A weak thermal trough over the mainland of Alaska allowed thunderstorms to develop in the Matanuska Valley. Steering flow was very light, making the storms almost stationary.
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The episode as NWS AFC wrote it up.
A weak thermal trough over the mainland of Alaska allowed thunderstorms to develop in the Matanuska Valley. Steering flow was very light, making the storms almost stationary. Combined with poor drainage, this produced localized flooding in Palmer, Alaska.
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 3, 3:43 PM AKST, 1 hour 17 minutes earlier.
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 443 PM AKDT Mon Jun 3 2019 .ANALYSIS AND UPPER LEVELS... An upper ridge centered over northwest Alaska (vicinity of Nome) is building southward over western Alaska, leading to low level warming and development of a well-defined thermal trough. This trough is centered right through the hear of the Kuskokwim Valley and on down into inland portions of the Bristol Bay area. Some remnant showers from yesterday's activity have been tracking southward across this region this morning. As these showers exit and breaks in the clouds develop new convection is initiating along the thermal trough. While the overall trends look on track for isolated to scattered thunderstorm activity, expect those areas with thicker cloud cover will remain more stable and see fewer showers and thunderstorms. Meanwhile, a weak trough is dropping southward across the eastern Alaska interior, across Southcentral, then undercutting the ridge as it heads across Bristol Bay and the Alaska Peninsula. Southcentral Alaska is also seeing low level warming and development of its own thermal trough, largely due to subsidence of air flowing from the north across the Alaska Range. The increased instability combined with weak forcing from the trough aloft are leading to formation of showers over and along the mountains, especially the Talkeetna Mountains. While instability looks to be great enough to form some showers over interior valleys, expect most of the convection for later today will advect off the mountains and over the valleys. With most of the convective activity initially over the mountains, abundant sunshine can be found in the lowlands. Out over the Bering Sea and Aleutians a ridge of high pressure is leading to stable conditions, with widespread low clouds along with areas of fog. A low pressure system moving up the west side of the ridge is bringing some light rain and marginally stronger winds to the far western Aleutian Islands. && .MODEL DISCUSSION... Models remain in fairly good agreement with larger scale features, with just some minor differences the next few days in the trough settling in over Southcentral and the short-waves rotating around it. In this pattern of "diurnally driven convection", the forecast of showers and thunderstorms each day will heavily depend on smaller scale features such as amount of sunshine, localized wind patterns (which help delineate stable/unstable air especially near the coast), storm motion, and the aforementioned short-waves aloft. Thus, while have some general idea of preferred areas for convection over next few days, will have to wait until about 12-24 hours out to lock into the details for each day. && .AVIATION... PANC...VFR conditions will persist. There will be some showers and thunderstorms north of the airfield this evening over the Mat-Su. The storm motion will track these off to the south-southwest. However, with notably more stable air over northern Cook Inlet, feel fairly confident thunderstorms will not make it down to the terminal. At worst, might see some light passing showers - most likely 06Z or later. Also, expect a weak Turnagain wind to bend into Anchorage at some point this evening, but the exact timing is in question and will partially depend on the evolution of convection to the north. Tuesday looks favorable for more convection over the Chugach. Based on northerly flow, storm motion should keep any thunderstorms which form confined to along and near the mountains. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Monday afternoon through Wednesday afternoon)... The weather over Southcentral for the next few days will be driven by an area of high pressure over the Bering and an upper level low over the Alcan border. As the low slowly moves to the southwest, several upper level waves will move through Southcentral from north to south. Diurnally enhanced showers and isolated thunderstorms are expected across most of Southcentral especially during the afternoon and evening hours each day. Warmer temperatures are expected through the middle of the week as a thermal trough in place along the south side of the Alaska Range allows for ample daytime heating. