Future Changes in the frequency of winter snowstorms and their impact on snowfall and snow water equivalent

This project will explore the combined effects of future increases in winter temperatures and
changes in the frequency and intensity of winter storms on snowfall and the subsequent
accumulation of winter snowpacks across the continental United States (US) and Alaska. Future
changes in the characteristics of snowfall and snow water equivalent (SWE) will have many
important socioeconomic implications for the US as they will influence water supply, drought
and wildfires, recreation, flooding, and damages corresponding with hazardous
snowstorms. Assessing future changes in snow is complex because it depends on the integrated
response of temperature, moisture, precipitation, and extratropical cyclones (ETCs). In order to
prepare for future changes in snow, US decision makers must understand the risks and
uncertainties associated with changes in winter storm characteristics and their influence on snow.
The proposed work will develop integrated projections of long-term climate changes for relevant
National Climate Assessment (NCA) regions using state-of-the-science CMIP6-endorsed and
related climate model simulations. We will focus on understanding the drivers of future changes
in the frequency, intensity, and spatial scale of winter snowstorms.

With this work we will address four key scientific questions: 1) Do the next generation, state-
of-the-science simulations accurately capture the characteristics of cold-season ETCs over the
US and is storm-relative snowfall well represented within simulated ETCs? 2) Will the
frequency, intensity, duration, and spatial scale of cold-season ETCs change over the United
States in a warming climate? 3) In a warming climate, does storm-relative cold-season snowfall
change in relationship to ETCs? 4) What are the implications of changes in ETC characteristics
and storm-relative snowfall for the occurrence of hazardous winter storms and the accumulation
of SWE?
This work directly supports NOAA’s mission to provide essential, high quality
environmental information vital to our Nation’s safety, prosperity, and resilience, because
changes in extratropical storms and snowfall will impact water supply, flooding, and financial
losses from heavy snowstorms. It will also deepen our understanding of challenges related to
weather and climate extremes, climate impacts on water resources, and overall resilience to
climate factors, all of which are major challenges CPO works to address. It also directly
addresses MAPP’s mission to enhance the Nation’s capability to understand and predict changes
in Earth’s climate system. This proposal is highly relevant to MAPP objectives #3 (improving
methodologies for global to regional scale analysis, predictions, and projections) and #4
(developing integrated assessment and prediction capabilities relevant to decision makers based
on climate analyses, predictions, and projections). Specifically, for this call, we are directly
addressing the combined effects of changes in multiple major climate factors (temperature,
ETCs, and snowfall) and characterizing long-term changes in climate extremes that will affect
the U.S. Storm-level statistics calibrated for NCA regions would improve our capacity to
understand the dynamical drivers of snowfall at the regional scale and are important for
prediction, particularly on the climate timescales outlined here.

Climate Risk Area: Water Resources