Chesapeake Bay Climate Impacts Summary and Outlook
Mid-Atlantic Regional Climate Impacts Summary and Outlook: Winter 2020-2021
- The winter season ranked among the ten wettest on record for sites in Virginia, Maryland and New York.
- From December 16 to 17, the northern parts of the Chesapeake Bay watershed experienced a historic snowstorm that resulted in storm snow totals that reached 36 to 44 inches.
- Snow, ice and freezing rain in parts of Virginia and Maryland on February 11 to 13 resulted in widespread power outages.
- With frequent storms during February, the number of days with measurable snow ranked among the ten greatest for February or on record at several sites including Dulles Airport, Virginia; Washington, D.C.; Baltimore, Maryland; and Williamsport, Pennsylvania.
- However, dry conditions in parts of the region led to below normal streamflow conditions in western Pennsylvania and southern New York.
- Across the Mid-Atlantic region, between 1981–2019, the years 1996 and 2010 saw the highest average annual snowfall for the region, with 1996 seeing an average of 64 inches of total snowfall.
Part 1: Significant Weather Events and Impacts
The winter season ranked among the ten wettest on record for Dulles Airport, Richmond, and Norfolk, Virginia; Salisbury, Maryland; and Binghamton, New York, and among the 20 wettest on record for Lynchburg and Charlottesville, Virginia; and Martinsburg, West Virginia.1
This December ranked among the five wettest on record for Salisbury, Maryland; Binghamton, New York; and Washington Dulles International Airport (Dulles Airport), and Richmond, Virginia.2,3 It ranked among the ten wettest Decembers on record for Martinsburg, West Virginia, and among the 20 wettest on record for Williamsport, Pennsylvania; Washington, D.C.; and Lynchburg and Charlottesville, Virginia.4,5 Conversely to December, this January ranked among the 20 driest on record for Dulles Airport, Virginia.6 Despite most of the rest of the watershed being drier than normal in January, no other notable records were observed.
This February ranked among the ten wettest on record for Dulles Airport, Norfolk, and Charlottesville, Virginia, and among the 20 wettest on record for Harrisburg, Pennsylvania; Washington, D.C.; Baltimore and Salisbury, Maryland; and Richmond, Virginia.7 For many of these sites, this winter was also notably wet.
At the beginning of December, much of central Pennsylvania and parts of central New York were experiencing moderate drought and abnormally dry conditions.8 Above-normal precipitation during December eased drought in these areas but abnormal dryness lingered.9 Conditions continued to improve during January, with only a small area of the region in northern Pennsylvania and central New York remaining abnormally dry.10 These abnormally dry conditions lingered through February.11 This has in part led to below normal streamflow conditions in these areas.12
From December 16–17, the northern parts of the Chesapeake Bay watershed experienced a historic snowstorm that resulted in storm snow totals exceeding 12 inches in many parts of central Pennsylvania and south-central New York, with the greatest totals of 36 to 44 inches in Broome, Tioga, and Delaware counties in New York and in Bradford County, Pennsylvania.13 Due to the storm, two-day snowfall totals ranked as the largest on record for any month in Binghamton, New York, which saw 40 inches of snow, and in Williamsport, Pennsylvania, which picked up 24.7 inches.14,15 These two sites went on to have one of their three snowiest Decembers on record.16 In addition, December 17 became the snowiest December day on record for Binghamton, New York, with 26.4 inches.17 Daily and two-day snowfall totals also ranked among the ten greatest for December at other sites impacted by the storm, including Harrisburg and Scranton, Pennsylvania.18
The December 16–17 snowstorm resulted in numerous vehicle crashes, including a pileup involving 66 vehicles on Interstate 80 in central Pennsylvania.19 Interstate 81 near Binghamton, New York, was shut down for several hours due to disabled vehicles.20 The December 16-17 snowstorm brought a mix of conditions to the southern portion of the region, with areas within West Virginia, Virginia, and Maryland seeing freezing rain accumulations of up to 0.38 inches.21 These icy conditions led to power outages in Virginia, contributed to a plane sliding off a taxiway at Baltimore-Washington International Airport, and hundreds of vehicle accidents.22,23 Due to a northward shift in the band of heaviest snow, the storm outperformed forecasts by as much as 20 inches in some locations such as Tioga and Broome counties in New York.24
