Afternoon thunderstorms produced large hail, damaging winds and torrential rainfall over portions of the western Nebraska Panhandle.
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 CYS wrote it up.
Afternoon thunderstorms produced large hail, damaging winds and torrential rainfall over portions of the western Nebraska Panhandle.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at May 15, 4:57 AM MST, 8 hours 33 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 557 AM MDT FRI MAY 15 2015 .SHORT TERM...(TODAY THROUGH SUNDAY NIGHT) ISSUED AT 415 AM MDT FRI MAY 15 2015 SHOWERS AND A FEW STRONG THUNDERSTORMS HAVE BEEN ONGOING FOR MUCH OF THE NIGHT OVER THE PLAINS. THIS IS IN RESPONSE TO STRONG LLVL THETA- E ADVECTION NORTH OF A STATIONARY BOUNDARY DRAPED FROM WEST TO EAST ALONG THE I-80 CORRIDOR. BUFKIT SOUNDINGS FROM THE RAP MODEL SHOW UP TO 500 J/KG OF MUCAPE TO THE NORTH OF THIS BOUNDARY...WHICH COMBINED WITH MODEST DEEP LAYER VERTICAL SHEAR IS CONTRIBUTING TO SOME SMALL HAIL PRODUCTION. ISSUED A FEW SPS PRODUCTS THIS MORNING TO HIGHLIGHT THE STRONGEST CELLS...BUT EVERYTHING IS STAYING SUB-SEVERE. AIR MASS ACROSS MUCH OF SOUTHEAST WYO/WESTERN NEB IS BECOMING VERY MOIST THIS MORNING WITH LLVL EASTERLY/UPSLOPE FLOW. DEWPOINTS OVER WESTERN NEB WERE ALREADY IN THE 50-55 F RANGE AT 10Z...AND THESE ARE EXPECTED TO BE ADVECTED WESTWARD ALONG THE LARAMIE RANGE WITH TIME AS STRONG SFC CYCLOGENESIS OVER EASTERN CO KEEPS NEAR-SFC FLOW BACKED OVER OUR CWA THROUGH THE DAY. FORECAST SOUNDINGS AND THE OPERATIONAL HRRR SHOW AT LEAST SOME POTENTIAL FOR FOG OVER THE PLAINS THROUGH 15Z. HOWEVER... WIDESPREAD SHOWER ACTIVITY SHOULD KEEP THE BOUNDARY LAYER MIXED. WE DECIDED TO REMOVE MENTION OF FOG FROM THE GRIDS AS ANY REDUCED VSBYS WOULD BE QUITE ISOLATED. ATTENTION THEN SHIFTS TO A MORE WIDESPREAD...POTENTIALLY SIGNIFICANT SEVERE WEATHER EPISODE EVOLVING LATER TODAY. WE WILL REALLY NEED TO WATCH THE POSITION OF THE SURFACE LOW TODAY AS LLVL WIND FIELDS WILL PLAY A SIGNIFICANT ROLE IN CONVECTIVE MODE AND STORM INTENSITY. THE GFS IS STILL AN APPARENT OUTLIER WITH 18-00Z POSITIONING OF A 995 MB SURFACE LOW LIFTING OUT OF NORTHEAST CO. NOTHING UNUSUAL FOR THE GFS AS THIS MODEL DOES HAVE A TENDENCY TO PUSH SURFACE FEATURES EASTWARD TOO QUICKLY. THE NET RESULT IS THE DEVELOPMENT OF WESTERLY FLOW NEAR THE SURFACE OVER MOST OF THE CWA BY AROUND 21Z. THE PREFERRED SOLNS ARE STILL THE ECMWF AND NAM WITH THE SLOWER PROGRESSION...AND LONGER RESIDENCE TIME OF EASTERLY FLOW EAST OF THE LARAMIE RANGE. THE BIG QUESTIONS RIGHT NOW WILL BE ONGOING CONVECTION/LOW CLOUDS AND THEIR OVERALL IMPACT ON INSTABILITY PARAMETERS. MORNING WATER VAPOR SHOWS A MID LEVEL DRY SLOT MOVING INTO EASTERN CO...AND CLOUD TOPS ON THE LATEST IR LOOP HAVE BEEN WARMING OVER THE LAST FEW HOURS. THUS...DO NOT EXPECT PCPN TO BE A MAJOR INHIBITING FACTOR. STRONGLY DIFLUENT FLOW ALOFT IS NOW DEVELOPING ACROSS THE CWA AHEAD OF A VIGOROUS