Post frontal thunderstorms developed across the Northeast Blue Mountains during the late afternoon hours. Just enough sunshine in the afternoon destabilized the atmosphere to create surface based convective available potential energy of 500 to 1,000 J/KG.
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The episode as NWS OTX wrote it up.
Post frontal thunderstorms developed across the Northeast Blue Mountains during the late afternoon hours. Just enough sunshine in the afternoon destabilized the atmosphere to create surface based convective available potential energy of 500 to 1,000 J/KG. This was just enough energy in a marginally sheared environment for a supercell thunderstorm that produced severe hail.
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 3, 3:27 PM PST, 33 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WA 427 PM PDT Tue Sep 3 2013 .SYNOPSIS... Showers and thunderstorms will persist over the Inland Northwest today and Wednesday. Some storms could be severe. A large area of low pressure will move over the region for the end of the week, leading to the potential for widespread heavy rain on Thursday and continuing through Saturday. A drying and warming trend is expected by the beginning of next week && .DISCUSSION... Tonight into tomorrow morning: The first part of the this period will see a decreasing chance for showers and thunderstorms as we lose our afternoon heating. By the late overnight or early morning hours tomorrow, we will see an increasing chance for some elevated convection. The next shortwave trough pivoting around the upper level low pressure system in the eastern Pacific will eject more mid level moisture into the region. This will result in steepening mid level lapse rates and create an environment conducive for some elevated showers and thunderstorms. Models are in general agreement that the best axis of instability up through the Columbia Basin. Any forcing for these showers will be closer to the Cascade Mtns. The best combination of dynamics and instability will lie somewhere between the Cascade Mtns and the Upper Columbia Basin. Both of these factors do not look all that impressive, so we are generally going with the potential for isolated thunderstorms developing from northern OR and extending up to the Canadian border with time from late tonight through tomorrow morning. /SVH ...Strong thunderstorms possible Wednesday night. Heavy rain likely Thursday... Wednesday afternoon through Thursday night: Upper low offshore continues to bring in warm moist air to the region on Wednesday. Temperatures should be a little warmer on Wednesday than today, around 80 for many locations. This will result in better instability. However, even with that we will still be battling some mid-level clouds to reach our true convective potential. So for now it looks like Wednesday afternoon will see thunderstorms mainly over the mountains. Wednesday night is considerably different. The upper low finally starts to push onshore, with a negative tilt orientation. This coupled with the destabilization on Wednesday afternoon will lead to a potentially significant thunderstorm event. Storms would fire off over north-central Oregon late in the afternoon and then propagate directly northward as they intensify. There are some similarities to the to event ten days ago on Sunday evening 25 August. The 4km NAM has been insisting on this for the past 6 runs and the larger scale models (12km NAM, ECMWF, GFS) have also been suggesting this scenario. We will be watching this closely. Thursday the low moves onshore for a very wet day. The exact details of how this unfolds are difficult to determine. At this point, it appears that if the Wednesday night event occurs, then there could be a 6 to 12 hour break in the action. The atmosphere will once again destabilize, this time from aloft as the colder temperatures with the low move in. Then we could see another widespread round of showers/thunderstorms Thursday late-afternoon or evening. Instability and shear forecasts from the models certainly suggest the potential for severe storms. SPC has a slight risk out for our area. Along with this will be the potential for heavy rain and flash flooding. Precipitable water values will be near record values for the month of September. Too early to issue a watch but expect to do so tonight or Wednesday. RJ Friday through Tuesday: The upper level low will take its tour across the Inland Northwest by Friday as the low center slips east of the Cascades. Most of the medium range models are showing agreement of the slow progression of the low, and the wrap around moisture that forms near and to the north of its center. A good soaking of rain is likely across the Cascades and north central Washington. Near the cold core center, instability will be the greatest and wouldn't rule out isolated thunderstorms. Considerable cloudiness can be expected and this coupled with the circulation over the region and the