Overview
A line of thunderstorm swept through eastern North Dakota and into northwest and west-central Minnesota on July 17th. A tornado was reported as well as damaging winds and baseball size hail. See the tabs below for more information.
Tornadoes:
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Tornado - Churchs Ferry
Track Map (click to enlarge)  
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The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:
| EF0 Weak 65-85 mph |
EF1 Moderate 86-110 mph |
EF2 Significant 111-135 mph |
EF3 Severe 136-165 mph |
EF4 Extreme 166-200 mph |
EF5 Catastrophic 200+ mph |
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Wind & Hail:
Several thunderstorms developed on the afternoon of July 17, producing large hail and damaging winds in portions of central and eastern North Dakota. The thunderstorms eventually formed a large complex that moved into the Red River Valley and western Minnesota, producing mostly wind damage.
In the map below, green Hs represent hail reports of 1" in diameter or greater. Blue Ws represent wind reports of 58 mph (50 knots) or higher.
Photos
Photos from around the region (click to enlarge)
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| Rolled Football Bleachers at Argyle, MN (Derek Knutson) |
Damaged Grain Elevator in Argyle, MN (Derek Knutson) |
Shelf Cloud near Mentor, MN (Brandie Trandem) |
Tree Down in East Grand Forks, MN (Michelle Bedard) |
Radar
Radar Loops
Storm Reports
PRELIMINARY LOCAL STORM REPORT...SUMMARY NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND 510 PM CDT SAT JUL 18 2020 ..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON... ..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE.... ..REMARKS.. 0240 PM TSTM WND DMG 1 NE WALES 48.90N 98.59W 07/17/2020 Cavalier ND PUBLIC SEVERAL LARGE 3-5 INCH DIAMETER BRANCHES BROKEN DOWN IN SHELTER BELTS. 0255 PM HAIL 4 N CANDO 48.55N 99.20W 07/17/2020 E1.00 INCH Towner ND PUBLIC 0259 PM TSTM WND GST 5 WSW CHURCHS FERRY 48.24N 99.29W 07/17/2020 M55.00 MPH Benson ND MESONET PEAK WIND MEASURED AT AN NDAWN STATION. 0259 PM TORNADO 3 WNW CHURCHS FERRY 48.29N 99.25W 07/17/2020 F0 Benson ND STORM CHASER A BRIEF TOUCHDOWN WAS NOTED IN AN OPENED FIELD JUST NORTH OF HIGHWAY 2, WITH THE TORNADO ENDED BY 3PM CDT. PEAK WINDS ESTIMATED TO 70 MPH. MAXIMUM WIDTH TO 30 YARDS. TRACK LENGTH WAS TO THE EAST FOR LESS THAN ONE QUARTER MILE. THIS WAS A TORNADO WRAPPED IN HEAVY RAIN AND DOWNBURST WIND, ON THE LEADING EDGE OF A SQUALL LINE. 0300 PM TSTM WND DMG 3 ENE VANG 48.92N 98.06W 07/17/2020 Cavalier ND PUBLIC SEVERAL LARGE TREE BRANCHES AND LIMBS BROKEN DOWN NEAR FROST FIRE RESORT. 