FOUS30 KWBC 140816 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 316 AM EST Sat Nov 14 2026 Day 1 Valid 12Z Sat Nov 14 2026 - 12Z Sun Nov 15 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS NORTHWEST WASHINGTON STATE IN THE AREA OF THE OLYMPIC PENINSULA AS WELL AS NORTH-CENTRAL TEXAS... North-Central Texas Global and CAM models have begun to resolve upper-level trough phasing and continued to converge on the placement of heavy to potentially excessive convective rainfall today. A mid-level trough cutting across the Rockies while phasing with a southern stream disturbance prior to the start of the Day 1 period will likely lead to surface cyclogenesis later tonight followed by convective initiation. Storms will then propagate from eastern portions of the Texas panhandle through northern-central parts of the state overnight. Instability of about 100-400 J/Kg MU/ML CAPE paired with 1-1.25" precipitable water values through central Texas could yield efficient rain rates. Relative soil moisture is fairly dry so some of this rain may be more beneficial. 14/00Z RRFS 40km neighborhood probability of 24 hr QPF exceeding 1-3" is over 5%, which is consistent with WPC's marginal risk (at least 5% chance) area. ...Previous Discussion... 00Z guidance continues to show the arrival of another round of moderate to heavy rainfall across portions of the Pacific Northwest later today. The two-day rainfall total may be enough to result in isolated flash- and areal- flooding with the 24-hour rainfall amount ending 12Z on Sunday generally being 1 inch to 3 inches in addition to what fell Friday and early this morning. Timing largely remains consistent with the expectation being that much of the rainfall is expected to occur later tonight in advance of the approaching cold front. This could send some of the river banks overflowing and cause some local flood concerns, some of which could be flashy. Bann Day 2 Valid 12Z Sun Nov 15 2026 - 12Z Mon Nov 16 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF COASTAL TEXAS ON SUNDAY... Enough ingredients appear to be coming together to warrant a Slight Risk area on Sunday as convection associated with a mid-level trough approaches from the west/northwest early Sunday. Even if the models prove to be correct in keeping the highest rainfall totals off-shore...the there are an increasing number of signals that problematic rainfall amounts could develop inland (especially true in urbanized areas and where there is overlap with areas that received 1.5 to 4.0 inches of rain within the past week). Synoptically, low-level flow off the Gulf will be drawn northward across portions of the Upper and Central Texas coast early in the period in response to the approach of an upper level trough (potentially an upper low). The GFS and ECMWF both depict 30 to 45 kt flow with decent directional shear in the 925-700 mb layer...suggesting potential for organized convection. At the same time, precipitable water values approach 1.5 inches (or 1.5 to 2.0 standardized anomalies greater than climatology for this time of year). The models do show a plume of air with precipitable water values greater than an inch extending northward. Maintained the Marginal risk area here over questions about how much instability will be present. The upper system approaching from the northwest helps shnut the heaviest rainfall off the coast with time, Bann Day 3 Valid 12Z Mon Nov 16 2026 - 12Z Tue Nov 17 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann Day 4 and Day 5 Valid 12Z Tue Nov 17 2026 - 12Z Thu Nov 19 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF NORTHERN AND CENTRAL CALIFORNIA WEDNESDAY... An upper-trough and accompanying cold front will progress eastward from the West Coast into the Interior West day 4/Tuesday. Increasing moisture along and with the frontal passage will lead to scattered showers and thunderstorms across the Desert Southwest and into the Four Corners Region. However, limited instability and modest moisture should keep rates low and the progressive nature of the system passage should limit rain totals overall. Another Atmospheric River (AR) will quickly follow in the wake of this previous system bringing heavy precipitation to northern/central California day 5/Wednesday. Snow levels will briefly increase with the approach of the warmer, moist Pacific air, though likely not reach levels seen with more significant ARs, particularly along the foothills of the Sierra given remnant colder air still in place from the prior system (~4500 feet). The AR is also expected to generally be on the weaker side and progressive overall. However, the forecast IVTs of ~ 500 kg/ms still should contribute to some heavy rainfall amounts, and the latest round of 00Z deterministic guidance all support areal average rainfall in the 1-2" range with locally higher amounts upwards of 3-4". This would be more than sufficient to raise isolated flooding concerns, and thus have introduced a Marginal Risk covering upslope regions of the northern/central Coastal Ranges and inland through the Bay Area to the Sacramento Valley and foothills of the Sierra. Putnam 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 $$