We left Nipika at 11:20 AM (MDT) to take some rest, knowing that we would have to go back on site tonight for another night shift, to catch the 15 mm of total rain forecasted by the model GEM for the next 24 hours. After a whole night spent to get only 1 mm of rain or so, hopefully the weather will finally give us the dose of storm we are waiting for. Team Nipika’s day started with the arrival of Cécile and Selina at noon (1800 UTC). Their arrival was greeted with light precipitation that continued for the duration of their shift. There were a wide variety of clouds, but the wind was but a whisper throughout the day. The usually rambunctious ground squirrels crawled along slowly beneath the gentle, but constant onslaught of precipitation. Meanwhile, the observers hid beneath a well-orchestrated tarp. Towards the end of the afternoon the precipitation grew a little more exciting, with a precipitation intensity of about 3 as we drove the truck out to Nipika Resort to meet up with Hadleigh and André at 1645 (2245 UTC). After this period, rainfall continued to be steady and light to moderate until it stopped quite sharply at 2130 MDT. During this event we were able to see some very interesting results from our Parsivel and Micro Rain Radar. Overall, Team Nipika received about 8 mm of precipitation throughout the day.
- Selina and André
Field Participants: Cécile Carton, André Bertoncini, Hadleigh Thompson & Selina Mitchell
May 16 & 17 (MDT)
During our SPADE meeting on May 16 at 6 PM MDT, I discussed the GEM 2.5 model updates, however I (Juris) completely disregarded the radar and what was approaching. Thankfully, Stephen mentioned that precipitation was occurring to the South of our station and making its way north. We split into teams and made our way to Fortress as quickly as we could.
We (Hilary & Juris) arrived at Fortress by 0120 UTC on May 17 and began observations at 0130 UTC. We were curious about what the direction of the wind would be at top, given that the radar was showing a southerly flow. We weren’t surprised when we arrived on site to find that the winds were generally coming from the NW, which is more than often the case. We had mixed precipitation at the top at 0130, which transitioned to solid precipitation by 0200 UTC.
At 0340 UTC visibility became quite poor due to heavy fog and, finally, the switch in wind direction occurred that we were hoping for - some southerly to southeasterly winds! There was an organized heavier precipitation band (2-4 mm/h) situated along the foothills of the Rockies. There were moments of large aggregates and at 0405 UTC the parsivel measured aggregates up to 1.3 cm in diameter. By 0430 UTC, 1.5 cm of snow was measured on the snow depth board with a SWE of 1.5 mm.
Around 0420 UTC particles became much smaller and were often bouncing off the velvet pad. It remained very foggy with different types of precipitation, such as needles and rimed irregulars. Later in the evening at 0610 UTC, needles were observed and shortly after, at 0613 UTC, it transitioned to graupel. Pictures became easier to take as temperatures cooled off around 0840 and dipped below 0C.
Early morning May 17 (MDT)
Aurélie & I (Charlie) left from BGI just before 0900 UTC but took a bit more time than usual to get to the site. The road was particularly foggy and we did a car sonde as soon as we observed the transition of rain to snow in Fortress Mountain. We experimented with our first night shift doing our observations in the dark. The snowfall intensity was pretty light almost all of our part of the event, except for a short peak of moderate snow around 1130 UTC. We observed mostly small hydrometeors, more precisely some beautiful fernlike dendrites, some rimed dendrites and a lot of needles! The weather conditions were stable; the temperature was between -2 and 1 degrees, the wind was very light from north and the visibility stayed very reduced. It was interesting to observe another event with north winds measured at the station even if Strathmore radar was showing cells coming from South.
Afternoon May 17 (MDT)
When Hilary and I (Juris) first arrived at 1811 UTC, precipitation was light and it appeared as though precipitation was making its way eastward across the foothills of the Rockies. Snow intensity was heavier (4) with aggregates of dendrites and stand alone needles. Blanketed precipitation occurred across all the continental divide.
However, it was noticeable that although the radar was showing light blue across the continental divide, the Kananaskis valley down Hwy 40 often showed no precipitation according to the radar (screenshot). This continued on, whereby the Kananaskis valley was evidently clearing, while the Columbia valley was blanketed in stratiform precipitation.
Temperatures starting at 1904 UTC on May 17 were hovering around 0°C +/- 0.2°C until May 18 at 0047 UTC. These temperatures made it hard to take photos. It was especially noticeable when temperatures climbed slightly above 0°C because the particles melted too quickly on the velvet pad, whereas when temperatures were just below 0°C, we found that it was possible to take pictures. Particles became large aggregates around 0210 UTC on May 18 and we were able to take some really beautiful pictures for about half an hour (maybe even our best photos yet!). The snow ended suddenly around 0250 UTC and we took our last observation at 0300 UTC and headed home.
Field Participants: Hilary Smith, Juris Almonte, Charlie Hébert-Pinard & Aurélie Desroches Lapointe