0335 PM TSTM WND DMG 3 W ESMOND 48.03N 99.83W 07/17/2020 Benson ND TRAINED SPOTTER SEVERAL 12 INCH DIAMETER OR LARGER TREE BRANCHES AND LIMBS BROKEN DOWN IN SHELTER BELT. ALSO DIME TO NICKEL SIZED HAIL. 0339 PM TSTM WND GST 5 WSW CHURCHS FERRY 48.24N 99.29W 07/17/2020 M77.00 MPH Benson ND MESONET PEAK WINDS MEASURED AT AN NDAWN STATION AT 10 METERS. A NEARBY NORTH TO SOUTH RUNNING IRRIGATION SYSTEM WAS FLIPPED TO THE EAST. 0342 PM FUNNEL CLOUD 4 WNW CHURCHS FERRY 48.29N 99.27W 07/17/2020 Benson ND BROADCAST MEDIA BRIEF FUNNEL NOTED UNDER PERSISTENT WALL CLOUD, VIA WEBCAM. 0346 PM TSTM WND GST 3 W CHURCHS FERRY 48.27N 99.26W 07/17/2020 E101 MPH Benson ND MESONET PEAK WIND MEASURED AT AN RWIS STATION ALONG HIGHWAY 2. 0347 PM TORNADO 3 W CHURCHS FERRY 48.27N 99.26W 07/17/2020 F0 Benson ND NWS STORM SURVEY A BRIEF TORNADO TOUCHED DOWN NEAR HIGHWAY 2 AND LIFTED BY 3 48 PM CDT. TREES WERE SNAPPED IN A SHELTER BELT AND A NEARBY RWIS STATION REPORTED A PEAK WIND TO 101 MPH. THE TORNADO WAS LIKELY WRAPPED IN HEAVY RAIN AND DOWNBURST WINDS. PEAK WINDS ESTIMATED TO 105 MPH. MAXIMUM WIDTH TO 40 YARDS. TRACK LENGTH OF ONE QUARTER MILE. 0352 PM TSTM WND GST 5 N ADAMS 48.49N 98.07W 07/17/2020 M58.00 MPH Walsh ND MESONET PEAK WINDS MEASURED AT AN NDAWN STATION MEASURED AT 10 METERS. 0401 PM TSTM WND GST 3 W CHURCHS FERRY 48.27N 99.26W 07/17/2020 M59.00 MPH Benson ND MESONET SECONDARY PEAK WINDS AT AN RWIS STATION ALONG HIGHWAY 2. 0425 PM TSTM WND DMG DRAYTON 48.56N 97.18W 07/17/2020 PEMBINA ND BROADCAST MEDIA A DEW LARGE 3-5 INCH BRANCHES BROKEN DOWN AROUND TOWN. REPORT POSTED VIA SOCIAL MEDIA. 0432 PM TSTM WND DMG GRAFTON 48.42N 97.40W 07/17/2020 WALSH ND PUBLIC METAL ROOFING AND SIDING BLOWN OFF A BUILDING. TIME ESTIMATED BASED ON RADAR. PHOTO AND REPORT POSTED VIA SOCILA MEDIA. 0435 PM TSTM WND GST 2 ESE GRAFTON 48.40N 97.36W 07/17/2020 M56.00 MPH Walsh ND ASOS PEAK WIND MEASURED AT THE GRAFTON AIRPORT. 0441 PM TSTM WND DMG MANVEL 48.07N 97.18W 07/17/2020 GRAND FORKS ND PUBLIC SEVERAL LARGE BRANCHES DOWN. 0445 PM TSTM WND DMG ARVILLA 47.92N 97.49W 07/17/2020 GRAND FORKS ND PUBLIC A TREE SNAPPED IN HALF. PHOTO AND REPORT POSTED VIA SOCIAL MEDIA. 0446 PM TSTM WND GST 3 W CHURCHS FERRY 48.27N 99.26W 07/17/2020 M66.00 MPH Benson ND MESONET PEAK WIND MEASURED AT AN RWIS STATION ALONG HIGHWAY 2. 