Another storm system, this time wet rather than frozen, moved through the region from December 24 to 25. Between one inch and four inches of rain fell, with Binghamton, NY, and Williamsport, PA, having one of their ten wettest December days on record.25,26 In areas of central Pennsylvania and south-central New York that had seen record snowfall just a week prior, the combination of heavy rain and melting snow led to flooded roads and some evacuations.27 Wet antecedent conditions in southern parts of the region also led to flooding and road closures.28 Also as a part of this storm system, wind gusts of up to 67 miles per hour (mph) were recorded in coastal areas of Maryland and Virginia.29 In addition, two Enhanced Fujita Scale 1 (EF-1) tornadoes damaged homes and downed trees in Suffolk, Virginia; these tornadoes were the latest in the calendar year to occur based on available records in southeastern Virginia.30,31
A nor’easter brought snow to the entire watershed from February 1 to 3. Storm snow totals ranged from less than 6 inches in much of Virginia to more than 18 inches in northern Pennsylvania and central New York.32,33 February 1 ranked among the five snowiest February days on record for Scranton, Pennsylvania, and among the ten snowiest February days for Williamsport, Pennsylvania. 34
Parts of Virginia and Maryland saw several inches of snow and as much as 0.50 inches of ice accumulation from freezing rain from February 11 to 13.35 There were widespread power outages, particularly in central Virginia where nearly all customers in some counties lost power.36,37 In some cases, power outages lasted for days.38 There were hundreds of downed trees and power lines, leading to numerous road closures including parts of Interstates 85 and 95.39,40 According to the National Weather Service office in Wakefield, Virginia, “this [storm] resulted in the worst icing impacts in parts of our area in over two decades.”41 In addition, Virginia State Police responded to hundreds of vehicle crashes.42
Another storm from February 18 to 19 brought more snow and ice to the region. Many areas in Maryland and Virginia saw ice accumulation from freezing rain, with the greatest totals of up to 0.40 inches in southern Maryland and central and southern Virginia.43 Much of the rest of the watershed saw snow and sleet totals of 8 inches or less.44,45
With frequent storms during February, the number of days with measurable snow ranked among the ten greatest for February or on record at several sites including Dulles Airport, Virginia; Washington, D.C.; Baltimore, Maryland; and Williamsport, Pennsylvania.46 For example, Baltimore, Maryland, had nine days with measurable snow during February, tying as the second greatest number for any month on record.47 In terms of total snowfall, this February ranked among the ten snowiest on record for Scranton, Pennsylvania, and Binghamton, New York and among the 20 snowiest on record for Harrisburg, Pennsylvania.48 Binghamton, New York, had its snowiest winter season on record, while Williamsport and Scranton, Pennsylvania, had one of their ten snowiest winters on record.49
Part 2: Seasonal Temperature and Precipitation
Figure 1 shows the December 2020 to February 2021 average daily temperature compared with the climate normal—i.e., the average daily temperature from 1981 to 2010.50 The figure shows that almost the entirety of the Mid-Atlantic region experienced above normal temperatures during the winter season, with the central and northern portion of the region experiencing 1 degree or greater than normal temperatures. Only central and southern Virginia had temperatures that were below normal. This December and January, and the entire winter season, ranked among the 20 warmest on record for Dulles Airport, Virginia. 51,52,53
Precipitation departures from normal for December 1, 2020–February 28, 2021 are shown in Figure 2. Departures from normal indicate where this winter season’s average daily precipitation was above or below the climate normal—i.e., the average temperature from 1981 to 2010. Figure 2 shows that the Mid-Atlantic region experienced a range of precipitation conditions, with south-central New York, northeastern Pennsylvania (in part due to the December 16-17 snowstorm), eastern Maryland and portions of southern Virginia experiencing higher than normal snowfall. Western Pennsylvania experienced below normal precipitation.
