Abundant pacific moisture and upslope flow brought heavy snow to northwest Wyoming. SNOTEL sites reported 12 to 14 inches of snow.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS RIW wrote it up.
Abundant pacific moisture and upslope flow brought heavy snow to northwest Wyoming. SNOTEL sites reported 12 to 14 inches of snow.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Riverton, WY wrote its last area forecast discussion before the first event at Dec 26, 2:44 PM MST, 3 hours 16 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
244 PM MST THU DEC 26 2002
...TONIGHT THROUGH SUNDAY...
ANOTHER COLD DAY IN THE WIND RIVER AND BIG HORN BASINS WITH THE TEMP
IN THE SINGLE DIGITS. LEE SIDE TROF STRENGTHENING BY THE MINUTE HAS
THE WIND CRANKING UP OVER THE TYPICAL FAVORED AREAS...INCLUDING
CODY WHERE THE TEMP IS 36. 40 MILES EAST OF CODY...GREYBULL SITS AT
5 ABOVE. CHANGE IS IN THE WIND THROUGH AS SHORTWAVE SHOWN BY
SATELLITE SLAMMING INTO THE THE PACIFIC COAST. WEST TO NORTHWEST
FLOW INCREASES AHEAD OF THE WAVE TONIGHT. WYOMING TO BE UNDER RFQ
OF 100 KT JET OVER NIGHT WHICH WILL HELP INCREASE THE WINDS FURTHER.
THIS WITH THE LEE SIDE TROF WILL MAKE FOR HIGH WIND CONDITIONS.
WILL ISSUE HIGH WIND WATCH FOR GREEN MTNS...NATRONA COUNTY AND CODY
FOOTHILLS FOR FRIDAY. SURFACE CHARTS SHOWING ABUNDANT LOW CLOUDS AND
PRECIP UP AND DOWN THE COAST AND EAST TO JACKSON, WY. WITH ALL THIS
MOISTURE IN PLACE UNDER GOOD ZONAL FLOW...WILL ISSUE WINTER STORM
WATCH FOR THE WESTERN MOUNTAINS FOR FRIDAY MORNING THROUGH SATURDAY
MORNING. MAIN SHORTWAVE ENERGY STAYS WITH UNDER JET AS IT GLIDES
NORTH OF WYOMING OVER SOUTHERN CANADA AND NORTHERN MONTANA. THERE
WILL LIKELY BE WEAK BITS OF ENERGY THAT WILL AID IN LIFT...BUT
OROGRAPHICS WILL BE ENOUGH TO PROMPT THE WATCH. THIS MOIST FLOW
WEAKENS SATURDAY MORNING SO WILL END THE WATCH THEN. WILL HOLD OFF
ON ANYTHING FOR THE VALLEYS AT THIS TIME...BUT THEY WILL POSSIBLY
NEED AN ADVISORY. ANOTHER WAVE IS EXPECTED SUNDAY...WHICH COULD
PRODUCE SIMILAR RESULTS. 7H TEMPS WARM TO -2 TO 0C OVER THE CWFA
OVERNIGHT. GOOD DOWNWARD FORCING WITH THE LEE SIDE TROF SHOULD BE
ENOUGH TO MIX OUT WIND RIVER BASIN...BUT EXPECT MAV TEMPS OF 43 FOR
LND TO BE OVER DONE AS SNOW COVER IS VERY COLD. WILL GO WITH TEMPS
NEAR 30 TOMORROW AND 35 SATURDAY. CASPER...BUFFALO AND CODY SHOULD
SEE 45 TO 50. TWB
...SUNDAY NIGHT THROUGH THURSDAY...