0449 PM TSTM WND GST 8 W ARGYLE 48.34N 96.99W 07/17/2020 M58.00 MPH Marshall MN MESONET PEAK WINDS MEASURED AT A PERSONAL WEATHER STATION. 0453 PM TSTM WND GST 3 NNW GRAND FORKS 47.96N 97.10W 07/17/2020 E65.00 MPH Grand Forks ND AMATEUR RADIO GUSTS ESTIMATED FROM 60 TO 65 MPH. 0455 PM TSTM WND DMG GOLDEN LAKE 47.58N 97.64W 07/17/2020 STEELE ND PUBLIC TREES BLOWN DOWN. TIME ESTIMATED BASED ON RADAR. 0456 PM TSTM WND GST 6 WNW GRAND FORKS 47.95N 97.19W 07/17/2020 M61.00 MPH Grand Forks ND ASOS PEAK WIND MEASURED AT THE GRAND FORKS AIRPORT /KGFK/. 0501 PM TSTM WND GST 3 NNW GRAND FORKS 47.96N 97.10W 07/17/2020 M68.00 MPH Grand Forks ND MESONET PEAK WND MEASURED AT AN RWIS STATION. 0504 PM HAIL TOKIO 47.92N 98.82W 07/17/2020 M2.75 INCH BENSON ND PUBLIC PHOTO AND REPORT POSTED VIA SOCIAL MEDIA. 0505 PM TSTM WND DMG EAST GRAND FORKS 47.93N 97.02W 07/17/2020 POLK MN BROADCAST MEDIA NUMEROUS LARGE BRANCHES AND LIMBS BROKEN DOWN AROUND TOWN. A LARGE OLD TREE SNAPPED. PHOTOS AND REPORTS POSTED VIA SOCIAL MEDIA 0506 PM TSTM WND GST ARGYLE 48.34N 96.82W 07/17/2020 E90.00 MPH Marshall MN PUBLIC BLEACHERS AT THE FOOTBALL FIELD WERE ROLLED AND DESTROYED. A ROOF WAS PEELED OFF A SHOP. GRAIN ELEVATOR COMPLEX HAD TOP AUGER TORN OFF AND LARGE BIN CAVED IN. PHOTO AND REPORT POSTED VIA SOCIAL MEDIA. TIME ESTIMATED BASED ON RADAR. PEAK WINDS ESTIMATED TO 90 MPH. 0510 PM HAIL 10 E SHEYENNE 47.83N 98.90W 07/17/2020 M2.75 INCH Eddy ND FIRE DEPT/RESCUE GOLFBALL TO BASEBALL SIZED HAIL. 0515 PM TSTM WND GST 2 NNW CROOKSTON 47.80N 96.62W 07/17/2020 M56.00 MPH Polk MN AWOS PEAK WINDS MEASURED AT THE CROOKSTON AIRPORT /KCKN/. 0517 PM TSTM WND DMG 1 S GRAND FORKS 47.90N 97.07W 07/17/2020 Grand Forks ND AMATEUR RADIO A LIGHT POLE WAS BLWN DOWN NEAR THE POST OFFICE. SEVERAL LARGE BRANCHES BROKEN DOWN AS WELL. 0520 PM HAIL 5 WSW DEVILS LAKE 48.09N 98.97W 07/17/2020 M1.50 INCH Ramsey ND PUBLIC HAIL NEAR WOODLAND RESORT. PHOTO AN DREPORT POSTED VIA SOCIAL MEDIA. 0529 PM TSTM WND DMG 1 NW NEWFOLDEN 48.37N 96.35W 07/17/2020 Marshall MN BROADCAST MEDIA BALL FIELD DUGOUT BLOWN OVER. REPORT AND PHOTO POSTED VIA SOCIAL MEDIA. 0540 PM TSTM WND DMG 7 N CLIMAX 47.71N 96.81W 07/17/2020 Polk MN PUBLIC TREE BLOWN DOWN OVER POWER LINES. 0545 PM TSTM WND DMG MENTOR 47.70N 96.14W 07/17/2020 POLK MN PUBLIC TREE DAMAGE IN TOWN FROM 545 THROUGH 550 PM CDT. 0545 PM HAIL TOLNA 47.83N 98.44W 07/17/2020 E0.88 INCH NELSON ND PUBLIC 0545 PM TSTM WND GST 2 N HOLT 48.32N 96.19W 07/17/2020 M73.00 MPH Marshall MN FIRE DEPT/RESCUE PEAK WIND MEASURED WITH A PERSONAL WEATHER STATION. 