Starting tomorrow morning, we are in for another dose of winter. This storm will be hefty. For the first time I can remember this winter, the National Weather Service has posted a Winter Storm Warning (see below) for Flagstaff. Flagstaff will start Friday in the snow. The snowfall rate will be higher in the evening and through the night Friday. The storm should move out of the area during the middle of the day on Saturday. As you can see in the winter storm warning, 8-14 inches are possible above 6000 feet. This is a major storm.

High resolution models show heavy precipitation totals over the next 48 hours. Both models shown below have 0.75 to 1.75 inches of snow for the Flagstaff area. This matches the 8-14 inches of predicted snow fall.

The good news, at least to me, is that next week will be warm and beautiful!

High resolution 48-hour total precipitation ARW model from the Climate Prediction Center

High resolution 48-hour total precipitation NMM model from the Climate Prediction Center

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
411 AM MST THU MAR 7 2013

...STRONG WINTER STORM SYSTEM TO AFFECT NORTHERN ARIZONA FRIDAY
THROUGH SATURDAY...

.A STRONG PACIFIC STORM SYSTEM WILL MOVE INTO NORTHERN ARIZONA
FRIDAY MORNING AND SPREAD ACROSS THE STATE THROUGH THE DAY. HEAVY
SNOW WILL DEVELOP FRIDAY...CONTINUING INTO SATURDAY. MANY AREAS
ABOVE 5500 TO 6000 FEET WILL RECEIVE HEAVY ACCUMULATIONS. LIGHTER
ACCUMULATIONS CAN BE EXPECTED AS LOW AS 4000 FEET. EXPECT WINTER
DRIVING CONDITIONS WITH SLICK ROADWAYS AND LOW VISIBILITIES DUE TO
SNOW AND BLOWING SNOW.

AZZ015-016-071915-
/O.NEW.KFGZ.WS.W.0003.130308T1300Z-130310T0700Z/
WESTERN MOGOLLON RIM-EASTERN MOGOLLON RIM-
INCLUDING THE CITY OF...FLAGSTAFF
411 AM MST THU MAR 7 2013

...WINTER STORM WARNING IN EFFECT FROM 6 AM FRIDAY TO MIDNIGHT
MST SATURDAY NIGHT ABOVE 5500 FEET...

THE NATIONAL WEATHER SERVICE IN FLAGSTAFF HAS ISSUED A WINTER
STORM WARNING FOR SNOW...WHICH IS IN EFFECT
FROM 6 AM FRIDAY TO MIDNIGHT MST SATURDAY NIGHT.

* TIMING...SNOW WILL BEGIN FRIDAY MORNING AND CONTINUE...HEAVY AT
  TIMES THROUGH SATURDAY.

* SNOW ACCUMULATIONS...8 TO 14 INCHES ABOVE 6000 FEET...5 TO 10
  INCHES ABOVE 5500 FEET. LOCALLY GREATER AMOUNTS ARE POSSIBLE.

* OTHER IMPACTS...SLICK ROADWAYS AND SEVERELY REDUCED VISIBILITIES
  DUE TO SNOW AND BLOWING SNOW.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
EXPECTED OR OCCURRING...DUE TO SIGNIFICANT AMOUNTS OF SNOW AND
STRONG WINDS PRODUCING LIMITED VISIBILITIES. DRIVING WILL BE
EXTREMELY DANGEROUS DURING THIS STORM. FOR THE LATEST ROAD
CONDITIONS AND CLOSURES...CALL THE ADOT FREEWAY MANAGEMENT SYSTEM
AT 1 888 411 7623 OR VISIT THEIR WEB SITE AT WWW.AZ511.COM.
ADDITIONAL WEATHER INFORMATION IS ON THE WEB AT
WWW.WEATHER.GOV/FLAGSTAFF.

Our cold winter will continue with another round of clean, dry snow. The snow level will drop to very low levels(2500-3500) by the time the storm passes. This storm will tap tropical moisture. The storm should start very late tonight or first thing Wednesday morning. Wednesday could be a snowy mess with the bulk of the precipitation hitting in the day.

We are going back into the deep freeze. Temperatures on Thursday will be 15-20 degrees below normal. I wish I could tell you this weekend will be warm and wonderful. We should have bright sunny days by Saturday, but clear skies overnight will result in temperatures in the low teens.

I think there are good explanations about why our forecasts was so off this weekend. For me, it starts with me growing dependence on the computer models. I haven’t been looking at the data about the real weather as much as I used to. The models are usually pretty darn good. So, I didn’t look to see how much water content was coming our way.

Water vapor satellite image. Orange indicates areas of dryness. Greens and blues indicate moisture

Still I might have missed it here. Notice how much orange, dry air is south and west of us. These areas are typically our moisture supply in the winter. For this weekend, our moisture has come from the north and west; Nevada and Utah. I this that might have thrown me. I need to keep looking at data like this.

The next problem I should have considered on Friday. If you read my post from Friday morning, you’ll notice that I pointed out that a single, high-resolution model had over an inch of water for us.  When massive storms happen, especially in heavily populated areas, the National Weather Service focuses their time, energy and computer models on those storms. The model that had the accurate prediction of lots of water, focuses only on the Western United States. National forecasters can be distracted while the strong nor’easter hit New England. The National Weather Service tweaks their models to give better detail at times of concern like this. It also means that less populated areas, like the Desert Southwest, get less attention and less accurate forecasts. They may disagree, but it seems real.

Here is the latest 48-hour total precipitation forecast from the high-resolution model I mentioned before.

ARW high-resolution precipitation model for 48 hours.

We are in for a lot more snow and very cold wintry conditions for the next few days. Between now and Monday evening, we are looking at 6-18 inches depending on luck and location. Some places will see more that this. Notice that this storm leaves areas south of the Mogollon Rim mostly dry. This points back to the moisture coming from the northwest.

Sorry for missing this one.

Clouds and rain are on tap through the weekend. Cooler temperatures and snow are coming early next week. We should end the month well below normal for the month.

Most of the precipitation will be rain for the next 48 hours. We could receive over a half-inch of rain, with locally higher amounts up to one inch.

48 hour precipitation through Sunday morning

After this first storm moves out, a second storm will drop in for the north and bring cooler temperatures and snow. This storm will bring several inches of snow from Sunday night through Tuesday night. This storm will leave us with below normal temperatures to end the month.

48 hour precipitation, Sunday night to Tuesday night.