LOW OVER CA/NV...ALONG WITH A COUPLED H25 JET. MOST CONVECTION-ALLOWING MODELS SHOW CIN ERODING ENTIRELY BY 18Z...SO STRONGLY BELIEVE THIS WILL BE AN EARLY SHOW WITH TSTMS BECOMING WIDESPREAD BY AFTN. H7 TEMPS AROUND +7 DEG C OVER THE PANHANDLE WOULD SUGGEST CAPPING AND LESS COVERAGE THERE. THE AFOREMENTIONED SURFACE BOUNDARY WILL LIFT NORTHWARD AS A WARM FRONT LATER TODAY...SO THIS WILL SERVE AS THE PRIMARY FOCUS FOR INITIATION AS WELL AS ENHANCED CONVERGENCE ALONG THE LARAMIE RANGE. ENVIRONMENTAL PARAMETERS CONTINUE TO SUGGEST INCREASING POTENTIAL FOR DANGEROUS THUNDERSTORMS ALONG/EAST OF THE LARAMIE RANGE. GOOD INSOLATION AND DEW POINTS IN THE MID 50S BENEATH VERY STEEP MID LEVEL LAPSE RATES SHOULD YIELD SBCAPE OF 2000-3000 J/KG INVOF THE WARM FRONT. 0 TO 6 KM SHEAR OVER 45 KTS IS EXPECTED TO BE MORE THAN SUFFICIENT FOR SUPERCELLS INITIALLY...WITH 0-3 KM SRH VALUES WELL IN EXCESS OF 200 M2/S2. THIS IS ESPECIALLY TRUE WHEN SHEAR VECTORS ARE ORIENTED PERPENDICULAR TO THE FRONT AROUND 18Z. THE CONVERGENCE ZONE EVENTUALLY BECOMES ORIENTED MORE SW-TO-NE BY 00Z...WHICH COULD HELP TRANSITION THINGS TO A LINEAR STORM MODE. WOULD STILL EXPECT A FEW EMBEDDED SUPERCELLS IN SUCH AN ENVIRONMENT. THE LATEST DAY 1 OUTLOOK FROM THE STORM PREDICTION CENTER MAINTAINS AN ENHANCED RISK ACROSS MUCH OF THE PANHANDLE INTO FAR EASTERN WYO. HRRR AND OTHER SIMULATED RADAR PRODUCTS SHOW CONVECTION DEVELOPING OVER THE LARAMIE RANGE BY LATE MORNING OR EARLY AFTERNOON...AND THEN MOVING EAST BEFORE MOVING OUT AROUND 03Z. UPDRAFT HELICITIES WOULD SUGGEST SUPERCELLS. VERY LARGE/DAMAGING HAIL AND STRONG DOWNBURST WINDS SHOULD BE THE PRIMARY HAZARD TODAY...BUT TORNADOES ARE ALWAYS POSSIBLE IN BACKED LLVL FLOW REGIMES SUCH AS THESE. SOUNDINGS SHOW VERY LARGE/CURVED HODOGRAPHS WITH 0-1 KM SHEAR OVER 20 KTS. NAM EHI VALUES ARE OVER 3...SO WOULD NOT BE SURPRISED TO SEE A FEW TORNADOES TODAY. OUR MAIN CORRIDOR OF INTEREST WOULD BE FROM WHEATLAND/CHUGWATER (ENHANCED CONVERGENCE WITH A MESOSCALE LOW) EASTWARD ACROSS THE NEB PANHANDLE. VERY LOW LCLS ARE ALSO OMINOUS. ONE THING THAT WOULD REALLY MESS UP OUR SEVERE POTENTIAL TODAY WOULD BE A LIKELY MESSY STORM MODE. A LOT OF DIFFERENT FORCING MECHANISMS TODAY...AND IT COULD BE DETRIMENTAL IF STORMS BECOME TOO WIDESPREAD. THAT SAID...THE BUST POTENTIAL IS HIGH. THAT IS NOT TO SAY WE WILL NOT NEED ALL HANDS ON DECK TODAY THOUGH. A MUDDLED PATTERN WILL CONTINUE THROUGH THE REST OF THE WEEKEND WITH DEEP TROUGHING OVER THE WESTERN CONUS. DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS WILL EXIST WITH A VIRTUALLY UNLIMITED SUPPLY OF MIDLVL DISTURBANCES ROUNDING THE BASE OF THE TROUGH. GFS 700 MILLIBAR TEMPS AT OR BELOW -2 DEG C SUGGESTS POTENTIAL FOR ACCUMULATING SNOW OVER THE MOUNTAINS...BUT THIS SHOULD BE SUB ADVISORY AT BEST AS DYNAMICS DO NOT APPEAR TO BE ANYTHING TO WRITE HOME ABOUT. TEMPERATURES WILL GENERALLY BE BELOW NORMAL WITH WIDESPREAD CLOUDS AND OCCASIONAL PCPN. .LONG TERM...