NWS Products and Criteria

APPENDIX A - NATIONAL WEATHER SERVICE PRODUCTS & CRITERIA 
(What to listen and watch for)

WARNINGS

The hazard (tornado, severe thunderstorm, flash flood, etc.) is imminent. The probability of occurrence is extremely high. Warnings are issued based on eyewitness reports or clear signatures from remote sensing devices such as radar and satellite. Lead-time for thunderstorm type events is generally 30 minutes or less. Lead-time for river floods, and winter storms can be 6 to 18 hours or longer.

When severe weather approaches your area, our forecasts become so short term that we are actually "warning" you that a potentially life threatening event is about to happen and to put your protection plan into action. When we issue a warning it means a certain weather phenomena is occurring or imminent.

WATCHES

When meteorologists have determined that conditions appear right for the development of the hazard and the probability of occurrence is usually greater than 60% a weather watch is issued. Watches generally cover larger areas than warnings. In the case of thunderstorms, less than 30% of the watch area may experience the hazard. However, with larger storms such as winter storms, the entire watch area may be affected. Severe thunderstorm and tornado watches are usually issued 1 to 2 hours before the event begins. The Storm Prediction Center in Norman, OK currently issues all Severe Thunderstorm and Tornado Watches. With flash floods, the length of time can be 3 to 12 hours. For river flood and winter storm watches, lead-times are usually 12 to 36 hours or longer.

The NWS issues watches up to 36 hours in advance of potentially hazardous weather, giving you plenty of time to plan ahead and protect yourself and your family. A Watch means conditions are favorable for certain weather phenomena to occur but it is not expected immediately. Go about your normal activities, but be aware of rapidly changing weather conditions and notify school emergency contact points for potential activation later on. A list of various watches appears on the next page.

ADVISORIES

An advisory is issued for weather that is expected to be a disruption to the normal routine and an inconvenience, but it is not expected to be life-threatening. Advisories are issued for 3 to 5 inches of snow, dense fog, minor street flooding, etc. The time frame is similar to that of a warning. A list of various advisories appear below.

STATEMENTS

Statements are issued to update current weather situations or highlight significant changes to come. Statements are also used to explain why watches, advisories, or warnings have been issued. Four special types of statements include:

• Special Weather Statements - If strong or severe thunderstorms are expected, a statement is issued discussing this outlook (or potential). The Storm Prediction Center issues special statements when there is the potential for a severe thunderstorm or tornado outbreak.
   
• Severe Weather Statements - These are follow-ups to severe weather Warnings. They highlight which warnings currently are in effect and detail any reports of severe weather that have been received.

• Short-term Forecasts ("NOWCASTS") - These are short, concise statements discussing the movement of precipitation during the next few hours or even a shorter time frame (in the case of thunderstorms). They also highlight any other short-term changes, such as increasing cloudiness, drops in temperature, wind shifts, etc. During active weather, these could be issued hourly or even more frequently.

• Public Information Statements - These statements provide information of special interest such as a summary of recent records set, weather safety information, special activities (weather related) that may be occurring, etc.

FORECASTS

General weather and hydrologic information issued daily (times given are listed in Pacific time).

• 1 to 2 day forecasts are broken into 12 hour increments while the 3 to 7 day extended forecasts list cover a 24 hour period. Both are issued twice a day at roughly 4 AM, and 4 PM, with updates as needed. These zone forecasts are broken down into "zones" across Idaho based on related to climatology and topography. Figure 1 on the next page shows the different zones for Idaho. Special weather events are highlighted with headlines at the top of the forecasts such as ...
  
  "Severe Thunderstorm Watch in effect until 8 PM this evening"
  "Wind Advisory in effect until 4 PM this afternoon"
  "Flash Flood Watch is in effect until 8 AM Wednesday."

• State Forecast Products are issued routinely at 400 AM and 400 PM. This product shows a more general forecast trend for three specific regions of Idaho including Northern Idaho, Southwest Idaho and Southeast Idaho.

• Special hydrologic forecasts are issued during flood season usually around noontime.

NOTE: All of the above (Watches, Warnings, Statements, Advisories, Forecasts) are broadcast continuously on the NOAA Weather Radio.

However, the NWS Forecast Offices also issue other forecasts, such as Aviation Terminal Forecasts and Fire Weather Forecasts (for prescribed burning operations or wildfires). These products are not announced on the Weather Radio.

Spokane Weather Office Forecast Responsibility in Washington

Spokane Weather Office Forecast Responsibility in Idaho