Jul 312014
 

For the next four days, some of the forecasts and the computer models show as much as an 1.5-2 inches of rain for parts of Northern Arizona. This will give us a good start to August. The scope of the precipitation over the next few days isn’t reflected in every forecast. Some, like the NOAA’s Graphical forecast and the National Weather Service’s forecast seem much drier and warmer. For instance, if you are heading to Lake Powell, I expect Sunday will be cooler(everyone may not think high 80s, low 90s are cool) and wetter compared to normal.

Looking deeper into August, the 6-10 and 8-14 day outlooks have dry conditions moving into Arizona. Dry period during a reasonably wet monsoon season isn’t unusual. Later today, the Climate Prediction Center should issue a new 30-day outlook. The question is whether or not the long-range outlook will continue to forecast above average precipitation.

North American Mesoscale Model of four day total precipitation. (National Centers for Environmental Prediction, 31 July 2014)

North American Mesoscale Model of four-day total precipitation. (National Centers for Environmental Prediction, 31 July 2014)

 

 Posted by at 6:40 am
Feb 192014
 

There are a couple of curious things to note about Lake Powell. First, it’s at its lowest level for this date since 2005. Outflows from the lake are around the historic average.

Lake Powell water levels since 2010 - http://lakepowell.water-data.com/

Lake Powell water levels since 2010 – http://lakepowell.water-data.com/

Second, the snow pack above Lake Powell is well above normal for this time of year.

Upper Colorada Basin Snowpack - http://lakepowell.water-data.com/

Upper Colorada Basin Snowpack – http://lakepowell.water-data.com/

Unlike Arizona, this year’s storm track has hit the Upper Colorado River Basin. If this year ends up similar to 2011, lake levels could recover considerably. In 2011, level lake increase by roughly 60 feet. We are still well before the peak in snowfall.

Here is the Bureau of Reclamation’s outlook for this summer. I have highlighted the max, likely and min lake level projections.

Based on the current forecast, the February 24-Month study projects Lake Powell elevation will peak near approximately 3,611 ft next summer and end the water year near 3,604 feet with approximately 12.16 maf in storage (50% capacity).  Note that projections of elevation and storage have significant uncertainty at this point in the season, primarily due to uncertainty regarding the season’s total snowpack and the resulting inflow to Lake Powell.  Under the minimum probable inflow scenario, updated in January, the projected summer peak is 3,592 ft and end of water year storage is 9.7 maf (40% capacity).  Under the maximum probable inflow scenario, updated in January, the projected summer peak is 3,631 ft and end of water year storage is 15.0 maf (62% capacity).  There is a 10 percent chance that inflows will be higher, resulting in higher elevation and storage, and 10 percent chance that inflows will be lower, resulting in lower elevation and storage.  The minimum and maximum probable model runs will be updated again in April.  The annual release volume from Lake Powell during water year 2014 is projected to be 7.48 maf under all inflow scenarios. 

Seems odd to be thinking about Lake Powell in February, but the weather has been so nice. That could all change. Here is a new graphic from the National Weather Service for spring precipitation following dry winters. Near normal spring amounts seem to the highest likelihood. Currently, the weather pattern seems to be shifting across North America. The Eastern US is going to see a warming trend. There is a strong storm for Arizona in the long-range outlook.

Spring precipitation following dry winters - National Weather Service Flagstaff

Spring precipitation following dry winters – National Weather Service Flagstaff

 Posted by at 4:11 am
Aug 292013
 

TR pointed out a weather warning earlier this week. The warning mentioned that precipitation would mostly fall to the west of a line from Page to Black Canyon City. What could be interesting about such a line? In this case,  a combination of where the moisture was and the prevalent wind direction that day caused the line. Sure enough, looking at the radar estimated precipitation the next day, one could clearly make out most of that line.

