During the morning of April 7th a strong cold front swept across the Idaho Panhandle. In addition to gradient winds which in general gusted to 30 to 40 mph across the Idaho panhandle, a squall line along the southern part of the front contributed rain cooled downdrafts accelerating winds to locally over 60 mph in Nez Perce County.
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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.
During the morning of April 7th a strong cold front swept across the Idaho Panhandle. In addition to gradient winds which in general gusted to 30 to 40 mph across the Idaho panhandle, a squall line along the southern part of the front contributed rain cooled downdrafts accelerating winds to locally over 60 mph in Nez Perce County. These winds triggered scattered power outages in the area.
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 7, 4:25 AM PST, 5 hours 35 minutes earlier.
Area Forecast Discussion National Weather Service Spokane WA 525 AM PDT Sat Apr 7 2018 .SYNOPSIS... Rain will be widespread this morning followed by the potential for widely scattered showers and thunderstorms this afternoon. Gusty southwest winds are expected this afternoon and again on Sunday across the Palouse, West Plains, and Columbia Basin. Mild and dry weather is expected Monday before a series of frontal systems bring periods of showers and breezy winds back to the region Tuesday through Friday. && .DISCUSSION... ...HEAVY RAIN IN THE MORNING TODAY FOLLOWED BY WINDY CONDITIONS AND A CHANCE FOR THUNDERSTORMS IN THE AFTERNOON... Today: A strong frontal system will sweep across the Inland Northwest today. The surface front is just off the coast at 2 AM this morning with rain moving in across coastal areas of California up to Washington. The front will sweep through east of the Cascades quickly through the morning hours. The Atmospheric River directed into the sate of California is unusually moist. We will only see a fraction of this moisture make its way up into the Inland Northwest, but it will be enough for a 3 to 5 hour period of moderate to heavy rainfall with frontal passage. Lapse rates above the 600 mb level also become very steep along the front indicating unstable conditions at upper levels. Isolated cells may produce some lightning within the stratiform precipitation shield this morning. I do not expect much lightning though and elected not to include thunderstorms in the forecast because of how sporadic it is expected to be. Thunderstorms will be more likely directly behind the front for the afternoon. We should see some sun breaks just behind the surface front that will quickly destabilize lower levels of the atmosphere before the upper level wave swings through. The dynamics aloft as it swings through will be strong with the NAM model indicating the potential for 300 to 600 J/kg of surface based CAPE within the area from the Waterville Plateau to the Northeast Mtns to the Central Panhandle Mtns to the Camas Prairie and Northeast Blue Mtns. This pretty much includes all of the basin, Spokane-Coeur d'Alene corridor, Palouse and L-C Valley. Any thunderstorms that develop will be moving quite quickly in the neighborhood of around 45 mph. It won't take much more additional momentum aloft added with the general motion of these storms to produce damaging wind gusts. There will be the potential for broken tree limbs or toppled trees, power line damage and/or roof damage, especially if storms organize into a squall, which is definitely a possibility. Other impacts with this system will be for quick rises on small streams and our flashier rivers (e.g. Palouse River). We will need to keep a close eye Paradise Creek as it will likely rise quickly with the heavy rains this morning. Flooding is not expected at this time though; although, ponding of water on roads will be likely and hydroplaning will be a concern. Other than the concern for strong winds from thunderstorms, general winds this afternoon are expected to remain under advisory criteria, but will be windy with widespread gusts up around 40 mph across the basin, Spokane West Plains and on the Palouse. Tonight through Sunday night: Showers and thunderstorms will dissipate through the evening. Winds will also be decreasing into the overnight hours, but will pick up again for the afternoon on Sunday. Another shortwave disturbance will reinvigorate showers across the eastern half of the forecast area. Colder temperatures will result in lower snow levels with snow above 4000 feet in the mountains through Sunday morning. Not nearly as much precip though as much of the moisture with the Atmospheric River will be pushed off to the east. Showers will dwindle further heading into the afternoon on Sunday with dry conditions in the lee of the Cascades. Small streams and rivers will likely be cresting late Sunday with water flows through our watersheds on the decrease by early next week. /SVH Monday: The models continue to forecast a transient high pressure ridge on Mon. At this time, it looks like our best chance for a dry day for Washington and Idaho will be on Monday. With the exception of a few light morning showers over the Panhandle mountains, the remainder of the Inland Northwest will have a chance to dry out. Most of the