TUCSON – With only a few days remaining in November, it seems likely that the month will go into the record books as slightly cooler than average.
October was also cooler than average. The last time Tucson strung together consecutive months with below average temperatures was November 2015 – January 2016. It’s a tight race but with a big pattern change arriving the last day of the month, odds favor another below average.
High pressure will result in mostly sunny and warm conditions Wednesday as highs warm well above average into the mid 70s. Thursday begins warm but then we track a cold front barreling down from the north. This front will pick up our winds and give us the best rain chance we’ve seen in almost a month. Most of our forecast tools indicate light rain – up to a 1/4″ with 1-3″ of snow for Mt. Lemmon.
Rain is likely early Friday morning and highs will top off only into the low 60s. This cooler air mass will stick around through the entire weekend and another shot of light rain is possible through Monday. Sunday through Tuesday look very cold as temperatures struggle to get out of the mid-to-upper 50s.
Snow levels will come crashing to 4500′ early Sunday morning, and some of the higher towns in the region could pick up a dusting of snow.
The Climate Prediction Center keeps well below average temperatures around for much of next week as well.
So giddy up Rudolph, it’s beginning to look – and feel – a lot like Christmas.
Many years we talk about the latest 100 degree day occurring in October: well forget about that. The highest temperature we’ve recorded this month has been a “cool” 89 degrees.
Don’t look now but warmer weather is in the forecast, but even highs on the warmest days look to only be a degree or two above average.
With two weeks still remaining of the month, it would take a major heat wave to put the entire month of October above average…and that isn’t in the forecast. This means October 2018 will be the first below average month we’ve seen since September of 2016.
TUCSON – Rain overspread much of metro Tucson – AGAIN – tonight and more rain is in the forecast tonight through Tuesday. And oh, don’t look now, but more rain is possible this weekend and even into next week if we can tap into Tropical Storm Tara.
Okay back to the big chill: the first 15 days of October have been colder than the first 15 days of November last year. (How is that even possible?)
So halfway through the month, we now rank as the 19th coldest October since records have been kept (1894). What’s more staggering is if you take out most of the colder October’s which occurred at the beginning of the 20th century, this October ranks as the 4th coldest since 1959! Only the first 15 days of October in 1966, 1970, and 1982 were colder!
And by the way, it’s currently snowing on top of Mt. Graham. See the image below.
We’re off to a good start this year when it comes to our monsoon rain. Nearly 1″ of rain fell at TIA on Friday, and way more out toward Vail.
We have two positive factors for the potential of heavy rain this week and one potentially negative.
I’ll address the ‘good’ first, good if you were hoping for rain.
1) Tropical Storm Erick
A very favorable factor is on our side if you like rain. Tropical Storm Erick is churning to the West off Baja in Mexico. Often times we get what’s called a ‘gulf surge’ from tropical storms – even when they’re well to our south. Essentially, mid level moisture travels up the Sea of Cortez and helps us in the rain category. We still need a ‘trigger” or a mechanism to lift this tropical moisture to create rain. Enter factor #2.
2) A disturbance moving from East to West.
Remember the definition of monsoon? A seasonal shift of the wind. While most of the year we look to the West for our weather, disturbances this time of year come from the East and can help lift our moist air to create the rain. A disturbance is moving our way and should help lift our moist air for good rain chances. In the following picture you can see an area of lower pressure to our Southeast- this would be our trigger.
I’ve seen this too many times during the summer months. Often times despite a ‘trigger’ and good moisture, we do NOT get good rain in the Desert. This can be a function of too much of a good thing.
Ample storms may fire-up, many miles away from Tucson, but they can weaken sending us only clouds. If we are left with leftover clouds, we do not get warm enough at the surface to destabilize the atmosphere for convection (aka storms).
So as of now, I think the two ‘good’ factors outweigh the one ‘bad’ one and parts of Southern Arizona get abundant rain this week. But keep in mind, as contrary as it may sound, waking up with sunshine is a good thing if you are hoping for rain!