An unforgettable snow day in Catalina, Arizona

Three separate bands of snow in one day?  Unforgettable, if not unbelievable, for Catalina, Arizona, made more so because its late February occurrence.  Here at the top of Wilds Road we received a total of 5.5 inches from those three bands, with a peak amount of 4 inches on the “ground” (actually it was measured on a hitching post) just as the third and final band ended at 9 PM last night.  The totals with each band, measured just about the time the snow was ending1:

Time of band                  Top of Wilds Road:        Sutherland Heights (1 mi NE and 170 feet higher)

11:30 AM to 2:30 PM          2 inches                              3 inches

4:30 to 6:00 PM                   2.5 inches                           2.7 inches (most fell in an hour and a half!)

8-9 PM                                1  inch                                  2 inches (this just in), 6 inches on the ground there in sheltered locations)

Totals:  5.5 inches at the top of Wilds; 7.7 inches in Sutherland Heights.  What a day, Mr. and Mrs. Catalina!

Water content in this snow here, 0.49 inches, so far.  Waiting for melt down to get last few hundredths still frozen on the sides of the collector of the tipping bucket raingauge.  Measured at Sutherland Heights:   a fabulous 0.73 inches!

It’ll be gorgeous in the first few hours today after dawn, but with our late February  sun, our great local scenes won’t last long.   While more cold air is ahead, though with no precip in the few days, a HEAT WAVE has reared up in the models for the beginning of March,  8-10 days out!

Some photos for yesterday’s memorable snows2 (plural here is even amazing),  From the beginning…

7:37 AM. A blustery cool dawn, snow showers in progress on the Catalinas from relatively shallow Stratocumulus clouds.
7:37 AM. A blustery, cool, and dramatic dawn scene, with snow showers in progress on the Catalinas from relatively shallow Stratocumulus clouds racing along them from the south.
9:39 AM. A very exciting moment here! A non-preciping line of heavy Stratocumulus gets cold enough on top to start preciping over Oro Valley. Here we go!
9:39 AM. A very exciting moment here! A non-preciping line of heavy Stratocumulus gets cold enough on top to start preciping over Oro Valley. Here we go!  How cold were those tops getting?  You want to guess, “Oh, about -10 C or so.” The TUS sounding at 5 AM AST had tops in that range already.
11:37 AM. Just after the windshift and a 10 degree temperature drop from 44 F to 34 F, the snow begins to fall in Sutherland Heights.
11:37 AM. Just after the windshift and a 10 degree temperature drop from 44 F to 34 F, the snow begins to fall in Sutherland Heights.

 

SONY DSC
6:11 PM. Wider angle view of that same scene after the second band dropped 2-3 more inches of snow in just over an hour. Getting pretty dark, camera or photog not doing the greatest job here.

 

 

5:59 PM. Can you imagine what this blue palo verde tree is thinking?
5:59 PM. A blue palo verde tree bowing to snow.
5:57 PM. "Piling it higher and deeper", a common expression likely referring to snow.
5:57 PM. “Piling it higher and deeper”, a common expression likely referring to snow and one that’s valid here.
5:22 PM. How'd it get like that shown in the prior photo? Like this, a shot in the middle of S+ ("heavy snow" in weather teletype parlance)
5:22 PM. How it got there…  This is a shot during the heavier, second snow band during its prime S+ burst.  “S+”, is “heavy snow” in weather teletype parlance, an early form of “texting.”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Will be taking more photos of course, early today!

The situation aloft (500 millibars) as S+ snow band 2 hit:

cropped 500
For 5 PM AST February 20th. The low center aloft is perfectly positioned for us as new precip bands are generated near its center as it sped eastward. Newer bands are heavier than older bands as a rule, and Band 2, was quite young with lightning in it. Band 3 is just forming, and it too, was mighty, though less extensive than Band 2.

 

Today’s clouds

Some Cu-Stratocu, patches of CIrrus and Altocumulus as a another lobe of cold air races SE from the Pac NW today.  There’s a chance of snow flurries late tonight into tomorrow morning (can you imagine?) as the core of the trough goes by.

The End.

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1Measuring snowfall and snow on the ground, is one of the biggest bugaboos we have in meteorology.  If there is any wind at all, forget about getting an accurate total, too much blows over the collector can. So, the precip amount reported for this storm is going to be on the low side.  And,  as the snow piled up yesterday, it was also disappearing at the same time on the bottom due to melting.  Finally, as it piles up, it sinks down due to weight.  So, the depths reported above are conservative, since if all the snow landed on a below freezing metal plate, we would only be dealing with one of those problems, settling, as with snowpacks in the high mountains.

2Hardly any of which was forecast from this keyboard.  Wish there was a font smaller than ” 1 point” and this is it, in case you’ve never seen it.  You don’t want to rub it people’s faces that maybe you were a little asleep at the wheel; too preoccuppied with the amount of precip which you forecast was going to be MORE than the models were predicting, and which happened, not the phase (solid or liquid) of the precip.  But then, what REALLY matters to the vegies out there?  The amount, of course, well, OK I guess vegies like it if more if the water sits there in a form that melts and has a lot of time to soak in.

By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.