FOUS30 KWBC 221931 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 231 PM EST Sun Feb 22 2026 Day 1 Valid 16Z Sun Feb 22 2026 - 12Z Mon Feb 23 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. A band of strong convection was currently located just west of Eureka, CA and was exhibiting slow eastward movement and rain rates approaching 0.5-0.75 inch/hr. This band may hold together long enough to spread locally heavy rain into Humboldt County, CA - although larger-scale/synoptic forcing should gradually and progressively limit flood/flash flood potential through the day. Heavy rainfall risk from Humboldt County, CA into Curry County, OR should remain isolated enough to preclude Marginal/5% probabilities for this outlook, though isolated instances of excessive runoff cannot be completely ruled out. Cook Day 2 Valid 12Z Mon Feb 23 2026 - 12Z Tue Feb 24 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF SOUTHWESTERN WASHINGTON, ALL OF WESTERN OREGON, AND INTO PORTIONS OF NORTHERN CALIFORNIA... 1930 UTC Update: Only minor changes made to the Day 2 Marginal Risk area based on the latest QPF guidance. Hurley A deep positively tilted trough extends from around Vancouver Island southwest down past the Hawaiian Islands at the start of the period 12Z Monday. This trough extending that far south will draw deep tropical warmth and moisture and rapidly draw it northeastward into the Pacific Northwest on a 170 kt southwesterly jet. At the surface, a low west of Vancouver Island will track southwestward and merge with a weaker, smaller low. This will allow an impulse of tropical moisture departing from the Hawaiian Islands to track into the Oregon and Washington coasts by Monday night as a weak surface low develops within the moisture plume. Rain associated with the onshore flow will impact mainly the Washington and Oregon coasts during the day Monday, gradually sinking south in response to the approaching impulse of moisture from the tropics. The low and associated heavy rain moves into the coast near the OR/CA border Monday night. Since its track is somewhat parallel to the coast, a rather small percentage of the moisture will penetrate into the interior, so the coastal mountains are likely to take the lion's share of the associated rain. The warmth moving into the coast will allow snow levels across much of Northern California to rise above 8,000 ft Monday night around the OR/CA border, and above 10,000 ft further south towards the Bay Area and Sacramento. This will initiate the snowmelt process across all of the coastal Ranges and Sierra Nevada Mountains. The inherited Marginal Risk remains unchanged for this area as recent cold and snow has kept stream and creek levels at low levels. Thus, the rain and snowmelt will begin to contribute to stream rises but flooding should remain rather isolated as much of the rain gets absorbed into the snowpack. Wegman Day 3 Valid 12Z Tue Feb 24 2026 - 12Z Wed Feb 25 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE NORTHERN SIERRA NEVADA MOUNTAINS AND ADJACENT FOOTHILLS... 1930 UTC Update: Made minor modifications to the Slight Risk area, based on the latest model QPFs, as well as the latest 48hr snowmelt projection from the National Snow Analyses page (nohrsc.noaa.gov/nsa). Meteorological details below continue to suffice for this event. Per additional collaboration with the National Water Center (NWC) earlier today, the combination of heavy rainfall and snowmelt may result in localized flash flooding along small streams as well as in poor drainage areas. Hurley Previous discussion below... A deep positively tilted trough that extends from Vancouver Island southwest through the Hawaiian Islands will remain the primary steering mechanism for an atmospheric river from the tropics and into Oregon. This moisture will be aided by a 150 kt southwesterly jet. This jet and the downstream ridging over the Southwest will flatten out as the trough cuts off into an upper low well north and east of Hawaii. This will cut off the feed of tropical moisture into the West Coast by Tuesday night. Thus, the period of heaviest rains will be primarily during the day Tuesday. A surface low Tuesday morning will be near where the coast meets with the CA/OR border. Since the rain associated with the low has origins in the tropics, associated elevated instability, anomalous warmth and moisture will all move into northern California. Snow levels will rise to over 8,000 ft over much of northern California, and over 9,000 ft across much of the northern Sierra Nevada. This will result in occasionally heavy rain associated with elevated convection that quickly tracks northeastward into northern California. Rainfall rates could exceed 3/4 inches per hour at times. Meanwhile recent abundant heavy snow from abnormally low snow levels will be replaced with this tropical moisture and warmth. The now very high snow levels will initiate the snow melting process. When the heavy rain moves in over that snow pack, expect initial absorption of the rain by the snow pack Tuesday morning, but as more rain moves in Tuesday afternoon, it's likely that areas of less deep snowpack, such as the foothills of the Sierra Nevada and the Shasta, Siskiyou, and Salmon Ranges will all see rapid runoff occur, sending local streams, creeks, and rivers rising very quickly. This will be the combined result of both heavy rain and fast snow melt. Given the expected rapid rises from both small creeks to large rivers, flash flooding is likely to be a bit more widespread. Thus, a Slight Risk upgrade has been hoisted for the Sierra Nevada foothills, where the heaviest rains are expected due to the greatest magnitude of upslope. However, heavy rains into the other Northern California ranges may necessitate an expansion of the Slight Risk with future updates. Wegman Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt