Moderate instability in place across the Idaho Panhandle under large scale southwesterly flow resulted in isolated strong thunderstorms during the early afternoon hours of April 24th. Two particular cells, one in Bonner County and second in Lewis County intensified into strong storms capable of producing severe hail.
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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 OTX wrote it up.
Moderate instability in place across the Idaho Panhandle under large scale southwesterly flow resulted in isolated strong thunderstorms during the early afternoon hours of April 24th. Two particular cells, one in Bonner County and second in Lewis County intensified into strong storms capable of producing severe hail. The public confirmed one inch hail with the northern storm located in Bonner County. The cell over Lewis County was most intense while crossing through rural sections of the county and began weakening upon reaching populated areas, yielding only half inch hail reports.
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 Spokane, WA wrote its last area forecast discussion before the first event at Apr 24, 1:35 PM PST, 1 hour 55 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WA 235 PM PDT Tue Apr 24 2012 .SYNOPSIS... Wednesday will be the last in the recent string of mild weather days, with more afternoon and evenings showers. A wet Pacific front will move through the Inland Northwest on Thursday for much cooler temperatures. Friday will be the coolest day followed by a gradual warming and drying trend over the weekend. && .DISCUSSION... Tonight and Tomorrow...Ridge axis east of the area allowing the southwest to northeast oriented storm track on the west side of the ridge will maintain a favorable orientation to steer showers and thunderstorms through Eastern Washington and Northern Idaho. Most storms will take a track to the northeast at near 30 mph but some that form at edge of a disturbance brushing up against the ridge will spark thunderstorms that move with a more west to east storm motion at the same near 30 mph speed. Gusty wind and small hail look favorable for occurrence given some progged wet bulb zero heights of near 8000 feet MSL this afternoon for KGEG and points to the south. The expectation is much of the convection associated with these passing triggering mechanisms will be out of the area by 7 pm PDT to allow for a brief break. The storm track remains in place overnight and into tomorrow as an approaching large long-wave trof with significant feed of moisture feeding into its eastern edge impinges on the coast Tomorrow. With this in mind pops increase substantially near the Cascades through the day mainly in addressing the approaching moisture plume while locations further east have pop increases and thunderstorms mention to accommodate disturbance migration ahead of it in a similar southwest to northeast motion as which is happening today. Cooling trend into tomorrow remains reasonable given the gradual eastward migration of the ridge as well as the cooling brought about by convection and the cloud cover associated with it. /Pelatti ...Moderate to heavy rain possible Wednesday night through Thursday bringing the potential for continued main stem flooding along with sharp rises within regional creeks and streams... Wednesday night through Friday: Models continue to indicate a very wet pattern setting up Wednesday night through Thursday which raises a lot of concern for most river basins in addition to the potential for sharp rises in small streams and landslides. In general, the deep upper-level low currently taking residence over the Gulf of Alaska will phase with the closed upper-level low off the California Coast and lift through the region taking on a strong negative tilt. Rich subtropical moisture will be pumped into the region ahead of the trough allowing layer precipitable water to surge near 0.90"...roughly 200% of normal. The pcpn will arrive in two waves. The first wave, which carries the highest uncertainty comes through the region Wednesday night associated with shortwave energy ejecting out ahead of the main upper-level trough. Each model picks up on this feature earlier Wednesday afternoon...morphing into a cluster of thunderstorms through Oregon before lifting northward into the Spokane CWA. While the models agree on this feature, they are struggling on where and how intense the pcpn will be upon reaching E WA and N ID and over the last few runs, there has been anywhere from a quarter of an inch to just a few hundredths painted along and/or east of the WA/ID border. Needless to say, confidence is very low through 12z Thursday for the eastern two-thirds of the CWA. Closer to the Cascades and Okanogan Country, we have a bit more confidence in the forecast being closer proximity to the parent incoming trough, stronger diffluent flow aloft, right