FOUS30 KWBC 151957 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 257 PM EST Sun Nov 15 2026 Day 1 Valid 16Z Sun Nov 15 2026 - 12Z Mon Nov 16 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF EASTERN TEXAS... 16Z Update: Based on the latest (12Z) guidance, including the REFS QPF exceedance probabilities, along with the current mesoanalysis (CAPE trends), expect the heaviest rain rates to reside off the TX coast through the remainder of the Day 1 period (through 12Z Mon). This includes the next batch of widespread rain out ahead of the main shortwave, which again is traversing across a more stable (or much less 'unstable') environment with higher FFGs. Because of this, and per collaboration with WFOs HGX, CRP, and LCH, have dropped the Slight Risk while retaining the Marginal Risk. B. Hurley Day 2 Valid 12Z Mon Nov 16 2026 - 12Z Tue Nov 17 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Hurley Day 3 Valid 12Z Tue Nov 17 2026 - 12Z Wed Nov 18 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE FLORIDA EAST COAST.... ...Eastern Florida... 2000Z Update: Based on the latest guidance, including the 12Z AI ECMWF and GFS, have hoisted a Slight Risk (Level 2/4) across east- southeast parts of the FL Peninsula, including the Gold Coast, Treasure Coast, and parts of the Space Coast up to Cape Canaveral. Positively-tilted mid-upper level trough across the eastern Gulf on Tue-Wed will slowly track across the Peninsula during the rest of the week, setting up a multi-day rainfall event. PWs are expected to climb to 1.75-2.00", while the strengthening low-level easterly flow off the Atlantic (20-30kts at 850 mb) opposes the mean 850-300 mb flow. Deep-layer instability will be a limiting factor across this area, north of the surface front which will drop south of the Keys. MUCAPEs are expected to remain below 1000 J/Kg, generally peaking around 500-750 J/Kg. However given the persistence (longer duration), expect there could be a few more runoff issues towards the tail end of the Day 3 period (Tuesday night into Wednesday morning), likely carrying over into Day 4. We confined the Slight Risk to the areas that had the highest 3" probabilities on Day 3 per the GEFS/ECENS/CMC. Hurley Previous Discussion... Surface high pressure parked over the central Appalachians will keep persistent easterly low-level flow in place across much of the eastern Florida peninsula on Tuesday into early Wednesday morning from the Georgia line to Lake Okeechobee (in broad geographic terms), 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 as high as 1.75" would be possible wherever short, training bands manage to materialize. Maintained the Marginal Risk area introduced on Saturday for portions of Eastern Florida with few changes needed. Bann ...Parts of the Southwest and Lower Great Basin... 2000Z Update: Expanded the Marginal Risk across central-northern AZ into southeast NV and southern UT based on the 12Z guidance trends. These are the areas where the guidance shows MUCAPEs peaking between 250-500 J/Kg during the day Tuesday. The QPF signal is highest across southwest into south-central UT (southern Wasatch); however, that is also the region devoid of instability and where a good portion of the precipitation is expected to fall as snow. Hurley Previous Discussion... An upper-trough and accompanying cold front will progress eastward from the West Coast into the Interior West on Tuesday. Increasing moisture along and with the frontal passage will lead to scattered showers and thunderstorms at lower elevations across the Desert Southwest given precipitable water values on the order of 1 inch in the Lower Deserts. The fact that the system being progressive is one factor against the potential for flooding. Despite that...a Marginal Risk was introduced mainly in the west facing terrain of northern Arizona...generally at or below 6500 feet (with precipitation more likely to fall as snow at elevations above 7000 ft). Present indications are that hourly rainfall rates of 1.25 inches are possible whenever/wherever cells can align or merge or mesocyclones manage to form. Rainfall this intense could lead to issues in dry washes/arroyos or burn scars. Bann Day 4 and Day 5 Valid 12Z Wed Nov 18 2026 - 12Z Fri Nov 20 2026 ...THERE IS SLIGHT RISK OF EXCESSIVE RAINFALL FOR CENTRAL COASTAL CALIFORNIA WEDNESDAY... ...California... An upper-trough is expected to dig southward along the West Coast and move inland across the western U.S. early this week, with additional reinforcements to the longwave trough coming in mid-week. Guidance trends have been quicker/more southerly with this system over the past couple of days. A plume of Pacific moisture/ moderately strong Atmospheric River (AR) accompanies the associated surface system/Pacific front. The deterministic guidance shows areal average amounts in the 2-4" range and locally higher totals anticipated. Much of this rain is likely to fall in a 3-6 hour period with the passage of the Pacific front. Given the hilliness of the coastal range, including the cities in the Bay Area, kept the Slight Risk going as there are bound to be scattered instances of localized flooding/ponding of water in low spots. However, despite the influx of warmer, moist Pacific air, colder air will still be in place overall given the upper- troughing already over the western U.S., limiting snow- level rises to around 4000 feet. This should keep the flooding threat lower along the foothills of the Sierra Nevada as the heaviest precipitation occurs as snow into its higher elevations. Heavy rainfall will continue into Thursday, increasingly impacting the Transverse Ranges of southern California. As the guidance shows reasonable agreement, extended the Slight Risk for Wednesday into the western Transverse Ranges and introduced a Slight Risk on Thursday for the Transverse & Peninsular Ranges, including the larger metro areas near the coast (Los Angeles & its suburbs as well as San Diego). ...Eastern Florida... A synoptic pattern with vague similarity to the one that materialized on October 31-November 3 appears to be setting up by mid week. Nearly antiparallel flow (low- level easterlies and upper level westerlies) will continue through mid- to late week across eastern Florida as a positively tilted upper level trough cuts off a cold low near the northwestern Peninsula which then remains quasi-stationary. Precipitable water values of 1.5-1.75" are forecast near the East Coast of FL, 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 2" would be possible wherever short, training bands or mesocyclones manage to materialize. As the GFS has a strong signal for heavy rainfall (10"+ local amounts Wednesday and 6"+ local amounts Thursday), and the heavy rain pattern in eastern FL has expanded in the 12z ECMWF run when compared to its older run, added Slight Risk areas for areas between Cocoa Beach and coastal Palm Beach County, areas that received very heavy rainfall two weeks ago. Localized Moderate Risk impacts cannot be ruled out. Roth/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 $$