Rainy at Times Through Tuesday, Drier by Midweek

FastCast--Monday, Nov. 6 to Thursday, Nov. 9:

The next storm is impacting Western Washington with rain at times through Monday, transitioning to isolated showers on Tuesday, with a potential Convergence Zone over the Central Sound in the afternoon. Across the lowlands, expect 0.5-1", with isolated higher amounts possible due to heavier showers. Rain should wrap up completely by Tuesday night. Expect partly sunny conditions on Wednesday, followed by increasing clouds on Thursday as systems return. Details on those systems are uncertain, so stay tuned on that. Temperature-wise, expect highs in the mid to upper 50s on Monday and Tuesday, with lows in the upper 40s to low 50s. Wednesday and Thursday will reach the low to mid 50s, with Wednesday's lows in the upper 30s to low 40s, and Thursday's lows in the low to mid 30s, with some sub-freezing temperatures and frost possible.

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The next storm system is moving through Western Washington, bringing another round of rain to the area. Rain should clear out by Tuesday night, with drier weather on Wednesday and most of Thursday. Let's take a look at the forecast!

First, the European model forecast for rain through Tuesday evening. 

This forecast runs a bit wetter than the rest of the forecasts, showing 0.5-1.5" of rain for the lowlands. This forecast also shows 0.9-1.4" for the Willamette Valley, 0.5-3" on the coast (most along the Oregon Coast), and 1-3" in the mountains. This forecast also brings 0.3-0.8" to Eastern Washington, with the most rain around Spokane and Pullman (0.6-0.8").

Next, let's take a look at the GFS (American) model for rain through Tuesday evening.

This forecast shows 0.5-1" for the lowlands, most in a Convergence Zone between Seattle and Everett. This forecast also brings 0.7-1.3" to the coast, 1.4-2" to the Willamette Valley, and 2-3" to the mountains. This shows significantly less rain for Eastern Washington, except around Spokane and Pullman (0.5-0.75").

Next, let's take a look at the NAM high-resolution forecast for rain through Tuesday evening.

This forecast shows 0.3-0.8" for the lowlands, with isolated higher amounts from Seattle to Mount Vernon. This forecast also shows 0.5-2.5" on the coast, 0.8-1.5" in the Willamette Valley, 2-4" in the mountains, and 0.1-0.2" in Eastern WA, except more (0.5-0.8") around Pullman and Walla Walla.

Finally, let's take a look at the UW WRF high-resolution forecast for rain through Tuesday evening, zoomed in on the Seattle area.

This forecast shows 0.5-1.25" for the lowlands and the coast, with less in the Olympic rain shadow, and 1.5-3" in the mountains.

As the rain moves through, the snow level will drop from around 5,500-6,000 feet to 3,500 to 4,000 feet, bringing a few inches of wet snow to the higher passes. Below is the European model forecast for snow through Tuesday night.

The European model shows 2-4" at the passes (most at Stevens and White Passes), with around 1-1.5" at Snoqualmie Pass. Higher elevations such as Paradise, the North Cascades Highway, and Chinook-Cayuse Passes will get up to 6-8".

Finally, let's take a look at upcoming temperatures for Seattle and Spokane from the European EPS forecast. First, Seattle.

Temperatures will slowly decline over the next few days, with highs and lows remaining near average, except a chilly morning on Thursday.

Next, the forecast for Spokane.

Spokane will generally follow a similar pattern as Seattle, just with cooler temperatures. Highs and lows look to remain near average for the foreseeable future, with highs in the mid to upper 40s and lows in the low to mid 30s.

Stay tuned over the next few days for more information on the upcoming systems at the end of the week.

Saturday Storm: Heavy Rain, Strong Winds, Chance of Thunderstorms

FastCast--Saturday, Nov. 4 to Wednesday, Nov. 8:

The next storm has arrived in Western Washington, with an embedded atmospheric river bringing heavy rain at times, with widespread gusty winds likely as well. Expect 0.9-1.5" of rain in the lowlands through Sunday morning, with less (0.3-0.5") in the traditional rain shadowed area. Overnight from Friday into Saturday, winds will peak on the coast, with gusts of 40-50 mph from Westport northward and 50-60 mph from Westport southward. During the day on Saturday, expect gusts of 40-50 mph on Whidbey, Camano, and the San Juan Islands, plus along Admiralty Inlet and in western Skagit and Whatcom Counties. The remainder of the lowlands will likely gust 30-40 mph, strongest near the water. Additionally, there is a region-wide chance of thunderstorms from mid-morning to late afternoon on Saturday, with the highest chance on the coast. Heavy rain could cause areas of ponding/standing water, localized urban flooding, and low visibility. Winds could cause isolated power outages and some tree damage. Remember to stay indoors if you hear thunder! Keep reading below for a full update on the storm!

