April 2017 will come in as the second wettest on record at YOW with 147.6mm as the final tally. There were only 9 completely precip-free days during the month and the highest single-day value was 36mm on the 6th. The average daily mean temp was 7.4c which is above-normal.

The top 5 Aprils in terms of rainfall totals would now be:

2011 – 166mm

2017 – 147.6mm

2005 – 143.8mm

1991 – 130.6mm

1984 – 124.1mm

This is in stark contrast to April 2016’s meager 20mm and is in excess of 200% of average rainfall for the month vs climate normals.

This was also the second wettest April for YUL with 156.2mm (behind 2005’s 158.8mm) and the 5th wettest April for YYZ with 108.8mm recorded.

May looks as if it will pick up where April left off in that regard as a vigorous downstream -NAO blocking pattern should develop as advertised by the various ensembles, the impetus for additional eastern storminess through the medium range.

Here is the IR satellite view of the current system:


The late-week storm mentioned in earlier posts remains a likelihood based on the overnight guidance. The eventual track looks farther east compared to the ongoing low.

00z GFS @ hour 120:


00z ECMWF, same timeframe:


Total precip from the 00z GFS ensembles @ day 7:


Meanwhile the expected pattern amplification featuring lower heights along the west coast and carving into the GL will also flex a longwave ridge into the Prairie Provinces, leading to a significant warm spell for that region. Parts of AB and SK could see noteworthy deviations from normals and readings in the mid-20’s under sunny skies.

00z GFS 2m temp anomalies (F) @ hour 120: