ordinary spillway process. It is an almost out of control erosion event on the shoulder buttress of the dam… I don’t expect it to get any worse, but like I pointed out, it all comes down to 50 year old engineering and rest of season weather…
My old home town is about 12 miles down river from this… So I’m watching closely.
About the only other option that they could do to increase the out flow without doing more damage would be to quickly build a siphon tube to pass more water out of the dam.
Here in Colorado they had a huge siphon tube in the Big Thompson canyon to move water to a different drainage.
What an interesting idea… As they use a lot of siphons for irrigation in the region, folks are familiar with them. Since the “rise’ is only a few feet over the rim of the Emergency concrete barrier, it would be relatively easy to put a siphon over the top of it (from a few feet down the backside to maybe 20 feet down the low side, then attach a large fabric hose the rest of the way (if anyone makes fabric hoses that large… ought not to be that hard to sew up some sail canvas tubes…) The degree of reduction in lake height would be limited by the two ends of the siphon, but all you would need is a dozen feet lower to be out of danger land.
Starting the siphon would be easy too. Clamp the hose part and pump water into the top part (or pump the air out) then open the fabric. Move on to the next one.
It would take a load of labor to make, and more to operate (modulating flow by opening the fill valve at the top and breaking the siphon, then restarting if needed, later). But it would give a lower lake level and better modulate of outflow rates.
The limit on siphon height is about 30 feet for practical ‘pulling a vacuum” reasons, but I doubt you would need more than a 10 foot lift into a 4 foot diameter pipe segment. Then however many of those fill the length of the overflow area.
I doubt anyone will do it though. For the simple reason that it isn’t SOP, so folks would fear liability.Probably depends on how much erosion they expect on the emergency overflow slope. If that is thin dirt over bedrock, nobody would bother, but given the erosion seen near the regular spillway, it looks like a lot of dirt over jagged rock with channels in it. That would really be helped by some giant hoses taking the water down slope.
I think there isn’t any other drainage to use, nor do you need one, as the Feather River can carry a lot.
Standard pipe line diameters go up to 48 inch. You could move a lot of water in a couple 48 inch siphons. The down leg beyond what is needed for the necessary suction for the lift needed does not even need to be enclosed it could be an open top sluice once you get beyond that point and could even be made of wood.
From twitter, Fox has an image of the spillway and the water flow.
Lots of information, videos, comments (both pertinent and impertinent, as well as technical and concern trolling, and live feeds, when only KCRA (3) was there for the MSM) at
http://www.ar15.com/forums/t_1_5/1964182_Biggest-dam-in-the-country-is-going-to-overflow-this-friday-Big-Update-with-pictures-and-video-pg38.html&page=68 (yep, 68 pages today…).
One funny comment: Has Governor brown considered asking President Nieto for help?
EM. I believe it is CFS ( per second) not minute.
The issue I see is emergency spillway only comes into effect when the lake is at 100 percent. So the majority of the effort to lower the lake before the next storm, and ones following must be discharge from the regular spillway. ( This last storm peaked at 190,000 CFS.) Full lake then means inflow and outflow equal, means major flooding below at that rate.
So I see no choice but to use the damaged spillway between storms and hope it does not erode upslope too far towards the shoulder. Many 48 inch siphons would be required to continue lowering the lake through the emergency spillway.
[Reply: You are correct and I’ve edited my comment to reflect CFS. -E.M.Smith]
Link to california resivor data including Oroville. Shows daily inflow, outfliw, elevation change, etc.
FWIW, at the high 150,000 CFS inflow rates the lake rises about 15 feet in one day.
The powerhouse outflow is shut down and the regular spillway is being limited to 55k CFS to save the structure for the rest of the season. That leaves the Emergency Spillway to take anything (average) above that. Briefing from DWR in a new posting here:
The debris build up is risking the power plant due to water backup, and the power plant can only run grid-connected while that connection crosses the spillway and emergency spillway (oops…).
They are looking at bringing in dredges to clear the debris to get the power plant running again so it can help let water out…
Why not use siphons to by-pass the damage on the primary spillway ?
Since there seems some confusion about spillways at the Oroville dam and a picture is worth a thousands words.
“Why not use siphons to by-pass the damage on the primary spillway ?”
