Marine Weather and Tide Forecast for Spokane Valley, WA

SYNOPSIS
A low pressure system will spread clouds and light showers across the region today. Temperatures see a gradual warming trend into the holiday weekend and will become warm by Sunday into early next week with temperatures climbing into the 80s.
There is growing potential for showers and thunderstorms from Sunday night into Memorial Day.

DISCUSSION
Today and tomorrow: Open mid level wave moving through the region bringing increasing clouds and a band of rain through the Columbia Basin, Palouse, and eventually Spokane/Cda area around sunrise. Precip amounts with this band look light - only around a trace to a few hundreths. Late this afternoon into the evening there is a 10% chance of thunderstorms over the southern ID Panhandle as late afternoon sun breaks allow for SB CAPE of up to 200 J/KG to develop. CAMs still show the best potential for thunderstorms south and east of the area over central ID into NW Montana closer to the upper level jet right exit region. As the wave exits Thursday night and the lower atmosphere stabilizes showers will come to an end. A weak vort max moving through the region Friday will bring low end shower chances (15-20%) to northeast Washington and north Idaho but similar to today the best dynamics and thermodynamics are displaced to the southeast in central ID and MT.

Saturday through Thursday: A strengthening ridge along the coast will keep the region under dry and warm conditions through at least Sunday. Temperatures Saturday in the 70s and 80s warm into the 80s and low 90s by Sunday. Changes come Monday as 80% of the ensemble shows an upper low over the Gulf of Alaska sending a shortwave through the PNW. With this wave there will be very deep southerly flow that will bring in an anomalous amount of moisture to the region (PWATs 150-200 percent of normal). Will have to monitor the potential for nocturnal thunderstorms Monday morning and perhaps stronger thunderstorms Monday afternoon. By Tuesday, models start to slowly rebuild a ridge. Where this ridge ends up will dictate how warm and dry we become. Currently Spokane International Airport has a 15% chance of 90+ degrees Wednesday May 28. That would be well above the previous 30 year average of June 21. DB

AVIATION
12Z TAFS: A low pressure system pushing into north-central Oregon will push across a weak deformation band across eastern Washington into the Idaho Panhandle this morning. Light rain for a 2-4 hour window is expected primarily east of line from KEAT to KOMK. The boundary layer is starting out dry and the incoming rain won't do much to moisten it up with ceilings anticipate to only drop down to between 4-6 kft agl. and VFR conditions prevailing. The center of the low will track into the southern Idaho Panhandle (near KGIC) in the afternoon. Although winds will be fairly light today up to 7-10 kts, there will be a wind shift of northeasterly to westerly between 18-20Z with the passage of the low to the south. Showers will continue to be prevalent closer to the low in the afternoon with isolated thunderstorms south and east of KLWS.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions today. Chances for enough moisture to produce lower ceilings for MVFR conditions at KPUW/KGEG/KSFF/KCOE have decreased down to around a 10% chance. There is high confidence that thunderstorms this afternoon will remain south and east of KLWS with less than a 10% chance for thunderstorms developing at the terminal. /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 60 42 67 44 74 48 / 30 10 0 0 0 0 Coeur d'Alene 61 43 67 43 74 47 / 30 30 10 0 0 0 Pullman 61 40 65 43 72 46 / 40 10 10 0 0 0 Lewiston 68 47 73 48 78 51 / 40 10 0 0 0 0 Colville 62 36 68 38 75 43 / 20 10 20 10 0 0 Sandpoint 61 42 67 43 73 46 / 30 30 30 0 0 0 Kellogg 61 45 65 46 73 49 / 50 50 20 0 0 0 Moses Lake 69 42 75 46 80 50 / 30 0 0 0 0 0 Wenatchee 71 47 75 50 80 56 / 20 10 0 0 0 0 Omak 70 43 74 46 79 49 / 10 10 0 0 0 0

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