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A multi-faceted storm is currently impacting Western Washington. Main impacts will be heavy rain, strong winds, and a chance of thunderstorms. Let's start with the rain forecast.

Below is the European model forecast showing the atmospheric river aimed at the Northwest.

This atmospheric river will bring heavy rain to the Northwest through Sunday morning (lasts longer the further south you are).

Now, let's take a look at the European model rain forecast through early Sunday morning.

In the lowlands, expect 0.9-1.5" of rain with this storm, except less in the traditional rain shadow areas NE of the Olympic Peninsula. On the coast, expect 1-2", with 1-1.5" in the Willamette Valley and 1.5-3" in the mountains. Eastern Washington will get 0.5-0.8" on the east slopes of the Cascades, 0.2-0.4" in the central part, and 0.6-1.2" for the eastern third of Eastern WA.

Let's compare this to the GFS (American) model forecast, also through early Sunday morning.

The GFS forecast is very similar to the European, showing 1-1.5" in the lowlands, 1.5-3" on the coast and mountains, and a clear rain shadow NE of the Olympics. Two noticeable differences are slightly less rain in the Willamette Valley (0.8-1"), and less for Central WA (0.05-0.2"). 

Let's take a look at 2 high-resolution forecasts, starting with the NAM forecast.

The NAM forecast shows 0.5-1.3" of rain in the lowlands, 0.9-1.3" in the Willamette Valley, and 1.5-2.5" on the coast. The mountains will get 4-8", and Eastern Washington will get 0.1-0.4", except 0.4-0.8" near the Idaho border.

Finally, we'll look at the UW WRF high-resolution forecast for rain in Western Washington through Sunday morning.

This high-resolution forecast shows 0.75-1.5" of rain in the lowlands, with the most from Tacoma to Monroe and in the foothills. The rain shadow is prevalent from Port Angeles to Everett, where 0.05-0.2" are possible. The coast will get 1-2.5", and the mountains will get 2-5".

Now, let's take a look at the high-resolution wind forecasts from the NAM and HRRR models, starting with the HRRR, showing peak gusts.

This forecast is by far the strongest in terms of region-wide winds, showing gusts of 40-45 mph for the entirety of the lowlands, with the coast hitting 45-55 mph. This scenario will bring more tree damage and potentially more power outages, but is somewhat less likely.

Let's compare this to the NAM forecast, seen below showing gusts at 8 AM Saturday.

Around 8 AM, the NAM forecasts peak wind gusts of 30-40 mph for the lowlands, up to 45 mph around Island, San Juan, Skagit, and Whatcom Counties. The coast will gust up to 40-50 mph according to this forecast.

Finally, there is a region-wide chance of thunderstorms on Saturday, mainly from mid-morning through late afternoon. Below is the NAM high-resolution forecast for instability on Saturday afternoon.

This forecast shows instability for most of the lowlands and the coast, with the highest chance of thunderstorms likely on the coast, spreading into the lowlands in the afternoon. Remember, if you hear thunder, go indoors and wait at least 30 minutes to go outside again.

Stay tuned for another update on Saturday night, as the next system is ahead.

Atmospheric River Arrives, Heavy Rain Region-Wide

FastCast--Thursday, Nov. 2 to Monday, Nov. 6:

The atmospheric river has arrived in Western Washington, and will spread rain across the state over the next day. In the lowlands, expect 1-2" of rain, with less in the traditional rain shadow areas NE of the Olympic Peninsula. Mountains and coastal areas will receive more rain (2-3" at the coast, up to 5" in the mountains). Keep in mind that the lowlands will be receiving a high amount of rain in a short amount of time (12-18 hours), so ponding, standing water, and urban flooding are possible. Be aware of clogged storm drains as well. Expect rain to be heaviest from late Wednesday night through early Thursday morning, tapering off through the day Thursday. Warm southerly flow will bring much warmer temperatures, with highs from Thursday to Saturday in the upper 50s to low 60s. From Sunday to Monday, expect temperatures in the mid 50s. Winds will pick up on Thursday morning, likely gusting 25-35 mph across the lowlands, but stronger on Whidbey Island and near the water. Expect a break in the weather from Thursday afternoon through most of Friday. Then, the next storm (and potential atmospheric river) will arrive late Friday, continuing through late Saturday, before the next storm arrives from late Saturday through Monday. Details on those storms are uncertain, so stay tuned for more information. 

