Severe thunderstorms developed over the Matanuska and Susitna Valleys before moving over Cook Inlet and dying out. One storm over populated areas produced large hail.
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 AFC wrote it up.
Severe thunderstorms developed over the Matanuska and Susitna Valleys before moving over Cook Inlet and dying out. One storm over populated areas produced large hail. Another thunderstorm appeared severe on radar but was not in a populated area and did not produce any local storm reports.
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 Anchorage, AK wrote its last area forecast discussion before the first event at Aug 18, 3:32 PM AKST, 7 minutes earlier.
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ANCHORAGE AK 432 PM AKDT TUE AUG 18 2015 .ANALYSIS AND UPPER LEVELS... THE LAST VESTIGES OF THE RAINY PATTERN OF RECENT DAYS IS BLASTING OFF TO THE EAST...DRIVEN BY A FAIRLY STRONG AND MOSTLY ZONAL JET STREAM SOUTH OF MAINLAND ALASKA. AS EXPECTED...A LOW DEVELOPED RAPIDLY OVERNIGHT NEAR PRINCE WILLIAM SOUND AND TRACKED INTO THE COPPER RIVER BASIN. STRONG MID LEVEL DEFORMATION LED TO A FAIRLY BROAD BAND OF RAIN FROM THE MOUNTAINS EAST OF ANCHORAGE INTO THE NORTHEAST COPPER RIVER BASIN...WITH GENERALLY 1 TO 2 INCH RAIN AMOUNTS IN THE LAST 24 HOURS IN THESE AREAS. MEANWHILE...EASTERN PRINCE WILLIAM SOUND AND THE NORTH GULF COAST RECEIVED HIGHER AMOUNTS...GENERALLY 2 TO 4 INCHES OF RAIN...AS THE DEEP ATMOSPHERIC MOISTURE SLAMMED INTO THE COASTAL MOUNTAINS AND WAS WRUNG OUT LIKE A SPONGE. STEADY RAIN IS CONTINUING OVER EASTERN PORTIONS OF THE COPPER RIVER BASIN AS OF MIDDAY...BUT WILL BE SOON COMING TO AN END AS MORE WESTERLY/ZONAL FLOW MOVING IN FROM THE WEST HELPS TO DRY OUT BOTH THE UPPER AND LOWER LEVELS OF THE ATMOSPHERE. SOME LIMITED CONVECTION HAS BROKEN OUT IN THE CLEARER SKIES BEHIND THE DEPARTING STORM...FUELED BY COOLING TEMPERATURES ALOFT THAT ARE DESTABILIZING THE ATMOSPHERE. A FEW THUNDERSTORMS REMAIN POSSIBLE THROUGH THIS EVENING...BUT ARE NOT EXPECTED TO BE A WIDESPREAD EVENT BY ANY MEANS. GUSTY WINDS THROUGH THE FAVORED GAPS OF TURNAGAIN ARM AND THE KENAI PENINSULA HAVE BEGUN TO BLOW OUT OF THE NORTH AND WEST...WITH "OUTFLOW" WINDS EXPECTED TO SLOWLY SPREAD TO THE OTHER GAPS ALONG THE NORTH GULF COAST AND PRINCE WILLIAM SOUND OVERNIGHT AND INTO TOMORROW. OUT WEST...DEEP-LAYER WESTERLY FLOW IS IN PLACE ACROSS VIRTUALLY ALL OF THE BERING/ALEUTIAN REGION AND THE SOUTHWEST MAINLAND. A BROAD SHIELD OF CLOUDINESS OVER THE BERING SEA IS BEING PUSHED INLAND ACROSS THE KUSKOKWIM DELTA AND PARTS OF BRISTOL BAY. THE STRONGEST GAP WINDS ARE BLOWING FROM THE NORTHWEST THROUGH THE ALASKA PENINSULA IN RESPONSE TO RISING PRESSURES IN THE BERING