We have been in a persistent pattern of above-normal temperatures without major heatwaves for the past week.
But after a short warming today and tomorrow, a cool-down to normal or even below-normal temperatures is in store for the region. A week without significant thunderstorm activity, but with coastal drizzle.
To understand what will happen, consider the forecast upper-level maps for the next week.
But not just any maps. Let me show you the average of many forecasts...an ensemble of predictions.
Why? Because an average of a diverse collection of forecasts generally has more skill than any individual forecast. These maps show the upper-level heights (solid lines) at 500 hPa pressure, about half of sea-level pressure. Alternatively, you can think of them as representing pressure at 18,000 ft. The shading shows the difference from normal (blue is below normal--troughs, reds indicate above normal or ridges).
There is an offshore trough and a ridge centered over Alberta. This pattern results in modestly above-normal temperatures for the NW.
The latest NOAA National Blend of Models (statistical combination of many forecast models) indicates a substantial cooling from Saturday through mid-week, with highs only getting into the mid-70s on some days. Mid-50s at night, which means good sleeping!
To put it a different way: expect temperate, moderate, and delightful weather this week after a warm weekend. The string of 80s at SeaTac will be ended. And the below-normal wildfire situation over Washington will continue.
Portland and Medford NWS both mention possibility of convection with this weekend's short wave.
ReplyDeleteMichael... the models are not suggesting thunderstorms in western Washington. And the Portland office's discussion you mentioned was downplaying the thunderstorm threat:
Delete"Bumped up chances for showers across the area
(best chances along the coast), but have held off on mentioning
thunder as both NBM and SREF probabilities max out around 10%. That
said, elevated convection still possible so will need to continue to
monitor the situation."
You say "no major heat waves" recently. Maybe not for western Washington but at the Tree Fruit Research Center in Wenatchee it is now going into the 15th consecutive day with maximum temperatures above 98 degrees, a record period of temperatures above this level(period of record back to 1935). So far, 13 of those days have been above 100 with a maximum reading of 107 on one day which is only a few degrees below the all time high for July at the TFRC. It looks possible for about four more days of temperatures near or above 100 and if we do not get too much smoke from forest fires, the maximum temperature for Sunday could be near the record of 110. So far, Eastern Washington has been lucky regarding lightning but you only need to look at what is happening in Oregon to realize what could also happen in Washington if we do get dry lightning storms in the future, and note that the one larger lightning fire we did get (Easy fire in the North Cascades) spread quickly in an area that does not usually get this type of fire behavior.
ReplyDeleteas I noted in my blog, once we get through this weekend, temperatures will cool for the next week. Remember...you need wind as well as ignition (lightning) for big fire growth.
DeleteI'm looking forward to the change to end the boredom, grins. For what it's worth, here near Mt Baker yesterdays high was 91 F in the sun, but -- woo-hoo -- there was actually only one full hour at 90+ (3:12 to 4:15 per the chart). Most of the day was temperate, between 70-80. "Highs and lows" don't quite capture conditions here. I do expect that other places (particularly cities) retain heat much differently than we do, here. 'Watching a few clouds form and disperse above ridges (minor amusement). Onward, all.
ReplyDeleteSo Seattle is behind in their 90+ days this year, so far we only had 4 which is below normal. Anything in the models that shows more 90+ temperatures?. A lot of catching up to do.
ReplyDeletetim, may I ask your source for the normal number of 90+ days in Seattle? I've lived here since the mid-1980's and I'd be very surprised if it was normal to have more than four 90+ days by mid-July. I'd even be a little surprised if it was normal for the entire summer, except maybe in recent years.
DeleteIf weather.com is right Seattle will break the record for the most 80+ days in July, old record is 18 days.
ReplyDelete