As I looked at weather forecasts at Lake Powell for the weekend, I started in Page. As of this morning Page is showing a 50% chance of rain on Saturday. (Page Weather forecast from NWS) I then scrolled their “Click Map For Forecast” tool to the Lone Rock Area which is on the Utah side of the border. I’m more interested in a better estimate of temperatures, but notice only a 30% chance of rain. I scrolled a bit east to the southern edge of Padre Bay, but still in Utah. The chance of rain there is 40%. Then I drop south of the border into Labyrinth Canyon. I find 50% here. Next I go up by Cookie Jar.  Only 30% here. Deep into Last Chance Canyon, 30%. It seems that if you are in Utah on Lake Powell, on Saturday, you have a lower chance of rain. Also, the Arizona-side will be 2-3 degrees cooler.

Why would the state line make a difference? As it turns out, the Flagstaff National Weather Service is responsible for the Arizona-side of the lake. The Salt Lake City NWS is responsible for the Utah-side of the lake. So, the forecasting office could be the cause. But, as I look that the North American Mesoscale model for the next 84 hours(below), an issue seems to be right around the border. An area of heavier precipitation seems to be centered around Page and south of the border. I may have to go up there and see for myself.

Arizona is going to be wet all over this weekend. Enjoy it! We need the water.

84-hour precipitation forecast from the North American Mesoscale Model at the National Centers for Environmental Prediction

84-hour precipitation forecast from the North American Mesoscale Model at the National Centers for Environmental Prediction

 Posted by at 7:26 am
May 252011
 

Even with the windy, cooling trend ahead for this weekend, you might be thinking about going to Lake Powell. If you show up on Friday, you can expect things to look much different by Monday. Right now, the water level is raising about 6 inches per day. This rate could increase. So you should think ahead; 18 inches of water level can dramatically change your campsite/anchorage’s appearance and functionality.

The cooler than normal May temperatures and the recent storms have dramatically increased the snow pack above Lake Powell.

Snow pack above Lake Powell - snowpack.water-data.com

Snow pack above Lake Powell - snowpack.water-data.com

This has prompted a change in the peak level for the summer. The Bureau of Reclamation is still planning on generating lots of electricity by running all their generators as they fill Lake Mead. That’s 40 megawatts! Still, the peak level may reach 15-20 feet above last year’s peak. This could make it the highest level since 2001.

 

Lake Powell water level projection. Bureau of Reclamation

Lake Powell water level projection. Bureau of Reclamation

 

 Posted by at 6:40 am

More on Lake Powell

 Lake Powell  Comments Off
May 012011
 

For folks from Northern Arizona, one of the big questions from recent years is whether or not the Castle Rock Cut is open. As of Friday, the water level, at 3611.74 feet, was 3.74 feet above the absolute minimum usable level, and just under the 3612 feet safe usable level. With the water level rising about a quarter of a foot per day, lake level should allow for safe passage this weekend. Again, this season’s levels will rise similar to last year.

I’d like to thank MN for putting me on the path to finding this link to more detail about estimated lake levels for this summer. Bureau of Reclamation – Glen Canyon/Lake Powell

Here is  their future water level outlook. Visit their site for the deeper technical details.

 

Historic and projected Lake Powell elevations - Bureau of Reclamation

Historic and projected Lake Powell elevations - Bureau of Reclamation

 

 

 Posted by at 5:57 am
Apr 242011
 

A quick search turns up several news reports which tell the tale for the current plan for Lake Powell water levels. And, the associated story becomes clear very quickly. Lake level has just hit the transition point from lowering water levels to rising water levels.

Lake Powell Water Levels - www.water-data.com
Lake Powell Water Levels – www.water-data.com

But, the curious aspect of this graph is the difference in the rate at which the lake level has been dropping through last winter. The curve is much steeper than previous years. Also, as a result, the turning point from draining to filling has been extended early March to late April. Looking at daily inflow and outflow rates for this date over the last few years shows that the outflow rate this year is the highest of the last 10 years and roughly 30% greater than avereage for this time period.