SEA. && .MODEL DISCUSSION... MODELS ARE IN OUTSTANDING AGREEMENT THROUGH THE FIRST FEW DAYS OF THE FORECAST PERIOD...DEPICTING WESTERLY/ZONAL FLOW ACROSS MOST OF THE REGION. THIS WILL LEAVE THE AREA VULNERABLE TO FAST-MOVING BUT RELATIVELY WEAK SHORTWAVES...WITH THE NEXT SUCH FEATURE EXPECTED TO MOVE THROUGH THE SOUTHER MAINLAND DURING THE DAY WEDNESDAY. BY THE END OF THE WEEK THE ZONAL JET WILL AGAIN AMPLIFY/BUCKLE IN A MORE SIGNIFICANT WAY...WHICH MODELS ALL AGREE WILL LEAD TO ANOTHER LOW PRESSURE SYSTEM WORKING INTO THE GULF. THE BIG QUESTION AT THIS POINT REMAINS HOW FAR NORTH AND WEST RAIN WILL BE SPREAD FROM THIS LOW...WITH THE NAM KEEPING INLAND AREAS LIKE ANCHORAGE TOTALLY DRY...BUT THE GLOBAL MODELS BRINGING ANOTHER ROUND OF RAIN INTO THE POPULATION CENTERS. WILL SPLIT THE DIFFERENCE RIGHT NOW WITH THE GLOBAL MODELS...PENDING BETTER MODEL AGREEMENT...AND BRING STEADY RAIN NO FURTHER NORTH OR WEST THAN THE EASTERN KENAI PENINSULA ALIGNED MOST CLOSELY WITH THE ECMWF. && .FIRE WEATHER... WITH ALL THE RECENT RAINFALL ACROSS THE AREA EVEN CLEARING SKIES ARE NOT EXPECTED TO TAKE RH VALUES DOWN NEAR CRITICAL VALUES OVER THE NEXT FEW DAYS. THE STRONGEST WINDS WILL BE FOUND THROUGH THE USUAL TERRAIN GAPS ALONG THE GULF COASTLINE...WITH LIGHTER AND GENERALLY NORTH TO WEST WINDS INLAND. AS MENTIONED ABOVE...A FEW THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY IN THE UNSTABLE FLOW SOUTH AND EAST OF THE ALASKA RANGE BEHIND THE DEPARTING SYSTEM. ANOTHER WEAK SHORTWAVE MOVING THROUGH TOMORROW MAY PROVIDE ENOUGH OF A DYNAMIC LIFT TO TAKE ADVANTAGE OF CONTINUING INSTABILITY. IN ANY EVENT...NO SIGNIFICANT OR WIDESPREAD THUNDERSTORM OUTBREAKS ARE EXPECTED. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)... RAIN ACTIVITY ACROSS SOUTHCENTRAL ALASKA HAS TAPERED OFF AS EXPECTED THIS AFTERNOON BUT NOT BEFORE SOME LOCATIONS ACROSS THE COPPER RIVER BASIN AND NORTHERN GULF COAST RECORDED PRETTY SIGNIFICANT RAINFALL. SHOWER ACTIVITY ASSOCIATED WITH NORTHWEST FLOW ON THE BACKSIDE OF THE TROUGH PASSAGE CONTINUES THIS AFTERNOON BUT HAS GENERALLY BEEN DISSIPATING AS THE MAJORITY OF THE UPPER LEVEL ENERGY IS NOW PUSHING EAST OF THE AREA. THE WAVE THAT WAS EXPECTED TO HELP SPARK SOME THUNDERSTORM ACTIVITY HAS PUSHED THROUGH ON CUE...WITH THUNDERSTORMS DEVELOPING ACROSS THE MATANUSKA AND SUSITNA VALLEYS. SOME OF THESE STORMS WILL CONTAIN SMALL HAIL AS THE SFC LAYER HAS DESTABILIZED UNDER MOSTLY CLEAR SKIES THROUGHOUT THE DAY AND COLD AIR ALOFT HAS CREATED QUITE THE UNSTABLE ENVIRONMENT. THESE SHOWERS AND THUNDERSTORMS WILL SLOWLY DIMINISH OVERNIGHT WITH THE LOSS OF DIURNAL HEATING...BUT A FEW MAY LINGER INTO THE LATER EVENING AS THE COLD AIR ALOFT MAY BE ENOUGH TO SUPPORT THE STORMS A TAD