A Winter Storm Watch is issued by the National Weather Service of the United States when there is a potential for heavy snow or significant ice accumulations. The watch is usually issued 12 to 48 hours before the storm's arrival in the area. As is true with a Winter Weather Advisory, the criteria for this watch can vary from place to place. If strong winds are expected with reduced visibilities, a winter storm watch may be upgraded to a Blizzard Watch. A Winter Storm Watch is different from a Winter Weather Advisory in the sense that a Winter Weather Advisory is meant to advise those of the conditions that currently exist outside, while a Winter Storm Watch simply means that there is a chance of a storm coming. A Winter Storm Watch will become a Winter Storm Warning when the storm is in happening or about to happen. Winter Storm Watches are given so that communities can prepare in the chance that the winter storm does in fact hit. Winter storm watches often go in place when there is a chance between 50-80% of the storm occurring.
Example of a Winter Storm Watch
918 WWUS43 KLOT 301126WSWLOTURGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE CHICAGO IL526 AM CST SUN JAN 30 2011...SIGNIFICANT WINTER STORM TO AFFECT THE SOUTHERN GREAT LAKESREGION TUESDAY INTO WEDNESDAY....A PERIOD OF WINTRY WEATHER IS EXPECTED TO AFFECT NORTHERNILLINOIS AND NORTHWEST INDIANA THE FIRST HALF OF THE WORK WEEK.SIGNIFICANT AMOUNTS OF SNOW ARE EXPECTED TO ACCUMULATE BETWEENMONDAY MORNING AND WEDNESDAY EVENING...WITH SNOWFALL TOTALS OF 12OR MORE INCHES QUITE POSSIBLE IN NORTHEAST ILLINOIS AND NORTHWESTINDIANA BY WEDNESDAY NIGHT.THE FIRST ACCUMULATING SNOW IS EXPECTED TO SPREAD ACROSS THE AREAMONDAY MORNING. SNOWFALL IS EXPECTED TO INTENSIFY FOR MONDAYAFTERNOON AND EVENING...THEN LIGHTEN UP AGAIN LATE MONDAY NIGHTINTO TUESDAY MORNING. ACCUMULATIONS OF 2 TO 4 INCHES CAN BEEXPECTED BY MIDDAY TUESDAY. HOWEVER...THIS WILL ONLY BE THEPRELIMINARY ROUND OF SNOW AS AN INTENSE WINTER STORM WILL BETRACKING FROM ARKANSAS NORTHEASTWARD UP THE OHIO VALLEY TUESDAYAFTERNOON THROUGH WEDNESDAY MORNING. THIS STORM SYSTEM WILLLIKELY PRODUCE AN BAND OF VERY HEAVY SNOW ALONG AND TO THE NORTHOF ITS TRACK. THIS PUTS THE ENTIRE AREA UNDER THE GUN FOR A MAJORSNOWFALL EVENT.AS THE LOW PRESSURE CENTER REACHES THE UPPER OHIO VALLEY BY LATEWEDNESDAY MORNING A STRONG FLOW OF COLD AIR WILL BE MOVING ACROSSSOUTHERN LAKE MICHIGAN...WITH LAKE EFFECT SNOW DEVELOPING ON THEILLINOIS SIDE OF THE LAKE. AS THE DAY PROGRESSES WEDNESDAY THESTRONG LOW LEVEL FLOW WILL BECOME MORE NORTHERLY AND THE LAKEEFFECT SNOW WILL SHIFT TO FAR NORTHWEST INDIANA.BY LATER WEDNESDAY THE SNOW FROM THE DEPARTING WINTER STORM WILLBE WINDING DOWN ACROSS THE AREA BUT A BAND OF SIGNIFICANT LAKEEFFECT SNOW IS EXPECTED IN NORTHWEST INDIANA WHERE SEVERALADDITIONAL INCHES OF SNOW ARE POSSIBLE BEFORE THE LAKE EFFECTSHIFTS FURTHER OFF TO THE EAST INTO SOUTHWESTERN LOWER MICHIGANAND NORTH CENTRAL INDIANA.BETWEEN THE INITIAL LIGHTER SNOW MONDAY INTO TUESDAYMORNING...THE HEAVY SNOWFALL FROM THE MAJOR WINTER STORM DURING TUESDAY AFTERNOON THROUGH WEDNESDAY MORNING...AND THE INCREASINGLYINTENSE