Rain, snow (s), extreme cold ahead in mod run (pretty worked up today)

Was going to rest brain today, not blog-blab, but then went to mods; brain rest over.

“Holy Smokes!”, “Good Grief!”, my modest brain erupted with when perusing the 00 Z1 (5 PM AST) WRF-GFS model run this early AM.   If the predicted features verfify over the next 15 days, what appears to happen beyond that, this could be one of the most severe January’s in the Southwest in decades.  Yikes.  And our “test the effects of flapping butterfly wings on the model run” (figuratively) “spaghetti” plots from NOAA, those slightly perturbed/disturbed model runs,  seem to support last night’s ACTUAL run, at least into the first two events described below2.  “Hence”, as they used to say, the excitement this morning from this keyboard, but maybe some dread, too.

Quickie overview for Catalina

(taking the current model run (00 Z) at face value:

Jan 7th into the 8th:  Some rain, maybe a tenth or two.

Jan 11th-12th:  rain changing to snow, total precip maybe half an inch, with an inch or two of snow. Post event, temperatures dropping into the 20s at night, lower in washes and such.

Jan 16th.  Another chance of snow, doesn’t look like as much precip as the prior event, but colder yet afterward.  Temperatures lower yet, could get into the lower 20s, teens in the washes.

Furthermore, the pattern doesn’t appear to break after this last storm on the 16th.  It remains cold here through the end of the model run on January 20th.  As you likely know by now, once the jet stream gets into a pattern, it likes to keep it going.  No one knows why, or when it will break.  If we did, our longer term forecasting would be better.

Some more discussion below of this forecasted pattern, one that could lead to one of the more severe Januarys in the West in some decades.  While precip is always dicey here until the last moment, the exceptional cold seems very probable.  Be ready!

Here’s what the model (as usual, rendered here by IPS MeteoStar) has churned out for us in the way of rain/snow events for us,with the storm formerly mentioned here as arriving on the 8th, now arriving on the 7th.   (Heck, for awhile it was GONE!) This series of three trough/storm events shown below might be thought of as cool, colder, coldest.  Not so good as a series if you’re visiting here to enjoy warm weather.

Valid for middle of the day, January 7th. Not a bad storm, but not a great one, either, but good in the sense it keeps the stream of storms up after a week’s break. Maybe a tenth or two of rain.


Here’s the next one, valid for the evening of the 11th, and this one starts to get your attention, as in “Yikes! If that materializes, its snowing here!”:

Valid for 11 PM January 11th: Summary; yikes! So cold, rain turning to snow in Catalina, maybe a couple of inches. The thing to notice is the central contour number here, “12” lower than the “ordinary” storm shown above. The lower these numbers (contours where the height of the 500 millibar pressure is reached, the colder the air must be underneath it. The denser the air is, the faster the pressure changes as you go up. So a “540” contour represents really cold air in the Southwest moving into Arizona. I would not want to be a grapefruit in the few days after this goes by.

Finally, this, a brutally cold trough over us again, with the jet stream running a straight shot just down the interior of the West Coast from pretty much the place where Santa Claus lives, Barrow, AK.  Below, valid for the morning of January 16th:

Valid for 5 AM AST, January 16th. Egad! While precip might not be as much in the prior trough passage, this one looks colder after it goes by. Part of the contribution will be that the prior storm would have laid snow down over a vast area interior of the West, and that will help to keep the cold air blasting southward here colder here than it otherwise would be.


These particular depictions, especially the latter ones with rain and snow in them for us will be flopping around like a just-caught trout in a boat in the model runs ahead.  The main thing that seems “in the bag” for Arizona as a whole, is COLD air.  Cold to write home about.

Snow?  Of course, its less certain as the troughs wiggle around in the models, and to get that snow the apex of the troughs pretty much have to go over us and those little wiggles could take them to a bit to the east of us, making the coldest spells just dry ones.  That would be too bad, because if you’re going to have to endure cold, there might as well be some snow on the ground to play around in.

Now in a personal disclosure, one of the faults I have as a weather discussant, is to get TOO excited about extreme events that are forecast, rationality diminished, hence the “newsy” logo here:

“Right or wrong, you heard it here first!!!!”

It WILL be so much “fun-dread” day by day, to see if these things come to pass, how the models change these depictions above as new data are processed.  To repeat, though, be ready!

The End.





1Or, “CUT”, Coordinated UNIVERSAL time, as it is called today.  I hope those people on the edge of the universe are aware of our time convention.   Used to be known as GMT, Greenich Mean Time, starts at the 0th Meridian over “jolly old England.”  “Jolly”?  Huh.   Are they referring to Monty Python?  Rowan Atkinson? .

2Don’t forget to order your “I ‘heart’ spaghetti!”, tee shirt that shows you’re one of the scientific literati because “spaghetti” gives us insights into whether a model run is a bunch of crap (oops, “model excrement”.  New! Now available in down jackets….