Tuesday, March 1, 2016 The day started out at sunrise with broken Ci, some St in the bowl and frost after a mainly clear night. 1-2mm of hoar frost was found on the roof in the morning, that may have resulted in a TR of precip recorded. A system to the SW bringing heavy rain to Vancouver gradually spread As across the sky (BKN-OVC by noon and OVC by 4pm) with increasing amounts of lower clouds too. The increase in incoming longwave radiation seen at the roof station is evidence of the increasing cloudiness through the day. By 10 AM radar shows scattered precip had reached Williams Lake; by 3 pm the leading edge of precip. Coming from SW was at the XPG radar location. Rain started in the bowl at about 8 pm Tuesday. Pressure was falling rapidly during the day reaching a minimum in the evening and then rising sharply again. Winds were light north to northeasterly all day. Wednesday March 3, 2016 There was light rain in the bowl at sunrise – there had been some wet snow accumulation overnight. On campus at 7:15 am it was snowing lightly, overcast Ns cloud. The snowbench on the roof had been accidentally cleared by facilities, however a patch of snow on the ground was saved for student snow depth measurements – estimated (not measured) at about 5 cm and quite wet. Intermittent light snow during the day (rain in afternoon) with periodic cloud brightening, by late afternoon low stratus, tending to fog at UNBC with drizzle. Precip accumulations during the day were about .2 mm. Thursday March 3, 2016 There had been snow overnight – wet slush in the bowl and snow (approx 5 cm) on roof – similar to on Wednesday morning. Morning clouds were about half St with As behind – overcast although patches of blue could be seen and the sky was brightening. Conditions remained broken to overcast with mainly St for most of the day; no precipitation however. There were even some sunny periods. The variable incoming longwave radiation from mid-day onward indicates the variable cloudiness. By late afternoon OVC in St and a band of showers (seen on radar) is approaching from the SW. By 8 pm in the evening fog was starting to form on campus with breaks to clear sky observed with patches of cloud - likely Ci to As with small amounts of St. Friday March 4, 2016 Morning, strong wind from south, sky with cloud in all three layers plus some patches of blue, temps around +6 in bowl, ground is dry. By noon sky is broken but over half the cloud is thin cirrus, so it is “sunny” with blue sky to the southwest. The variable incoming longwave radiation is indicative of variable cloudiness. Also strong southerly winds and warm – temps over 10C. Afternoon windy from south with “chaotic sky” (complex variety of different clouds in all layers that change frequently), temperatures around 11C. Weekly summary: Two weather events were apparent, bringing overnight snow that was observed Wednesday (a) and Thursday (b) mornings. Pressure gradients and southerly winds increased on Friday in advance of a system (c) that was to bring strong convection on Saturday. 1 2 3 4 a b c T W R F

b a a b Thu 4am Tue 4am b a b c Wed 4am Fri 4am The upper-level charts are less useful. There is an upper ridge over BC that gets suppressed when systems pass through. The a b c systems are the short-wave troughs - upper-level counterparts to the surface systems b a b c Wed 4am Fri 4am

Tuesday, Mar 1 * a b Tue 10 am AF * * b a a b Tue 10 am Tue 10 pm Increasing clouds becoming lower as a approached As a crossed the coast mtns and the upper ridge position it lost its identity as a frontal system: a trough on the 10 pm map, corresponding to the pressure minima observed at the roof wx stn Throughout most sfc maps arctic front (AF) is a quasi-stationary frontal feature marking the boundary between cA air to the north and mA / mP air – it is not associated with weather changes at PG * a b Tue 10 am AF * * b a a b Tue 10 am Tue 10 pm

Wednesday, Mar 2 morning System a that delivered about 5 cm of snow overnight has passed through and b is nearing the coast, beginning to spread cloud over PG through the day Meanwhile the AF keeps its position across NE BC * a b Wed 10 am AF AF * * b a b a Wed 10 am Wed 4 am

Wednesday, Mar 2 afternoon/evening System b crosses PG overnight on Wednesday, bringing overnight snowfall that was observed Thursday morning Meanwhile the AF keeps its position across NE BC b * Wed 10 pm c AF AF b b * c * a c a Wed 10 pm Wed 4 pm

* c Thu 10 am b AF d * b c * c Thu 10 pm Thu 10 am Thursday Mar 3 System b passed through the preceding night, depositing about 5 cm of snow at UNBC for the morning observation During the day the clouds were BKN to OVC with some partial clearing overnight System c approached through the night and on Friday bringing a strong pressure gradient with it for Friday AF d * b c * c Thu 10 pm Thu 10 am

* c Fri 10 am d AF * c AF d d c Fri 10 am Fri 4 pm Friday Mar 4 This day is characterized by strong southerly winds that formed ahead of the system c as it neared BC Note the strong pressure gradient over BC ahead of c at 10 am. On Saturday strong convection in the unstable air behind d brought lightning and hail to PG. * Fri 10 am c d AF AF d d c Fri 4 pm