LONGER. WEDNESDAY WILL BE DRIER BUT SOME SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL ONCE AGAIN BE POSSIBLE. WHILE MODELS HAVE BEEN STRUGGLING TO PLACE A SHORTWAVE TRAVERSING THE NEAR ZONAL FLOW...THEY HAVE NOW DECIDED ON A SOLUTION THAT PUSHES THIS WAVE ACROSS SOUTHCENTRAL ALASKA AROUND PEAK HEATING ON WEDNESDAY. THIS COUPLED WITH MODEST MID-LEVEL LAPSE RATES SHOULD BE ENOUGH TO SUPPORT A FEW ELEVATED THUNDERSTORMS. CONDITIONS ONLY IMPROVE HEADING INTO THURSDAY WHEN SUNNY SKIES SHOULD BE OBSERVED ACROSS ALL OF SOUTHCENTRAL ALASKA AHEAD OF THE NEXT SYSTEM LOOKING TO IMPACT THE REGION HEADING INTO THE WEEKEND. && .SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)... ZONAL FLOW ALOFT IS BEGINNING TO TAKE HOLD AS HIGH PRESSURE BUILDS IN AT THE SURFACE. DIURNAL SHOWERS ARE POSSIBLE OVER THE NEXT COUPLE OF AFTERNOONS HOWEVER COVERAGE WILL BE ISOLATED TO SCATTERED...MAINLY OVER THE KUSKOKWIM DELTA AND VALLEY. PERSISTENT WESTERLY FLOW IN THE LOW LEVELS WILL KEEP LOW CLOUDS AROUND THE DELTA. OTHERWISE GENERALLY BENIGN WEATHER CONDITIONS WILL PERSIST OVER THE MAINLAND THROUGH THURSDAY. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)... WEAK HIGH PRESSURE SITS OVER THE SOUTHERN BERING SEA MAKING PATCHY FOG POSSIBLE OVERNIGHT. A FRONT AND UPPER LEVEL TROUGH ENTERS THE WESTERN BERING TONIGHT BRINGING RAIN AND GUSTY SOUTHERLY WINDS. ANOTHER WEAKER FRONT AND DISTURBANCE WILL SKIRT THE EASTERN ALEUTIANS AND ALASKA PENINSULA ON WEDNESDAY NIGHT BRINGING A SHOT OF RAIN. && .LONG TERM FORECAST (DAYS 3 THROUGH 7..FRIDAY THROUGH TUESDAY)... MODELS CONTINUE TO STRUGGLE GREATLY IN THIS TIME PERIOD...SO FORECAST CONFIDENCE IS LOW TO MODERATE. FIRST ITEM IS A DEVELOPING SYSTEM EAST OF KODIAK ON FRIDAY. MODELS DID NOT RESOLVE THIS FEATURE MUCH AT ALL YESTERDAY. TODAY THE NAM HAS IT...BUT MUCH FURTHER EAST IN THE GULF THAN THE GLOBAL MODELS. SO FAR IN FACT THAT IT ACTUALLY KEEPS MOST OF THE PRECIPITATION OFFSHORE. THE GLOBAL MODELS CLIP THE COOK INLET WITH SOME LIGHT RAIN AND BRING ANOTHER ROUND OF HEAVY RAIN TO THE PRINCE WILLIAM SOUND LATE FRIDAY INTO EARLY SATURDAY. GOING INTO THE WEEKEND...THE GENERAL PATTERN IS STILL TRYING TO SHOW A SHIFT TOWARDS RIDGING BUILDING OVER THE EASTERN BERING. THIS WOULD BRING A DRYING NORTHWESTERLY FLOW TO MUCH OF SOUTH CENTRAL. HOWEVER THE OTHER NEW DEVELOPMENT TODAY IS THE COLDER UPPER LEVEL LOW OVER THE ARCTIC IS TRYING TO PUSH FARTHER SOUTH NEAR THE ALASKA RANGE SUNDAY INTO MONDAY. THIS WOULD ALLOW SOME STRONGER SYSTEMS TO RIDE DOWN FROM THE YUKON DELTA AND BRING SHOWERS TO MUCH OF THE MAINLAND. THIS WILL BE VERY INTERESTING TO WATCH HOW MODELS HANDLE IT OVER THE NEXT SEVERAL DAYS. IT WILL BE THE NORTH PACIFIC RIDGE...WHICH HAS CERTAINLY BEEN DOMINANT THIS