Marine Weather and Tide Forecast for Spokane Valley, WA

SYNOPSIS
Today will be the last warm and dry day of the week before a weather system moves in this weekend. Chances for showers increase tonight into Saturday along with isolated afternoon thunderstorms, breezy winds, and slightly cooler temperatures.
Showers continue over the Idaho Panhandle on Monday before a break between systems Monday night into Tuesday. A cold front passage Tuesday night into Wednesday will bring additional rain in the lowlands outside the rain shadow areas east of the Cascades, mountain snow, and breezy to windy conditions.

DISCUSSION
Today: The Inland Northwest gets one more mostly dry, mild day as a ridge of high pressure gives way to an developing system.
Clouds will gradually increase today, mainly as high clouds this morning and then thickening and slowly lowering clouds this afternoon. Winds will be from east-northeast today, breezy over the north ID Valley and out toward the Upper Columbia Basin with gusts in the 10-20 mph range with a moderate northeast to southwest gradient developing ahead of the approaching system. The main chance for rain comes this afternoon near the Blue Mountains and Camas Prairie. Highs will be in the upper 60s to mid-70s.

Tonight to Monday: The incoming trough bring the Inland NW into a more active pattern. Models have been evolving over the past few days. A trough is digging south from the Gulf of AK, while low pressure sits off the OR/CA coast. As we head into tonight and this weekend the more southern low weakens and pushes east- northeast into the Great Basin and the northern Rockies through Saturday. Meanwhile the Gulf of AK low digs toward the CA coast and follows that first low inland through Monday morning. This is different than previous days when the merged and brought a stronger system at least into the vicinity of our area.
Nonetheless, a PWAT plume of 150-200% of normal lifts in tonight into Saturday and lingers into Sunday, before starting to dry out some Monday. A deformation axis lifts northward into the region between tonight and Saturday and lingers into Sunday, before starting pull out Monday. All this means increasing precipitation chances through the weekend, decreasing Monday. What has declined is the overall precipitation amounts for some of the area.

It still looks like mostly rain and high mountain snow. Around 0.25 to 0.50 inches are possible between Saturday and Monday over southeast WA and the central and southern Panhandle, with locally higher amounts possible. Those higher amount areas could waver depending on the precise location of the boundaries, so further adjustments are possible but right now the Camas Prairie to southern Shoshone county could see around 1 inch of rain this period. Toward the northern mountains and north ID around 0.15 to 0.40 inches are in the forecast, while the Spokane metro and CdA area have around 0.05 to 0.20 inches in the forecast right now, less than this time yesterday. Similar amounts are possible toward the Cascades, while the central WA/deeper basin could see trace to a couple hundredths of an inch of rain. If any snow does fall in the mountains it look like minor, with little to no impacts.

There remains a 10-30% chance for thunderstorms each afternoon between Saturday and Monday. The highest risk is on Saturday, with most areas seeing at least some risk. Sunday the risk become more localized to the eastern third of WA and ID and by Monday mainly over the far northeast WA and north ID counties. Brief gusty wind, lightning, maybe small hail will be the main risk.

Winds will be breezy this weekend, with gusts around 10-20 mph.
Then heading into Monday as the system starts to move out and the drier westerly flow develops some higher winds start to in. Gusts of 20-30 mph will be possible, higher near the Cascades to western Columbia Basin and near the Blues.

Highs will be largely in the 60s to low 70s this weekend, then the upper 50s to 60s Monday. Lows are forecast to be in largely in the 40s.

Tuesday to Thursday: The region starts off in the westerly flow, but another strong low pressure drops in from the Gulf of AK Tuesday night into Wednesday and only slowly starts to migrate east Thursday. This more direct track into the region will mean more precipitation chances and lower snow levels, including a potential for moderate snows around the mountain passes, and breezy/gusty winds and cooler than normal temperatures. Tuesday precipitation chances linger around the mountains, then start to expand back out Tuesday night and Wednesday, before retreating toward the mountains again Thursday. The highest potential will be around the mountain zones and some moderate precipitation amounts are possible. This will be largely mountain snow and lowland rain, but a rain/snow mix will be possible Tuesday night and Wednesday. Also between Tuesday and Wednesday a foot of snow may fall around Stevens Pass, with 7 inches possible near Snoqualmie Pass, 4 inches at Lookout and 2 inches are Sherman. Some current ensemble 48-hour snowfall probabilities:

2" 4" 6" 12" Stevens Pass 95% 90% 85% 40% Snoqualmie Pass 85% 75% 55% 20% Lookout Pass 85% 60% 45% 3% Sherman Pass 30% 10% 5% 0%

So winter conditions are not done, even for perhaps for the lowlands. Winds will also be breezy/gusty with gusts on Tuesday and Wednesday between 25-40 mph. Winds decline some for Thursday with gusts right now forecast between 10-20 mph. Highs will be in the upper 40s and 50s. Lows will be in the mid-20s to 30s, with Thursday morning the coldest with potential for many areas seeing near to sub-freezing temperatures. So if any have started to do anything with sensitive plants, you might want to keep an eye on this forecast. /Solveig

AVIATION
12Z TAFS: High pressure peaks early Friday before low pressure starts to take over. The next 18 hours through 06Z looks dry.
Mostly high clouds through Friday morning thickening mid level clouds increase Friday afternoon into Friday evening. Some rain chances start to develop near the Cascades and southern WA into the southern to central Panhandle Friday night after 03Z. VFR conditions expected through Friday night, but ceilings will continue to lower into Saturday with increasing low level moisture.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions. A possible scenario is some light rain may come to PUW/LWS/EAT/MWH between 00-06Z Saturday (Friday evening), but confidence is low. /SVH

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Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance

For additional probabilistic information for NWS Spokane airports,please refer to the Aviation Dashboard on our webpage: https:/ www.weather.gov/otx/avndashboard

Preliminary Point Temps/PoPs
Spokane 69 45 61 42 65 43 / 0 20 50 30 30 30 Coeur d'Alene 68 46 61 43 64 43 / 0 20 60 50 50 50 Pullman 68 45 60 42 62 43 / 10 30 70 40 60 60 Lewiston 70 49 65 45 64 47 / 10 30 70 30 60 60 Colville 71 44 65 42 68 41 / 0 10 50 50 50 30 Sandpoint 65 44 60 44 61 42 / 0 20 60 60 60 50 Kellogg 69 46 58 43 62 43 / 0 20 80 50 70 60 Moses Lake 73 47 68 41 70 44 / 0 20 30 10 10 10 Wenatchee 69 50 65 45 67 46 / 10 20 30 10 10 10 Omak 71 49 67 46 68 43 / 0 10 30 30 20 10

OTX WATCHES/WARNINGS/ADVISORIES
WA...None.
ID...None.