APPENDIX C
Weather Event Timelines

RED RIVER OF THE NORTH FLOOD, GRAND FORKS, 1997

February 13. First Snowmelt Outlook issued using data from the airborne snow survey. The potential for spring flooding was characterized as “Severe,” defined as levels at or exceeding the previous flood of record.

February 27. Snowmelt Outlook updated. Outlook called for 47.5 feet with no additional precipitation and 49.0 feet with normal additional precipitation. The 49.0-foot forecast exceeded the existing flood of record that occurred on April 26, 1979 (48.8 feet). Record numerical peak forecasts allowed the USACE (U.S. Army Corps of Engineers) to initiate advanced flood protection measures earlier than would otherwise have been possible.

March 18. Press conference was held in Washington, D.C., presenting the Spring Hydrologic Outlook. The situation for the Red River of the North was described as severe, resulting in “more water than you’ve ever seen before.”

March 30. Flood Warning issued for all NWS river forecast points in the Red River of the North Basin.

April 3. Current stage is at 18.1 feet. Forecast to continue to rise. Outlook with normal precipitation is for 49.0 feet. (Note that river model indicates forecast peak may be well below the outlook peak of 49.0 feet, but forecasters were reluctant to lower the guidance.)



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A Workshop Summary Communicating Uncertainties in Weather and Climate Information APPENDIX C Weather Event Timelines RED RIVER OF THE NORTH FLOOD, GRAND FORKS, 1997 February 13. First Snowmelt Outlook issued using data from the airborne snow survey. The potential for spring flooding was characterized as “Severe,” defined as levels at or exceeding the previous flood of record. February 27. Snowmelt Outlook updated. Outlook called for 47.5 feet with no additional precipitation and 49.0 feet with normal additional precipitation. The 49.0-foot forecast exceeded the existing flood of record that occurred on April 26, 1979 (48.8 feet). Record numerical peak forecasts allowed the USACE (U.S. Army Corps of Engineers) to initiate advanced flood protection measures earlier than would otherwise have been possible. March 18. Press conference was held in Washington, D.C., presenting the Spring Hydrologic Outlook. The situation for the Red River of the North was described as severe, resulting in “more water than you’ve ever seen before.” March 30. Flood Warning issued for all NWS river forecast points in the Red River of the North Basin. April 3. Current stage is at 18.1 feet. Forecast to continue to rise. Outlook with normal precipitation is for 49.0 feet. (Note that river model indicates forecast peak may be well below the outlook peak of 49.0 feet, but forecasters were reluctant to lower the guidance.)

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A Workshop Summary Communicating Uncertainties in Weather and Climate Information April 5–6. Severe blizzard conditions occur throughout the Red River of the North Basin. One to three inches of precipitation falls. Cold, windy, and snowy conditions hampered data collection and flood-fight activities. April 12. Current stage is 42.3 feet. Outlook crest is for 49.0 feet beginning fourth week of April. April 13. Current stage is 42.8 feet. Outlook crest is 49.0 feet. This crest will be very broad, occurring as early as April 19 and extending as late as April 21–22. April 14. Current stage is 43.7 feet. Crest upped to 50.0 feet for April 19–22. April 16. Current stage is 47.5 feet. Rise to 49.0 to 49.5 feet by April 17, then slow rise to 50.0 feet April 22–23. USACE field construction personnel alerted to raise emergency flood protection by raising top of the levee to a stage of 54.0 feet. April 17. Current stage is 50.9 feet. Crest 51.5 to 52.0 feet April 18; April 19. Ice effects in the area appear to be causing fluctuations in the rate of rise. April 18, 9:00 A.M. Current stage is 52.0 feet. Crest 53.0 feet April 18–19. Numerous levee failures occurred on both sides of the river. USACE reported that all levee breeches and over-toppings appear to have occurred between river stages of 51.6 and 53.0 feet. April 18, 7:00 P.M. Stage is 52.6 feet. Crest forecasted to be near 54.0 feet late on April 19. April 19, NOON. Stage is 53.1 feet. Rise to near 54.0 feet over the next few days. April 21. Estimated stage is 54.0 feet. Near crest; remain near this level for several days. EAST COAST WINTER STORM, MARCH 2001 February 26, Monday. NCEP models began to show a significant storm for March 4. Local and national media and public and private forecasters began to discuss the potential for a significant storm on March 3–4. February 28, Wednesday. A Philadelphia weathercaster predicted a possible 16 to 20 inches of snow beginning March 5.

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A Workshop Summary Communicating Uncertainties in Weather and Climate Information March 1, Thursday. Many East Coast weathercasters now making deterministic forecasts for significant snowfall amounts. March 2, Friday. Pressure builds from the emergency management community to identify how much snow to expect. 11:00 A.M. NWS/NCEP conference call discussing the forecast. 4:00 P.M. NWS press release indicating the potential for a significant storm with blizzard conditions. 6:00 P.M. National news media carry the story of a paralyzing East Coast storm. March 3, Saturday. NOAA press conference highlights the historic nature of upcoming storm. Winter storm watches issued for all of the mid-Atlantic region. Winter storm warnings issued for Philadelphia north. March 4, Sunday. Storm became well organized with most of the mid-Atlantic region receiving rain only. March 5, Monday. Heavy snows fell in the interior and most of New England. OKLAHOMA-KANSAS TORNADO OUTBREAK, MAY 3, 1999 (All times in Central Daylight Time) May 2   12:04 P.M. Slight risk of severe storms issued for all of Oklahoma for May 3. May 3   2:55 A.M. Slight risk of severe storms late this afternoon and tonight issued for most of Oklahoma. 6:30 A.M. Slight risk of severe storms issued for this afternoon and tonight; isolated tornadoes possible. 11:15 A.M. Part of the Slight-risk area upgraded to Moderate risk. 3:49 P.M. Western/central Oklahoma portion of the Moderate risk area upgraded to High risk.

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A Workshop Summary Communicating Uncertainties in Weather and Climate Information 4:47 P.M. First tornado warning of the event issued for Comanche and Caddo counties. 4:51 P.M. Spotters in Comanche County report first tornado of this event (near Interstate 44). 5:41 P.M. Oklahoma City metropolitan area identified as having a potential for tornadoes to move into the area that evening. 6:57 P.M. NWS issued the following statement: “…Tornado Emergency in South Oklahoma City Metro Area…" Predicts large damaging tornado will enter southwest metro area between 7:15 and 7:30 P.M. “Persons in Moore and south Oklahoma City should take immediate tornado precautions!” 7:11 P.M. First tornado in Cleveland County (immediately south of Oklahoma City). Tornado crossed South Canadian River near S.W. 149th Street. 7:17 P.M. First tornado warning was issued for Oklahoma County valid through 8:00 P.M. 7:25 P.M. Tornado moved through Moore (south of Oklahoma City). 7:30 P.M. First tornado in Oklahoma County (entered southern part of county east of Interstate 35). 7:31 P.M. NWS issued the following statement: “…Large Damaging Tornado Moving Through Oklahoma City Metro…” Also states, “Persons in southeast Oklahoma City and Midwest City are in danger!” 7:34 P.M. Tornado near Tinker Air Force Base (Midwest City).