The weather in the Northwest, especially the western slopes, has changed dramatically.
Over the past month, much of the area has been warmer and drier than usual, in contrast to much of California, Nevada, and the Plains States that have been cooler and wetter than usual (see temperature difference from normal over the past 30 days, below)
But now, the patterns have agreed: an unusually strong Pacific front will move through late Monday, bringing wet rain to the region and much cooler temperatures.
Furthermore, extended projections show average, typical temperatures for the next week, with no regional heatwaves for the remainder of July.
Take a look at the total amount of rain predicted through 5 a.m. Tuesday. Several dozen inches over much of western Washington. Southwest BC will be even wetter.
To get an idea of the timing and uncertainty in the forecast, here is the cumulative predicted precipitation in Seattle from the UW aggregator system of many high-resolution forecasts. Time ascends to the right, and the average of all forecasts (usually the good ones) is the black line. Time in UTC (25/00 is 5pm on Monday)
Temperatures won’t break above 60 on Monday, before dropping to 70:
And there will be significant cooling for our friends east of Washington, with temperatures fell in general in the low 90s.
This intriguing bonus is related to an unusually strong low-pressure system and a cold front moving on Monday. Below is the forecast sea level pressure map for Monday at 11 a.m. (low temperatures are also shown in colored shading, and I’ve indicated where ahead with the red line).
Well…low 1004 with some strong winds behind it, and the front is still offshore at this point.
As pointed out by normalized anomaly chart also, this low is highly unusual for this time of year (light purple indicates an anomaly from normal by more than four standard deviations to the mean).
Crucially, Central Europe’s slick set of forecasts suggests that this upper-level depression associated with surface lows will persist for the next week (see forecast below, blue indicates lower-than-normal pressure overhead)
This pattern would reduce the threat of wildfires in the area, although grass fires east of the Cascade Peak are still possible and could be aided by strong westerly winds due to cooling westerly temperatures.
Finally, let me end by noting that tomorrow’s rain will ironically occur on one of the driest climates of the year in western Washington (see below)
It all goes downhill from here.😆
