Heavy Snow in Wyoming, May 1, 2002

Name: Heavy Snow in Wyoming, May 1, 2002
Start: 2002-05-01T00:00
End: 2002-05-01T20:00
Location: Wyoming

May 1, 2002 · NWS RIW · 5 events in 5 counties and zones

A storm system brought heavy snow to southwest and central Wyoming. Snowfall amounts ranged from 6 to 10 inches.

Where it happened

Every event with a place to put it; 5 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 5

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.

What happened

The episode as NWS RIW wrote it up.

A storm system brought heavy snow to southwest and central Wyoming. Snowfall amounts ranged from 6 to 10 inches.

What forecasters said that day

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 Apr 30, 12:31 PM MST, 11 hours 29 minutes earlier.

Area forecast discussion, Apr 30, 12:31 PM MST, 11 hours 29 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
131 PM MDT TUE APR 30 2002

THE 18Z SFC CHART/METARS PLACING THE SFC FT FROM BYG TO WRL TO COD.
SW WIND WAS LIGHT AHEAD OF THE FRONT. VIS SAT LOOP INDICATING SOME
BKN CLDS BEHIND THE FRONT. COMP RADAR LOOP DETECTING SOME -SHRA
NEAR THE NRN WY BORDER AND WEST OF THE DIV NEAR THE TETONS/YNP. WATER
VAPOR IMAGERY SHOWS THE CIRCULATION OVER CTRL CA WHICH DOES NOT
APPEAR TO BE CLOSED AT THIS TIME. THE NRN STREAM TROUGH CAN BE SEEN
DIVING SOUTHEAST WITH CONSIDERABLE DIFFLUENCE SHEARING THE CTRL CA
CIRCULATION.

THE AVN/ETA DIFFER IN THAT THE ETA CLOSES THE LOW OVER UT BY 18Z WED
AND KEEPS IT CLOSED THROUGH 00Z THU. THE AVN HAS BEEN CONSISTENT
WITH ITS SOLUTION THE LAST SEVERAL RUNS. THE AVN OPENS THE LOW UP
BY 18Z AND SHIFTS THE TROF AXIS INTO ERN WY BY 00Z THU. THE
PRACTICAL OUTCOME OF THE AVN MODEL IS LESS SNOW THAN THE ETA
IS ADVERTIZING. THE AVN SOLUTION SEEMS REASONABLE FOR THIS TIME OF
YEAR WITH THE HIGH SUN ANGLE AND WARM GROUND TEMPS. FURTHERMORE...
BEST DYNAMICS FROM THE NRN STREAM ARE NORTH OF THE FA WITH
WY. FOR THIS EVENING...CURRENT LIS INDICATE SOME MARGINAL
INSTABILITY/CAPE WEST OF JAC. THIS IS NEAR CONVERGENCE OF NRN STRM
TROUGH AND SW FLOW FROM CA LOW AND THETA-E RIDGE AXIS. VIS SAT/RADAR
INDICATES SHOWER ACTIVITY IN THAT AREA. SUBSIDENCE/DRYING IS
INDICATED OVER THE SW UNTIL AFT 06Z. SFC-H7 UPSLOPE IS PROGGED TO SET
UP TON/ERLY WED OVER THE FA BUT H7 WINDS TURN NORTH WED AFT. CURRENT
ADVISORIES LOOK GOOD EXCEPT IN THE NRN FA FROM THE OWL CREEK MTNS AND
NORTH. NORTHWEST FLOW AND SUBSIDENCE SETS IN WED AFT AND CONTINUES
THROUGH THU NIGHT. ON FRI...A SHTWV APPROACHES THE NWRN FA IN ZONAL
FLOW. LIS ARE UNSTABLE SO WILL KEEP ISOLD AFT -SHRA/-TSRA OVER THE
NW INCLUDING THE BH BASIN...BIG HORN MTNS AND JO CO.

IN THE EXTENDED...ZONAL FLOW BECOMES MORE WSW SAT/SUN AS NEXT LOW IN
THE PAC NW MOVES SOUTH. THIS WILL KEEP THE FA EAST OF THE DIV DRY
WITH DOWNSLOPING CONDITIONS. WEST OF THE DIV WILL HAVE A CHC FOR
-SHRASN SUN THROUGH TUE AS ENERGY FROM THE UPPER LOW MOVES INTO THE
WRN FA IN SW FLO. EAST OF THE DIV WILL HAVE A CHC OF SHOWRS AND
ISOLD -TSRA MON/TUE AS THE TROUGH GETS CLOSER AND SW FLOW BRINGS IN
BETTER RH AND DYNAMICS.

.RIW...WINTER WEATHER ADVISORY WYOMING ZONES 11..12..14..15
FOR LATE TONIGHT THROUGH MID DAY WEDNESDAY.

FS

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

5 heavy snow. Local standard time, as filed.

Heavy Snow, Wind River Mtns East / Wc Fremont

When: May 1, 12:00 AM MST to 8:00 PM MST
Where: Wind River Mtns East / Wc Fremont forecast zone
Reported by: GENERAL PUBLIC
Coordinates: 44.039, -106.585 (the zone’s center; the record gives no point)

Heavy Snow, Lander Foothills / C Fremont

When: May 1, 12:00 AM MST to 8:00 PM MST
Where: Lander Foothills / C Fremont forecast zone
Reported by: GENERAL PUBLIC
Coordinates: 43.002, -109.948 (the zone’s center; the record gives no point)

Heavy Snow, Green Mountains / S Fremont

When: May 1, 12:00 AM MST to 8:00 PM MST
Where: Green Mountains / S Fremont forecast zone
Reported by: GENERAL PUBLIC
Coordinates: 42.904, -109.273 (the zone’s center; the record gives no point)

Heavy Snow, Natrona / Natrona Except X Se

When: May 1, 12:00 AM MST to 8:00 PM MST
Where: Natrona / Natrona Except X Se forecast zone
Reported by: GENERAL PUBLIC
Coordinates: 42.904, -109.273 (the zone’s center; the record gives no point)

Heavy Snow, Upper Green River Basin / C and Se Sublette / E Lincoln / Nw Sweetwater

When: May 1, 12:00 AM MST to 8:00 PM MST
Where: Upper Green River Basin / C and Se Sublette / E Lincoln / Nw Sweetwater forecast zone
Reported by: GENERAL PUBLIC
Coordinates: 42.962, -106.798 (the zone’s center; the record gives no point)

What these are

Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Wyoming in 2002 Every state in 2002 This day in weather history Warnings in Wyoming, May 2002

Sources

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: 5293945, 5293946, 5293947, 5293948, 5293949.