A feast of moisture is set to persist for regions of the country where additional precipitation is an unwelcome guest, aided and abetted by a stubborn upper-level blocking pattern.

A Pacific frontal system will drive some convective activity ahead of it’s trek through BC where SWS are in place for the SW and interior regarding associated heavy downpours.

06z RDPS total precip @ hour 48:


The expansive low expected in the east is advancing towards ON where rainfall warnings are up for the S/SW and weather statements cover a good deal of S QC & the Maritimes. Flooding is already a major issue for many parts of this region due to the preceding winter and spring conditions.

06z 3km NAM total precip @ hour 60:


Atlantic Canada will also feel the effects of this system as rounds of rainfall pinwheel around the deepening low.

06z GFS @ hour 60 / 84 / 108:


This upper complex will meander into next week as the established ridging in the NAO domain puts a road jam in place, though precip looks more spotty and scattered by that point as things gradually degenerate.

At what point we see a full breakdown of this regime remains to be seen, at least in terms of the trough/ridge/trough setup over NA. The Euro ensembles suggest that it may endure in some form through the medium range as of the overnight run.

00z EPS 500mb height anomalies @ day 10:


Wrapping up April 2017, the 500mb / temp / precip outcome:


Temps vs forecast:




One of the big stories (unsurprisingly) revolves around how wet the season has been so far, particularly through the west and the GL into QC. Exceptions have been through northern/central regions and sections of the Maritimes.

30-day precip as a percent of average, April 2nd to May 1st:


Stats breakdown by select locations.

YZF Yellowknife NWT

Mean temp -6.2c (-5.3c)

Rainfall 0mm (2.5mm)

Snowfall 7.4cm (10.3cm)


YVR Vancouver BC

Mean temp 9.5c (9.4c)

Rainfall 134mm (88.1mm)

Snowfall 0cm (0.3cm)


YYC Calgary AB

Mean temp 4.8c (4.6c)

Rainfall 46.7mm (10.8mm)

Snowfall 16.6cm (18.8cm)


YYZ Toronto ON

Mean temp 9.4c (7.1c)

Rainfall 108.8mm (63mm)

Snowfall 2cm (4.5cm)


YOW Ottawa ON

Mean temp 7.4c (6.3c)

Rainfall 147.6mm (63mm)

Snowfall 0.4cm (11.3cm)


YUL Montreal QC

Mean temp 7.9c (6.4c)

Rainfall 156.2mm (67.7mm)

Snowfall 3.6cm (12.9cm)


YQM Moncton NB

Mean temp 4.9c (3.5c)

Rainfall 42.5mm (62.3mm)

Snowfall 6.8cm (31.2cm)


YHZ Halifax NS

Mean temp 5.2c (4.4c)

Rainfall 83.4mm (98.2mm)

Snowfall 8.8cm (15.9cm)


YYT St. John’s NL

Mean temp 1.3c (1.9c)

Rainfall 59.3mm (96.1mm)

Snowfall 44.6cm (25.3cm)


This was the fifth wettest April on record for YYZ Toronto ON, YHM Hamilton ON and YYJ Victoria BC. It  was the second wettest for YOW Ottawa ON, YUL Montreal QC and YVR Vancouver BC. It was the third wettest for YYC Calgary AB.