Highlights: Northwest U.S. and Western Canada dryness to accelerate this summer season while wet conditions in California to the Great Basin Executive summary: The Climate Impact Company HYDRO forecast for Western Canada, the Northwest U.S., and California to Great Basin region is largely drier and hotter than normal. Low stream flows in the Northwest U.S. are likely to worsen while moderately high stream flows in California to the Rocky Mountains due to heavy winter snowfall are gradually expected to ease back. Western Canada drought worsens through the summer months. The forecast is based mostly on the presence of marine heatwave NEP22A approaching and reaching the West Coast of North America from near San Francisco Bay northward. Climate discussion: Currently, river gauge observations are split between dry 50-60% of normal stream flows across the Northwest to wet 150-200% of normal stream flows across the Sierra Nevada, parts of the Great Basin, and Colorado Rockies (Fig. 1). The U.S. Drought Monitor identifies borderline drought to strong drought soil moisture conditions affecting 48% of the West which has lowered slightly the past couple weeks and is much less dry than recent years (Fig. 2). The NOAA/CPC daily soil moisture analysis reveals the problem area for bad drought is across the Canadian Prairies and throughout the central/southern Canadian Rockies (Fig. 3). Rainfall needed to neutralize dry Palmer Drought Severity Index (PDSI) is a titanic 15+ inches across the Cascades implying drought conditions in Eastern Washington are stronger than implied by other analysis (Fig. 4). Forecast summary: The forecast is based on developing El Nino during the summer months while the Northeast Pacific marine heat wave (NEP22A) is likely to stay off the West Coast of North America (Fig. 5-6). The forecast of Northwest/West U.S. and West Canada temperature and precipitation is taken from a previously issued U.S. month 1-3 ahead outlook issued last week. In June, anomalous warmth extending south from the prevailing West Canada ridge pattern continues (Fig. 7). Washington is dry and drought accelerates while the Great Basin to Southern Idaho observes strong thunderstorms (Fig. 8). During mid-summer, anomalous heat dominates particularly the Northwest U.S. and Canada (Fig. 9) while a showery pattern lingers across the East Great Basin although drier elsewhere (Fig. 10). In August, the anomalous heat eases off slightly while dryness expands (Fig. 11-12). Forecast confidence on the drier/hotter regime for the Northwest U.S. hinges on the coastal approach of NEP22A. If close to the coast, or reaching the coast, the drier/hotter forecast is more confidently predicted. The summer 2023 fire risk outlook is focused on Canada and extends to the Interior Northwest, Upper Midwest, and touches the Interior Northeast (Fig. 13). Fig. 1: Streamflow analysis for various river gauges across the Northwest/West U.S. valid May 29, 2023. Fig. 2: U.S. Drought Monitor and attendant soil moisture conditions for the West U.S. as of May 23, 2023. Fig. 3: North America daily soil moisture anomalies according to NOAA/CPC. Fig. 4: Rainfall needed to neutralize dry Palmer Drought Severity Index (PDSI). Fig. 5-6: Northeast Pacific daily SSTA analysis and 14-day change identifies the Northeast Pacific marine heat wave edging toward the North America West Coast. Fig. 7-8: The Climate Impact Company June 2023 temperature and precipitation outlook. Fig. 9-10: The Climate Impact Company July 2023 temperature and precipitation outlook. Fig. 11-12: The Climate Impact Company August 2023 temperature and precipitation outlook. Fig. 13: Climate Impact Company summer 2023 southern extent into U.S. of Canadian fire risk.