0546 PM TSTM WND DMG 1 NW THIEF RIVER FALLS 48.12N 96.19W 07/17/2020 Pennington MN PUBLIC TREES UPROOTED ON NORTHWEST SIDE OF TOWN. REPORTS AND PHOTOS POSTED VIA SOCIAL MEDIA. 0548 PM HAIL 3 NE NEW ROCKFORD 47.71N 99.09W 07/17/2020 E1.00 INCH Eddy ND PUBLIC 0549 PM TSTM WND GST 2 SSW THIEF RIVER FALLS 48.09N 96.19W 07/17/2020 M61.00 MPH Pennington MN AWOS PEAK WIND MEASURED AT THE THIEF RIVER FALLS AIRPORT /KTVF/. 0550 PM TSTM WND GST 2 S BROOKS 47.79N 96.00W 07/17/2020 M54.00 MPH Red Lake MN MESONET PEAK WINDS MEASURED AT AN RWIS STATION. 0555 PM TSTM WND DMG 2 NE MAPLE BAY 47.66N 96.19W 07/17/2020 Polk MN PUBLIC AT LEAST ONE TREE WAS DOWN ON A CAMPER/TRAILER AT THE POLK COUNTY PARK. LARGE TREES WERE BLOWN DOWN AT VARIOUS LOCATIONS AROUND MAPLE LAKE. PHOTOS AND REPORTS POSTED VIA SOCIAL MEDIA. TIMES VARIED BETWEEN 550 AND 6 PM CDT. 0601 PM TSTM WND DMG MCVILLE 47.77N 98.18W 07/17/2020 Nelson ND PUBLIC TREES BLOWN DOWN BY THUNDERSTORM GUST FRONT. REPORT AND PHOTO POSTED VIA SOCIAL MEDIA. TIME ESTIMATED BASED ON RADAR. 0610 PM TSTM WND DMG 2 S HUNTER 47.16N 97.22W 07/17/2020 Cass ND PUBLIC ROAD SIGN BLOWN DOWN. REPORT POSTED VIA SOCIAL MEDIA. TIME ESTIMATED BASED ON RADAR. 0620 PM TSTM WND DMG 4 SE HENDRUM 47.22N 96.75W 07/17/2020 Norman MN PUBLIC TREES BLWON DOWN IN A SHELTERBELT. PHOTO AND REPORT POSTED VIA SOCIAL MEDIA. 0630 PM TSTM WND DMG 4 SE GEORGETOWN 47.04N 96.73W 07/17/2020 Clay MN PUBLIC TREE BLOWN DOWN IN YARD. 0637 PM TSTM WND DMG CLEARBROOK 47.69N 95.43W 07/17/2020 CLEARWATER MN PUBLIC SMALL TREE BLOWN DOWN IN TOWN. PHOTO AND REPORT POSTED VIA SOCIAL MEDIA. TIME ESTIMATED BASED ON RADAR. 0641 PM TSTM WND GST 5 SSE MAHNOMEN 47.25N 95.93W 07/17/2020 M55.00 MPH Mahnomen MN MESONET PEAK WIND MEASURED AT AN RWIS STATION. 0645 PM TSTM WND DMG BINFORD 47.56N 98.35W 07/17/2020 GRIGGS ND PUBLIC A NUMBER OF LARGE TREE BRANCHES WERE BROKEN DOWN IN AND AROUND TOWN. 0654 PM TSTM WND DMG DAVENPORT 46.71N 97.07W 07/17/2020 CASS ND BROADCAST MEDIA TREE BLOWN DOWN. TIME ESTIMATED BASED ON RADAR. 0655 PM TSTM WND DMG GLYNDON 46.87N 96.58W 07/17/2020 CLAY MN BROADCAST MEDIA ROOFING WAS TORN OFF A TRAILER HOME. REPORT AND PHOTO POSTED VIA SOCIAL MEDIA.
0700 PM TSTM WND GST 1 N CASSELTON 46.92N 97.21W 07/17/2020 M55.00 MPH Cass ND MESONET PEAK WIND MEASURED AT A PERSONAL WEATHER STATION. 0702 PM TSTM WND DMG CASSELTON 46.90N 97.21W 07/17/2020 CASS ND PUBLIC A FEW LARGE TREE BRANCHES AND LIMBS BROKEN DOWN AROUND TOWN.