From December 1, 2020 through February 28, 2021, winter snowfall in southern New York, northeastern and western Pennsylvania, and southwestern Virginia experienced significantly higher than normal precipitation (above 200 percent of normal). Figure 3 shows that southern Maryland and southeastern Virginia saw 50%–75% of normal snowfall for the winter season. Washington, D.C., and parts of Virginia and Maryland, experienced below normal snowfall despite the winter storms described in Part 1.
More information on how recent precipitation and temperature compares to historical trends for the East Coast, including the Mid-Atlantic region, can be found on the Northeast Regional Climate Center webpage.54
Part 3: Spring 2021 Outlook
Temperature and Precipitation
As of February 18, 2021, the NOAA Climate Prediction Center forecasts a 40–50 percent chance of above-normal temperatures for spring for the majority of the Chesapeake Bay watershed and Mid-Atlantic region for April, May and June 2021.55 The precipitation forecast shows an equal chance of precipitation above, at, or below normal for March through May 2021 for the majority of the region, and a 40–50 percent chance of wetter than normal conditions in in western Pennsylvania. 56
The U.S. Seasonal Drought Outlook identifies how drought might change across the United States and categorizes areas by whether drought could develop or become more or less intense. As of February 28, 2021, the outlook indicates no tendency toward drought for the Mid-Atlantic region.57
Climate Circulation Patterns
NOAA’s Climate Prediction Center, which monitors the likelihood of occurrence of El Niño and La Niña climate phenomena, has a La Niña Advisory active as of February 11, 2021 with a 60% chance of transition to El Niño-Southern Oscillation (ENSO) neutral conditions between April to June 2021.58 ENSO-neutral conditions occur when tropical Pacific sea surface temperatures are close to normal and neither El Niño or La Niña conditions are present.59
Part 4: Historic Changes in Annual Snowfall
This winter season saw frequent storms, particularly during February, breaking snowfall records in many sites across the region. Part 1 above describes the number and type of snowfall records hit across the region. While the prior two winter seasons—December to February 2018–201960 and 2019–202061— experienced below normal snowfall, this season was not alone in being above normal across the last decade, particularly in the northern parts of the Mid-Atlantic region. Scientists have noted the “emergence of a feast or famine pattern, where winters either over-deliver snow or underperform relative to the seasonal average”.62,63 To allow localities, states and users to understand their local changes in snowfall over the last several decades, this section includes an interactive data tool of station-based measurements of total annual snowfall from 1981–2019.
The Mid-Atlantic Regional Integrated Sciences and Assessments (MARISA) Seasonal Climate Impacts Summary and Outlook is a quarterly series produced by the MARISA program, a collaboration funded by NOAA through the RAND Corporation and researchers at Pennsylvania State University, Johns Hopkins University, Cornell University, and the Virginia Institute of Marine Science. This series draws information from regional climate centers, news and weather information, and regional-specific climate data sets for the benefit of policymakers, practitioners, residents, and community leaders in the Mid-Atlantic region. Projections of weather and climate variability and change in the Mid-Atlantic region come from the best available scientific information. For any questions or comments, please contact Krista Romita Grocholski at Krista_Romita_Grocholski@rand.org.
This edition of the MARISA Seasonal Climate Impacts Summary and Outlook was authored by Michelle E. Miro (RAND Corporation), Krista Romita Grocholski (RAND Corporation), Jessica Spaccio (Cornell University), Samantha Borisoff (Cornell University), Arthur T. DeGaetano (Cornell University), and Jordan R. Fischbach (RAND Corporation).
Climate normals, as defined by the National Oceanic and Atmospheric Administration (NOAA), are "three-decade averages of climatological variables including temperature and precipitation."" The latest climate normal released by NOAA is the 1981–2010 average. See: https://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/climate-normals#:~:text=Climate%20Normals%20are%20three%2Ddecade,variables%20including%20temperature%20and%20precipitation Return to text ⤴
For more information on how NOAA defines at, above or below normal and determines percent chances, see: https://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal_info.php Return to text ⤴
The Mid-Atlantic has experienced severe to extreme droughts in the past, most notably in the mid-1980s, the late 1990s, and the 2000s. https://www.cpc.ncep.noaa.gov/products/expert_assessment/season_drought.png;https://onlinelibrary.wiley.com/doi/pdf/10.1111/1752-1688.12600 Return to text ⤴