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An atmospheric river is currently impacting Washington, with heavy rain expected through Thursday for most of the region. Let's take a look at the forecast!

First, the European model forecast for total rain through Friday morning.

This forecast shows 1-2" in the lowlands (most from Seattle to Tacoma, in the foothills, and in Whatcom County). Additionally, this forecast shows 1.5-3" on the coast and from Shelton westward, with 0.7-1.3" in the Willamette Valley and 3-5" in the Olympics and Cascades. Eastern Washington gets widespread rain with this forecast, showing 0.5-0.8" for Ellensburg and Yakima, 0.3-0.6" for Moses Lake and the Tri Cities, and 0.6-1.2" for Spokane and Pullman.

Let's compare this to the GFS (American) model, seen below (also showing total rain through Friday).

This forecast has a few differences. It also shows 1-2" for the lowlands, with the most from Seattle to Olympia. Areas from Seattle north will get 0.8-1.3" in this forecast, with a rain shadow over the NE Olympic Peninsula and Whidbey/Camano Islands. Eastern Washington gets less rain overall in this forecast, with the Spokane and Pullman areas getting the most, around 0.4-0.6". The Cascades and Olympics get 2-4", with 1-3" on the coast.

Now, let's take a look at the high-resolution NAM forecast, showing total rain through Friday morning.

The NAM shows 0.9-2" for the lowlands, with the most between Seattle and Olympia and in the foothills. This forecast also shows 1.5-3.5" on the coast, 5-10" in the mountains, and 0.3-1.3" in Eastern Washington, most near the Idaho border. This forecast also has a small but very pronounced rain shadow near Port Townsend and Sequim.

Finally, the UW WRF high-resolution forecast for rain through Friday morning, specifically zoomed in on Western Washington.

This forecast shows 0.75-1.25" of rain from Seattle to Olympia, with up to 1.25" in the foothills, 1-2" on the coast, and 2-5" in the mountains. Areas from Seattle northward get 0.3-1.25" in this forecast, most along the I-5 corridor from Arlington to the Canadian border.

Forecasts have a relative consensus on the metro area getting 0.75-2" of rain from late Wednesday night through midday Thursday. Ponding, standing water, and urban flooding are possible. Hydroplaning and low visibility will be a concern, so drive prepared!

There is also a potential (but somewhat unlikely) for winds gusting up to 40 mph, especially from Tacoma south and from Everett north, mainly Thursday morning, adding to potential storm impacts. Coastal areas, especially from Ocean Shores southward, will gust up to 45-50 mph, strongest early Thursday morning on the immediate coastline.

We will round out this blog by taking a look at the warming temperatures. Below is the European model forecast for Thursday's highs.

On Thursday, expect lowland highs increasing to the upper 50s to low 60s, with coastal highs in the mid 50s, Willamette Valley highs in the low to mid 60s, and mountain highs in the mid to upper 40s. Eastern Washington will reach the mid 40s to low 50s, except the upper 50s to low 60s for the lower Columbia Basin.

Next, Friday's highs, also from the European model.

On Friday, temperatures will warm in the lowlands, with highs reaching the low 60s for most locations, with some areas, mainly in Whatcom County and on the coast, remaining in the upper 50s. The Willamette Valley will reach the low to mid 60s. Eastern Washington will reach the mid 50s to low 60s south of I-90, and will remain in the mid 40s to low 50s north of I-90.

Finally, the highs for Saturday, seen below.

Saturday will be balmy across the region, with lowland and Willamette Valley highs reaching the low to mid 60s (warmest in the foothills). The coast will remain in the upper 50s, but Eastern Washington will begin warming up more, with most areas except Wenatchee and the North Cascades warming to the mid 50s to mid 60s, warmest around the Tri Cities and Walla Walla.

Finally, a quick preview of what's ahead for the metro area. Below is the European EPS ensemble forecast for 24-hour precipitation in Seattle through the next 2 weeks.

Notice the current system (red outline) and the upcoming Saturday system (purple outline). For the current system, nearly every ensemble member shows 1-2" of rain, but there is less agreement amongst the ensemble members for the Saturday system. Forecasts are still coming into agreement on that system and the next system, slated for Sunday/Monday. Regardless, an active period is upon us in the Northwest, so stay tuned for updates!