National Weather Service United States Department of Commerce

Thunderstorms and Heavy Rain Across the Southern and Eastern US; Heat and Fire Weather Concerns in the West

Showers and thunderstorms are expected across the southern and eastern US this week, with heavy rain and localized flooding, particularly near the Gulf Coast. Monsoonal moisture will bring rain and potential flooding to parts of the Southwest. Heat and fire weather threats will continue to impact the West. Read More >

Winter Guidelines and Criteria

 

Winter Guidelines For Calling WFO Boulder…

  • 12 and/or 24 hour snow depth and new snowfall by 8 AM and 8 PM.

  • Moderate to heavy snowfall. Example: 1/2-1 inch per hour for several hours and visibilities less than 1/2 mile.

  • Strong winds above 50 mph (sustained or gusts).

  • Freezing rain/drizzle (any intensity).

  • Report changeover from rain to snow or fro.m snow to rain. Dense Fog (visibility less than a quarter of a mile).

  • If current conditions do not coincide with the current WFO Boulder Forecast.

  • Adverse road conditions.

  • If any of the below snow criterion is met.

 

**Our criteria for issuing warnings and advisories are listed above.   Please pay close attention to when your snowfall approaches 4 inches and again at 8 inches at the higher elevations (at or above 6500 feet).    3 and 6 inches are the critical numbers for the stations at lower elevations (below 6500 feet).


NWS Winter Storm Weather Criteria…

 

Mountains and Foothills Criteria…

 
  • WINTER STORM WARNING

    • 8 inches or more in a 12 hour period.

    • 12 inches or more in a 24 hour period.

 
  • SNOW ADVISORY

    • 4 to 7 inches in a 12 hour period.

 
  • HIGH WIND CRITERIA

    • Sustained winds of 50 mph or greater or

    • wind gusts to 75 mph or more

 

Urban Corridor and Plains Criteria…

  • WINTER STORM WARNING

    • 6 inches or more in a 12 hour period.

    • 8 inches or more in a 24 hour period.

 
  • SNOW ADVISORY

    • 3 to 5 inches in a 12 hour period.

 
  • HIGH WIND CRITERIA

    • Sustained winds of 40 mph or greater or

    • Wind gusts to 58 mph or more

 
  • Blizzard Criteria

    • Sustained winds of 35 mph or greater (and)

    • Visibilities frequently less than 1/4 mile (and)

    • Considerable snow and/or blowing snow