The following are National Weather Service Burlington criteria for issuing Watches / Warnings / Advisories:
- Watches: 50% confidence of meeting Warning criteria (generally within 36-48+ hours).
- Advisories and Warnings: 80% confidence in the event occurrence (generally within 24-36 hours).
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Thunderstorms with wind gusts ≥ 58 mph (50 kts) and/or hail ≥ 1-inch in diameter.
Likelihood of a tornado within the given area based on radar or actual sighting; usually accompanied by conditions indicated above for "Severe Thunderstorm Warning".
When any of the following is expected within the next 12 to 36 hours
More than one predominant hazard
- Winter weather event having more than one predominant hazard {ie. heavy snow and blowing snow (below blizzard conditions), snow and ice, snow and sleet, sleet and ice, or snow, sleet and ice} meeting or exceeding warning criteria for at least one of the precipitation elements.
Snow and/or Sleet
- 7 inches averaged over a forecast zone
- Depending on impacts, a combination of precipitation elements may be considered in issuing Winter Storm Warnings.
Sustained winds or frequent gusts ≥ 35 mph AND considerable falling and/or blowing snow frequently reducing visibility < ¼ for ≥ 3 hours.
Blizzard conditions need to be the predominant condition over a 3 hour period.
½ inch or greater accretion of freezing rain in any forecast zone.
When any of the following is expected within the next 12 to 24 hours
More than one predominant hazard
Winter weather event having more than one predominant hazard (i.e., snow and ice, snow and sleet, or snow, ice & sleet) meeting or exceeding advisory criteria for at least one of the precipitation elements, but remaining below warning criteria.
Snow and/or Sleet
- 4 inches averaged over a forecast zon
Snow and Blowing Snow
- Sustained or frequent gusts of 25 to 34 mph accompanied by falling and blowing snow occasionally reducing visibility to ≤ ¼ mi for < 3 hours
Blowing Snow
- Widespread or localized blowing snow reducing visibility to ≤ ¼ mi with winds < 35 mph
Freezing Rain
- Any accretion of freezing rain or freezing drizzle on road surfaces.
Black Ice
- A Special Weather Statement will usually be issued when sufficient moisture is expected to cause a thin layer of ice on road surfaces, typically on cloudless nights ("black ice"). At forecaster discretion a formal Winter Weather Advisory may be issued instead.
Sustained winds ≥ 74 mph (≥ 64 kts) (no gust criteria) associated with a hurricane expected to affect a forecast zone within 36 hours.
Sustained winds 39-73 mph (34-63 kts) (no gust criteria) associated with a tropical storm expected to affect a forecast zone within 36 hours.
Short-fused warning for onset of extreme winds, defined as sustained at 111+ mph (equivalent to a Category 3+ hurricane).
This is typically used for the approach of the eyewall of a major landfalling hurricane.
Rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within a short time-frame from the onset of heavy rain.
A dam or levee failure, or water released from an ice jam is also considered.
Expected overflow or inundation by water which causes or will cause damage and/or a threat to life.
Water level at a River Forecast point along a main stem river (such as the Winooski or Ausable) is expected to reach or exceed flood stage.
Expected inundation by water of some low lying and poor drainage areas, resulting in a nuisance to the public but not a threat to life and property.
Sustained winds ≥ 40 mph (≥ 35 kts) for at least 1 hour; OR any gusts ≥ 58 mph (≥ 50 kts)
Sustained winds 31-39 mph (27-34 kts) for at least 1 hour; OR any gusts to 46-57 mph (40-49 kts)
Daytime heat indices of ≥ 105°F
Daytime heat indices of 95°F-104°F
Issued for non-criteria warning/advisory heat. A heat wave is defined as 3 or more days of ≥ 90°F temperatures.
When minimum shelter temperature drops to ≤ 32°F during growing season
Issued under clear, light wind conditions with forecast minimum shelter temperature 33-36°F during growing season
Apparent Temperature ≤ -30°F
Apparent between -20°F and -29°F.
High degree of confidence that dry fuels and weather conditions support extreme fire danger within 24 hours using the following criteria as a guide:
- Winds sustained or with frequent gusts ≥ 25 mph
- Relative Humidity at or below 30% anytime during the day
- Rainfall amounts for the previous 5 days less than 0.25 inches (except 3 days in pre-greenup)
Widespread visibility ≤ ¼ mile for at least 3 hours.
Very light ice accumulation from predominantly fog at or below freezing temperatures.
Widespread or localized smoke reducing visibilities to ¼ mile or less.
Atmospheric conditions stable enough to cause air pollutants to accumulate in a given area. Criteria developed in conjunction with the local or state EPA and the product issued at their request.
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