A thermal trough lying across the Interior portion of the state extended towards Kuskokwim Delta and Bristol Bay. Abundant moisture at the surface combined with cold temperatures aloft to cause thunderstorms over the region.
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The episode as NWS AFC wrote it up.
A thermal trough lying across the Interior portion of the state extended towards Kuskokwim Delta and Bristol Bay. Abundant moisture at the surface combined with cold temperatures aloft to cause thunderstorms over the region. Convergence along the Kilbuck mountains aided in a few of these thunderstorms becoming severe.
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 Jun 5, 4:48 PM AKST, 6 hours earlier.
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 548 PM AKDT Tue Jun 5 2018 .ANALYSIS AND UPPER LEVELS... Generally easterly upper level flow with weak embedded waves continue across Southcentral Alaska. The axis of the thermal trough extends from the Tanana Valley to the Lower Yukon Valley. As of noon, numerous lightning strikes had already been detected from the Tanana Valley to the upper Yukon Valley. Visible satellite imagery showed convection initiating along the Alaska Range and Talkeetna Mountains this afternoon. Low stratus and fog are evident this morning over the lower Kuskokwim Valley is rapidly dissipating. A wave moving west across the northern and western gulf is bringing light rain to the coast and southern and eastern Kenai Peninsula. Patchy flow in interior areas of the Bristol Bay have dissipated. Many areas in Southwest Alaska was under generally fair skies setting up prime conditions for solar heating and convection. A weakening trough extends over much of the western and central Bering Sea/Aleutians holding clouds and areas of light rain. && .MODEL DISCUSSION... Models are in generally good agreement through the short term. Tracking weak upper waves and timing and location of convection will be the main forecast challenge. && .AVIATION... PANC...VFR conditions with showers are expected through the overnight hours. Gusty southeast winds across the airport complex will end late this evening. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3...Wed through Fri)... For tonight, southeast winds will remain gusty through the usual areas like the Knik Arm and west Anchorage. Several showers are tracking from northeast to southwest across the area, with some tracking right along the Glenn Highway. This could lead to a wet commute for many folks. Some models show that the convection from the Copper River Basin consolidates overnight and moves into the Cook Inlet Region as steadier rain. We opted to increase PoPs overnight to account for this. There is likely to be some fog/stratus that develops after this precipitation moves through the Susitna Valley, but trying to nail down exactly where it will be remains challenging. Went with a persistence forecast for now. Otherwise, the overall pattern will remain much the same into the end of the work week. Days will generally start out with partly to mostly sunny skies and temperatures at or slightly below normal. By afternoon, expect convection to develop along the higher terrain, generally over the Copper River Basin and Susitna Valley. As the sun helps to warm the surface and build instability, convection will increase in coverage with showers blossoming over the Talkeetna Mountains and parts of the Chugach. The best chance for afternoon/evening thunderstorms still looks to hold further north towards the AK Range, but there should still be some isolated cells further south. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)... With strong instability pushing into Southwest Alaska accompanying the thermal trough this afternoon and evening as well as plenty of sunshine, things look good for scattered thunderstorm development through the Kuskokwim Valley and northern portions of the Kuskokwim Delta. Tonight's easterly wave will track further south than yesterday's, pushing across the Greater Bristol Bay area and turning the showers and thunderstorms to more of a stratiform sort of rain overnight and further expanding the expected coverage of wetting rains beyond what this evenings storms will put down. With the thermal trough further strengthen Wednesday afternoon and evening, the accompanying strong instability will push even further into southwest Alaska for another afternoon of numerous showers and scattered thunderstorms. While instability will diminish somewhat Thursday and Friday, there will still be plenty to continue a pattern of afternoon/evening convection producing scattered showers and isolated thunderstorms. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)... A ridge gradually moving south into the Bering will push the weaken trough stretching from the Kamchatka Peninsula east southeast across the eastern Aleutians, Alaska Peninsula and western Gulf to the south as it shears apart and dissipates. A North Pacific low will track past the western and central Aleutians but now looks to remain south of 50N. A second developing frontal system will track northeast towards the central and eastern Aleutians Friday and Friday night but likely brush by just to the south. && .LONG TERM FORECAST (Days 4 through 7)... The long term forecast begins on Friday night with an upper level ridge moving into the Gulf of Alaska, bookended by two low pressure systems, one in the Southeastern Gulf and the other just south of the Central Aleutians. A weak to no-flow pattern will set up over most of mainland Alaska leading to pleasant and warm weather for the weekend. Rising 1000-500 mb thicknesses will promote above average temperatures for most of the southern mainland Saturday and Sunday, with Sunday looking to be the warmest day of the weekend. A thermal trough will develop over the interior promoting diurnally driven convection over the higher terrain in the afternoon. One kink to the forecast is the possibility of an upper trough digging south across the state from the North Slope over the weekend. Models are consistent in the fact that there will be a trough sweeping across the northern half of the state but are not in agreement as to how far south the trough will get. The GFS has the trough splitting west as it reaches the AK Range while the EC is more bullish and keeps the system fairly intact as it crosses the mountain range. If the EC solution verifies, widespread thunderstorms will likely develop over the Northern Susitna and Copper River Valleys Saturday night, possibly exasperating recent fires that have popped up in those areas. Those with a keen interest in the fire weather conditions should pay close attention to the forecast this weekend as the situation develops. Looking into next week, models are in agreement with an area of high pressure building over the mainland, resembling a typical pattern associated with very warm summertime temperatures. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...None. MARINE...None. && SYNOPSIS AND MODEL DISCUSSION...RMC SOUTHCENTRAL ALASKA...MSO SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR LONG TERM...KVP
The Bethel radar (PABC), 64 km away, was scanning. The volume nearest the first event began at 07:47 UTC.
2 hail. Local standard time, as filed.
Radar indicated the possibility of severe hail and strong downdrafts within this storm.
Radar indicated the possibility of severe hail and strong downdrafts within this storm.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alaska in 2018Every state in 2018This day in weather historyWarnings in Alaska, June 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: 759363, 759365.