(MONDAY THROUGH THURSDAY) ISSUED AT 415 AM MDT FRI MAY 15 2015 RATHER COOL AND UNSETTLED EXTENDED PERIOD CONTINUES TO BE SHOWN BY THE MODELS. MONDAY WILL LIKELY BE THE DRIEST DAY ACROSS THE REGION WITH THE RIDGING ALOFT AND VERY LIMITED INSTABILITY (MAINLY OUT WEST). THE BEST CHANCE OF SHOWERS WILL BE ALONG AND WEST OF THE LARAMIE RANGE. SOUTHEASTERLY SFC WINDS WILL PUSH HIGHER DEWPOINTS TOWARD THE LARAMIE RANGE BY TUES MORNING. AN UPPER LEVEL SYSTEM OVER CALIFORNIA ON MON WITH MOVE QUICKLY NORTHEASTWARD ON TUES. UPPER LEVEL DIVERGENCE AND DEEP LAYER ASCENT WILL INCREASE BY TUES AFTN AND EVENING AND INTERACT WITH GOOD MOISTURE (PW VALUES ARE ABOVE 0.75 INCHES) TO PRODUCE WIDESPREAD RAIN AND MAYBE AN ISOLATED TSTM. LOOKING MORE LIKE A STRATIFORM EVENT...AND STRONG STORMS WOULD NOT BE A CONCERN WITH THE GFS SHOWING REALLY NO CAPE ACROSS THE PLAINS. WEAK SHORTWAVE WILL BE IN THE VICINITY OF SOUTHWEST SOUTH DAKOTA ON WED WITH SCATTERED SHOWERS PERSISTING. THERE IS SOME INDICATION THAT IT WILL DRY OUT BY THURS...HOWEVER CAN NOT RULE OUT ISOLATED CONVECTION WITH LLVL UPSLOPE TO THE EAST OF THE LARAMIE RANGE. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING) ISSUED AT 549 AM MDT FRI MAY 15 2015 LOW CLOUDS AND IFR/MVFR CONDITIONS WILL PERSIST THROUGH THE MID MORNING AT MANY OF THE PLAINS SITES. THE LOW CLOUDS WILL LIFT AND BECOME MORE SCATTERED AFTER AROUND 16Z. GOOD MOISTURE AND INSTABILITY WILL PROMOTE WIDESPREAD THUNDERSTORM DEVELOP BY EARLY THIS AFTERNOON...ESPECIALLY TO THE EAST OF THE LARAMIE RANGE. SOME OF THE STORMS COULD BE STRONG WITH GUSTY WINDS...HAIL...AND BRIEF HEAVY RAIN. PREVAILING WINDS OUTSIDE OF THE STORMS WILL GENERALLY BE FROM THE SOUTH TO SOUTHEAST. && .FIRE WEATHER... ISSUED AT 351 AM MDT FRI MAY 15 2015 MILD AND WET WEATHER PATTERN WILL CONTINUE OVER THE NEXT SEVERAL DAYS. WETTING RAINS CAN BE EXPECTED FOR MANY AREAS. AS A RESULT... FIRE WEATHER CONCERNS WILL BE MINIMAL WITH NON-CRITICAL CONDITIONS LIKELY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && SHORT TERM...CLH LONG TERM...ZF AVIATION...ZF FIRE WEATHER...CLH
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHEYENNE WY 120 PM MDT FRI MAY 15 2015 NEZ002-003-019>021-054-055-095-096-WYZ101-102-106>108-117>119- 161930- DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE- NORTH SIOUX-SOUTH SIOUX-CONVERSE COUNTY LOWER ELEVATIONS- NIOBRARA COUNTY-CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY- EAST PLATTE COUNTY-GOSHEN COUNTY-SOUTH LARAMIE RANGE FOOTHILLS- CENTRAL LARAMIE COUNTY-EAST LARAMIE COUNTY- 120 PM MDT FRI MAY 15 2015 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN NEBRASKA...EAST CENTRAL WYOMING AND SOUTHEAST WYOMING. .DAY ONE...THIS AFTERNOON AND TONIGHT SHOWERS AND THUNDERSTORMS WILL DEVELOP TO THE EAST OF THE LARAMIE RANGE BY MIDDAY AND CONTINUE INTO THE EARLY EVENING. A FEW THUNDERSTORMS MAY BECOME SEVERE WITH LARGE HAIL AND DAMAGING WINDS THE PRIMARY THREATS. AN ISOLATED TORNADO OR TWO CANNOT BE RULED OUT. A TORNADO WATCH IS IN EFFECT UNTIL 8 PM FOR LARAMIE AND GOSHEN COUNTIES AS WELL AS ALL OF THE WESTERN NEBRASKA PANHANDLE. