CLIMATE NEWS

● Water Conditions: AKA No “Miracle March”...or April For That Matter!

● Seasonal Outlook

● Spotlight: 1991-2020 Climate Normals

May 2021

1Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

What HappenedFebruary - April Temperature Anomaly

● Most spots in western NV near or slightly below average

●

● Sierra leaned above average, especially above valleys. Highs and lows show a similar pattern.

● Possible explanation: lack of storms! Fewer storms/more high pressure can mean higher

temperatures above valley floors (especially

notable in Sierra this year)○ For lower valleys, fewer storms means less

mixing/more valley inversions and lower temperatures during the colder months

2Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

What HappenedFebruary - April Precipitation Anomaly

● No “Miracle March” this water year

● Most of eastern CA and western NV saw below 50% of average precipitation for the February

to April period.

● Our region, especially near the Sierra, often relies greatly on a few significant events

(“atmospheric rivers”) each fall-spring to

provide the bulk of snowpack/water supply.

Clearly that didn’t happen this wet season!

3Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

What’s Left For Snowpack?● Area river basins 22-54% of median as of May 1…

falling to 0-27% by May 19.● Snowmelt has progressed ~2 - 4 weeks ahead of

normal due to well below average snowpack and rapid melt in late March and April.

● Chart below: an overall look at snowpack/snow water equivalent for the eastern Sierra (which flows out into western NV). Black line 2020-21...below to well below median (green line) whole winter!

4Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

May 1

May 19

Drought Monitor

● Most of the western and southwestern U.S. in significant drought, especially after two consecutive winters of below average precipitation/snowfall

Map Source: drought.gov

5

https://www.drought.gov/

Late Spring - Summer Outlook Main Source: Climate Prediction Center

Nothing Major/Unusual To Note Of Some Interest Moderate - Major InterestColor Key

May 22-31 First Half of June June thru August

Precipitation Most likely below average Below average ? No signals to aid prediction

TemperaturesBelow average early rising to around average by 24th...and then leaning above average late

in periodAbove average favored Above average heavily favored

Snowpack?Much below average: melt season wrapping

up with most snow already gone

Minimal: mostly just highest elevation snowpack

remaining

Insignificant snowpack (little or no)

El Niño/La Niña N/A...longer time scale prediction

Neutral Conditions (tropical Pacific temperatures within 0.5 degrees C of average)

6Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

https://www.cpc.ncep.noaa.gov/

Temperature Outlook● The Climate Prediction Center is heavily favoring

above average temperatures overall for the

June-August period.●

● Prediction based on the increasing temperature trend over the past decade and extremely low soil

moisture (allows stronger heating).

7Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

Source: Climate Prediction Center

https://www.cpc.ncep.noaa.gov/

Precipitation Outlook● Nothing to see here!●

● No large-scale signals to help determine precipitation chances this summer.

8Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

Source: Climate Prediction Center

https://www.cpc.ncep.noaa.gov/

Drought: Summer Large Fire Potential

● Dry winters/springs can make for a lower chance for large fires where brush/grass is the main vegetation. This includes the valleys of northeast CA and western NV.

○ Why? These areas historically depend on continuous grasses between brush for large fires

● However, higher elevations with trees and larger vegetation have higher risk. This includes the Sierra and foothills/mountains of northeast CA and western NV.

Great Basin Rangeland Fire Probability (> 1000 acres)

9 Map Source: https://rangelands.app/great-basin-fire

https://rangelands.app/great-basin-fire

Climate Spotlight

● On May 4th, the National Centers for Environmental Information (NCEI) released their one-in-a-decade update to climate normals

●

● While there are new maps for 15-year normals, the official normals per World Meteorological Organization (WMO) guidelines are based on a 30-year period (1991-2020 currently)

●

● The map (left) shown is just one example of information that can be gleaned from the new data

10Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

New Climate Normals (1991-2020)

https://www.ncei.noaa.gov/https://public.wmo.int/en

Climate Spotlight

● In the example shown, the average high temperature for Mina, NV in summer went from 94 to 96 for the 1980-1990 and 2010-2020 periods, respectively.

●

● This is significant as, since the whole distribution is shifted to the right with the higher average, the likelihood and frequency for more extreme temperatures (to the hotter side) is increased.

●

● The bottom chart shows that the frequency of temperatures below 94 has decreased (blue shading) while the frequency of temperatures above 94 has increased (red shading)

●

● KEY MESSAGE: this doesn’t mean that every summer’s average temperatures will be hotter...just that the “deck is stacked” for more extreme heat overall.

NOTES: Mina (records since 1897) is an excellent site to see how conditions have

changed in areas unaffected by urbanization! Source: Iowa State Plotter

11Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

What’s the Big Deal About a Small Increase in Average Temperatures?

https://mesonet.agron.iastate.edu/plotting/auto/?q=215

Thanks for Reading!We hope you enjoyed (or at least got something

out of!) this edition of the NWS Reno climate

newsletter!

Plan on seeing another edition towards the start

of fall to wrap up summer events and take a look

ahead towards next winter.

* BONUS: Party conversation starter for science nerds! Jupiter’s Great Red Spot has shrunk from around 25,000 miles wide in the 1870’s to “only” 10,000 miles recently!

12Reno National Weather Service

Forecasting for the Sierra and western Nevada since 1905

About 10,000 miles