amount of precipitation, temperatures will be rather cool, making it feel quite fall-like on Friday with high temperatures in the 60s. The low center will slowly wobble across eastern Washington on Saturday, and exit north Idaho on Sunday. Precipitation looks to be more showery while temperatures slowly recover to more seasonal levels. When this feature finally kicks to the east seems to be slower and slower each model run so would lean toward showery conditions through Sunday for eastern Washington, and into Monday for North Idaho as depicted by ECMWF. After the low's departure, high pressure will return to the region and with a drier westerly flow aloft. Expect warming temperatures and drier weather for the upcoming week. /rfox. && .AVIATION... 00Z TAFS: Moist and unstable southerly flow continues over the region and will continue through the next 24 hours. Any disturbances transiting the area will be enough to trigger scattered showers and at least isolated thunderstorms. This evening a weak disturbance will allow a thunderstorm threat mainly at the KLWS and KPUW TAF sites until 02Z-03Z...with isolated thunderstorms possible on the mountains ringing the Columbia Basin. Overnight tonight a generally quiet period is expected with no significant weather...but models hint at a weak disturbance moving up the Cascades between 12Z and 18Z Wednesday which may trigger showers and isolated thunderstorms near the KEAT TAF site. During the afternoon hours surface based instability will once again create a chance of thunderstorms over the mountains around the basin...and another threat of storms approaching the KLWS and KPUW TAF sites. /MJF && .PRELIMINARY POINT TEMPS/POPS... Spokane 63 88 64 75 55 63 / 10 50 70 90 80 50 Coeur d'Alene 60 87 61 76 55 64 / 20 50 60 90 90 50 Pullman 57 88 62 75 54 65 / 20 40 60 90 60 30 Lewiston 66 93 68 80 60 72 / 30 40 60 90 70 30 Colville 56 91 59 77 57 65 / 30 50 60 100 100 70 Sandpoint 53 86 59 78 55 64 / 20 50 60 100 90 60 Kellogg 59 85 59 77 53 64 / 40 50 50 100 90 50 Moses Lake 60 89 65 77 57 68 / 20 30 80 90 80 30 Wenatchee 64 85 65 71 58 67 / 20 30 80 90 90 50 Omak 59 87 63 73 58 66 / 20 40 70 100 100 80 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...&&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SPOKANE WA 230 PM PDT TUE SEP 3 2013 WAZ041-042-042130- WENATCHEE AREA-EAST SLOPES NORTHERN CASCADES- 230 PM PDT TUE SEP 3 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL WASHINGTON. .DAY ONE...THIS AFTERNOON AND TONIGHT THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY ALONG THE EAST SLOPES OF THE CASCADES AND WENATCHEE AREA. THESE STORMS MAY PRODUCE LOCALLY HEAVY RAIN ESPECIALLY IF STORMS DEVELOP AND MOVE OVER THE SAME LOCATIONS. WHILE THE RISK FOR FLASH FLOODING IS NOT HIGH TODAY...LOCALIZED DEBRIS FLOWS ARE POSSIBLE IN BURN SCAR AREAS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY THERE WILL BE THE POTENTIAL FOR THUNDERSTORMS OVER THE WASHINGTON CASCADES AGAIN ON WEDNESDAY AND THURSDAY. LOCALLY HEAVY RAIN IS POSSIBLE ON WEDNESDAY WHERE THUNDERSTORMS DEVELOP...WITH MORE SIGNIFICANT RAIN EXPECTED THURSDAY INTO FRIDAY. SOME LOCATIONS COULD PICK UP BETWEEN 1 TO 2 INCHES OF RAIN. FORECASTS ARE SUBJECT TO CHANGE...BUT RESIDENTS LIVING NEAR THE BURN SCARS AROUND WENATCHEE AND CHELAN SHOULD MONITOR THE WEATHER. IN ADDITION TO A HEAVY RAIN POTENTIAL...SOME STRONGER THUNDERSTORMS CONTAINING GUSTY WINDS....HAIL AND OF COURSE DANGEROUS LIGHTNING WILL BE POSSIBLE. IDZ001>004-026-027-WAZ031>038-043-044-042130- 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-OKANOGAN VALLEY- WATERVILLE PLATEAU- 230 PM PDT TUE SEP 3 2013 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 THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER THE REGION TODAY. A FEW STORMS COULD BE SEVERE...WITH THE BEST POTENTIAL OVER THE NORTHERN MOUNTAINS...CENTRAL PANHANDLE MOUNTAINS...AND CAMAS PRAIRIE. HEAVY RAIN COULD RESULT IN URBAN FLOODING IF A STORM MOVES OVER YOUR CITY. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY SCATTERED THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS WEDNESDAY AFTERNOON. STRONGER AND MORE WIDESPREAD THUNDERSTORMS ARE EXPECTED WEDNESDAY NIGHT...WITH ANOTHER ROUND OF STORMS LIKELY ON THURSDAY. HEAVY RAIN COULD RESULT IN URBAN FLOODING WHERE THUNDERSTORMS MOVE OVER CITIES. IN ADDITION STRONG WINDS AND LARGE HAIL WILL BE POSSIBLE WITH THESE STORMS. FORECASTS ARE SUBJECT TO CHANGE...SO RESIDENTS SHOULD MONITOR THE WEATHER OVER THIS WEEK.
The Pendleton radar (KPDT), 111 km away, was scanning. The volume nearest the first event began at 00:00 UTC.
2 hail. Local standard time, as filed.
Hail was mostly half an inch in diameter, but there were some hail stones up to 1.5 inches in diameter. Time of the event was estimated by radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2013Every state in 2013This day in weather historyWarnings in Washington, September 2013
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: 474812, 474813.