SUMMER...VS THE ARCTIC LOW DROPPING SOUTH...WHICH HAS CLIMATOLOGY ON ITS SIDE AS WE MOVE INTO LATE AUGUST. BY TUESDAY...MODELS STILL AGREE THAT THE PATTERN WILL BECOME MORE AMPLIFIED ACROSS THE DOMAIN. THE NORTH PACIFIC RIDGE STARTS TO ASSERT ITSELF MORE TUESDAY INTO WEDNESDAY. THIS SHOULD BRING A FEW DAYS OF UNSEASONABLY SUNNY AND WARM CONDITIONS ACROSS MUCH OF THE MAINLAND. MEANWHILE...THINGS WILL START TO BECOME MORE ACTIVE OVER THE ALEUTIANS. TYPHOON REMNANTS WILL BEGIN TO PHASE WITH COLDER AIR DROPPING SOUTH FROM EASTERN RUSSIA. THIS BAROCLINIC ENVIRONMENT COULD BE THE START OF SOME DECENT LOW PRESSURE SYSTEMS...BUT WE ARE NOT BITING OFF ON ANY ONE SOLUTION AT THIS TIME. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE MARINE...GALE WARNING 127 131 FIRE WEATHER...NONE && SYNOPSIS AND MODEL DISCUSSION...AD SOUTHCENTRAL ALASKA...MMC SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL LONG TERM...MSO
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE ANCHORAGE AK 304 PM AKDT TUE AUG 18 2015 AKZ111-190039- MATANUSKA VALLEY- INCLUDING THE CITIES OF...PALMER...WASILLA...SUTTON...CHICKALOON 304 PM AKDT TUE AUG 18 2015
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
337 PM AKDT TUE AUG 18 2015
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0330 PM HAIL HOUSTON 61.62N 149.78W
08/18/2015 E0.25 INCH AK PUBLIC
PEA SIZE HAIL REPORTED
&&
RDUELLPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
415 PM AKDT TUE AUG 18 2015
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0355 PM HAIL MEADOW LAKES 61.62N 149.60W
08/18/2015 E0.25 INCH AK PUBLIC
MULTIPLE REPORTS OF PEA SIZED HAIL IN MEADOW LAKES AND
NEAR THE GLENN HIGHWAY. REPORTS RELAYED THROUGH SOCIAL
MEDIA.
0400 PM HAIL MEADOW LAKES 61.62N 149.60W
08/18/2015 E1.00 INCH AK PUBLIC
SOCIAL MEDIA REPORT AND PICTURE OF HAIL UP TO ONE INCH IN
DIAMETER. MULTIPLE OTHER REPORTS OF SUB SEVERE HAIL
THROUGHOUT MEADOW LAKE AND HOUSTON.
&&
MCLAYPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
426 PM AKDT TUE AUG 18 2015
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0415 PM HAIL 1 SE HOUSTON 61.61N 149.76W
08/18/2015 E0.25 INCH AK NWS EMPLOYEE
ABOUT 1 INCH DEEP OF HAIL REPORTED ON ROADS BY NWS
EMPLOYEE. LARGEST REPORTED WAS PEA SIZE.
&&
RDUELLThe Kenai radar (PAHG), 137 km away, was scanning. The volume nearest the first event began at 00:38 UTC.
1 hail. Local standard time, as filed.
Largest hail reports were estimated from social media to be around 1.0 inch. An NWS employee reported 1.0 inch drifts of pea-sized hail.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alaska in 2015Every state in 2015This day in weather historyWarnings in Alaska, August 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: 593758.