LAKE EFFECT SNOW DEVELOPING DURING WEDNESDAY...A FOOT ORMORE OF SNOW WILL NOT BE UNCOMMON OVER MUCH OF NORTHEAST ILLINOISAND FAR NORTHWEST INDIANA.THE STORM SYSTEM WILL BE AFFECTING A LARGE PORTION OF THESOUTHERN GREAT LAKES...MIDWEST AND OHIO VALLEY REGIONS. ANYONEWITH TRAVEL PLANS TUESDAY AND WEDNESDAY...INCLUDING THOSETRAVELING THROUGH CHICAGO OHARE AND MIDWAY AIRPORTS...SHOULDCONTINUE TO MONITOR LATER FORECASTS REGARDING THE DEVELOPMENT OFTHIS WINTER STORM.ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-301930-/O.NEW.KLOT.WS.A.0001.110201T1800Z-110203T0000Z/WINNEBAGO-BOONE-MCHENRY-LAKE IL-OGLE-LEE-DE KALB-KANE-DUPAGE-COOK-LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-IROQUOIS-FORD-LAKE IN-PORTER-NEWTON-JASPER-BENTON-INCLUDING THE CITIES OF...ROCKFORD...BELVIDERE...WOODSTOCK...WAUKEGAN...OREGON...DIXON...DEKALB...AURORA...WHEATON...CHICAGO...OTTAWA...OSWEGO...MORRIS...JOLIET...KANKAKEE...PONTIAC...WATSEKA...PAXTON...GARY...VALPARAISO...MOROCCO...RENSSELAER...FOWLER526 AM CST SUN JAN 30 2011 /626 AM EST SUN JAN 30 2011/...WINTER STORM WATCH IN EFFECT FROM TUESDAY AFTERNOON THROUGHWEDNESDAY AFTERNOON...THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A WINTER STORMWATCH...WHICH IS IN EFFECT FROM TUESDAY AFTERNOON THROUGHWEDNESDAY AFTERNOON.* TIMING...HEAVY SNOWFALL WILL SPREAD NORTHEASTWARD ACROSS THE AREA MIDDAY WEDNESDAY AND CONTINUE THROUGH TUESDAY NIGHT. AS THE SNOWFALL FROM THE STORM SYSTEM STARTS TO WIND DOWN DURING WEDNESDAY MORNING AND EARLY AFTERNOON...LAKE EFFECT SNOW WILL HAVE DEVELOPED ON THE ILLINOIS SIDE OF THE LAKE. INCREASINGLY HEAVY AND MORE CONCENTRATED LAKE EFFECT SNOW WILL SHIFT INTO FAR NORTHWEST INDIANA DURING WEDNESDAY AFTERNOON AND PERSIST INTO WEDNESDAY EVENING BEFORE SHIFTING FURTHER OFF TO THE EAST INTO SOUTHWEST LOWER MICHIGAN AND NORTH CENTRAL INDIANA.* ACCUMULATIONS...TOTAL ACCUMULATIONS FROM MONDAY MORNING THROUGH WEDNESDAY EVENING ARE EXPECTED TO BE IN EXCESS OF 8 INCHES IN NORTH CENTRAL ILLINOIS...AND IN EXCESS OF 12 INCHES OVER NORTHEAST AND EAST CENTRAL ILLINOIS...AS WELL AS NORTHWEST INDIANA. LOCAL AMOUNTS IN EXCESS OF 18 INCHES ARE POSSIBLE IN FAR NORTHWEST INDIANA...DEPENDING ON EXACTLY WHERE THE LAKE EFFECT SNOW BAND SETS UP AND HOW PERSISTENT IT IS OVER ANY ONE LOCATION.* HAZARDS...HEAVY SNOWFALL AS WELL AS BLOWING AND DRIFTING SNOW.* IMPACTS...VERY DIFFICULT TO NEAR IMPOSSIBLE TRAVEL CONDITIONS AS SNOW WILL BE ACCUMULATING AT A RAPID RATE DURING THE PEAK OF THE SNOW STORM TUESDAY AFTERNOON AND NIGHT. HEAVY LAKE EFFECT SNOW IN NORTHWEST INDIANA LATER WEDNESDAY AND WEDNESDAY EVENING WILL CONTINUE TO HAMPER TRAVEL THERE.PRECAUTIONARY/PREPAREDNESS ACTIONS...A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANTSNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.CONTINUE TO MONITOR THE LATEST FORECASTS.&&$$<ref>{{Cite web|url=http://www.weather.gov/lot/2015_Feb01_Snow|title=Historic Winter Storm of January 31-February 2, 2015|last=Service|first=US Department of Commerce, NOAA, National Weather|website=www.weather.gov|language=EN-US|access-date=2016-10-27}}</ref>References
Winter storm watch Wikipedia(Text) CC BY-SA