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS CAN BE EXPECTED ON MOST DAYS. SEVERE STORMS ARE NOT EXPECTED. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON THROUGH THE EARLY EVENING. WYZ103>105-109>116-161930- NORTH LARAMIE RANGE-FERRIS/SEMINOE/SHIRLEY MOUNTAINS- SHIRLEY BASIN-CENTRAL CARBON COUNTY-NORTH SNOWY RANGE FOOTHILLS- SOUTHWEST CARBON COUNTY-SIERRA MADRE RANGE- UPPER NORTH PLATTE RIVER BASIN-SNOWY RANGE-LARAMIE VALLEY- SOUTH LARAMIE RANGE- 120 PM MDT FRI MAY 15 2015 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL WYOMING...SOUTH CENTRAL WYOMING AND SOUTHEAST WYOMING. .DAY ONE...THIS AFTERNOON AND TONIGHT SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP BY MIDDAY AND CONTINUE THROUGH THE AFTERNOON. SEVERE STORMS ARE NOT EXPECTED TO THE WEST OF THE LARAMIE RANGE...HOWEVER SOME OF THE STRONGER STORMS COULD PRODUCE SMALL HAIL AND GUSTY WINDS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS CAN BE EXPECTED ON MOST DAYS. SEVERE STORMS ARE NOT EXPECTED. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 102 PM MDT FRI MAY 15 2015 WYZ105-110-114-151945- NORTH SNOWY RANGE FOOTHILLS WY-SHIRLEY BASIN WY-SNOWY RANGE WY- 102 PM MDT FRI MAY 15 2015 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN ALBANY AND EAST CENTRAL CARBON COUNTIES UNTIL 145 PM MDT... AT 102 PM MDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR ARLINGTON...OR 35 MILES NORTHWEST OF LARAMIE...MOVING NORTH AT 30 MPH. NICKEL SIZE HAIL AND WIND GUSTS OF 50 TO 55 MPH WILL BE POSSIBLE WITH THIS STORM. LOCATIONS IMPACTED INCLUDE... ARLINGTON. THIS INCLUDES INTERSTATE 80 IN WYOMING BETWEEN MILE MARKERS 264 AND 278. LAT...LON 4151 10610 4149 10626 4182 10642 4190 10607 TIME...MOT...LOC 1902Z 170DEG 25KT 4155 10619 RUBIN
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 145 PM MDT FRI MAY 15 2015 NEZ021-055-152030- CHEYENNE NE-MORRILL NE- 145 PM MDT FRI MAY 15 2015 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN CHEYENNE AND SOUTH CENTRAL MORRILL COUNTIES UNTIL 230 PM MDT... AT 145 PM MDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR SIDNEY...MOVING NORTHWEST AT 25 MPH. NICKEL SIZE HAIL AND WIND GUSTS OF 50 TO 55 MPH WILL BE POSSIBLE WITH THIS STORM. THIS STRONG THUNDERSTORM WILL BE NEAR... GURLEY AROUND 205 PM MDT. DALTON AROUND 220 PM MDT. PRECAUTIONARY/PREPAREDNESS ACTIONS... TO REPORT SEVERE WEATHER...CONTACT YOUR NEAREST LAW ENFORCEMENT AGENCY. THEY WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE OFFICE IN CHEYENNE. && A TORNADO WATCH REMAINS IN EFFECT UNTIL 800 PM MDT FOR CENTRAL NEBRASKA. LAT...LON 4118 10285 4112 10299 4143 10334 4155 10293 TIME...MOT...LOC 1945Z 154DEG 23KT 4118 10296 RUBIN
