Matt Makens

Looking at the precipitation over the past two weeks and past month, there is an uptick in the moisture that has fallen across the West, however, a lot of caution needs to be used when considering drought conditions the next couple of months.

Drought conditions to persist despite recent wet period

Although our recent posts have addressed wetter patterns emerging, those pattern
may not last long enough to be able to change much of the drought conditions
across the Western and Central U.S.

Here is the latest drought monitor published Thursday the 28th.

Looking at the precipitation over the past week and the past month, there is an
uptick in the moisture that has fallen across the West recently, however, not a
lot for the month. 

The long term pattern has been quite dry for the West, so a lot of caution needs
to be used when considering drought conditions the next couple of months.

In an email publication from NIDIS, a few key points were mentioned regarding
California and Nevada.

> Moderate-to-Extreme drought remains across California and Nevada which typically
receive about half of their precipitation in December thru February.
> Recent storms have brought some relief to Southern California with widespread
precipitation on the horizon. This may alleviate some drought conditions but is
likely not enough to remove long-term drought conditions and impacts.
> Low snowpack (i.e., snow drought) and decreasing reservoir levels in the Sierra
are leading to below normal total water storage (natural+human built). Soil
moisture remains low.
> Preparation for continued drought impacts (e.g., pasture conditions, water
supply, fire risk) should be considered, especially in the driest areas. A
precipitation regime change may improve conditions, but based on climatology a
water deficit in the region will most likely continue.
The last sentence there is quite telling, and a theme that we have been
emphasizing in previous posts regarding moisture and seasonal outlooks.

As we continue to see La Niña conditions persist this winter through spring, we
will see its influence grow for the southwestern U.S.

Here I've processed the correlation between a La Niña and the associated
precipitation pattern.

The series of maps go from November to April broken into two-month periods.

That series shows the driest signal associated with La Niña patterns starts in
the American Southeast, progressing westward toward the desert Southwest by
Spring. 

The key takeaway is La Niña's impact becomes drier and drier progressively
throughout the snow season. 

With that in mind, the most extreme drought areas - including California and
Nevada along with the Four Corners - are not likely to keep the moisture flow
for very long. 

Let's look at the next of weeks for precipitation potential. This map shows
projected areas of wetter (greens) than average and drier (brown) than average
regions for the next 15 days.

If the moisture pans out for the Southwest and Colorado, take it!

Farther into the future, we may see some storms that offer periods of wet
weather but overall the drought stricken areas are not likely to see 'the needle
move.'

One way to look at the long term outlook is by the shallow groundwater
projection through the end of March. 

The projection has drought conditions persisting despite a recent increase in
moisture chances.

I'll post more on soil conditions soon as it's a topic worthy of its own
attention.

Thursday, January 28th, 2021: Drought update & the outlook