entrance of a 100kt jet streak, and strengthening easterly flow along the nw periphery of a deepening surface low over the central Basin ...all supporting synoptically driven pcpn. If moderate rains arrive Wednesday night or not associated with the aforementioned convective cluster, moderate to heavy rains will likely develop and spread east into NE WA and N ID on Thursday as the upper-level trough translates inland and ushers a strong cold front into the region. Forcing along the front will be centered under highly diffluent flow aloft, also coupled with additional lift from a departing jet streak and increasing orographic flow as winds trend toward the SW leading to impressive saturated layer omega fields. Additionally, the strong negative tilt to the trough will slow down or possible stall the eastward progression of the front and theta-e tongue from completely clearing out of the region until late Thursday evening. Meanwhile, cooler 500mb temperatures sliding in with the trough coupled with lingering warmth over the far SE...ID Panhandle...and extreme NE WA will add an increasing convective nature to the pcpn. All things considered, models and our forecast call for half to an inch and a half of rainfall from Wednesday night through Friday morning with the heaviest amounts for the NE WA Mountains and Idaho Panhandle. River models indicate continued rises for already swollen basins. The potential for moderate to heavy rains over short periods will also increase the potential for smaller streams and creeks to rise sharply and may lead to landslides. The trough will slide east into western Montana on Friday with drier air and westerly winds dominating the lee of the Cascades while upsloping showers and decreasing afternoon instability keep the chance for showers and perhaps an isolated thunderstorm ongoing for ID and far E WA through the afternoon. Additional pcpn amounts for Friday will be a few hundredths to up to a quarter of an inch under the most persistent bands. The good news is that mid and low levels will cool substantially allowing snow levels to crash between 3000-4000 feet ending the snow melt threat. SB Saturday through Tuesday: The remnants of the wet negative tilt trough slide off to the southeast on Saturday with a broad ridge of high pressure building along the coast. As a result we should still see some showers in the Panhandle and extreme eastern WA but the weather should be dry for the Cascades and Basin. On Sunday the high pressure has moved onshore a dry forecast save for a few mountain showers. This pattern continues into Monday and Tuesday. I have maintained a mention of showers for the Panhandle and extreme eastern Washington. The ridge is rather flat, which on the ECMWF and GEFS allows some short wave energy and moisture to move across the area. Given the general westerly flow the Basin and East Slopes areas should stay dry. Temperatures should be near normal for this time of year. RJ && .AVIATION... 18Z TAFs: storm track set to steer mostly showers, but also some thunderstorms too in a southwest to northeast direction at about 30 miles per hour. Any influence on ceilings and visibilities should be minimal and thus VFR conditions expected to prevail. Additionally some small hail possible down near KPUW down to KLWS today that ends near 03Z Wednesday. Gusty wind near thunderstorms. /Pelatti && .PRELIMINARY POINT TEMPS/POPS... Spokane 47 67 49 57 39 53 / 30 40 80 100 60 40 Coeur d'Alene 46 68 49 58 41 50 / 40 40 80 100 60 60 Pullman 47 68 51 58 38 50 / 40 30 80 90 50 50 Lewiston 50 73 55 62 42 57 / 40 30 80 80 50 50 Colville 46 70 50 62 42 60 / 20 40 90 100 70 50 Sandpoint 44 68 47 59 39 51 / 50 30 80 100 80 70 Kellogg 45 67 47 57 37 46 / 70 40 80 100 80 60 Moses Lake 49 71 53 60 40 62 / 10 40 80 60 20 20 Wenatchee 50 68 52 58 42 60 / 10 30 80 60 20 20 Omak 45 71 50 62 40 62 / 20 40 90 100 30 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SPOKANE WA 247 PM PDT TUE APR 24 2012 IDZ001>004-026-027-WAZ031>038-041>044-252200- NORTHERN PANHANDLE-COEUR D'ALENE AREA-IDAHO PALOUSE- CENTRAL PANHANDLE MOUNTAINS-LEWISTON AREA- LEWIS AND SOUTHERN NEZ PERCE COUNTIES-NORTHEAST BLUE MOUNTAINS- LOWER GARFIELD AND ASOTIN COUNTIES-WASHINGTON PALOUSE- MOSES LAKE AREA-UPPER COLUMBIA BASIN-SPOKANE AREA- NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-WENATCHEE AREA- EAST SLOPES NORTHERN CASCADES-OKANOGAN VALLEY-WATERVILLE PLATEAU- 247 PM PDT TUE APR 24 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO... NORTH CENTRAL IDAHO...CENTRAL WASHINGTON...EAST CENTRAL WASHINGTON...NORTH CENTRAL WASHINGTON...NORTHEAST WASHINGTON AND SOUTHEAST WASHINGTON. .DAY ONE...THIS AFTERNOON AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SPOKANE WA
238 PM PDT TUE APR 24 2012
IDZ001-242230-
BONNER ID-KOOTENAI ID-
238 PM PDT TUE APR 24 2012
THE NATIONAL WEATHER SERVICE IN SPOKANE HAS ISSUED A
SIGNIFICANT WEATHER ADVISORY FOR...