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 150 PM MDT FRI MAY 15 2015 NEZ055-152030- CHEYENNE NE- 150 PM MDT FRI MAY 15 2015 ...SIGNIFICANT WEATHER ADVISORY FOR WESTERN CHEYENNE COUNTY UNTIL 230 PM MDT... AT 150 PM MDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR LORENZO...OR NEAR SIDNEY...MOVING NORTHWEST AT 25 MPH. NICKEL SIZE HAIL AND WIND GUSTS OF 50 TO 55 MPH WILL BE POSSIBLE WITH THIS STORM. THIS STRONG THUNDERSTORM WILL BE NEAR... BROWNSON AROUND 205 PM MDT. THIS INCLUDES INTERSTATE 80 IN NEBRASKA BETWEEN MILE MARKERS 41 AND 58. A TORNADO WATCH REMAINS IN EFFECT UNTIL 800 PM MDT FOR CENTRAL NEBRASKA. LAT...LON 4107 10295 4100 10314 4133 10337 4140 10311 TIME...MOT...LOC 1950Z 154DEG 23KT 4109 10307 RUBIN
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 158 PM MDT FRI MAY 15 2015 WYZ103>105-109-110-115-152045- NORTH LARAMIE RANGE WY-NORTH SNOWY RANGE FOOTHILLS WY- SHIRLEY BASIN WY-LARAMIE VALLEY WY-CENTRAL CARBON COUNTY WY- FERRIS/SEMINOE/SHIRLEY MOUNTAINS WY- 158 PM MDT FRI MAY 15 2015 ...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL ALBANY AND EAST CENTRAL CARBON COUNTIES UNTIL 245 PM MDT... AT 158 PM MDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR MEDICINE BOW...OR 45 MILES NORTHWEST OF LARAMIE...MOVING NORTH AT 35 MPH. DIME SIZE HAIL AND WIND GUSTS OF 50 TO 55 MPH WILL BE POSSIBLE WITH THIS STORM. THIS STRONG THUNDERSTORM WILL BE NEAR... MEDICINE BOW AROUND 205 PM MDT. BATTLE MOUNTAIN AROUND 230 PM MDT. LAT...LON 4168 10594 4167 10621 4219 10641 4224 10579 TIME...MOT...LOC 1958Z 177DEG 30KT 4184 10610 RUBIN
The Cheyenne radar (KCYS), 137 km away, was scanning. The volume nearest the first event began at 20:28 UTC.
11 hail, 1 flood, 1 thunderstorm wind. Local standard time, as filed.
Ping pong ball to golf ball sized hail was observed five miles northwest of Brownson.
Quarter size hail was observed nine miles west of Gurley.
Half dollar size hail was observed 10 miles north of Brownson.
Two inches of rain from a slow moving thunderstorm produced flooding in Bridgeport. Water was running over the curbs. Highway 385 was blocked by high water with traffic detoured.
Golf ball size hail damaged vehicles in Bridgeport.
Quarter to half dollar size hail was observed in Bridgeport.
Dime to quarter size hail was observed in Alliance.
Quarter to hen egg size hail was observed a mile south-southwest of Brownson.
Wind tossed a picnic table 20 feet and destroyed it.
Golf ball size hail was observed four miles west of Bridgeport.
Marble to quarter size hail was observed in Broadwater.
Quarter to golf ball size hail was observed in Broadwater.
Nickel to golf ball size hail was observed six miles west-northwest of Broadwater.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Nebraska in 2015Every state in 2015This day in weather historyWarnings in Nebraska, May 2015
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: 572363, 572364, 572365, 572366, 572367, 572369, 572375, 572378, 572398, 572401, 572404, 572405, 572406.