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This nowCOAST™ time-enabled map service provides maps of the latest NOAA/NWS Outlooks for Severe Thunderstorms (Convective Outlooks) and Critical Fire Weather for both Dry and Non-Dry Thunderstorms. These outlooks are issued by the NOAA/NWS/NCEP Storm Prediction Center (SPC) in Norman, Oklahoma. The colors used on the maps to indicate the locations and risk level of severe thunderstorms and critical fire weather conditions are the same as (or very close to) those used on SPC's outlook maps. To ensure the latest information is displayed, the maps of these outlooks are updated in this nowCOAST™ map service every half hour, but the underlying outlooks produced by SPC are usually issued only at 0100, 0600, 1300, 1630, 1730, and 2000 UTC. However, amendments or more frequent updates will be issued as necessary. For more detailed information about layer update frequency and timing, please reference the nowCOAST™ Dataset Update Schedule.
Geographic areas expected to have thunderstorms or severe thunderstorms are depicted on the outlook maps. For Days 1-3, six categorical levels (general thunderstorms, marginal, slight, enhanced, moderate, and high) are used to indicate the level of risk that severe thunderstorms will occur in the outlined geographic area. The levels of risk and associated display colors and described below.
For days 4-8, the risk categories listed above are replaced by two thresholds:
Even when there are no outlook lines or polygons drawn on nowCOAST™, users are encouraged to read SPC text outlook discussions to be aware of the potential for a severe weather threat to develop. The SPC outlook discussions are available at http://www.spc.ncep.noaa.gov.
Geographic areas expected to have a critical fire weather risk are displayed on nowCOAST™. The severity of the risk is indicated using five categorial levels: elevated, critical, and extreme fire weather conditions based on wind, relative humidity, and pre-existing moisture content of fuels as well the likely areas for isolated dry thunderstorms and scattered dry thunderstorms where dried fuels exist.
For non-dry thunderstorms:
For dry thunderstorms (<0.10" of rain expected):
According to NCEP/SPC, the convective outlooks serve as guidance to the local NWS forecast offices and are also used by emergency managers, private sector meteorologists, media, and others concerned with public safety. SPC uses six separate risk categories (general thunderstorms, slight, marginal, enhanced, moderate, and high) to describe the expected coverage and intensity for the categorical severe weather threat on days 1-3 along with severe weather probabilities for the potential threat. The NWS definition for a severe thunderstorm is any storm that produces one or more of the following: 1) a tornado, 2) damaging winds, or winds measured at 50 knots (~58 MPH) or more, or 3) hail 1 inch in diameter or larger.
The SPC Convective Outlooks are comprised of Day 1, Day 2, Day 3, and Day 4-8 Outlooks. The Day 1 Convective Outlook is issued 5 times daily: at 0600 UTC (initial issuance valid 1200 UTC that day until 1200 UTC the following day), 1300 UTC and 1630 UTC (the "morning updates," valid until 1200 UTC the next day), 2000 UTC (the "afternoon update," valid until 1200 UTC the next day), and 0100 UTC (the "evening update," valid until 1200 UTC the following day).
The Day 2 Convective Outlook is similar to the Day 1 Outlook in terms of a text and graphics. The biggest difference is instead of forecasting separate probabilities for wind, hail and tornadoes, a single combined severe weather probability is issued on the Day 2 probability Outlook. Also, the Day 2 Outlook is issued only twice a day, at 1:00 AM CST/CDT and 1730 UTC. This outlook covers the period from 1200 UTC the following day to 1200 UTC the day after that.
The Day 3 Convective Outlook text and probabilities are similar to the Day 2 Outlooks. However, it is only issued once a day, by 4:00 AM CST/CDT.
The Day 4-8 Convective Outlook depicts the severe weather threat during the forecast period. Two risk categories are depicted on the graphic: areas with 15% or greater chance (drawn in orange) and areas with 30% or greater chance (drawn in red) of well-organized severe thunderstorms.
The Convective Outlooks are updated on nowCOAST™ four times per day using the outlook information from NDFD.
According to NCEP/SPC, the fire weather outlooks serve as guidance to the local NWS forecast offices and are also used by emergency managers, wildfire agencies, private sector meteorologists, and others concerned with public safety. SPC issues two types of Fire Weather Outlook products: Non-Dry Fire Weather and Dry Fire Weather (< 0.10" of rain expected).
For non-dry thunderstorms:
Three categorical risk thresholds are used to highlight non-dry fire weather threats in the day 1-8 fire weather outlooks:
An Elevated, Critical or Extremely Critical fire weather area is issued for a given area if, in the judgment of the forecaster, these conditions will exist for a duration of three hours or more. The outlook type depends on the severity of both the forecast weather and the antecedent conditions relative to the given geographic region. Most outlook delineations are Elevated or Critical fire weather areas, as Extremely Critical areas are "reserved for significant deviations from climatological normals." Extremely Critical areas are rarely issued.
For dry thunderstorms:
Two categorical risk thresholds are used to highlight dry fire weather threats in the day 1-8 fire weather outlooks:
For additional information on criteria, please see http://www.spc.ncep.noaa.gov/misc/Critical_Criteria_for_web.pdf.
The SPC Fire Weather Outlook is comprised of a Day 1 and a Day 2 outlook, in addition to a Day 3-8 outlook. The Day 1 Outlook covers the 24-hour period from 12 UTC on the morning of product issuance to 12 UTC the following morning, with the update covering the 19-hour period from 17 UTC at issuance to 12 UTC the following morning. The Day 2 Outlook covers the following 24-hour period out to 48 hours. The Day 3-8 Outlook covers the period of 48 to 192 hours from 12 UTC on the morning of product issuance.
The Day 1 Fire Weather Outlook is scheduled for issuance at 4:00 AM CST/CDT and is updated at 17 UTC. The Day 2 Fire Weather Outlook is scheduled for issuance at 10Z and is updated at 20 UTC. The Day 3-8 Fire Weather Outlook is scheduled for issuance at 22 UTC.
The Fire Weather Outlooks are updated on nowCOAST™ four times per day using the outlook information from NDFD.
This map service is time-enabled, meaning that each individual layer contains time-varying data and can be utilized by clients capable of making map requests that include a time component.
In addition to ArcGIS Server REST access, time-enabled OGC WMS 1.3.0 access is also provided by this service.
This particular service can be queried with or without the use of a time component. If the time parameter is specified in a request, the data or imagery most relevant to the provided time value, if any, will be returned. If the time parameter is not specified in a request, the latest data or imagery valid for the present system time will be returned to the client. If the time parameter is not specified and no data or imagery is available for the present time, no data will be returned.
This service is configured with time coverage support, meaning that the service will always return the most relevant available data, if any, to the specified time value. For example, if the service contains data valid today at 12:00 and 12:10 UTC, but a map request specifies a time value of today at 12:07 UTC, the data valid at 12:10 UTC will be returned to the user. This behavior allows more flexibility for users, especially when displaying multiple time-enabled layers together despite slight differences in temporal resolution or update frequency.
When interacting with this time-enabled service, only a single instantaneous time value should be specified in each request. If instead a time range is specified in a request (i.e. separate start time and end time values are given), the data returned may be different than what was intended.
Care must be taken to ensure the time value specified in each request falls within the current time coverage of the service. Because this service is frequently updated as new data becomes available, the user must periodically determine the service's time extent. However, due to software limitations, the time extent of the service and map layers as advertised by ArcGIS Server does not always provide the most up-to-date start and end times of available data. Instead, users have three options for determining the latest time extent of the service: