All of a sudden, it looks like we have a real chance for snow tonight. Measurable, but not significant. However, some local areas could see heavier amounts.
About a month ago I added a tracking program to my blog. I wanted to see where in the world my visitors were coming from. Here is the result:
Visitor Map
While there is a chance for snow the next few days, particularly on Thursday, I don’t think we will see much. The winds should be very strong due to the jet stream dipping very far to the south.
This will probably be a keeper. I got lots of requests for clarity around Wednesday’s frozen precipitation varieties. It got some good discussions going about what are things like sleet and hail. What is the difference? Here are the National Weather Service’s definitions of the precipitation types I thought I saw last Wednesday.
Hail - Showery precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter, falling from a cumulonimbus cloud. Sleet - Sleet is defined as pellets of ice composed of frozen or mostly frozen raindrops or refrozen partially melted snowflakes. These pellets of ice usually bounce after hitting the ground or other hard surfaces. Heavy sleet is a relatively rare event defined as an accumulation of ice pellets covering the ground to a depth of 1/2" or more. Snow - Precipitation in the form of ice crystals, mainly of intricately branched, hexagonal form and often agglomerated into snowflakes, formed directly from the freezing [deposition] of the water vapor in the air. Graupel - Same as snow pellets or small hail. Snow Pellets - Precipitation, usually of brief duration, consisting of crisp, white, opaque ice particles, round or conical in shape and about 2 to 5 mm in diameter. Same as graupel or small hail. Small Hail - Technically used to refer to snow pellets or graupel.
Wow! Small hail, snow pellets, sleet, graupel. Hmmm. Very similar sizes. So, for clarity, I think hail and sleet are typically more like solid ice. Graupel and snow pellets are white and opaque. There wasn’t a definition for wintry mix. But, the names for the various sizes of hail are mildly interesting:
| Description | Diameter (inches) |
| Pea | 0.25 |
| Marble or Mothball | 0.50 |
| Penny or Dime | 0.75 |
| Nickel | 0.88 |
| Quarter | 1.00 |
| Half Dollar | 1.25 |
| Walnut or Ping Pong Ball | 1.50 |
| Golfball | 1.75 |
| Hen’s Egg | 2.00 |
| Tennis Ball | 2.50 |
| Baseball | 2.75 |
| Tea Cup | 3.00 |
| Grapefruit | 4.00 |
| Softball | 4.50 |
Today and Friday, we will get more precipitation in various frozen forms. There is more on the way for next week. It seems amounts were widely variable for the area. My rain gauge indicates 0.29 inches of precipitation. The airport reported 0.18 inches. Bellemont, WOW, reported 0.64 inches. Out at Gore’s Woody Mountain location, there was continuous precipitation for most of the morning, including an accumulating mix of snow, snow pellets, sleet and hail. I’ll try to do an informative post this weekend on all the forms of frozen precipitation.
There is a repeat performance on tap for the same time period next week. For the month, Flagstaff is still behind on precipitation. This is on top of a dry March. Temperatures will continue to be low and keep spring at bay.
Here is the short version of what we will get for the next two days:
wind – LOTS
rain – a little
snow – hmmm
Temperatures are going to drop through the day today as we head back into a wintry mode. Personally, I don’t think we will get much accumulating snow. But, the precipitation out look on this high resolution model for the next 48 hours tells a very wet story. This model takes into account terrain effects.
High Resolution Model - 48 hour Precipitation
It looks like the next few days will bring a so called wintry mix. Some rain, some snow, some wind. While we may see several inches of snow over the next few days, they will come in isolated clumps. Hopefully, it will melt in the in between time and we will be left with little to show for it. In fact, I don’t see us getting too much precipitation.
The recent warm weather is going to disappear for the rest of this week. The long range out look continues to look cooler and wet with another storm in the middle of next week.
Here are some snapshots of the growing season start from three locations in Northern Arizona with different altitudes.
Location Elevation June 1st Freeze July 1st Freeze Saturday's High
ft (32F)Probability (32F)Probability Temperature (F)
Williams, AZ 6750 40% <10% 69
Flagstaff, AZ 7000 80% <10% 67
Fort Valley, AZ 7350 >90% 35% 65
Keep in mind that there are other factors that play into local climates. Small valleys may see shorter days or temperature inversions. Direction of local winds can cause different heating and cooling trends. Treed areas versus open, grassy areas. These are all local considerations. Bellemont, for instance, is subject to a particular cooling flow off the San Francisco Peaks that keeps it cooler there. Saturday’s high temperatures would seem to reinforce the altitude difference for the 3 sites.
So, as you plant this spring, consider what effects you are seeing for your area. There are several amateur weather stations scattered across the Flagstaff area. You can find them at Weather Underground. This link takes you to their Wundermap for the Flagstaff Area. You can look to see how a nearby temperature compares to the Flagstaff Airport and get a feel for how you location compares. Also, you could get a good quality thermometer and compare it to the Airport.
It looks more and more likely that next week will bring a significant chill and a reasonable chance for rain and snow. First, the chill. Here is the Climate Prediction Center‘s (CPC) 6-10 day outlook covering April 22-26, Thursday-Monday.
6-10 day Temperature Outlook - April 22-26, 2010 - Climate Prediction Center
It’s very unusual for the CPC to show anything in the 80% range. With forecasted temperatures being in the mid-20′s, it is unlikely we will break any records. For late april, the record lows for Flagstaff range from 7-17F.
From a precipitation point of view, I think the models are highly variable. It looks like there will be an early week, low precipitation probability storm and a later week, high precipitation probability storm. The second storm looks to bring the colder temperatures with it. With projected lows for Flagstaff in the mid-20′s, the snow level could drop to the 5,500-foot level. It’s still a good ways out. Daytime temperatures will be warmer and may allow us to only see rain. Following the recent dry trend, we may just get wind.
Early Week Storm - 24hr Precipitation (GFS Model) Through Tuesday Morning
Late Week Storm - 48hr Precipitation (GFS Model) Through Friday Morning
The computer models keep fluctuating. There is a chance for some moisture for next week. Unfortunately, I think we are going to see wind and cooler temperatures.
This weekend, I am planning to get a post up on the start of the growing season and the effect of altitude.
And chilly. Today should be a brief respite from the sunny weather we have been suffering.
This week should bring a warmer, sunny period. More storm systems are in the future, though. We aren’t done, yet.
Neither is the Arizona Snowbowl!
With such a great weekend, we will be reopening for one final weekend of the 2009-10 season. We will reopen the Agassiz Lift Friday through Sunday, April 16 - 18 (closed April 12 - 15). Spring conditions are incredible and the sun is out with warm temperatures. The Agassiz Lift will operate from 10:00 AM to 4:00 PM, serving intermediate and expert skiers and snowboarders.
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