1. Significant and Potentially Dangerous Coastal Storm Tuesday Night into Wednesday March 25 th – 26 th, 2014 National Weather Service Monday Afternoon March 24 Update National Weather Service Boston, MA

2. Overview National Weather Service Boston, MA Powerful ocean storm will impact southeast New England Tuesday Night into Wednesday. The height of the storm is expected to be late Tuesday night through early Wednesday morning. Moderate to high confidence of heavy snow & strong to damaging northerly winds across Cape Cod & the Islands, lower confidence north and west of the Canal. This combination could create blizzard conditions for the Cape and Islands. The Wednesday morning commute may be impacted as there could be some snow accumulation along the Boston to Providence corridor. A shift in the projected storm track can change the outcomes significantly. This will be a dangerous storm for mariners. Storm force wind gusts near 50 knots and seas 20 to 25 feet are possible for the waters just east of Cape Cod and Nantucket. There is also the potential for coastal flooding with the high tide on Wednesday morning, especially for the north and east facing shorelines of Cape Cod and Nantucket.

3. Uncertainty in the Track

4. Watches Blizzard Watch Cape and Islands Winter Storm Watch rest of SE MA and SE RI Coastal Flood Watch Cape and Nantucket Storm Watch for waters south and eastern waters with a Storm Warning for the southeastern outer waters

5. Storm Highlights WhatLatest Thinking Moderate to Heavy Snow Timing: Tuesday Night into Wednesday Impacts: Heavy falling snow as well as blowing snow reducing visibility. Confidence of Area of Impacts: -Moderate to High Confidence … for Cape Cod and islands -Low to Moderate Confidence … Rest of southeast Massachusetts and southeast Rhode Island. Overall Forecast Confidence: Moderate

6. Preliminary Snowfall Estimates Gradient will tighten up

7. Snowfall Probabilities Probability of 2 Inches or More

8. Probability of 4 Inches or More Snowfall Probabilities

9. Probability of 6 Inches or More

10. Snowfall Probabilities Probability of 8 Inches or More

11. Storm Highlights WhatLatest Thinking Strong to Damaging Winds Timing: Late Tuesday Night through Wednesday Night Impacts: Northerly winds potentially gusting to 60 mph may result in some downed trees and power lines with resultant scattered power outages. Winds may aid in blizzard conditions across Cape Cod and the islands. Confidence: -High Confidence … Winds approaching high wind criteria (gusts to 60 mph) across the outer Cape and Nantucket. -Moderate Confidence … Winds approaching high wind criteria (gusts to 60 mph) across the upper Cape and Martha’s Vineyard. -MARINERS: High Confidence … Storm Warnings/Watches (wins greater than 48kts) for a good portion of the waters w/ gale watches (winds greater than 34kts)e verywhere else -AVIATION: High Confidence in LLWS of 40-60kts at 2000ft Overall Forecast Confidence: Moderate

12. Potential Wind Gusts (mph)

13. Potential Wind Gusts (knots)

14. Storm Highlights WhatLatest Thinking Potential Coastal Impacts Timing: Wednesday Morning high tide 8 to 9 am Impacts: Potential for minor to pockets of moderate coastal flooding and significant erosion along north and east facing shorelines of Nantucket and Cape Cod. Minor coastal flooding may occur along the Plymouth County coastline and portions of the Martha’s Vineyard coast. Confidence: -Moderate to High Confidence in overall Coastal Flooding -MARINERS: Moderate Confidence … Wave heights of 20 to 25 feet east of Cape Cod and east of Nantucket. Overall Forecast Confidence: Moderate

15. Coastal Flooding Wed AM

16. Closing Remarks National Weather Service Boston, MA Potential blizzard conditions for Cape and Islands. No changes to headline this afternoon. Less confidence on impacts elsewhere in southeast New England but at least some accumulation likely to Boston to Providence corridor. Minor to pockets of moderate coastal flooding potential with beach erosion along portions of Cape Cod and Nantucket shorelines. Dangerous storm for mariners with Storm Force wind gusts and seas 20 to 25 feet just east of Cape Cod and Nantucket.

17. Questions? Latest information: – www.weather.gov/boston www.weather.gov/boston Area Forecast Discussion Hazardous Weather Outlook Call us: 508-823-2228 NWSChat Online – https://nwschat.weather.gov https://nwschat.weather.gov E-mail: – box.operations@noaa.gov National Weather Service Boston, MA