0703 PM TSTM WND DMG ALIDA 47.38N 95.23W 07/17/2020 CLEARWATER MN PUBLIC NUMEROUS LARGE BRANCHES AND LIMBS BROKEN DOWN. REPORT POSTED VIA SOCIAL MEDIA. TIME ESTIMATED BASED ON RADAR. 0710 PM TSTM WND DMG 5 W BEMIDJI 47.48N 94.99W 07/17/2020 Beltrami MN PUBLIC SEVERAL TREES BLOWN DOWN. 0715 PM TSTM WND DMG 3 SE SOLWAY 47.49N 95.08W 07/17/2020 Beltrami MN EMERGENCY MNGR LARGE MATURE TREES SNAPPED AND BLOCKING ROAD. TIME ESTIMATED BASED ON RADAR.
0730 PM HAIL 2 S WALUM 47.24N 98.19W 07/17/2020 E1.00 INCH Griggs ND PUBLIC 0731 PM HAIL 3 NNE DAZEY 47.23N 98.18W 07/17/2020 E1.00 INCH Barnes ND PUBLIC
0735 PM TSTM WND DMG BEMIDJI 47.48N 94.88W 07/17/2020 BELTRAMI MN EMERGENCY MNGR BRANCHES AND POWER LINES DOWN NEAR THE UNIVERSITY. 0737 PM TSTM WND DMG MANY POINT LAKE 47.08N 95.53W 07/17/2020 Becker MN TRAINED SPOTTER TREES BLOWN DOWN ON MANY POINT SCOUT CAMP ROAD.
0750 PM TSTM WND DMG LAKE PARK 46.88N 96.10W 07/17/2020 BECKER MN BROADCAST MEDIA LARGE TREE SNAPPED. TIME ESTIMATED BASED ON RADAR. 0800 PM TSTM WND DMG CASSELTON 46.90N 97.21W 07/17/2020 Cass ND PUBLIC A FEW LARGE TREE BRANCHES AND LIMBS BROKEN DOWN AROUND TOWN. 0820 PM TSTM WND DMG 3 WSW OSAGE 46.90N 95.32W 07/17/2020 Becker MN PUBLIC TREES DOWN ON HIGHWAY 34. 0824 PM HAIL OSAGE 46.92N 95.26W 07/17/2020 E0.75 INCH BECKER MN PUBLIC 0830 PM TSTM WND DMG MENAHGA 46.75N 95.10W 07/17/2020 WADENA MN PUBLIC WIND DAMAGE TO PORCH. ESTIMATED WINDS OF 70 TO 80 MPH. 0839 PM TSTM WND GST 2 SSW PARK RAPIDS 46.89N 95.08W 07/17/2020 M58.00 MPH Hubbard MN ASOS PEAK WIND MEASURED AT THE PARK RAPIDS AIRPORT /KPKD/. A FEW TREES BLOWN DOWN IN TOWN. 0840 PM HAIL 7 N PARK RAPIDS 47.02N 95.06W 07/17/2020 E1.00 INCH Hubbard MN PUBLIC 0845 PM TSTM WND GST SEBEKA 46.63N 95.09W 07/17/2020 E60.00 MPH WADENA MN PUBLIC 0850 PM TSTM WND DMG AKELEY 47.00N 94.73W 07/17/2020 HUBBARD MN BROADCAST MEDIA TREES BLWON DOWN. REPORT AND PHOTO POSTED VIA SOCIAL MEDIA. TIME ESTIMATED BASED ON RADAR. 0900 PM HAIL WIMBLEDON 47.17N 98.46W 07/17/2020 E0.75 INCH BARNES ND STORM CHASER 0930 PM TSTM WND GST SEBEKA 46.63N 95.09W 07/17/2020 E60.00 MPH WADENA MN TRAINED SPOTTER SECOND BLAST OF WIND GUSTING TO 60 MPH. SEVERAL LARGE BRANCHES BROKEN DOWN IN A YARD. 0931 PM HAIL 2 W WADENA 46.44N 95.18W 07/17/2020 E1.25 INCH Otter Tail MN TRAINED SPOTTER 0939 PM TSTM WND GST 1 SE WYNDMERE 46.25N 97.12W 07/17/2020 M60.00 MPH Richland ND MESONET PEAK WIND MEASURED AT A PERSONAL WEATHER STATION. 0944 PM HAIL VERNDALE 46.40N 95.01W 07/17/2020 E1.00 INCH WADENA MN PUBLIC REPORT FROM SOCIAL MEDIA.
