The 4/15-18/2007 Event: Possible Great Snowstorm for Montrea

[donsutherland1]

The synoptic environment continues to appear favorable for the development of one of the larges snowstorms ever to hit Montreal on or after April 1. The 500 mb pattern forecast for 96 hours shows a deep trough that is in a location similar to two big April snowstorms: April 1975 and April 1997.

NCEP Ensemble Mean 500 mb Anomalies: 96 Hours:


Composite 500 mb Anomalies for the April 1975 and 1997 Snowstorms:


Both the 1975 and 1997 events saw more than 20 cm (8”) of snow fall during a 24-hour period. The storm totals for these events came to 32.6 cm (12.8”) for the April 3-7, 1975 snowstorm and 21.0 cm (8.3”) for the April 18, 1997 snowstorm. With the intense storm likely to move into central or eastern New England and then either stall or slowly drift away from there, the situation more closely resembles the larger 1975 event.

Since 1942, the biggest daily snowfalls that occurred on or after April 1 in Montreal were:

April 9, 2000: 33.9 cm (13.3”)
April 1, 1993: 31.2 cm (12.3”)
April 3, 1975: 25.7 cm (10.1”)
May 10, 1963: 21.8 cm (8.6”)
April 18, 1997: 21.0 cm (8.3”)

Since 1942, the biggest snowstorms that occurred on or after April 1 in Montreal were:

April 8-9, 2000: 37.7 cm (14.8”)
April 1-2, 1993: 33.8 cm (13.3”)
April 3-7, 1975: 32.6 cm (12.8”)
May 10-11, 1963: 25.4 cm (10.0”)
April 6-8, 1958: 24.9 cm (9.8”)
April 18, 1997: 21.0 cm (8.3”)

The heaviest snow is likely to fall from the evening of April 15 into mid-day on April 16. According to the Bufkit soundings from the 4/13 12z and 18z runs of the GFS, the snow could be falling at 2.5 cm to 5 cm (1”-2”) an hour during the height of the storm. The possibility of a slowing or stalling of the storm could change the timing of the heaviest snow. Nonetheless, if the latest computer guidance holds up, Montreal is likely to set 1 or more daily snowfall records during the upcoming event.

Montreal’s daily snowfall records for April 15-17 are as follows:

April 15: 1.0 cm (0.4”), 1962
April 16: 17.3 cm (6.8”), 1947
April 17: 5.0 cm (2.0”), 1996

In the end, the potential exists for Montreal to experience one of its heaviest falls of snow subsequent to April 1, both in terms of daily snowfall and the storm total snowfall. It is likely that the storm's total snowfall will reach or exceed 20 cm (8") and a genuine real possibility that the storm’s total snowfall could reach or exceed 25 cm (10”).

At this time, my snowfall estimates are as follows:

Albany: 2"-5"
Binghamton: 6"-12"
Burlington: 4"-8"
Concord: 4"-8"
Montreal: 7"-14" (17.8 cm - 35.6 cm)
Ottawa: 6"-12" (15.2 cm - 30.4 cm)
Worcester: 1"-2"

[coriolis]

Don, what about points south? Binghamton is not that far from me. I'm 12 miles east of Williamsport.

Please say rain.

[donsutherland1]

Coriolis,

I believe you'll wind up with 1"-3" of snow, but mainly rain. Elevation will be critical.

[coriolis]

Weather Channel this morning: 1-3 inches of snow.

[cpdaman]

don was there a blocking pattern set up/ or that developed in either of the two years with similiar 500 mb anomalies (april 75' or 97')?

[donsutherland1]

Cpdaman,

All three systems had blocks. The current system's block is headed for the Hudson Bay region. The 1975 and 1997 systems had a more typical Greenland block setup. However, at present a Greenland block is developing. However, it will likely prove short-lived, but long enough to help contribute the storm's slowing and possibly stalling for a time.

[donsutherland1]

Although Montreal has started with light rain, this does not indicate that the big snowfall that I'm expecting is in trouble. The column will gradually cool through the day and during the night, the snow will likely fall heavily. This change from rain to snow is depicted well on the Bufkit precipitation type profile from the 4/15 12z NAM.



All said, I'm still expecting 7"-14" (17.8 cm - 35.6 cm) of snow at Montreal, which would likely make this one of the biggest snowstorms on record to occur on or after April 1 in Montreal.

[cpdaman]

don do you think models are initializing the low over central NC/ southern VA well, it seems they have counted on the closed low (now over n. lower mich a bit 2 much) and thought it would slide SE instead of SSW

and do u see a storm taking a more southern route (even though it may remain elongated) as a reasonable possibility ( i finally got the courage up to ask this question btw)