175 FOUS30 KWBC 130058 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 858 PM EDT Thu Mar 12 2026 Day 1 Valid 01Z Fri Mar 13 2026 - 12Z Fri Mar 13 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE PACIFIC NORTHWEST... 01Z Update: Reduced the footprint of the Marginal Risk a little based on recent runs of the HRRR and HREF -- where guidance indicates the greater potential for overnight amounts exceeding 2 inches and mostly rain. But overall, no big changes to the previous outlook. Pereira 16z Update: The ongoing Marginal risk looks in good shape, with the incoming model guidance and observational trends remaining consistent. Chenard ...Previous Discussion... An axis of anomalous PW and 850-700 mb moisture flux values...1.5-2.5+ and 2 to 4+ standard deviations above the mean, respectively, will continue to impact southern WA state into northern Oregon from the Cascades westward to the Coast Ranges. Hourly rainfall rates are not expected to be very impressive, at most .10-.25"+. However, there is not expected to be a lot of movement, overall with this anomalous onshore flow, which will support rain for nearly all of the day 1 period in this axis. Heaviest precip likely in the upslope of the southern WA Cascades and far northern OR Cascades, where HREF and RRFS neighborhood probabilities are high for 2 and 3"+ amounts day 1. Changes to the previous outlook were to trim the marginal risk southward out of coastal southern WA, and through the Willamette Valley to better match the latest model qpf consensus. Oravec Day 2 Valid 12Z Fri Mar 13 2026 - 12Z Sat Mar 14 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE PACIFIC NORTHWEST... 19z Update: No Changes made to the inherited Marginal risk with this update. Rainfall rates should increase by this time, but still peaking in the 0.3"-0.4" range. Generally looking at 1-3" of additional rain, with localized amounts around 5" in the higher terrain east of Portland. Chenard ...Previous Discussion... Not a lot of changes expected overall to the large scale flow pattern off the northeast Pacific into portions of the Pacific Northwest day 2. The ongoing atmospheric river event will continue through much of the day 2 period, with the axis of anomalous PW and 850-700 mb moisture flux values...1.5-2.5+ and 2 to 4+ standard deviations above the mean, respectively, again impacting areas from southern WA state into northern Oregon from the Cascades westward to the Coast Ranges. Similar to the day 1 period, the hourly rainfall rates are not expected to be very impressive, at most .10-.25"+. However, there will continue to be little overall movement with this anomalous onshore flow axis, which will support additional heavy rainfall amounts in the upslope of the northern OR/southern WA Cascades and the northern OR Coast Range. Changes to the previous outlook were to trim the marginal risk area over southern WA and remove it from the Willamette Valley to better match the latest model qpf consensus. Oravec Day 3 Valid 12Z Sat Mar 14 2026 - 12Z Sun Mar 15 2026 The probability of rainfall exceeding flash flood guidance values is less than 5 percent. Chenard 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