WFO MPX Watch, Warning, Advisory Criteria

Winter Weather

Winter Storm Watch

Significant and dangerous winter weather is possible, generally within 72 hours.  Significant and dangerous is defined as:

• Blizzard conditions: Visibility less than 1/4 mile due to falling and/or blowing snow and frequent wind gusts to 35 mph, for 3 hours or more.
• 6 or more inches of snow with an event, not to exceed 48 hours in length.
• 1/4 inch of ice.
• 1/2 inch of sleet.
• Forecaster discretion: a combination of snow, sleet, freezing rain, blowing snow, and/or wind leading to significant impacts.

Wind Chill Watch (Decommissioned after winter 2023-2024 for Extreme Cold Watch in non-precip section)

Wind chills of -35ºF or colder are possible.

Blizzard Warning

All of the following are occurring or expected:

• Falling and/or blowing snow reducing visibilities to less than 1/4 mile.
• Sustained winds or frequent gusts to 35 mph or higher.
• Conditions persisting for 3 hours or longer.

Ice Storm Warning

Ice accumulation of 1/4 inch or more is expected.​

Winter Storm Warning 

Significant and dangerous winter weather is expected, generally within 24 hours.  Significant and dangerous is defined as:

• 6 or more inches of snow with an event, not to exceed 48 hours in length.
• 1/2 inch of sleet.
• Forecaster discretion: a combination of snow, sleet, freezing rain, blowing snow, and/or wind leading to significant impacts.

Wind Chill Warning (Decommissioned after winter 2023-2024 for Extreme Cold Warning in non-precip section)

Widespread wind chills of -35ºF or colder are expected.

Snow Squall Warning 

The occurrence of snow squalls (short bursts of intense snow) meeting or exceeding one or both of the following conditions:

• Visibility 1/4 mile or less in snow with sub-freezing road temperatures. Often accompanied by wind gusts greater than 30 mph.
• Plunging temperatures sufficient to produce a flash freeze, along with a significant reduction in visibility from falling and/or blowing snow.

Additional factors to consider:

• Time of day.
• Highways and interstates impacted.

These are polygon-based warnings that last usually an hour or less. Larger and longer events are covered by Winter Storm Warnings.

Severity tags:

• General (no tag): Used frequently. Snow squall conditions are expected or observed, but mitigating actions, combined with societal context, will reduce the threat to safe travel.
• "SIGNIFICANT" tag: Used only when suspected or observed conditions, both meteorological and non-meteorological, suggest a substantial threat to safe travel, such that WEA is warranted to alert all devices in the path of the squall.

Winter Weather Advisory

Winter weather that causes inconvenience, but is not dangerous if proper caution is exercised.  Criteria include:

• 3-<6 inches of snow.
• Blowing snow, causing local visibility reductions.
• Less than 1/2 inch of sleet.
• Less than 1/4 inch of ice.
• Forecaster discretion: a combination of light snow, sleet, freezing rain, blowing snow, and/or wind leading to impacts.

Wind Chill Advisory (Decommissioned after winter 2023-2024 for Cold Weather Advisory in non-precip section)

Severe Weather

Tornado Watch

Conditions are favorable for the development of severe thunderstorms and tornadoes within the next 6-8 hours.

Severe Thunderstorm Watch

Conditions are favorable for the development of severe thunderstorms during the next 6-8 hours, capable of large hail an inch in diameter or greater and/or wind gusts of 58 mph or greater. A couple tornadoes are also possible.

Tornado Warning

• A tornado has been spotted; and/or
• Radar indicated: thunderstorm features are evolving in a way that suggests a tornado may develop imminently; and/or
• Radar confirmed: debris has been sensed by radar in an area of strong rotation.

"CONSIDERABLE" tag: some or all of the following:

• Radar has overwhelming evidence of a damaging tornado.
• Credible reports of a damaging tornado from media, public safety personnel, or storm chasers.
• Environment is favorable for strong or violent tornadoes (EF2+).
• Storm is long-lived and has a history of tornadoes.

"CATASTROPHIC" tag: some or all of the following are required:

• Radar has overwhelming evidence of a tornado producing massive damage.
• Credible reports of structures being leveled from media, public safety personnel, or storm chasers.
• Tornado is heading into a populated area.
• Environment is favorable for violent tornadoes (EF4+).
• Storm is long-lived and has a history of potentially strong tornadoes.
• Branded as "Tornado Emergency".

Severe Thunderstorm Warning

• Hail 1 inch in diameter or greater; and/or
• Wind gusts of 58 mph or greater.

"CONSIDERABLE" tag:

• Hail 1.75 inch in diameter or greater (golf ball sized); and/or
• Wind gusts of 70 mph or greater.

"DESTRUCTIVE" tag:

• Hail 2.75 inch in diameter or greater (baseball sized); and/or 
• Wind gusts of 80 mph or greater.

Non-Precipitation

High Wind Watch

The possibility of sustained winds of 40 mph or greater for at least one hour and/or gusts of 58 mph or greater for any duration. ​

Excessive Heat Watch

• 7-county metro area: 
  • A possibility the heat index will reach 100ºF for one day.
  • The forecast max Wet Bulb Globe Temperature could reach 87 for one day.
  • The heat index could reach 100ºF for two days in a row, along with an overnight low no cooler than 73ºF.
• Outside of the 7-county metro area:
  • A possibility the heat index will reach 105ºF for one day.
  • The forecast max Wet Bulb Globe Temperature could reach 87 for one day.
  • The heat index could reach 105ºF for two days in a row, along with an overnight low no cooler than 75ºF.

