WFO FGF Watch, Warning, Advisory Criteria

Winter Precipitation

Statements for these hazards will be issued under the header "WSWFGF (WWUS43 KFGF)." for situations when the following criteria are met:

Central Region Winter Weather Products Specification

For Snow & Ice Threats:

• Winter Storm Watch: Possibility that Winter Storm Warning criteria may be met at longer ranges (Typically 1 to 3 days out).
• Winter Weather Advisory:  Snow thresholds
• Winter Storm Warning:  National Warning Thresholds 
• Ice Storm Warning: Ice accumulation meeting or exceeding 1/4 inch on an elevated horizontal flat surface.
• Blizzard Warning: Sustained wind or frequent gusts greater than or equal to 35 mph accompanied by falling and/or blowing snow, frequently reducing visibility to less than 1/4 mile for three hours or more.
  • Note: Blizzard conditions do not require snow to be falling i.e., ground blizzards

For Low Wind Chills:

• Wind Chill Advisory:  (See a map of Wind Chill Advisory thresholds)
• Wind Chill Warning:  (See a map of Wind Chill Warning thresholds)

Thunderstorm Threats

Severe Thunderstorm RISK Terminology
(used in Hazardous Weather Outlooks)

Severe Weather Risks

The level of categorical risk in the Day 1-3 Convective Outlooks is derived from probability forecasts of tornadoes, damaging winds, and large hail on Days 1 and 2, and a combined severe weather risk on Day 3.

• TSTM (light green) - General or non-severe thunderstorms - Delineates, to the right of a line, where a 10% or greater probability of thunderstorms is forecast during the valid period.
• 1-MRGL (dark green) - Marginal risk - An area of severe storms of either limited organization and longevity, or very low coverage and marginal intensity.
• 2-SLGT (yellow) - Slight risk - An area of organized severe storms, which is not widespread in coverage with varying levels of intensity.
• 3-ENH (orange) - Enhanced risk - An area of greater (relative to Slight risk) severe storm coverage with varying levels of intensity.
• 4-MDT (red) - Moderate risk - An area where widespread severe weather with several tornadoes and/or numerous severe thunderstorms is likely, some of which should be intense. This risk is usually reserved for days with several supercells producing intense tornadoes and/or very large hail, or an intense squall line with widespread damaging winds.
• 5-HIGH (magenta) - High risk - An area where a severe weather outbreak is expected from either numerous intense and long-tracked tornadoes or a long-lived derecho-producing thunderstorm complex that produces hurricane-force wind gusts and widespread damage. This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe (i.e., violent tornadoes or very damaging convective wind events).

SEVERE THUNDERSTORM or TORNADO WATCH Severe thunderstorms with large hail, damaging winds, and/or tornadoes are possible, but the exact time and location of storm development is still uncertain. A watch means be prepared for storms.

SEVERE THUNDERSTORM WARNING A severe thunderstorm is imminent or occurring; it is either detected by weather radar or reported by storm spotters. A severe thunderstorm is one that produces winds 58 mph or stronger and/or hail 1 inch in diameter or larger. A warning means to take shelter.

TORNADO WARNING A tornado is imminent or occurring; it is either detected by weather radar or reported by storm spotters. A warning means to take shelter.

FLOOD WATCH Conditions are favorable for flash flooding. A watch means to get prepared for possible flooding.

FLASH FLOOD WARNING Life-threatening flooding is imminent or occurring; it is either detected by weather radar, indicated by stream gauges, or reported by storm spotters. A flash flood is a flood that occurs very quickly; it is caused by heavy rainfall over a short period of time or from a dam break. A warning means to leave low-lying or flood prone areas.

Non Precipitation Phenomena Warning Terminology

Statements for these hazards will be issued under the header "NPWFGF (WWUS73 KFGF)." for situations when the following criteria are met:

Central Region Non-Precipitation Weather Products Specification

For Winds NOT associated with a specific Thunderstorm:

• High Wind Watch: Possibility that High Wind Warning Criteria may be met at longer ranges (24 to 48 hrs out).
• Wind Advisory: Sustained wind speeds of 30 to 39 mph lasting for 1 hour or longer, or winds of 45 mph to 57 mph for any duration.
• High Wind Warning: Sustained wind speeds of 40 mph or greater lasting for 1 hour or longer or wind gusts 58 mph or greater, for any duration.

For Widespread Frosts/Freezes, after the beginning and before the end of the "growing season":
The BEGINNING of the growing season is set by the average date of the last freeze in spring, and normally happens during early to late May in eastern ND and northwest MN. The NWS will then issue Frost Advisories and Freeze Warnings when appropriate, until the end of the growing season, according to the following rules:

• Frost Advisory: Low temperatures across the whole county/zone at or below 33 to 36°F in the early and late growing season.
• Freeze Watch: Possibility that Freeze Warning Criteria may be met at longer ranges (24 to 48 hrs out).
• Freeze Warning: Low temperatures across the whole county/zone at or below 32°F in the early and late growing season. The END of the growing season occurs when most of the county/NWS zone has had it's first freeze in the autumn (1/2 or more of the zone has reached 32°F or below) which usually occurs mid September to early October in eastern ND and northwest MN. See a map of the Average Date of the First Autumn Freeze.
• Hard Freeze Warning: Low temperatures across the whole county/zone at or below 28°F in the early and late growing season.

For High Heat Indicies:

• Excessive Heat Watch: Possibility that Excessive Heat Warning Criteria may be met at longer ranges (12 to 48 hours out).
• Heat Advisory: Issued when the Heat Index will be greater than or equal to 100°F, but less than 105°F for any 3 hour period. (see map of Heat Advisory Threshold)
• Excessive Heat Warning: Issued when the Heat Index will be greater than or equal to 105°F for any 3 hour period and greater than or equal to 75°F for 24 hours. (see map of Excessive Heat Warning Threshold)

For Widespread Dense Fog:

• Dense Fog Advisory: Widespread or localized fog reducing visibilities to 1/4 mile or less.

   

Fire Weather Products

Statements for these hazards will be issued under the header "RFWFGF (WWUS83 KFGF)" for situations when the following criteria are met:

• Fire Weather Watch

• A Fire Weather Watch in Minnesota is issued when there is a reasonable level of confidence that all of the following three weather conditions will be met within 18 to 72 hours, provided fuels are dry.

  1.    Sustained one-minute winds at 20 foot levels at or above 20 mph, 25 mph   in counties adjacent to the Red River .

  2.    Minimum relative humidity at or less than 25 percent.

  3.    Dry lightning may be considered but is rare in Minnesota.

• A Fire Weather Watch In North Dakota is issued when there is a reasonable level of confidence that within 12 to 72 hours red flag conditions will be met using the red flag relative humidity/sustained wind speed matrix when the fire danger will be in the high, very high or extreme category.

• Red Flag Warning: A Red Warning is issued when there is a high probability that all the weather criteria listed under Fire Weather Watch will be met within 48 hours for MN and 24 hours for ND.