A PACIFIC COLD FRONT WILL BE RAPIDLY FOLLOWED BY A CANADIAN COLD
FRONT SUNDAY NIGHT BRINGING A CHANCE OF SNOW TO MUCH OF THE AREA
WITH THE MOUNTAINS HAVING THE BEST CHANCE. THE TWO FRONTS WILL
BRING A COLDER AIR MASS TO THE AREA FOR MONDAY AND TUESDAY. A WARM
FRONT WILL LIFT NORTHEAST FROM THE GREAT BASIN TUESDAY NIGHT AND
WEDNESDAY BRINGING A CHANCE OF SNOW TO THE WEST WITH DRY AND BREEZY
TO WINDY CONDITIONS EAST OF THE CONTINENTAL DIVIDE. PROGRESSIVE
WESTERLY FLOW WILL BRING A SERIES OF TROUGHS INTO THE WESTERN
MOUNTAINS BRINGING SHOTS OF PACIFIC MOISTURE WHICH WILL LIKELY
PRODUCE SNOW OFF AND ON THROUGH THURSDAY. WITH A PROGRESSIVE
WEATHER PATTERN PROVIDING CLOUD COVER...WIND AND AREAS OF
PRECIPITATION...TEMPERATURES WILL BE MODERATED SOME...BUT WITH
SNOW COVER LIKELY CENTRAL AND WEST...A SIGNIFICANT WARM UP IS
UNLIKELY. OVERALL EXTENDED FORECAST ON TRACK. C.BAKER
.RIW...WINTER STORM WATCH FRIDAY MORNING THROUGH SATURDAY MORNING
WYOMING ZONES 01..02..12..14..15..24.
HIGH WIND WATCH FRIDAY THROUGH FRIDAY EVENING WYOMING ZONES
03..19..20.WYZ001>020-022>030-271200- HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 502 AM MST THU DEC 26 2002 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. LIGHT SNOW WILL BEGIN FALLING IN THE WESTERN MOUNTAINS TONIGHT...ACCUMULATIONS OF ONE TO TWO INCHES ARE EXPECTED. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A GOOD FETCH OF MOISTURE FROM THE PACIFIC WILL SET UP FRIDAY THROUGH SUNDAY FOCUSING ON WESTERN WYOMING WITH SEVERAL SHORTWAVE TROUGHS RUNNING INTO THE BACKSIDE OF A SHORTWAVE RIDGE OVER THE WESTERN US. STRONG MID LEVEL WINDS WILL PROVIDE EXCELLENT CONDITIONS FOR HEAVY OROGRAPHIC SNOW IN THE WESTERN WYOMING MOUNTAINS...ONE TO TWO FEET OF TOTAL SNOW ACCUMULATION CAN BE EXPECTED FOR THE EVENT IN THE MOUNTAINS...6 TO 12 INCHES IN JACKSON HOLE AND STAR VALLEY. SOUTHWEST TO WEST WINDS OF 30 TO 40 MPH WITH GUSTS TO 60 MPH CAN BE EXPECTED AT THE RIDGE TOPS AND OVER MOUNTAIN PASSES. THE POTENTIAL EXISTS FOR THESE WINDS TO MIX DOWN TO FOOTHILL LOCATIONS ALONG THE EASTERN ABSAROKAS. THE STORM SYSTEM WILL BRING A CHANCE OF SNOW TO THE REMAINDER OF THE FORECAST AREA ON SUNDAY. .SPOTTER INFORMATION STATEMENT... EMERGENCY MANAGERS IN WESTERN COUNTIES...CONTINUE TO MONITOR UPDATED STATEMENTS AND FORECASTS CONCERNING THIS POTENTIAL FOR SIGNIFICANT SNOWFALL AND WIND. EMERGENCY MANAGERS AND SPOTTERS IN AND AROUND THE CODY FOOTHILLS...CONTINUE TO MONITOR FORECASTS AND FUTURE STATEMENTS CONCERNING THE POTENTIAL FOR HIGH WIND THURSDAY NIGHT AND FRIDAY MORNING. WCJIN-WYNW-WYSW-WYNE MCDONALD
The national radar mosaic for the moment the first event began.
3 heavy snow. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2002Every state in 2002This day in weather historyWarnings in Wyoming, December 2002
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5321900, 5321901, 5321902.