48 inch pipe, about 12 sq feet opening, WAG at 20′ per sec, 240 CFS, say 4 to equal 1000 CFS.
Going to need a lot of a siphons.
At the present 12,000 CFS over the Emergency Spillway that would be 12 siphons. 55 for the regular spillway. At max load of about 200,000 CFS, 200 siphons. Yeah, may take a while to build and place them all ;-)
In that photo from RAH: The “Emergency Spillway” is that concrete wall like structure from the corner of the parking lot (lower left to middle right). The regular spillway runs off from middle of the frame to the right side as that ‘gash under the bridge’ where the ‘bridge’ is really a weir with gates. In the lower right you can see the road you take to the parking lot for launching boats… At full flow down the Emergency Spillway, that likely gets washed out… as it is now, water accumulates down at the ‘bend’ just after the regular spillway and as near as I can tell from photos takes a pipe under that road for low flow rates (as now).
You can get a vertical view of the structure by going to google maps and looking for:
Then going to satellite view
Detail images of the spillway damage.
Dam failure assessment in Annex D CITY OF OROVILLE, of their emergency plan is here, starting at page 15 of 53
Click to access Butte_County_LHMP_Update_Annex_D_City_of_Oroville.pdf
Normal 100 year/ 500 year Flood plain risk assessment pgs 22-29 of 53
Map of areas protected by levees see page 31-32 of 53
I find it interesting (in a bad way) that their plan has no flood inundation zone map for a dam breech, this implies to me that it was a scenario too scary to publicize and they dismissed it by claiming it highly unlikely.
Click to access SP-E4.pdf
On page 104 of 138 the above link mentions a dam break analysis but the appendix B referenced does not appear in this document
Click to access FeatherRFMP-MainReportDraft5-19-14last-revised-05-21-14.pdf
Discusses Oroville dam and maximum flow of releases
page 87 of 310 (section 4.2.1 Oroville Dam and Lake)
I still have not been able to locate any flood inundation maps for a dam failure at Oroville.
Well, at about 12 years old I was watching the dam finishing the being built phase. At about 15? A friend wanted his Scout badge for bikes so we pedaled the 50 miles up and back and wandering around with him… I’ve seen that canyon very “up close and personal”.
Why no inundation maps? Pretty simple, really. You have many miles long of lake reaching out into valleys in several directions, depth of 900 to 700 feet deep for most of it. It all funnels to that one dam. DIRECTLY down valley from that dam is the City Of Oroville (where my Mum worked in a restaurant and I’ve visited often). The Dam is uphill all the way (as my bike experience testifies… we took that road past the spillway on the way out…) The river is about 3 miles away from the main downtown footing, and it runs a little ways up the hill (maybe 200 feet to 400 feet). Now consider what a wall of water 900 feet tall does to a city on the ‘bank’ from zero to 400 feet up. I’ll wait…
How do you map the inundation of what is a scour channel?
My home town was about 12 miles further out into the valley. We were told we would be washed away entirely also… and flooding would extend 70 miles south to Sacramento… IIRC the estimates were something like “only 70 feet deep when it gets here”… but moving damn fast…
There is no need for an inundation map for Oroville. In case of a failure of the main dam all roads lead DOWN hill in front of the dam! There is really only 1 road road up hill out of town and it is narrow and crooked,.In the event of an evacuation alarm it would instantly become a parking lot.
There is another road from the south also narrow and crooked that ascends a bluff but then goes down hill into lower levels. Any real evacuation highways are in the direct path of any flood…pg
Just an opinion, the only real risk, that I see, of the main dam failure is a great earthquake while the lake is brim full. The emergency overflow dike could wash out, that would cause enough flooding problems in the valley to be a small disaster all the way to Stockton, but it is on top of a real ridge…pg
Niagra erosion on rock slowly eats it’s way upstream. Curious if the broken skills at is continuing to erode towards the dam top.??
@David A Anderson:
The rock in Oroville is volcanic. It doesn’t erode worth a damn, and that’s a good thing.
Yeah. I coasted downhill from the dam (at about 35 MPH on a 3 speed! passed a car, too!) and essentially all the way (modulo a couple of ‘almost flat’ sections of a few hundred feet) into Oroville.