NORTHWESTERN KOOTENAI COUNTY IN THE PANHANDLE OF IDAHO
SOUTHERN BONNER COUNTY IN THE PANHANDLE OF IDAHO
UNTIL 330 PM PDT
AT 233 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR SPIRIT LAKE..MOVING NORTHEAST AT 25 MPH.
HAIL UP TO THE SIZE OF PENNIES IS EXPECTED WITH THIS STORM.
LOCATIONS IMPACTED INCLUDE...
DOVER...
SANDPOINT...
WESTERN PORTIONS OF LAKE PEND OREILLE
THIS STORM MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND
TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS...FOR ADDITIONAL
INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.
LAT...LON 4814 11631 4790 11695 4801 11706 4808 11705
4834 11651
TIME...MOT...LOC 2138Z 237DEG 22KT 4803 11690
FXPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SPOKANE WA
307 PM PDT TUE APR 24 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0238 PM HAIL 5 NW SPIRIT LAKE 48.02N 116.93W
04/24/2012 M0.50 INCH BONNER ID PUBLIC
&&
RMILLERSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SPOKANE WA
353 PM PDT TUE APR 24 2012
IDZ001-242330-
BONNER ID-BOUNDARY ID-
353 PM PDT TUE APR 24 2012
THE NATIONAL WEATHER SERVICE IN SPOKANE HAS ISSUED A
SIGNIFICANT WEATHER ADVISORY FOR...
NORTHERN BOUNDARY COUNTY IN THE PANHANDLE OF IDAHO
EXTREME NORTH CENTRAL BONNER COUNTY IN THE PANHANDLE OF IDAHO
UNTIL 430 PM PDT
AT 343 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 16 MILES NORTHEAST OF NORDMAN...MOVING NORTHEAST
AT 35 MPH.
HAIL UP TO THE SIZE OF PENNIES IS EXPECTED WITH THIS STORM.
LOCATIONS IMPACTED INCLUDE...
COPELAND...PORTHILL...AND EASTPORT
THIS STORM MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND
TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS...FOR ADDITIONAL
INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.
LAT...LON 4900 11604 4891 11604 4875 11674 4897 11687
4901 11666 4901 11605
TIME...MOT...LOC 2252Z 247DEG 30KT 4886 11667
FXPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SPOKANE WA
408 PM PDT TUE APR 24 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0339 PM HAIL CLARK FORK 48.15N 116.18W
04/24/2012 E0.75 INCH BONNER ID PUBLIC
0340 PM HAIL 2 SSE CLARK FORK 48.13N 116.16W
04/24/2012 E0.75 INCH BONNER ID PUBLIC
0343 PM HAIL 3 SE CLARK FORK 48.11N 116.14W
04/24/2012 E1.00 INCH BONNER ID PUBLIC
0343 PM HAIL 4 SE CLARK FORK 48.11N 116.13W
04/24/2012 M1.00 INCH BONNER ID PUBLIC
&&
RMILLERThe Spokane radar (KOTX), 92 km away, was scanning. The volume nearest the first event began at 23:30 UTC.
1 hail. Local standard time, as filed.
Calls made to businesses three to four miles southeast of Clark Fork, Idaho reported hail to size of quarters.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2012Every state in 2012This day in weather historyWarnings in Idaho, April 2012
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: 370204.