FOUS30 KWBC 150025 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 725 PM EST Sat Nov 14 2026 Day 1 Valid 01Z Sun Nov 15 2026 - 12Z Sun Nov 15 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS NORTHWEST WASHINGTON & PORTIONS OF TEXAS... Texas... A negatively tilted upper level trough is crossing TX at this time. Moisture and instability are slowly increasing, with both interior and coastal TX showing pockets of 560+ J/kg of ML CAPE. Precipitable water values are 1.1-25" across interior TX and closer to 1.5" near the Middle TX Coast. Both areas are within regions of 850 hPa confluence. Activity across Northwest TX is expected to continue to forward propagate to the southeast with time while storms near the central TX coast continue to bubble overnight as they slowly shift offshore. A Marginal Risk of excessive rainfall remains in effect for both areas, with some changes made to account for radar reflectivity trends and the most recent REFS guidance. Hourly amounts to 2" with local totals to 4" are possible in both areas where storms manage to backbuild, train, or merge. Flash flooding issues are expected to be isolated to widely scattered at best. Pacific Northwest... A low pressure system will focus storms ahead of its attendant cold front as it arrives over the Pacific Northwest tonight. Some relatively modest instability (100-250 J/Kg MUCAPE) will work its way into the region along with moisture (0.5-1.5" precipitable water values). The REFS guidance indicates that a few hours of heavy rain (0.5"+) is possible overnight, which could lead to rises in the Skokomish River. Left the Marginal Risk area as-is, with no changes from continuity. Roth 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... ...2030z Update... The inherited marginal (at least 5% chance) and slight (at least 15% chance) risk areas were expanded south and westward through Corpus Christie and Matagorda Bay respectively. The synoptic setup outlined in the previous discussion remain true, with the upper trough responsible for storms over north-central Texas today continuing to dig southeastward toward the Gulf Coast. Lobes of shortwave vorticity propagate through southeast Texas Saturday afternoon. Convection is expected to reignite tomorrow afternoon over central Texas as instability builds over the area. The heaviest rainfall should wrap up by midnight Monday. The latest/12z guidance has shifted the max QPF axis to between Houston and Corpus Christie for the 24 hour period ending at 12z on Sunday. 24 hr 5" 40km RRFS exceedance probabilities are between 20-60%, while 3" EAS probabilities are between 15-30% within the highlighted slight risk area. GEFS first guess fields have a 15-25% chance of 1-2 year ARI exceedance, as well as UFVS verified flash flooding, which is consistent with the marginal and slight risk areas in effect for Saturday. Kebede ...Previous Discussion... 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 shunt 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. Kebede 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 THE FLORIDA EAST COAST TUESDAY-WEDNESDAY & CALIFORNIA WEDNESDAY... West... 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. Precipitable water values ~1" in the Lower Deserts combined with a lowering trend in the 1000-500 hPa thickness pattern associated with the system should nearly saturate the atmosphere. Effective bulk shear won't be lacking. But, the system is progressive. Should the atmosphere saturate much more, a Marginal Risk could prove useful. Whenever cells can align or merge or mesocyclones manage to form, hourly rain amounts to 1.25" are possible could lead to issues in dry washes/arroyos or burn scars. The situation continues to bear watching. Another Atmospheric River (AR) will quickly follow in the system's wake, 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 12Z deterministic guidance all support areal average rainfall in the 2-4" range with locally higher amounts. This would be more than sufficient to raise isolated flooding concerns, thus left the 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 as-is. Eastern Florida... A situation with nearly antiparallel flow (low-level easterlies and upper level westerlies) takes hold on Tuesday. Precipitable water values of 1.25-1.5" are forecast, and the low-level flow should bring instability off the warmer than average Gulf Stream. Effective bulk shear should be sufficient for organized convection. Hourly rain amounts to 1.75" would be possible wherever short, training bands manage to materialize. By Wednesday, an approaching upper level system closes off into an upper level low which could continue the situation for localized heavy rainfall. Marginal Risk areas were introduced for portions of Eastern FL for Tuesday through Wednesday night as a few pieces of global guidance advertised the heavy rain potential. Roth 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 $$