Feb 252014
 

Thursday will usher in a wetter pattern. With the “polar vortex” moving into the Midwest and Eastern United States, our temperatures are going to stay warm until the weekend. We probably won’t see significant precipitation until Friday night. While the precipitation will continue until Monday, the intensity will drop during the day on Sunday. Since temperatures will be warm, I don’t know how much of the precipitation will fall as snow.

There will be a significant amount of moisture with this system. Here is the 5-day precipitation outlook from the National Weather Service’s Weather Prediction Center. Notice the 2.5 inch peak precipitation amount. This won’t make up our 4 inch precipitation deficit to average since September, but it could nearly cut it in half. On another note, this storm will proceed to the east. It could be come a major spring storm.

5-day precipitation outlook, ending Sunday morning, 3-2-2014. From the National Weather Service's Weather Prediction Center

5-day precipitation outlook, ending Sunday morning, 3-2-2014. From the National Weather Service’s Weather Prediction Center

 Posted by at 4:22 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
Feb 052014
 

UPDATED: 5:45pm AZ time – See below

The Weather service is being clear about their expectations for the end of the week. On their forecast, they have Thursday night as the period with the heaviest precipitation. This is their Weather Story for today.

Snowfall outlook for the rest of the week, from the National Weather Service in Flagstaff

Snowfall outlook for the rest of the week, from the National Weather Service in Flagstaff

But the North American Mesoscale(NAM) model has us drawing a blank for the next few days. The lower resolution GFS model shows a situation similar to the Weather Story above. Aaarrrggghhh!

2-5 Inches is probably a good guess. At this point, 4-8 seems like a stretch. The computer models are often and by large amounts. We’ll see. It’s possible the next few days could be just like the last few.

UPDATE - So, just to make the point…. The NAM model has shifted tonight. We are back in the 3-8 inch range for snowfall amounts between now and midday Friday. All I can say is “Be ready.” It will probably snow. We may receive a decent amount.

North American Mesoscale Model forecast for precipitation between Wendesday evening and midday Friday. NOAA's Climate Prediction Center

North American Mesoscale Model forecast for precipitation between Wendesday evening and midday Friday. NOAA’s Climate Prediction Center

 Posted by at 7:04 am
Feb 032014
 

We continue to have a chance for snow over the next couple days. We should only get light accumulations. Temperatures will remain cooler than what we had experienced in January. A stronger storm remains in the forecast for Friday and Saturday. It won’t be a drought buster, but should bring us several inches of snow.

 Posted by at 6:23 am
Jan 312014
 

Finally, I real break in the storm pattern appears to be at the other end of next week. In the current GFS model run, the precipitation starts Thursday night and lingers into Saturday afternoon. On the map below, there is a very nice dark blue area over Flagstaff. This represents 1/2 to 3/4 of an inch of water, or roughly 6-8 inches of snow. Welcome back winter!

20140201-072928.jpg

 Posted by at 5:29 pm
Jan 292014
 

Just, exactly far enough south to give us a break.I must’ve told half a dozen people over the next week that it looked like it would be weeks before we saw any wet weather. Looks like that did the trick. Please, if you could, do something to help it snow. Wash your car, put away your snow shovels and blowers.

It looks like this week’s storm will have two parts to it. The first part will hit on Friday. The second part will hit Saturday night into Sunday. Scattered light precipitation could fall in between and linger in the area afterwards. There isn’t much water in either part. At best, it looks like either storm could produce a few inches of snow. Any precipitation will occur only the higher elevations of Northern Arizona. The San Francisco Peaks could see more.

Hopefully, this will represent a longer term shift. Currently, when the storms leave, we return to high pressure and warm, sunny conditions. The very long-range output of the GFS model has wetter conditions.

 Posted by at 6:34 am
Jan 132014
 

The short, medium and long-term outlooks for Arizona have a fairly common theme, sunny and warmer than normal. This mornings 16-day outlook on the GFS model paints a distinctive picture. This model forecasts high pressure to rule the rest of the month. This is always subject to change. But the jet stream is very far to the north. As a result, the storm track is nowhere near Arizona. We shouldn’t expect snow anytime soon.

384-hour (16-day) precipitation outlook. GFS model at the Climate Prediction Center.

384-hour (16-day) precipitation outlook. GFS model at the Climate Prediction Center.

 Posted by at 6:41 am
Dec 192013
 

Tonight through tomorrow, we should receive some snow. The computer models have been all over the place. Often they show the storm missing us and forming to the south and east. Currently, the outlook is for 1-6 inches over the next couple of days. This could make the “get out-of-town” drive rougher.

For now, our pattern seems as small storms forming in or around Arizona, the moving off to the east and clobbering the East Coast and New England.

 Posted by at 6:37 am
Dec 042013
 

Neither of the storms on the horizon are packing a lot of moisture for Flagstaff. A few inches will fall today through tomorrow. Then, a few inches will fall over the weekend. The real news is the very cold temperatures on the way. With highs in the twenties and lows in the single digits, we will be 5-10 degrees below normal on several days over the next few days.

The image below isn’t a pretty as it could be. It does tell the temperature story. This image shows the average maximum temperature anomaly for the next 5 days. Brrrr. Flagstaff is in the -12 to -15 degree band. The snow probably won’t be melting very fast.

5-day average maximum temperature anomaly. National Weather Service

5-day average maximum temperature anomaly. National Weather Service

 Posted by at 5:24 am
Dec 022013
 

I kept wondering what was going to happen to the storm that rolled up to the West Coast and then disappeared. Apparently, it brought the fog and freezing fog.

The next few storms (that’s right, the next few) will bring more significant precipitation and colder temperatures. Starting Tuesday, temperatures will drop. By Friday morning, we will see single digit temperatures in the Flagstaff area. Many lower elevations will experience freezing conditions. None of the storms over the next week or two seem will break records. But, a few inches here and a few inches there can add up with the low temperatures.

This afternoon will probably give the best set of outlooks since the Thanksgiving break. We’ll see if the outlooks hold.

 Posted by at 7:16 am
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