The Storm Parade: Rains, Winds, and Mountain Snows *Gasp*

Sunday, October 12, 2014, 8:13 PM - Dust off those umbrellas, Vancouver. This isn't October 2013.

Last October, Vancouver accumulated a paltry 37.4 mm of rainfall, well below climate averages. Unfortunately, to skiers dismay that trend continued for most of Winter 2013- 2014.

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If you're a fan of rain, Van, there's high confidence that next week will bring robust changes with several potent frontal systems impacting the BC coast. It's possible that rainfall amounts over the next 7-10 days for certain regions the South Coast will exceed the amount of rain that's fallen over the past several months! Truly astonishing.

One possibly overdone deterministic long range model, showing copious amounts of precipitation along western Vancouver Island and over the North Shore mountains indicative of strong SW flow.

A couple recurving typhoons along Japan's coastline will be responsible for this intense shift in weather as discussed last post — the evidence is mounting. Thanks Phanfone.

Using ensemble model evidence, the conclusion is undeniable.

A rainfall warning may need to be issued for portions of the South Coast for next week, as the jet stream takes direct aim at the South Coast:

NAEFS ensemble forecast shows a potent jet stream moving through the region early next week (200 hPa wind speed)

• A weak trough is forecasted to dissipate as it slides down the British Columbia coast Friday evening with another shortwave trough moving over the region on Saturday evening — both events bringing precipitation, although the latter looks heavier.
• Monday is now looking considerably less wet, especially for the morning, as a weak upper level ridge slides over Southern BC, which will hopefully delay the heaviest of the precipitation until Monday afternoon for Vancouver.

A weak temporary high pressure ridge may briefly break up the storm parade, Van. Finger's crossed.

• By Tuesday heavier precipitation reaches all areas of the coast and several models are now indicating a potentially potent low pressure system developing off a favourable jet stream Wednesday evening in the Pacific Ocean.
• Initial rainfall forecast: 50-100 mm+ likely next week with the highest amounts near the North Shore Mountains and Western Vancouver Island and lower amounts towards YVR.

Spot the rain shadow? Want to avoid the heavy downpours next week? head off to Victoria, but you'll have to thank the mighty Olympic mountain rain shadow to their south -- Their orographic influence is quite impressive

The Long Ranger

A couple long range models are attempting to create a strong, potentially damaging low for Wednesday evening into Thursday. Model data must be interpreted very carefully 5-7 days out, but the Canadian model is also showing hints of a developing system— and currently modeling the track a little further south with a higher pressure.

With West Coast wind storms, the most dangerous often intensity and mature as they make landfall, while the garden variety storms tend to weaken as they arrive in our waters and curve into Haida Gwaii.

GFS model highlighting the potential for a storm to undergo bombogenesis during the middle of next week, as favourable atmospheric dynamics look to intensify a low pressure system

There's a type of storm track West Coaster's have to pay special attention to. On the right, climatologist Wolf Reid outlines the most destructive Pacific Northwest wind storm tracks in history; note they all share that similar trademark southwesterly curve.

Image by Wolf Reid, Climatologist at UBC

Ensemble model support also shows our winds substantially increase, Van. Breezy to Windy conditions likely for most of next week.

Freezing levels will also fall from a towering 3500 metres, to a more meager and desirable (for skiers) 1500 metres, ushering in the first significant high elevation snows for the coastal range.

Wax those skis...

NCEP control model analyses a strong wind event for the middle of next week -- Stay tuned

Oh, did I mention high elevation snow yet? *Skiers Cheering*

GEM raw model output (10:1 snow ratio), indicating the Coastal Mountains could be in for a treat next week.

Although this is direct model output, this gives an idea of some of the regions that could potentially see some accumulating snow next week (above 1500 metres). Portions of the Vancouver Island Mountain Range including Mt. Washington also may see some accumulating snow, although there's still some uncertainty on where the freezing level ends up, depending on the track of the low(s).

Tune into The Weather Network for coverage of this changing and potentially active pattern in the west.

The freezing level going to be significantly lower next week, bringing heavy wet snow to higher elevations