Chesapeake Bay Climate Impacts Summary and Outlook
Chesapeake Bay Watershed Climate Impacts Summary and Outlook: Winter 2018-2019
The MARISA Seasonal Climate Impacts Summary and Outlook is a quarterly series produced by the Mid-Atlantic Regional Integrated Sciences and Assessments (MARISA) program, a collaboration funded by NOAA through RAND and researchers at Pennsylvania State University, Johns Hopkins University, and Cornell University. This series draws information from regional climate centers, news and weather information, and regional-specific climate datasets for the benefit of policymakers, practitioners, residents, and community leaders in the Chesapeake Bay Watershed. Projections of weather and climate variability and change in the Chesapeake Bay Watershed come from the best available scientific information. Part 1 details significant weather events that occurred in the Winter 2018-2019 season. Part 2 characterizes seasonal temperature and precipitation compared to historical averages. Part 3 describes seasonal weather forecasts and pertinent information for the upcoming Spring 2019 season. Part 4 includes an analysis of multi-decadal changes in seasonal precipitation, accompanied by interactive maps of climate projections.
Part 1: Significant Weather Events
From December 2018 through the end of February 2019, extreme weather events caused disruptions, delays, and damages within the Chesapeake Bay Watershed. A December snowstorm dropped up to 15.2 inches of snow on western and central Virginia from December 9th-10th. Richmond, VA, had its greatest daily snowfall for December 9th on record, with 11.5 inches over the storm duration recorded at the Richmond airport.1 The National Weather Service reported that for all stations monitored by the Blacksburg, Virginia weather forecast office, this was the earliest large December snowfall on record2. The storm caused travel delays and power outages.
From January 12 to 14, a winter storm brought up to 13 inches of snow to the region, with the greatest amounts falling in Maryland, northern Virginia, and the Eastern Panhandle of West Virginia.3 Freezing rain and sleet also fell, particularly in parts of central and western Virginia, and the storm caused more than 250 flight cancellations on January 13 at Washington D.C.’s three main airports.4
A week later, from January 19 to 20, another storm dropped up to a foot of snow on the region. Central Pennsylvania saw snow accumulations over the duration of the storm of 12 inches in Wellsboro, Pennsylvania and nine inches in Stormstown, Pennsylvania.5 A flash freeze that accompanied the storm brought dangerous temperatures and unsafe roadway conditions in Pennsylvania and Maryland.6
In late January 2019, the polar vortex (see Figure 1) pushed into the northern Midwest, resulting in cold, windy weather across the Mid-Atlantic region.7 On January 31, Washington, D.C.’s Dulles airport recorded a temperature of 5°F, with wind chill values between -3 to -5°F, prompting the closure or delay of numerous schools in metropolitan D.C.8,9 In Central Pennsylvania, in response to below 0°F temperatures and even lower wind chill values, many schools across the region, including Pennsylvania State University, closed on January 31, 2019.10,11
On February 20, a winter storm brought a mix of snow, sleet, freezing rain, and rain to the region. The greatest storm total snow accumulations were up to 10 inches in south central Pennsylvania12 and western Maryland.13 Impacts from the storm included dangerous travel conditions, thousands of power outages, and schools and government offices being closed.14
On February 24 and 25, wind gusts of up to 81 mph, recorded in Nelson County, Virginia, downed numerous trees and wires, leading to power outages and some closed roads across the Chesapeake Bay region.15
Part 2: Seasonal Temperature and Precipitation
An analysis of Winter 2018-2019 average temperature, compared to the normal average from 1981 to 2010, indicates above-normal departures from normal temperature for most of the Chesapeake Bay watershed, including increases above 3°F in winter temperatures in portions of West Virginia and along the Chesapeake Bay. Baltimore, Maryland, for example, had the warmest New Year’s Day since 2005 with temperatures hitting 61°F,16 compared to a normal daily temperature of 42°F.17
Between December 1, 2018 through February 28, 2019, precipitation departures from normal historical precipitation for the period 1981 to 2010 show that most of the region experienced increases in precipitation compared to historical normal precipitation. Western Virginia, southern and central Pennsylvania and western Maryland experienced the highest rates of precipitation departures—between 150 and 200 percent of normal. Areas vulnerable to flooding in the southern reaches of the Chesapeake Bay also saw precipitation nearly double, compared to historical averages during this period.
An analysis of how total winter snowfall between December 1, 2018 and February 28, 2019 compared to historical averages shows that the region experienced two different trends in snowfall. The majority of the northern two-thirds of the Chesapeake Bay watershed (northern Maryland and Pennsylvania) saw snowfall at 50-75 percent of normal, a decrease in total winter snowfall. Much of Virginia, however, experienced increases in snowfall compared to normal, with snowfall at 150-200 percent of normal or higher. The decrease in snowfall in the northern Chesapeake Bay watershed, combined with increases in total winter precipitation (see Figure 3), suggests that more precipitation is falling as rain, rather than snow, in northern Maryland and Central Pennsylvania.
Part 3: Spring 2019 Outlook
Temperature and Precipitation
As of February 5, 2019, NOAA's Climate Prediction Center forecasts a 33-40 percent chance of temperatures above normal. The precipitation forecast shows a 33-40 percent chance of precipitation above normal in the Southern half of the watershed for March–May 2019 in the Mid-Atlantic region.18
The U.S. Seasonal Drought Outlook identifies areas of drought across the United States and categorizes them by level of intensity. As of February 21, 2019, the outlook indicates no drought for the Chesapeake Bay Watershed.19
El Niño Watch
NOAA's Climate Prediction Center, which monitors the likelihood of occurrence of El Niño and La Niña climate phenomena, has issued a El Niño Advisory, meaning that weak El Niño conditions have formed and are likely to effect the Northern Hemisphere through Spring 2019.20 El Niño is a climate phenomenon characterized by a warming of the sea surface temperatures in the central and eastern tropical Pacific Ocean that leads to changes in weather across the globe. In the Mid-Atlantic, large storm events are more frequent during El Niño due to warmer ocean temperatures.21 While this generally results in wetter weather, weather impacts to the Chesapeake Bay Watershed can be difficult to predict.
Part 4: Seasonal Precipitation Trends and Projections
The following figures provide detail on how the total precipitation occurring each season has changed over time (Figure 5) and could change into the future (Figure 6). In some areas, such as the northern region of the Chesapeake Bay Watershed, total winter precipitation has increased between 2006-2017 compared to historical averages, while fall total precipitation has decreased. Further, our analysis of future projections of seasonal total precipitation suggests that increases in winter precipitation, compared to historical averages, could continue. Precipitation shifts in magnitude, intensity and timing will likely necessitate changes in management of stormwater systems, reservoirs, agriculture, and urban planning.
This summary is the start of a series of climate summaries produced by MARISA for stakeholders, decisionmakers and water managers in the Chesapeake Bay watershed. For any questions or comments, please contact Krista Romita Grocholski at Krista_Romita_Grocholski@rand.org.