A winter weather advisory (originally identified as a Traveler's Advisory until the 2002-03 climatological winter when officially renamed, and informally as such by some local television stations thereafter) is a hazardous weather statement issued by local Weather Forecast Offices (WFO) of the National Weather Service in the United States when one or more types of winter precipitation—snow, rain and snow mixed, freezing rain, sleet, graupel, etc.—presenting a hazard, but not expected to produce accumulations meeting storm warning criteria (usually below 4inches), are forecast within 36 hours of the expected onset of precipitation or are occurring in the advisory's coverage area.
In the United States, the criteria necessary to issue a Winter Weather Advisory is defined by each local NWS Weather Forecast Office, and is based on the climatological impact of frozen precipitation on travel and commerce within the specified region. For example, any measurable snow will constitute the advisory in Florida, while forecast accumulations of 3to will merit issuance in New England. If other forms of wintry precipitation are expected, then a Winter Weather Advisory or Winter Storm Warning (the latter being issued for frozen precipitation events portending amounts significant enough to cause hazardous conditions for life, property, commerce and travel) can be issued, also depending on the amount and accumulation of precipitation that is expected.
Until the 2007-08 winter storm season, the product was originally designated to indicate hazardous travel conditions within the advisory area, while standalone advisories based on the expected/ongoing precipitation type (usually encompassing the same areas) were issued to indicate hazards to life, property and commerce through the duration of the winter weather event forecast to occur within a given region. Beginning in the winter of 2008-09, the National Weather Service restructured the Winter Weather Advisory into a general purpose product, expanding its application to supersede and utilizing the respective criterial definitions previously applied to four deprecated precipitation-specific products:
Additional variants of the product were added by the National Weather Service on October 2, 2017 (implemented for the 2017-18 winter storm season), superseding two other precipitation-based advisory products:[2]
The generic Winter Weather Advisory terminology may be used on its own, typically to indicate moderate amounts of snow, sleet and freezing rain are expected in the alert area. However, the generic term may be used at the forecaster's discretion regardless of whether or not the condition applies.
In Canada, Environment and Climate Change Canada issues the similar Winter Weather Travel Advisory through regional Meteorological Service offices based in Vancouver, Edmonton, Winnipeg, Toronto, Montreal and Dartmouth for specified municipalities and census subdivisions.
Below is an example of a Snow Advisory for Snow issued by the National Weather Service office in Great Falls, Montana in December 2007:
URGENT - WINTER WEATHER MESSAGE NATIONAL WEATHER SERVICE GREAT FALLS MT 657 PM MST SUN DEC 9 2007 MTZ008>015-044-045-047-048-050>055-101100- /O.CON.KTFX.SN.Y.0025.071210T1100Z-071211T0000Z/ BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL- CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON- TOOLE-LIBERTY-BLAINE-SOUTHERN ROCKY MOUNTAIN FRONT-JUDITH BASIN- FERGUS-JEFFERSON-BROADWATER-MEAGHER-GALLATIN- INCLUDING THE CITIES OF...DILLON...BROWNING...CUT BANK...HAVRE... GREAT FALLS...FORT BENTON...HELENA...LINCOLN...ENNIS...SHELBY... CHESTER...CHINOOK...CHOTEAU...STANFORD...LEWISTOWN...BOULDER... TOWNSEND...WHITE SULPHUR SPRINGS...BOZEMAN...WEST YELLOWSTONE 657 PM MST SUN DEC 9 2007 ...SNOW ADVISORY REMAINS IN EFFECT FROM 4 AM TO 5 PM MST MONDAY FOR ELEVATIONS ABOVE 4500 FEET... A SNOW ADVISORY REMAINS IN EFFECT FROM 4 AM TO 5 PM MST MONDAY FOR ELEVATIONS ABOVE 4500 FEET. PERIODS OF LIGHT SNOW ARE EXPECTED TO FALL OVER THE ROCKY MOUNTAIN FRONT...THE CENTRAL MOUNTAINS...AND ACROSS MUCH OF SOUTHWEST MONTANA FROM MONDAY MORNING THROUGH MONDAY AFTERNOON. EXPECT NEW SNOW ACCUMULATIONS ON MONDAY TO RANGE FROM 2 TO 6 INCHES FOR ELEVATIONS ABOVE 4500 FEET...WHILE SNOW ACCUMULATIONS WILL GENERALLY BE LESS THAN 1 INCH AT LOWER ELEVATIONS. AREAS OF BLOWING AND DRIFTING SNOW WILL REDUCE VISIBILITIES AT TIMES. A SNOW ADVISORY MEANS THAT PERIODS OF SNOW WILL CAUSE PRIMARILY TRAVEL DIFFICULTIES. BE PREPARED FOR SNOW COVERED ROADS AND LIMITED VISIBILITIES...AND USE CAUTION WHILE DRIVING. LISTEN TO NOAA WEATHER RADIO...OR YOUR LOCAL MEDIA FOR THE LATEST UPDATES ON THIS SITUATION. $$
Below is an example of a Winter Weather Advisory for Snow issued by the National Weather Service office in Des Moines, Iowa in April 2019:[3]
IAZ004>006-016-017-026>028-270430- /O.UPG.KDMX.WS.A.0006.190427T1200Z-190428T0000Z/ /O.NEW.KDMX.WW.Y.0028.190427T1200Z-190428T0000Z/ Emmet-Kossuth-Winnebago-Hancock-Cerro Gordo-Franklin-Butler- Bremer- Including the cities of Estherville, Algona, Forest City, Lake Mills, Garner, Britt, Kanawha, Mason City, Clear Lake, Hampton, Parkersburg, Clarksville, Shell Rock, Greene, Aplington, Allison, Dumont, and Waverly 324 PM CDT Fri Apr 26 2019 ...WINTER WEATHER ADVISORY IN EFFECT FROM 7 AM TO 7 PM CDT SATURDAY... * WHAT...Snow expected. Total snow accumulations of 1 to 5 inches expected. Winds gusting as high as 30 mph. * WHERE...Northern Iowa. * WHEN...From 7 AM to 7 PM CDT Saturday. * ADDITIONAL DETAILS...Plan on slippery road conditions. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Winter Weather Advisory for snow means periods of snow will cause primarily travel difficulties. Expect snow covered roads and limited visibilities, and use caution while driving. The latest road conditions for the state you are calling from can be obtained by calling 5 1 1. && $$