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I I I I I I I I I I 2. Flash Floods - overbank flows due primarily to heavy rain in a short penod of time caused primarily by heavy, slow moving thunderstorms. The floods normally occur within 3 hours or so of the beginning of heavy rain. Thus little time is available for preparing and disseminating warnings. since the reaction time for these events is short, and past and future rainfall is such a large input to the forecast, the closest National Weather Service Office (in this case Pueblo) is tasked with preparing flash flood warnings. Watch.. are used to inform the public and cooperating agencies that current and developing hydrological and meteorological conditions are such that the area in the watch is subject to possible flash flooding. A WA'.fCII advi_. per.ona in the .atch anla t:o check pzep..-... pI...... keep ~o~. and. !:Ie _ady t:o ~. acUcm 1~ a na.h ~looci .azn1nq 1. 1.._ or ~lood1Dq 1. ab..zved. Wazn1nqa are used to inform the public and cooperating agencies that flash flooding is imminent or in progress for specific communities, and/or streams. Per.on. in the ~ING anla ani adv1.eci t:o ~. the ........azy act1cm. ~at.ly. The NWS issues flood warnings and watches when flooding is expected or when flooding has been observed. NWS will update the watches or warnings as conditions warrant. Flash flood watches or warnings are transmitted on the National Oceanic and Atmospheric Administration (NOAA) weather radio. NOAA weather wire, NAWAS (Civil Defense Radio) and radio and TV stations. They are described in the following paragraphs: (al A FLOOD WATCH will be issued by the Denver Office for the La JUnta area if the Arkansas River will be near bankfull and conditions look good for flooding 6 hours or more in the future. This watch will be followed by statements every few hours on how the watch was evolving, or canceling it if necessary. I I I I I I The Denver office monitors the Arkansas River gage at La Junta on a continual basis and would normally issue a flood watch at La Junta if the river level was anticipated to reach around 8 feet (31,000 cfs). This is right around the 7.7 feet (as shown in Figure 4) for Levell at La Junta so action would be required. See Page 17 for Levell Response Actions. (b) A FLOOD 'IllUUfING (flooding which is expected to cause loss of life or significant property damage is in progress or imminent) will also be prepared by the Denver office and transmitted the same way, with estimates and times of future river levels. A flood warning for the La Junta area will normally be issued for the Arkansas River if the stage at La Junta is expected to rise to 10 feet (53,500 cfs) or more. This is within the Level 2 at La Junta as indicated in this plan, but less than Level 3. In this case. estimates of future river levels and times at La Junta and downstream will normally be provided. Hopefully these would provide information on the possibility and timing of higher Level 2 & 3 conditions. (c) A Il'LASII !'LOOD ~ING is normally issued by the Pueblo office for the La Junta area if the Arkansas (or even the tributaries of the Arkansas) are expected to reach levels where significant damage will occur. These forecasts will I I I 7 i! Flood Watch - "keep informed" l!! Flood Warning - "take action immediately"