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)... Thunderstorms are primarily forming over the Kuskokwim Valley this afternoon where skies where partly cloudy skies earlier in the day allowed for greater heating. With northeasterly steering flow and the thermal trough continuing to strengthen and build south, still do think there is potential for some thunderstorm development around the Bristol Bay area through the evening although with somewhat sparser coverage. Conditions on Tuesday look more favorable for more abundant and potential stronger thunderstorm development in the late afternoon through evening. Both greater solar heating due clearer skies earlier in the day and the strengthening thermal trough will bring stronger instability to the area. The upper level ridging strengthening along the coast will push the thermal trough further to the east, pushing the focus for thunderstorm development closer to the Alaska Range for Wednesday and Thursday. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)... Persistent ridging will keep stratus abundant over the Bering through Thursday while several frontal systems lift north across the western Aleutians. Surface ridging centered near the Pribilof Islands will keep a tight onshore pressure gradient along the southwest Alaska coast supporting northerly winds in the 25 knot range along the Kuskokwim Delta coastal waters. Northerly winds will increase as well tonight and tomorrow through the gaps and passes in the Alaska Peninsula. && .MARINE (Days 3 through 5/Thursday through Saturday)... Quiet seas continue for all Marine areas due to high pressure. Forecast confidence remains high. && .LONG TERM FORECAST (Days 3 through 7/Thursday through Monday)... High pressure is still expected to be present through the week. We have high confidence in this forecast, especially since the pattern shift we were expecting is coming to fruition. Now that it has arrived, we can be confident that it will hold in place. The day-to-day weather will still need to be figured out in the short term as confidence is low in models picking out more subtle weather features. Later in the period, models are still identifying a low pressure system moving into the Gulf of Alaska. Weather associated with the low looks as though it won't arrive until Monday, but southcentral AK may start to see its influence over the weekend. Timing is also subject to change as model data is still suspect that far in out in time. Models all agree that we will see a shift back to a low in the Gulf of Alaska, but do not agree on low placement, which greatly affects what kind of weather we get and when we will get it. So, increasing confidence in a shift back to cooler and wetter weather next weekend, but low confidence on the details. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...155 165 177 178 180. FIRE WEATHER...NONE. && SYNOPSIS AND MODEL DISCUSSION...SB SOUTHCENTRAL ALASKA...KO SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR MARINE/LONG TERM...BB
PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE ANCHORAGE AK
533 PM AKDT MON JUN 3 2019
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0532 PM HAIL 1 N PALMER 61.61N 149.12W
06/03/2019 M0.25 INCH MATANUSKA-SUSITNA AK TRAINED SPOTTER
HAIL LASTED FOR 10 MIN WITH ACCUMULATION UP
TO 0.4 IN DURING THAT TIME FRAME.
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
534 PM AKDT MON JUN 3 2019
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0532 PM HAIL 1 N PALMER 61.61N 149.12W
06/03/2019 M0.25 INCH MATANUSKA-SUSITNA AK TRAINED SPOTTER
HAIL LASTED FOR 10 MIN WITH ACCUMULATION UP
TO 0.4 IN DURING THAT TIME FRAME.
&&PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE ANCHORAGE AK
540 PM AKDT MON JUN 3 2019
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0538 PM HAIL HIGHLAND ROAD - EAGLE R 61.23N 149.45W
06/03/2019 M0.25 INCH ANCHORAGE AK NWS EMPLOYEE
THUNDERSTORMS WITH HEAVY RAIN AND HAIL. LOTS
OF 1/4 INCH HAIL. 0.24 INCHES OF RAIN IN 8
MINUTES AND STILL COMING DOWN HEAVILY.
0532 PM HAIL 1 N PALMER 61.61N 149.12W
06/03/2019 M0.25 INCH MATANUSKA-SUSITNA AK TRAINED SPOTTER
HAIL LASTED FOR 10 MIN WITH ACCUMULATION UP
TO 0.4 IN DURING THAT TIME FRAME.
&&The national radar mosaic for the moment the first event began.
1 heavy rain. Local standard time, as filed.
Palmer ASOS reported 0.44 of precipitation between 5:32 p.m. and 6:00 p.m. This caused localized flooding of parking lots in the Palmer area. Quarter inch hail was also reported at this time.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alaska in 2019Every state in 2019This day in weather historyWarnings in Alaska, June 2019
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: 821203.