Extreme Cold Watch (Beginning winter 2024-2025)

• For areas north and west of the 7-county metro area: the possibility of wind chill OR air temperatures colder than -40ºF.
• For the 7-county metro area and counties to the south and east: the possibility of wind chill OR air temperatures colder than -35ºF.

Freeze Watch 

Issued during the growing season when there is a possibility temperatures could drop below freezing.

High Wind Warning

It is expected sustained winds will reach 40 mph or greater for at least one hour and/or gusts of 58 mph or greater for any duration. ​

Excessive Heat Warning

• 7-county metro area: 
  • It is expected the heat index will reach 100ºF for one day.
  • The forecast max Wet Bulb Globe Temperature will reach 87 for one day.
  • The heat index will reach 100ºF for two days in a row, along with an overnight low no cooler than 73ºF.
  • Advisory conditions for at least 4 consecutive days.
• Outside of the 7-county metro area:
  • It is expected the heat index will reach 105ºF for one day.
  • The forecast max Wet Bulb Globe Temperature will reach 87 for one day.
  • The heat index will reach 105ºF for two days in a row, along with an overnight low no cooler than 75ºF.
  • Advisory conditions for at least 4 consecutive days.

Extreme Cold Warning (Beginning winter 2024-2025)

• For areas north and west of the 7-county metro area: wind chills OR air temperatures colder than -40ºF are expected.
• For the 7-county metro area and counties to the south and east: wind chills OR air temperatures colder than -35ºF are expected.

Freeze Warning

Sub-freezing temperatures are expected within the growing season.

Dust Storm Warning

Polygon-based, shorter term warning.  Widespread or localized visibilities 1/4 mile or less due to blowing dust.  Sustained winds of 25 mph or greater are usually required. WEA activation. 

Blowing Dust Warning

Zone-based, longer term warning.  Widespread or localized visibilities 1/4 mile or less due to blowing dust.  Sustained winds of 25 mph or greater are usually required. 

Ashfall Warning

Issued for a volcano undergoing a major eruption where the public will be affected to a significant extent such as 1/4 inch or greater of ashfall accumulation.

Wind Advisory

It is expected sustained winds will reach 30-39 mph for at least one hour and/or gusts of 45-57 mph for any duration.

Heat Advisory

• 7-county metro area: 
  • It is expected the heat index will reach 95ºF for at least 3 hours one day.
  • The forecast max Wet Bulb Globe Temperature will reach 85 for 3 hours one day.
  • The heat index will reach 95ºF for two days in a row, along with an overnight low no cooler than 73ºF.
• Outside of the 7-county metro area:
  • It is expected the heat index will reach 100ºF for at least 3 hours one day.
  • The forecast max Wet Bulb Globe Temperature will reach 85 for 3 hours one day.
  • The heat index will reach 100ºF for two days in a row, along with an overnight low no cooler than 75ºF.

Dense Fog Advisory

Visibilities 1/4 mile or less are occurring due to fog. 

Freezing Fog Advisory

Very light ice accumulation from freezing fog/mist.  Only issued for visibilities greater than 1/4 mile and temperatures below freezing.  If visibilities are 1/4 mile or less, a Dense Fog Advisory is issued.

Dense Smoke Advisory

Visibilities 1/4 mile or less are occurring due to smoke. 

Dust Advisory

Polygon-based, shorter term advisory.  Widespread or localized visibilities 1 mile or less, but greater than 1/4 mile, due to blowing dust.  Winds of 25 mph or greater are usually required.

Blowing Dust Advisory

Zone-based, longer term advisory.  Widespread or localized visibilities 1 mile or less, but greater than 1/4 mile, due to blowing dust.  Winds of 25 mph or greater are usually required.

Frost Advisory

Frost formation is likely with air temperatures ranging from 33 to 36ºF over a widespread area during the growing season.

Ashfall Advisory

Issued for a volcano undergoing a major eruption where the public will be affected to a limited extent such as less than 1/4 inch of ashfall accumulation.

Flooding

Flood Watch

Antecedent and meteorological conditions are favorable for the development of areal or flash flooding within generally the next 6 to 24 hours.

Flash Flood Warning

Issued when the following are expected (generally not to exceed 6 hours in duration):

• Flash flooding is reported; and/or
• A dam or levee failure is imminent or occurring; and/or
• Precipitation capable of causing flash flooding is indicted by radar, rain gages, and/or satellite.

Base (no tag): Most flash floods, with the potential for impacts and damage.

"CONSIDERABLE": Flash floods capable of unusual severity of impact where urgent action is needed to protect lives and property. WEA activated.

"CATASTROPHIC": Exceedingly rare, violent flash floods which threaten lives and cause disastrous damage when floodwaters are placing or will place people in life-threatening situations by rapidly rising to levels rarely, if ever, seen.  Considered a "Flash Flood Emergency". WEA activated.

Flood Warning

Antecedent and meteorological conditions have led to the development of areal or urban flooding.

River Flood Warning

Fire Weather

Fire Weather Watch

Issued when the possibility of Red Flag Warning conditions are met within the next 6-24 hours.  Issuances of watches and warnings are closely coordinated with land managers in Minnesota and Wisconsin, who provide details about fuels and and their susceptibility to ignite.

Red Flag Warning

Minnesota:

• Relative humidity at or below 25%, and
• 20 foot wind sustained or exceeds 20 mph, or frequent gusts in excess of 25 mph.

Wisconsin:

• Temperature at or above 75ºF, and
• Relative humidity at or below 25%, and
• 20 foot wind sustained at or above 15 mph.