A line of instability stretching over Lower Idaho Panhandle generated thunderstorms and heavy rain during the afternoon of September 11 2024. The storms caused a debris flow near the Gwen Fire burn scar and generated a funnel cloud over Mann Lake near Lapwai.
Every event with a place to put it. 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 OTX wrote it up.
A line of instability stretching over Lower Idaho Panhandle generated thunderstorms and heavy rain during the afternoon of September 11 2024. The storms caused a debris flow near the Gwen Fire burn scar and generated a funnel cloud over Mann Lake near Lapwai.
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 Sep 11, 3:45 AM PST, 6 hours 15 minutes earlier.
Area Forecast Discussion National Weather Service Spokane WA 445 AM PDT Wed Sep 11 2024 .SYNOPSIS... A fall-like weather pattern arrives today with cooler temperatures and chances for showers and a few thunderstorms. Steady rains continue to fall over Idaho overnight and Thursday while Central Washington dries out with breezy northwest winds. Temperatures will cool into the 60s and 70s. Showers return to the northern mountains over the weekend, otherwise dry conditions are expected Friday into the weekend for most communities in the Inland Northwest with temperatures warming into the 70s. && .DISCUSSION... Today through Thursday: A pattern change is underway as a robust upper-level low swings into the Northwest. Fairly well modeled precipitation has developed this morning in two areas. Bands of showers with embedded thunderstorms are developing along the leading midlevel front from NE Oregon to the Central Panhandle Mountains of Idaho. Precipitation rates have been on the order of 0.01-0.05" per hour and we have observed scattered lightning strikes. NAM has picked up this ribbon of elevated instability well and indicates it is at its peak and will diffuse around 12z (5AM) with 700-500mb CAPE decreasing from 300 J/kg toward 100 J/kg. This should result in decreasing lightning but continued light rain. The other area of showers this morning is across the Cascades and into areas of Central WA from Wenatchee to Republic. We have not observed any lightning with this activity and precipitation rates will remain light and generally T-0.02" with any passing showers. As we head into today, the low will continue to swing inland across N Oregon-southern WA. A band of showers will continue to fall over North Idaho and buckle back to the west some with some showers expanding across the border into E WA. Highest rain amounts will stretch from the Camas Prairie to the Central Panhandle Mountains which carries a 70-80% chance for a quarter of an inch or more. Amounts outside the persistent band of showers will be less than a tenth. In Central WA, cooling temperatures aloft will promote afternoon instability and hit or miss showers and thunderstorms. Sun breaks will be key to the amount of instability and intensity of showers/storms. If surface heating is adequate, a few cells could be stronger with heavy downpours and potential for a quick 0.25" or more. These will be slow moving cells and need to be monitored for impacts near sensitive burn scars. Confidence is not high enough at this time to warrant any flood watches but something we will be monitoring closely. Temperatures today will feel more like September with readings in the 60s to 70s. Winds will remain breezy from the southwest with speeds of 8 to 15 mph. The focus for rain moving into tonight and Thursday will shift into the Idaho Panhandle and Western Montana with some chances expanding into the eastern third of WA as the upper low continues its trek through Central Idaho and into southwestern Montana. Rain wrapping around the northern periphery of the low within a trowal region will be capable of moderate rainfall amounts. There remains modest uncertainty how far east the heavier rainfall will reach. Does it remain in Western MT and Clearwater/Idaho Counties or can it expand east into Shoshone, Kootenai, Bonner, Boundary counties? The latest deterministic runs from the NAM/GFS are supporting the later with some areas receiving around half an inch or more. While the ECMWF supports rain in these areas, amounts are nearly half that. The latest ensembles have trend toward the wetter direction as well with rainfall amounts increasing again for locations like Kellogg, Coeur D Alene, Sandpoint, and Bonners Ferry during this period. The NAM which supports the moderate rains reaching into N Idaho has also shown superior initialization of the upper-low off the WA Coast at 06z tonight. There will be a sharp gradient from east to west into WA where the rain falls and dry conditions exist. Given differences in the models, NBM is still carrying 20-40% chances for rain across the border in extreme E WA but this comes with moderate uncertainty yet hard to ignore the increase in probabilities. As for amounts for WED NIGHT and THU, the latest NBM probabilities are as