10 year Lake Powell data for April 24 - lakepowell.water-data.com

10 year Lake Powell data for April 24 - lakepowell.water-data.com

The core issue is decreasing water levels at Lake Mead and a desire to maintain water level there. Here is a report from Southern Utah’s KCSG TV station,  Lake Mead Water Level to Rise 20 feet With Increased Water Flow From Lake Powell.

The good news is that the snow pack above Lake Powell is above average. Also, the Castle Rock cutoff is already 2 feet above the usable level. Over all, and I think with a little luck, this summer’s water level will be much like last summer’s. Hopefully, the rising levels at Lake Mead will help keep those mussel infested boats down in Las Vegas and out of Lake Powell.

Snowpack above Lake Powell

Snowpack above Lake Powell

 

 

 Posted by at 4:55 am
Jan 082011
 

With the storm track staying farther to the north, for now, it seems like a good time to look at how Lake Powell is doing and will be doing.But first, if you have ever wondered what Lake Powell looks like in the winter, check out their webcams: Lake Powell Webcams.

The lake level is following an almost identical path as last year. A steady decline due to power generation is eating up about 14,000 cubic feet per second (cfs) of water. The inflows are slowly dropping and are currently around 6,700 cfs.

The snowpack above Lake Powell is looking great!It has been running at 140-150% of normal for a while now. If this continues this will lead to a very nice increase for the lake next summer. Could we see a return to levels above the 3650 foot elevation? When haven’t been above that for roughly a decade.

It comes back to who do we believe. I thought we were going to have a dry, slightly warm winter. So, I think it’s fair to say it’s been wet and very warm. The very warm part will probably change if the current cold persists. Also, I thought this wouldn’t be the effect for the Upper Colorado River Basin. I thought they would be closer to normal. The Climate Prediction Center’s drought outlook seems to agree.

Drought Outlook - CLimate Prediction Center

Drought Outlook - CLimate Prediction Center

Notice that they updated this on January 6. It looks like the Upper Colorado River Basin will not see the development of a drought. This bodes well for Lake Powell’s water level this coming summer. Also, notice, most Northern Arizona is no longer project to develop drought conditions.

 Posted by at 6:11 am
Jun 212010
 

Dry southwest winds are on tap for the area again today. Not good for fire fighting.  It looks like the first dose of monsoonal moisture will be on it’s way Thursday, but it may not make it all the way to the Flagstaff area. But, the winds should slowly die down over the next few days. But, that will come with warmer temperatures as we head towards normal, to above normal temperatures

For today, I think the dewpoint forecast map tells the tale: http://www.wrh.noaa.gov/twc/monsoon/td700mb.php

On a nice note, the days were warm and the nights were cool at Lake Powell over the weekend. Remember not to park too close to the water and leave your car for several days. We watch many cars get towed from the parking lot near Wahweap Marina. Both sets of tires were in the water on them, and one car had it’s front end in the water. The water level went up over 3 feet in the last week. The rate is slowing, though.

 Posted by at 6:51 am
Jun 172010
 

There is a fire north east of Williams. The Eagle Rock Fire started yesterday. The high winds hampered efforts. The aerial crews were grounded because of the winds. The winds have also brought much low dewpoints. Overnight the dewpoint at my weather station dropped to 12F. The Airport is report 20F for the dewpoint. It had been hovering in the low to mid-30s. Winds are going to whip up again today. They should be out of the southwest. More fire information can be found at the Southwest Coordination Center. They run a Twitter update as well.

Lake Powell rocketed past my guess for max water level for this summer. I guessed 3635 feet as the max height. It gain 0.54 feet (over 6 inches) on Tuesday to reach 3635.14. The 3642-43 foot range may still be a reasonable end point as the rate of increase has fallen from it’s recent highs of about 3/4 foot per day. The inflow rates to the lake have dropped as well. More data can be found at the Lake Powell Water Database.