0944 PM TSTM WND GST 1 SE WYNDMERE 46.25N 97.12W 07/17/2020 M60.00 MPH Richland ND MESONET PEAK WIND MEASURED AT A PERSONAL WEATHER STATION. 1007 PM TSTM WND GST 2 W LISBON 46.44N 97.73W 07/17/2020 M51.00 MPH Ransom ND MESONET PEAK WIND MEASURED AT NDAWN STATION 1050 PM TSTM WND GST 2 W TENNEY 46.04N 96.50W 07/17/2020 M54.00 MPH Wilkin MN MESONET PEAK WIND MEASURED AT RWIS STATION 1050 PM TSTM WND DMG 4 W HOFFMAN 45.83N 95.87W 07/17/2020 Grant MN TRAINED SPOTTER SEVERAL LARGE TREE BRANCHES AND LIMBS BROKEN DOWN. WINDS ESTIMATED AT 60 TO 65 MPH.
1055 PM TSTM WND DMG 5 S LIDGERWOOD 46.00N 97.15W 07/17/2020 Richland ND PUBLIC
Environment
A low amplitude mid level shortwave moving through quasi-zonal flow moved eastward on the nose of a flat southwest oriented jet streak moving out of Montana into North Dakota. Closer to the surface, a tongue of strong instability advected north ahead of a cold front lagging behind to the west. A subtle, but important, leading low-mid level trough ahead of the shortwave helped convection initiate on the nose of instability where surface flow converged. Convection initiated earlier than forecast which played a role in the overall convective development of a large, long duration MCS (perhaps might have even helped subdue the significance of the event). Click the images below to enlarge.
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| Figure 1: 500mb | Figure 2: 700mb | Figure 3: MSLP |
This complex was expected to produce widespread damaging winds with swaths of significant wind damage possible. Indeed widespread severe winds were observed creating sporadic areas of wind damage, owing to the presence of strong MLCAPE and DCAPE through rich lower level moisture content beneath a very dry and rapidly cooling profile aloft. Additionally, the storm complex was able to organize itself with sufficient bulk shear over 35 kt.
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| Figure 4: MLCAPE | Figure 5: DCAPE | Figure 6: EBWD |
Still, the significantly severe wind potential may have been limited from two factors: an early initiation kept convection away from stronger winds expected to arrive later in the evening, and a storm motion that limited orthogonal component of available wind shear to the updraft/downdraft convergence zone. Essentially severe winds were most likely along more north-south oriented bowing segments within the larger complex. The orientation of deep convection that was more orthogonal (aka perpendicular) to the deep layer wind shear vectors was more effective at transferring higher winds aloft to the surface, while the cooling process of convection within the dry air mass aloft enhanced downdraft speeds to the surface. Otherwise, the deep convection components that were more east-west oriented aligned themselves more parallel to deep layer shear vectors proving inefficient for pushing and sustaining severe winds to the surface. These components also helped the outflow boundary of the cold pool extend well ahead of deeper convection, a process that is less conducive for sustained severe wind production. Eventually the low level jet did enhance towards the evening (a common occurrence), reinvigorating severe potential some overnight as the MCS was exiting the area.
In addition to widespread severe winds, very large hail up to the size of baseballs was observed in the Devils Lake basin where convection initially formed. This was likely due to the extreme instability towards central ND, very steep mid level lapse rates, and sufficient shear to organize updrafts.
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| Figure 7: MCS Maintenance | Figure 8: Corfidi Upwind Vector/Thickness or mid level lapse rates | Figure 9: SHIP |
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