follows: Probability for 0.10 or more" Bonners Ferry - 70% Sandpoint - 70% Coeur D Alene - 60% Kellogg - 80% St Maries - 70% Deary - 70% Lewiston - 50% Winchester - 80% Ione-Spokane-Pullman - 40% Probability for 0.25 or more" Bonners Ferry - 60% Sandpoint - 60% Coeur D Alene - 40% Kellogg - 65% St Maries - 50% Deary - 50% Lewiston - 35% Winchester - 70% Ione-Spokane-Pullman - 20% Probability for 0.50 or more" Bonners Ferry - 30% Sandpoint - 40% Coeur D Alene - 15% Kellogg - 50% St Maries - 30% Deary - 30% Lewiston - 10% Winchester - 40% Ione-Spokane-Pullman - 10% Central WA will experience dry conditions with breezy to gusty northwest winds drawn into the low. Sustained speeds of 10-20 mph will be common with gusts up to 30 mph. Ample sunshine in Central WA will allow for a few communities to reach the upper 70s. Otherwise, temperatures across the region will range from the lower 70s to 60s in North Idaho. Communities along the Montana border may struggle to hit 60F where persistent rains exist. Friday through Tuesday: Shortwave ridging returns on Friday as one system exits and the next one approaches. By Saturday, the region will become under the influence of southerly flow aloft as the next trof begins to swing onto the coast. The incoming system looks to undergo a good deal of meridional stretching which does not bode well for appreciable precipitation for the Inland NW. Showers are introduced into the forecast across the northern mountains Saturday and Sunday then split toward the Idaho Panhandle and Cascades Monday and Tuesday. This is less coverage for central and eastern WA than 24 hours ago. Temperatures warm back into the 70s (with a few low 80s) Friday through Sunday then cool back into the 60s for Monday and Tuesday. Winds will be breezy at times, especially Sunday into early next week as the air mass cools again. /sb && .AVIATION... 12Z TAFS: Cooler and unsettled weather pattern today as upper- level trof swings into the Northwest. Persistent showers to continue through the day from Lewiston to St Maries to Bonners Ferry with minor wavering of the north-south band east to west at times. Local MVFR vis have been observed under heavier showers. A few lightning strikes will be possible in the afternoon along this band. Less organized hit- miss showers possible for the remainder of Eastern WA to the Cascades. A few cells in the afternoon could mature into thunderstorms with heavier downpours and local MVFR cigs/vis. Highest probability will be in the Cascades from Plain to Winthrop though this comes with low confidence. Some gustiness to 20 mph possible near any showers. Aft 00z, showers end for Central WA but continue for North Idaho with an increasing potential for MVFR conditions as the atmosphere continues to saturate. Highest probabilities for lengthy MVFR conditions will be from Winchester to Mullan. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Erratic wind gusts 20-28 mph possible near showers through 00z as our antecedent dry air mass saturates. The exact placement of the band of persistent showers over N Idaho could pivot east to west at times and confidence is low for the coverage of showers forming immediately west of the band into far E WA from Ione to Spokane to Pullman. Confidence is also low for lightning coverage this afternoon with amount dependent on surface heating. Lastly, as the main precip threat shifts toward the ID/MT border Thursday morning, there are differences exactly where this setups and produces steady light to moderate rainfall. This is likely to create MVFR or lower conditions for some areas. Best guess by 12z is along a line from Winchester to Mullan but looks for this to pivot west into additional areas of N Idaho 12-18Z Thu. /sb && .PRELIMINARY POINT TEMPS/POPS... Spokane 71 52 73 50 74 50 / 60 30 20 20 0 0 Coeur d'Alene 68 51 68 49 71 49 / 80 60 60 40 10 0 Pullman 66 50 65 47 70 45 / 80 60 50 20 0 0 Lewiston 73 56 73 54 78 54 / 80 60 60 20 0 0 Colville 71 50 73 43 76 40 / 50 30 20 20 10 0 Sandpoint 65 51 65 47 69 46 / 70 60 80 60 40 0 Kellogg 63 50 59 50 67 51 / 90 80 90 60 40 0 Moses Lake 74 52 76 48 77 48 / 30 10 0 0 0 0 Wenatchee 71 52 74 52 77 55 / 40 20 0 0 0 0 Omak 73 51 79 50 80 53 / 60 20 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. &&
The Spokane radar (KOTX), 150 km away, was scanning. The volume nearest the first event began at 17:57 UTC.
1 debris flow, 1 funnel cloud. Local standard time, as filed.
Public report via social media stated rocks on Highway 12 within the Gwen Fire burn scar. This was confirmed by dispatch. Rocks were cleared and highway remained open. Nearby gauges reported 0.40 of an inch to 0.80 of an inch of rain over the last 18 hours.
Public reported to local media an EF0 funnel cloud near Mann Lake at 1613 PDT. No damage reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2024Every state in 2024This day in weather historyWarnings in Idaho, September 2024
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: 1217194, 1217193.