16 May, 2013 11:06

Started: 16/05/2013 2:48 AM by Chan

16 May 2013

Models are in good agreement for the next two days with broad upper trough near the coast and slow-moving impulses moving eastward. Flow over Yukon and BC coast will become more southerly as another trough and weak front approaches from the Gulf of Alaska.

Over the South Coast expect some light precip to linger this morning but slight ridging this afternoon should dry things out. 00Z REG and 6Z LAM are pretty aggressive in bringing showers back to the coast on Friday as a weak impulse approaches from the southwest. 6Z REG backs off a bit and delayed the onset for the inner coast. So we will probably put a high chance of showers for most of the day. The GFS is drier but the ECMWF is similar to 0Z REG. Interestingly CMC Ensem is dry over srn Vrisl but REG has the highest amounts there on Friday.

Relatively quiet convective day today with lack of instability and moisture as well as weak flow over BC. Highest chance of thunderstorms in srn intr and Chilcotin where it is most unstable. More active day in store for Friday over western half of interior as instability/moisture/shear increase in the afternoon.

Edited: 16/05/2013 4:11 AM by Geng

Marine:

A trough of low pressure will approach the offshore waters tonight through Friday giving strong southerly winds of 20-30 kts to the offshore waters. Strong wind warning for JDF late Friday afternoon as an offshore ridge pushes toward the south coast.

A strong ridge of high pressure will build and stay over the offshore waters Saturday through Monday giving marginal gale force northwesterly winds over northern offshore waters on Saturday. The winds will spread to southern offshore waters and inner south coast waters on Sunday and Tuesday.

Posted: 16/05/2013 3:16 AM by Chan

Longer range… Models are in general agreement over the weekend with trough axis moving across BC Saturday and Sunday. Scattered light precip on the coast Saturday will then shift into the interior Sunday. After that Global model remains the outlier with all the other models digging a deep upper low from the north onto coastal BC and Pacific NW early next week, with the Global is way weaker and slower in doing so. CMC Ensemble leans towards the other models but is still slower and stall the centre over the South Coast instead of Pac NW. Last night’s NCEP-WPC and CMC discussions both favour the foreign models. CMC Ensembles could be a compromise as well so day 6/7 forecasts in scribe had already accounted for some cooler temps and higher POPs. We have also adjusted for more clouds on Monday and some thus slightly cooler temps than raw scribe on the south coast.

Posted: 16/05/2013 10:54 AM by Au

Convection – A weak cold trough over the southern part of the province this afternoon will provide a bit of instability to the area. Upper flow is very weak so isolated single-cells thunderstorms are expected. CAPE and PW are quite low so heavy downpours are not of concern. Hail not expected as convective clouds will not be deep enough and there’s no shear support. T2=10C so gusts of up to 30kts are possible.

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