region will enjoy relatively light winds and high temperatures in the mid 50s to low 60s which will be right about average for early April. Tuesday: Tue has the potential to be our warmest day of the week with much of our region reaching the 60s. The timing of an incoming cold front will determine if we can achieve these mild high temps. The evening runs of the GFS and ECMWF have a similar arrival time of the front...during the afternoon. The operational GFS carries a stronger upper trough and subsequently produces more precipitation and a stronger frontal passage. The ECMWF, Canadian, and GFS Ensemble Mean are in decent agreement with scattered afternoon showers and gusty winds developing late in the day with the frontal passage. Our forecast resembles the ECMWF and GFS Ensemble Mean. Wednesday through Friday: The Polar Jet will likely carve into southern California over the second half of the week. As the storm track dives well south of our region, a shearing frontal system is expected to reach central/eastern Washington Wed afternoon or evening and linger over the Idaho Panhandle into Thursday. Fortunately, with the strongest jet energy digging into the Desert Southwest, precipitation amounts over the second half of the week should be relatively light compared to what we will get today into Sunday. Our temperatures and snow levels will also fall over the second half of the week slowing snowmelt runoff. Hopefully, the lighter precip amounts and decreased runoff will provide our rivers and streams an opportunity to recede after rises early in the week. /GKoch && .AVIATION... 12Z TAFS: ...STRONG FRONTAL PASSAGE WITH LOW LEVEL WIND SHEAR LATE MORNING THEN WINDY WITH CHANCE OF THUNDERSTORMS IN THE AFTERNOON... Cold front is moving into coastal WA at 5 AM this morning. Moderate to heavy rain will be possible along the front impacting KEAT to KMWH btwn 14-17Z then Spokane, Coeur d'Alene, Pullman and Lewiston btwn 16-20Z. Northeast winds to shift southwest with frontal passage late morning to around noon across the basin to Spokane/Coeur d'Alene corridor and Palouse. Low level wind shear expected for a few hours before frontal passage with winds veering with height from northeast to southwest with 35-40 kts at 2 kft agl. Thunderstorms are expected to form behind cold front after 20Z east of a line from KEAT to KOMK. Low confidence in thunderstorms organizing to form squalls with wind gusts up to around 50 kts possible. Best potential for thunderstorms will be between 22-02Z at KGEG, KSFF, KCOE, KPUW and KLWS. /SVH && .PRELIMINARY POINT TEMPS/POPS... Spokane 53 40 53 36 56 38 / 100 60 60 20 0 0 Coeur d'Alene 50 39 49 36 53 37 / 100 80 80 30 10 0 Pullman 53 41 49 37 57 40 / 100 80 80 30 0 0 Lewiston 60 46 57 40 64 43 / 100 60 60 20 0 0 Colville 51 38 56 34 58 35 / 100 50 40 10 0 0 Sandpoint 45 36 47 36 51 34 / 100 80 80 30 20 0 Kellogg 47 35 43 35 50 33 / 100 90 90 60 10 0 Moses Lake 61 45 62 37 62 39 / 100 20 30 10 0 0 Wenatchee 59 41 59 40 61 41 / 100 30 20 10 0 0 Omak 57 41 62 37 61 40 / 100 40 30 10 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. &&
Hazardous Weather Outlook National Weather Service Spokane WA 550 AM PDT Sat Apr 7 2018 IDZ002-003-026-027-WAZ031>036-081300- Coeur d'Alene Area-Idaho Palouse-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- 550 AM PDT Sat Apr 7 2018 This Hazardous Weather Outlook is for portions of North Idaho... North Central Idaho...East Central Washington...Northeast Washington and Southeast Washington. .DAY ONE...TODAY AND TONIGHT Isolated to scattered thunderstorms this afternoon, with the potential for locally heavy downpours and small hail and gusty winds. In addition windy conditions are expected on Saturday with gust potential up to 50 mph in the afternoon. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Wet conditions over the weekend will lead to saturated ground conditions with flooding concerns on small streams and in low spots. The risk of mudslides and debris flows on steep terrain will also increase. IDZ001-004-WAZ037-038-041>044-081300- Northern Panhandle-Central Panhandle Mountains- Northeast Mountains-Okanogan Highlands-Wenatchee Area- East Slopes Northern Cascades-Okanogan Valley-Waterville Plateau- 550 AM PDT Sat Apr 7 2018 This Hazardous Weather Outlook is for portions of North Idaho... Central Washington...North Central Washington and Northeast Washington. .DAY ONE...TODAY AND TONIGHT Isolated to scattered thunderstorms this afternoon, with the potential for locally heavy downpours and small hail and gusty winds. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Wet conditions over the weekend will lead to saturated ground conditions with flooding concerns on small streams and in low spots. The risk of mudslides and debris flows on steep terrain will also increase.
The national radar mosaic for the moment the first event began.
2 high wind. Local standard time, as filed.
The Lewiston Airport ASOS station reported a peak wind gust of 61 mph.
The Shirrod Hill Idaho Transportation Dept. wind sensor recorded a peak gust of 58 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2018Every state in 2018This day in weather historyWarnings in Idaho, April 2018
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: 750625, 750631.