The National Weather Service encodes every watch, warning, advisory, and statement with a short product code, and weather alert feeds (including ours) are full of them. This page decodes the codes that are not tornado- or severe-specific, plus the alerting infrastructure like VTEC, EAS, and WEA that delivers them to your phone. Severe and tornado products have their own page: Tornado & Severe Thunderstorm Alerts.
VTEC (Valid Time Event Code) is a standardized string embedded in every NWS warning/watch/advisory text product. It encodes the product type, issuing office, event number, and start/end time in machine-readable form. It's what allows apps and APIs to parse NWS products automatically without reading the full text.
The Emergency Alert System (EAS) is the national public warning system that allows authorized agencies — including the NWS — to interrupt TV and radio broadcasts with emergency alerts. NOAA Weather Radio (NWR) activates EAS for weather warnings using SAME tones. The three-tone chirp + digital data burst you hear on the radio is EAS in action.
A Wireless Emergency Alert (WEA) is the loud buzzing alert pushed directly to cell phones within a warning polygon — no app needed. For severe weather:
WEAs use the polygon boundary, not the county, so you only get the alert if your phone is physically inside the warned area.
An Area Forecast Discussion (AFD) is the local NWS office's plain-English explanation of their forecast reasoning. Written by forecasters several times daily — the best way to understand what your local WFO is actually thinking.
A Hazardous Weather Outlook (HWO) is a daily product issued by local WFOs highlighting any weather hazards expected over the next 7 days. Day 1 is most detailed; days 2–7 are broader. The HWO is where forecasters flag developing threats before watches or warnings become warranted — your earliest warning for a brewing event.
A Special Weather Statement (SPS) is an NWS product covering sub-severe storms or notable weather that doesn't meet warning criteria — strong (but not severe) thunderstorms, dense fog, snow squalls in some offices, etc.
A Special Weather Statement (SPS) is used by WFOs to communicate weather hazards that don't meet warning or advisory criteria, or to provide supplemental information. Examples: locally gusty winds, elevated fire danger, brief tornado possible in an ongoing storm, or a nuisance snowfall. SPS products are flexible by design.
A Local Storm Report (LSR) is an NWS product documenting severe weather events as they occur — tornadoes spotted, hail measured, wind damage, flooding. LSRs are the raw record of what actually happened during an event.
A Public Information Statement (PNS) is a general-purpose NWS product for significant non-warning information — tornado damage survey results, official EF ratings, record temperatures, post-storm summaries, and public safety messages. The PNS is how the NWS officially releases EF-scale ratings after conducting tornado surveys.
A Watch Outline Update (WOU) is the SPC product issued when a tornado or severe thunderstorm watch is declared. It contains the official polygon coordinates and county list for the watch. Broadcasters, emergency managers, and apps use the WOU to display the watch boundary accurately.
A Watch County Notification (WCN) is issued by local NWS WFOs when an SPC watch covers their County Warning Area. It provides county-level details and local messaging for the watch, complementing the SPC's WOU.
A Special Marine Warning (SMW) is the marine equivalent of a Severe Thunderstorm Warning, issued for coastal/lake waters when storms are producing 34+ knot winds, hail, or waterspouts.
TSA is the EAS/SAME code for a Tsunami Watch. It means a tsunami is possible, but its arrival, size, or exact threat is still being evaluated. Monitor official tsunami products and be ready to move inland or uphill.
A Rip Current Warning is issued when dangerous rip currents are occurring or imminent at beaches. Rip currents are the leading cause of aquatic rescues in the U.S. (100+ fatalities/year). If caught in one: don't fight it — swim parallel to shore until out of the current, then swim back in at an angle.
A Dense Fog Advisory (DFO) is issued when fog will reduce visibility to ¼ mile or less over a widespread area. Use low-beam headlights, reduce speed, and increase following distance dramatically. Common in river valleys, after overnight rain, and in coastal areas. Radiation fog often lifts by mid-morning; advection fog can persist all day.
A Frost Advisory is issued when temperatures are expected to fall to 33–36°F with clear skies and light winds, producing frost on surfaces. It's advisory-level (less serious than a Freeze Warning) but can still damage tender vegetation. Most commonly issued in spring and fall during the transition seasons.
A Hard Freeze Warning is issued when temperatures are expected to drop to 28°F or below for at least 2 hours. At 28°F, most unprotected vegetation (crops, ornamentals) suffers severe to fatal damage. It's the most serious frost/freeze product in the NWS suite — one level above a Freeze Warning (32°F).
An Air Quality Alert is issued when the Air Quality Index (AQI) is forecast to exceed 100 (Unhealthy for Sensitive Groups) or 150 (Unhealthy for all). Causes include wildfire smoke, ground-level ozone (hot stagnant days), and particulate matter from industrial sources. Sensitive groups (elderly, children, asthma) should limit outdoor exposure.