A heavy wet snow started on the morning of the 17th and continued into midday on the 18th. Snow amounts ranged from 7 inches at Hemlock Butte to 8 inches at Mountain Meadows and Schwartz Lake.
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 MSO wrote it up.
A heavy wet snow started on the morning of the 17th and continued into midday on the 18th. Snow amounts ranged from 7 inches at Hemlock Butte to 8 inches at Mountain Meadows and Schwartz Lake. Up to two feet fell at Lost Trail Pass near 7000 feet.
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 Missoula, MT wrote its last area forecast discussion before the first event at Apr 17, 2:30 AM MST, 3 hours 30 minutes earlier.
WESTERN MONTANA AND NORTH CENTRAL IDAHO FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
330 AM MDT WED APR 17 2002
.SHORT TERM...INTERESTING PATTERN SETTING UP FOR SOUTHERN HALF OF
CWA. DIGGING UPPER TROUGH MOVING ONTO WEST COAST THIS MORNING...
WITH SURFACE TROUGH/FRONT MOVING INTO SOUTHERN IDAHO. MODELS AGREE
IN DEEPENING SURFACE LOW THROUGH THIS MORNING AS IT PROGRESSES TO
SOUTHEAST IDAHO. MESO ETA PROGS CLOSED LOW TO DEVELOP AT 700 MB BY
12Z...AND A LOW CENTER TO DEVELOP AT 500MB BY 18Z NEAR LEMHI
COUNTY AND SOUTHWEST MONTANA. ON WATER VAPOR...THERE DOES APPEAR TO
BE A WAVE DEVELOPING NEAR THE NEVADA/OREGON BORDER AT 0530Z
SUPPORTING THE ABOVE IDEA. HOWEVER...THE MESO ETA...ALONG WITH THE
OTHER SHORT TERM MODELS...IS SOMEWHAT FAST IN EXTENDING QPF INTO
LEMHI COUNTY. NEVERTHELESS...THIS LOOKS TO BE A HEAVY SNOW EVENT
AS THE SURFACE THROUGH 500MB LOW HANGS AROUND SOUTHWEST
MONTANA/LEMHI COUNTY THROUGH THIS EVENING...THEN ARE EXPECTED TO
BE PULLED BACK TO THE WEST BY THE STRENGTHENING MAIN UPPER LOW.
THIS WOULD MAINTAIN MODERATE TO HEAVY SNOW AT TIMES OVER THE
SOUTHERN ZONES WELL INTO THURSDAY MORNING. THEREFORE...WILL
UPGRADE THE WINTER STORM WATCH TO A HEAVY SNOW WARNING TODAY THROUGH
EARLY THURSDAY. NEW RUNS ALSO SUGGEST MORE QPF OVER IDAHO ZONE 6...
AND WILL INCLUDE THAT AREA IN THE WARNING RATHER THAN THE
ADVISORY. THE HIGHER ELEVATIONS OF IDAHO ZONES 7 AND 8...AS WELL AS
ZONE 5...SHOULD BE ON THE FRINGE OF THE BEST SNOWFALL. WILL THUS
MAINTAIN ADVISORY FOR 7 AND 8...AND ADD IDAHO ZONE 5 TO THE
ADVISORY.
MODELS PREDICT INITIAL SNOW LEVELS TO BE AROUND 5K FEET OVER LEMHI
COUNTY TO NEAR 4K FEET OVER THE CLEARWATER AND CENTRAL BITTERROOT
MOUNTAINS...THEN RISE ONLY SLIGHTLY DURING THE DAY.
WHILE THE PRECIPITATION FOCUS WILL BE OVER THE SOUTH THROUGH THIS
EVENT...THE AIR MASS DOES BECOME FAIRLY UNSTABLE OVER THE NORTH BY
THIS AFTERNOON. WILL THEREFORE MAINTAIN SCATTERED RAIN/SNOW
SHOWERS...ALONG WITH ISOLATED THUNDERSTORMS...FROM ROUGHLY MISSOULA
NORTH. ALSO EXPECT BREEZY WINDS TO DEVELOP TODAY AS THE SURFACE AND
MID LEVELS LOWS STRENGTHEN.
DRIER AIR BEGINS TO INTRUDE LATE THURSDAY AS THE UPPER FLOW BECOMES
NORTHERLY. THIS TREND CONTINUES THROUGH FRIDAY...WITH SLOWLY
DIMINISHING SHOWER ACTIVITY.
.LONG TERM...NO CHANGES TO PREVIOUS FORECAST. POSITIVE-TILT RIDGE
STILL PROVIDING DRY AND WARMER WEATHER SATURDAY. BUT PROGRESSIVE
NORTHWEST FLOW WILL BRING IN A SERIES OF DISTURBANCES SUNDAY
THROUGH TUESDAY. THE STRONGEST DISTURBANCE IS CURRENTLY SCHEDULED
FOR MONDAY...AND WILL LIKELY BRING MORE UNSEASONABLY COOL AIR INTO
THE REGION. WHITMORE
.MSO...WINTER WEATHER ADVISORY IDZ005-007-008 TODAY THROUGH EARLY
THURSDAY ABOVE 3500 FEET.
...WINTER STORM WARNING FOR MTZ006-007-IDZ006-009-010 TODAY
THROUGH MIDDAY THURSDAY ABOVE 4500 FEET.
...7-DAY SPOT TEMPS AND POPS...
LIB CEE /049 035/049 028/053 3443222
BEEE 034/059 034/058 031/052 030/052 032/ 34002433333
FCA WEE /047 032/047 027/050 3444222
BEEE 032/057 034/058 032/050 030/050 032/ 34002433333
POL WEE /048 035/048 030/052 3455222
BEEE 035/059 038/060 033/053 031/053 033/ 34001433333
MSO WCE /045 032/047 027/050 3466322
BEEE 033/061 035/060 032/052 030/052 032/ 34001333333
HMM OOE /043 030/045 029/051 3488522
BEEE 035/062 038/062 035/054 033/054 035/ 34000233333
BTM SJE /040 026/040 020/042 3488622
BEEE 024/055 029/056 026/048 024/048 026/ 34100233333
ORO WCE /050 039/052 036/057 3486322
BEEE 040/064 043/065 042/057 040/057 042/ 34001333333
GRV OWE /045 035/045 030/051 3486522
BEEE 037/061 039/062 038/054 036/054 038/ 34001344333
SMN SJE /043 029/043 024/046 3499751
BEEE 032/058 034/059 030/052 028/052 030/ 34100133333The 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 Idaho in 2002Every state in 2002This day in weather historyWarnings in Idaho, April 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: 5289921, 5289922, 5289923.