We (gang of about 4 teenage males who had not packed nearly enough food) arrived at the first big restaurant at the end of the coasting bit just about 6 pm (or about 12 hours after we started..) and settled in at the “all you can eat buffet”. Well, about 2 fried chickens each + sides the manager came over and told us we had to leave as we were eating too much. Never mind that I was reaching the too stuffed to eat any more stage, I pointed to the “All you can eat sign” and suggested he call the County Sheriff so we could discuss it… (Didn’t mention he was a friend of mine and I was in the Eagle Scouts post he ran ;-) Well, the guy just blustered and went away, and I went back and got one more chicken leg just to prove a point… (and barely managed to eat it ;-) Then a pudding.
Next we went THROUGH town to the river crossing, then along the river route and a back road past the after bay to home (getting there about 9 PM dead tired…) So the river goes around the north side of Oroville and the canyon dumps straight out into the uphill side of town.
Of course, there’s a nice freeway south, I-70, folks can take if they make it to the river. Be interesting to see if the water or the freeway moves downhill faster… It follows the river all the way to the join with another river in Yuba City / Marysville area about 25 miles away. The only real uphill is toward the lake, and the downhill is a bad race condition. As the valley floor slope there is 32 feet / 200 miles, trying to run across the valley isn’t going to do much good…
So just calculate the volume of water in the lake, and then match that volume to a half circle of depth about 5 feet that matches. That radius is about the max destruction circle from downtown Oroville, and put the edge of the diameter straight side along the Sierra Nevada.
For Grins, then figure a 2 foot depth. That is the radius where folks will be pissed and annoyed, but alive.
Per the wiki:
so 3.5 Million Acre Feet. At 640 acres per square mile, that’s 5527 square miles or about 74 miles on a side for a square. The Valley is about 50 miles across to 70 miles across and it is 70 miles to Sacramento, so pretty much the entire central valley from Chico to Sacramento and mountains to mountains a full foot deep of flood. Of course, getting it spread out that flat will take time…
Pretty much what I figured.
That is the same situation we had in the Big Thompson canyon flood and then a little later when the small Lawn Lake dam let go and flooded Estes park. In those mountain valleys the only escape is to abandon the car hoof it straight up hill as fast as possible.
It won’t be a “wall of water” since it takes time for a large dam to fail, it will be like a very fast rising tide that goes from a foot or two of water to 10 – 20 ft deep in a matter of minutes, then once the full flood gets underway (full dam breach is complete) the faster flood water in the back will catch up with the early flow and “stack up” into a wall of water maybe 50 – 100 ft high in choke points and bends in the drainage.
Like you say that kind of flow scours the channel to bed rock.
Saw that up close and personal in the Lawn lake dam failure. I was one of the first people to head up that canyon after the flood subsided, and boulders the size of Volkswagens were still moving down the channel in the water flow, which had scoured the soil 12 – 15 ft deep to bed rock. At the foot of the Fall river as it exits into the meadows of Rocky Mountain National Park and turns to head down hill to Estes Park it dumped boulders the size of large trucks in a boulder field that the water could no longer carry after a 2700′ vertical descent.
Here are some pictures of the Alluvial fan it created of boulders and rocks at the bottom of its steep down hill run.
That dam was only about 25′ ft high or so where it breached.
(water cut out the dam around the flume valve and pipe and then the dam collapsed to about a 20′ wide open cut. The water ran down hill a mile or two and when it got to a tight right angle bend to right it stacked up about 30′ deep. I found debris scars on trees 30′ above the ground level at the outside of that bend, and just down hill from there, the churning water was breaking up aspen trees and tossing 18″ long pieces out into the nearby woods as it ground the forest up in its ball mill of boulders and mud.)
Click to access flood_2009.pdf
We now have signs along that stretch of road, that say.
I case of flooding head for higher ground and have an image of stick figure people running up hill.
Wet weather ahead…
Models remain consistent advertising a return to wet weather for
norcal later this week. Initial frontal system expected to spread
precipitation across the area Thursday with snow levels 7-8k ft.
Showers will be possible Friday into Saturday with lower snow
levels (4-6k ft) as the brunt of the following system is forecast
to move into socal. Potential for stronger systems next Sunday-
Monday with favorable pattern (wsw flow) for heavy orographic
precip and deeper moisture entrainment. Details of timing and quantitative precipitation forecast
will be adjusted as the event approaches.
&& eat over week for Sierras, 4 to 8 inches
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