First Wind Storm in 6 Months Friday

April 6, 2017

4pm Thursday

As mentioned in last night’s post, the last time we saw a deep low tracking up the coastline to give us strong south wind was way back in October.  All morning/midday models are in and show a windstorm both at the coast and likely for spots in the valley too.  The NWS is on board with high wind warnings up for the coastline and wind advisories for the valley.  Read the previous post for more detail since not much has changed.

COAST

Our forecast hasn’t changed much for the coast.  The wind appears to come in two waves out there.  First wind arrives right at sunrise (6am) or just before, then a 2nd stronger surge during the late morning hours:

IN THE VALLEYS

All areas south of Portland should turn windy by sunrise with general 30-45 mph gusts then spreading INTO the metro area by mid-morning.

Between 10am-2pm bands of heavy showers and thunderstorms should mix even stronger wind gusts down to the surface (where we all live) in isolated spots.   This is a setup where some neighborhoods could get a 50-55 mph gusts and others stay down in the 30-40 mph range depending on where the heavy showers show up.  We can’t predict that well, but plan on some power outages and a few trees down.

In this pattern with cold air moving in overhead, a few thunderstorms, and some twisting in the atmosphere, it’s quite possible we get a few reports of funnel clouds.  Keep an eye on the sky tomorrow!

The screaming message here is that Friday should be a very active day (mainly before 3pm).  And for the first time in 6 months we get a southerly windstorm west of  the Cascades here in the valleys.

 

For the geeks:

A tough forecast for Friday since once again the isobar alignment for strong south wind in the valley is far from ideal (for strong wind).  In the past, without high-res models, I would have just forecast 30-40 mph gusts at best tomorrow.  But all models are very insistent on mixing down the strong south wind that we know will be just a couple thousand feet overhead.  Multiple models are showing 50-65 mph gusts in the north valley tomorrow morning.  Just one example from the NAM below.  If these models are correct, then this will be the strongest April windstorm in the valley since the 1960s!

For good reason our forecast didn’t go that extreme, but I bumped up the numbers slightly from what we were forecasting last night at this time.  We’ll see how it goes!

Chief Meteorologist Mark Nelsen