High Wind and Blizzard Warning!

A robust storm, as it were, is barreling toward Arizona and the effects across the area promise to be dramatic.  The headline is the strong wind.  A strong southerly jet stream is driving this strong storm and the combination will translate into very strong winds in the lower elevations and even stronger winds higher up.  Gusts to 55 mph by this afternoon will be likely in the Tucson area and gusts to near 70 mph are possible in the mountains.  That’s why the National Weather Service has issued a HIGH WIND WARNING  from 11 this morning until 2am Friday.

Tonight is when the main impact of the storm will be felt.  Normally winds will decrease at night because you lose the mixing of the atmosphere leaving the strongest winds above your head.  Tonight that may not be the case as scattered thunderstorms will have the capability of pulling some of those higher winds down to the surface.  It’s possible that the high winds won’t decrease tonight at all.

Last time we had winds this strong there was a fatal pileup on Interstate 10 near Casa Grande.  Thankfully we had some rain yesterday morning and again this morning.  I’m hoping that the rain we’ve had combined with what is coming will be enough to keep the dust down.  Still, caution should always be observed driving on the Interstate near those usual blowing dust areas.  Also high profile vehicles may have difficulty with this wind.  Definitely a two hands on the wheel kind of driving day.  It’s also going to be possible to see some damage from these winds.  Downed trees and stuff like that may occur in town.

Higher up, the winds will combine with a lot of snow.  That’s why the National Weather Service has issued a BLIZZARD WARNING above 7,000 feet for tonight and tomorrow morning.

Initially, the snow level will be around 8,000 feet.  Our last storm left a few inches of snow as low as 6,000 feet.  The rain combined with some melting snow could result in some flooding in mountain streams and perhaps downstream.  Otherwise, snow levels will drop below 7,000 tonight and 1 to 2 feet of new snow is possible in the mountains around Tucson combined with winds gusting as high as 70 mph.  The White Mountains could get as much as 4 feet of snow from this storm!

As far as rain amounts in the lower elevations, we are expecting generally 3/4 of an inch to an inch and a half with this system.  Some areas could exceed 2 inches if they get a thunderstorm or two.  This is great news!  We need the rain.  The snow pack will help us out too.

Snow in Tucson?

Well, maybe in the Foothills and out towards Vail.  After the cold front moves through tonight, temperatures will start to drop and so will the snow level.  It’s possible that by early Saturday morning there may be some snow showers right down to the valley floor!  Accumulating snow is expected above 4,000 feet, but it’s worth watching.  This will be the back side of the storm so we aren’t talking about a whole lot of snow, but it’s possible that Oracle, Tombstone, Sierra Vista, Benson, and some other places could pick up a few inches.  IF the snow level can manage to get down to the 2,500 foot level maybe we could finally see snow here at the apartment in Oro Valley.  It’s not likely, but when the possibility gets this close, I start holding out hope.

Bottom line to all this?  Enjoy the adventure but be careful out there!

Another much much weaker storm is headed our way early next week as the El Nino pattern is kicking in.  El Nino dried out or Monsoon last Summer, let’s hope we can now make up for it in the remaining months of Winter into early Spring.

Tucson Weather, 11/29/09: Winter Storm Watch

I love El Nino years in the Southwest.  As the southern jet stream gets going, more storms take the southern route.  That means more rain and snow for places like Tucson.

After a very pleasant (and a warmer than average) November, the Thanksgiving weekend is ending with a nice pattern change.  A vigorous storm system is dropping in from the north.  The expected track is south through Yuma today and then turning the corner just south of the border.  As it tracks to the east just south of Tucson through Monday expect chilly temperatures with rain, and snow as low as 4,000 feet!

This morning we have an area of showers moving north through much of Tucson.  The low is still well to our west and the low has been pulling up moisture from the south.  Expect areas of showers to continue through the day today.  Even though a cold front has already moved through we are still on the warm side of the storm.  Today’s high should be near 60.

Tonight, the storm gets closer and the fun should really begin!  Scattered showers this evening and overnight with temperatures falling and snow levels dropping.  Could see snow sticking above 4,500 feet in places like:  Sierra Vista, Tombstone, Sonoita and Bisbee.  Snow could fall as low as 4,000 feet which means Oracle has a chance to see the snow fly, although it’s not expected to stick so much.  Places like my apartment at 2,600 feet should see chilly rain.

The National Weather Service has issued a Winter Storm Watch above 4,500 feet for Sunday night through Monday afternoon for the Upper Gila River Valley, Tucson Metro, Marana, Green Valley, Santa Cruz and Cochise Counties.  Could see 2 to 7 inches of snow between 4,500 and 7,000 feet with 8 to 17 inches above 7,000 feet!

With southern Arizona in the favorable northern part of the storm, we should get the best part of the snow as it tracks on by.  After the storm leaves we should stay on the chilly side.  Highs in the 60s and lows in the 30s through much of next week.  Should be a great week to head up to Mt. Lemmon and play in the snow!  This won’t be enough to open up the ski area, but sledding, snowball fights and making snowmen will definitely be on the menu.

Under Pressure

Southeast Arizona is under pressure this week.  Strong high pressure is building and that may mean a new record high our two for the area Tuesday and Wednesday.  Here are some numbers I stole right out of the Tucson National Weather Service’s Forecast Discussion:

                        TUE NOVEMBER 3       WED NOVEMBER 4
                      FORECAST  RCD/YEAR   FORECAST  RCD/YEAR
 TUCSON INTL APT         92      91/1931      91      91/2001
 AJO                     94      95/1924      93      95/1915
 ORGAN PIPE CACTUS       93      92/1997      92      92/1999
 KITT PEAK               73      73/1999      72      72/1997
 ORACLE                  80      86/1916      79      88/1916
 PICACHO PEAK            92      91/2001      91      93/2001
 NOGALES 6N              85      87/2005      84      87/2001
 BISBEE-DOUGLAS APT      83      85/2001      82      84/2007
 SIERRA VISTA            81      86/1916      80      87/1916
 SAFFORD AG STATION      83      86/1952      82      89/2001
 FORT THOMAS             82      84/1962      81      87/2001

So why so hot?  Blame it on high pressure and the sinking air.  With high pressure, the atmosphere is actually “thicker.”  Not thinker in density, but thicker in height.  That’s why it’s called a “dome” of high pressure.  And that air is sinking.  As air sinks from higher elevations, it gets squeezed by the weight of the air above.  As the air gets compressed, it warms.  Also, the sinking air makes it harder for clouds to form so you have clear nights and sunny days.  This far south the Sun can still be pretty strong, even in November.

Sometimes high pressure can be really cold.  Arctic highs form where there is little, or no sunshine in the Winter.  So.  Clear nights and no Sun make the air mass colder and colder and colder.  Arctic highs are both thicker in height AND density.  Your barometer under a strong Arctic high may approach the red line!  When an Arctic high moves south, it brings the severe cold of the arctic with it, slowly “modifying” (warming up) over time in the southern Sun.  Southeast Arizona usually doesn’t have to worry about Arctic highs moving in (unfortunately)…