Lake Powell Water Level

Lake Powell Water Level

 Posted by at 6:40 am
May 302010
 

A recent post, (Western Snowpack is 137% of Normal) at Watt’s Up With That? (www.wattsupwiththat.com) raised questions in my mind about the current and future water level for Lake Powell. The post covered current snowpack in the west and the changing levels of Lake Powell. While Arizona had a very wet winter, 12 feet of snow fell in Flagstaff, the areas that contribute to Lake Powell’s inflow did not have great years. Also, since the snow stopped falling in earnest, Flagstaff has seen a significant dry spell, with lots of wind. So, how to dissect all of this?

First, let’s take a look at the season’s snowpack. Here is a chart that tells an interesting story and was shown at Watts Up With That.

Western US Snowpack 5-25-2010

Western US Snowpack 5-25-2010

The overall average is impressively positive. But, Colorado and Utah are both below average. While not as dry as some recent Flagstaff winters have been, Utah and Colorado are both below normal. For much of last winter, the snowpack above Lake Powell has been below normal. Today, the snowpack is reported as being 68% of average for this date. The total precipitation is reported as 88% of average. (Reference: http://lakepowell.water-data.com/) Again, 88% of normal isn’t terrible when considering some recent years. In 2002, the lake level pretty much fell all spring and summer.

Lake Powell Snowpack - 2007 to 2010

Lake Powell Snowpack - 2007 to 2010

This last winter has been consistent. The percent of normal snowpack has remained a 70-90% band for most of the winter. Notice how early warmth of 2007 and 2009 caused the snowpack to diminish rapidly. There is more to this story. Take a look at the departure from normal daily mean temperatures for late April and early May in Grand Junction, Colorado.

Departure from Normal Daily Mean Temperatures Late April to Early May 2010, Grand Junction, Colorado

Departure from Normal Daily Mean Temperatures Late April to Early May 2010, Grand Junction, Colorado

Like most of the Southwest, several cool storms pushed May temperatures below normal. This helps prevent the snow melt from accelerating. It also put a hiccup in the inflow rates for Lake Powell. For a while in May it looked like the spring run-off had ended early.

Lake Powell Water Levels 2010

Lake Powell Water Levels 2010

Early May water level measurements show a small plateau. Still, given the low snowpack levels for the year, this years increase in level is going to be as noticeable as the massive recoveries of 2008 and 2009. Thankfully, the water level stayed high enough this year to keep the Castle Rock cut-off open through the winter. This saves a considerable amount of gas by not having to go around to the south.

Lake Powell Water Levels - 2006-2010

Lake Powell Water Levels - 2006-2010

The post at Watts Up With That? goes on to discuss the overall lower precipitation rates in the West since last October. Yes, lower than average. While we had record breaking storms in December and January, many of the other months in the last year have been below average. Remember, the summer of 2009 was nearly a summer without a monsoon season. But, most of the West has been cooler than normal as well.

So, where will Lake Powell end up this year? I think we will see a later peak that 2007 with an increase of 15-20 feet. This will put the lake in the 3635 foot level (my official guess). Below last year and about the same as 2008. The cool temperatures have delayed the spring melt for a while. The absence of heavy precipitation late in the season prevented a big boost to snowpack from being realized. Still, the snowpack remaining is much higher than the 2007 and 2009. So, there is still time to see the water arrive at the lake.

At Wayne’s Words website (www.wayneswords.com), Wayne Gustaveson run an annual contest to guess Lake Powell’s peak water level. A survey of the guess’s posted there shows an average guess of ~3642 feet and a median guess of ~3643 feet. Knowing that none of us is as smart of all of us, I wouldn’t be surprised to see the peak level to come in at 3642-3643 feet. Wayne keeps tons of great information at his site. I highly recommend visiting it before you go to Lake Powell.

 Posted by at 4:19 am
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