Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
312 FOUS30 KWBC 140057 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 857 PM EDT Mon Oct 13 2025 Day 1 Valid 01Z Tue Oct 14 2025 - 12Z Tue Oct 14 2025 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHEASTERN ARIZONA, SOUTHWESTERN NEW MEXICO, AND SOUTHERN COLORADO AS WELL AS PORTIONS OF SOUTHERN CALIFORNIA... ...California... As a strong mid-level closed low (-4 standardized height anomaly at 500 mb) drops southward just off the coast of central California tonight, an occluded/cold front will follow suit, reaching southern California`s Transverse Ranges between 06-12Z. An anomalous moisture plume, with PWAT values between 0.9 and 1.2 inches, will focus along the coast ahead of the cold front and be directed inland via 20-35 kt of wind at 850 mb. An inland flash flood threat will remain where weak instability (generally less than 500 J/kg CAPE) will align with 20-30 kt of cyclonically curved low level flow to the east of the mid-level low to support localized hourly rainfall of 0.5 to 1.0 inches. Along the coast, and especially the Transverse Ranges later tonight, low level flow of 20-30 kt becomes aligned perpendicular to the terrain, increasing rainfall via orographic influences. Recent RAP forecasts have shown pockets of MLCAPE in the 250-750 J/kg range just offshore with inland values up to a few hundred J/kg which will combine with left-exit region jet divergence to allow for higher intensity rainfall potential. A frontal convergence axis of showers and thunderstorms appears likely to form and steadily translate southward with the cold front. While the front will be progressive, brief training with the front along with pre-frontal activity could support localized 2 to 3 inch rainfall totals through 12Z for the Transverse Ranges. The main flash flood concern across California for the overnight period will be urban and burn scar overlap of heavy rain, with the threat carrying over into the Day 2 ERO period beginning 12Z Tuesday. ...Southwest to the Central Rockies... South-central Arizona remained convectively active as of 00Z with a bubble of 500-1500 J/kg MLCAPE remaining with little to no inhibition. Strong right entrance region upper level jet divergence was also present across a good portion of Arizona, helping with ascent. PWAT standardized anomalies of +2 to +4 above the mean remained over the eastern half of Arizona into Utah, Colorado and New Mexico as of 00Z tonight, but drier air will be pushing into Utah and Arizona through 12Z from the west out ahead of a lead impulse located ahead of a large closed low along the coast of California. 25 to 45 kt of 700 mb flow and unidirectional SSW flow will be supportive of repeating and training rounds of heavy rain with the best potential for higher rates remaining co-located with remaining instability pockets. A second area of instability is expected to support locally higher rain rates later tonight from near El Paso into portions of southern/central New Mexico, although this region`s flash flood concern is a bit lower than locations to the west due to drier antecedent conditions and weaker forcing for ascent. Very wet antecedent conditions exist across southwestern Colorado/San Juan Mountains and portions of central Arizona due to 3 to 4 day rainfall totals of 2 to 6 inches. Additional totals of 2-3 inches may occur in localized portions of the San Juan Mountains due to upslope enhancement with 1-2 inch maxima forecast elsewhere. The main change for the 01Z update include the removal of the Slight Risk for southeastern Arizona into far southwestern New Mexico where a lack of instability and better forcing is expected to suppress convective coverage in the overnight. A portion of the Marginal Risk was also removed from the northern California coast where the heavy rainfall threat has ended with the movement of the closed low. Otto Day 2 Valid 12Z Tue Oct 14 2025 - 12Z Wed Oct 15 2025 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL OVER PORTIONS OF SOUTHERN CALIFORNIA... 2030Z Excessive Rainfall Discussion Update... Few changes needed to the previously-issued ERD. Present thinking is that the main threat for excessive rainfall across California will be in the first 12 hours of so given the progressive nature of the anomalous upper low dropping southward along the coast. Elsewhere...the large scale features were handled similarly amongst the various models. Bann 0830Z Excessive Rainfall Discussion... ...Central to Southern California... Our western disturbance will continue its progression slowly inland with a steady south-southwesterly component situated over the terrain of southern CA. Expect a continuance from the D1 to bleed into the first half of D2 with heavy rainfall aligned within the eastern Transverse Range and the northern Peninsular Range to the north and northeast of Los Angeles. PWAT anomalies on the order of 1-2 deviations above normal are sufficient for a deep layer moisture regime capable for heavy rainfall rates between 0.5-1"/hr with a chance for a few stronger cores to exceed 1"/hr, a signal more than capable of producing flash flooding in-of the area most susceptible given the burn scar remnants positioned in the Peninsular Range. Additional totals of 1-3" are forecast with locally higher possible in those areas northeast of Los Angeles in the terrain. Totals for the event will run between 1-4", plentiful over a span of 12-24 hrs. to cause issues in what is a sensitive locale for flash flooding and debris flow. The previous SLGT risk was linked together and spans the eastern Transverse into the northern Peninsular Range. MRGL risk is in place surrounding, including an extension into parts of the Central Valley and adjacent Sierra Foothills as locally heavy rainfall is still forecast through the first 6-12 hrs. of the period which could spur some isolated flash flood signals. ...New Mexico and West Texas... Remnant elevated moisture across far west TX into NM within a persistent axis of diffluent flow will yield a period of scattered thunderstorms over the two areas leading to isolated flash flood concerns, mainly in urban zones and over the complex terrain aligned from the Sacramento`s up into the Sangre de Cristos. Totals are not very appreciable at this juncture, but environmental conditions still support some heavier rainfall prospects over areas that will have seen a decent amount of rain leading in. Combination of antecedent conditions and additional rainfall place the threat inside the MRGL risk threshold leading to general continuity from previous forecast. Kleebauer Day 3 Valid 12Z Wed Oct 15 2025 - 12Z Thu Oct 16 2025 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL OVER PORTIONS OF THE CENTRAL AND SOUTHERN ROCKIES... 2030Z Excessive Rainfall Discussion Update... The forecast reasoning remained similar to the previously issued discussion and the outlook was largely unchanged. Bann 0830Z Excessive Rainfall Discussion... ...Rockies... Longwave pattern out west will continue to evolve with upstream troughing pushing east-northeast leading to a final prospect of isolated to scattered convection over the terrain of the central and southern Rockies. A lot of the threat stems from RER positioning with a broad upper jet aligned over the Mountain West with an extension into the High Plains by the end of the forecast cycle. The main areas of concern will likely be in those complex terrain locations in-of the Sangre de Cristos, San Juans, and down near the Sacramento`s. These areas will all have either very wet antecedent soil moisture that would promote easier run off capabilities, or burn scar remnants that maintain a posture for localized flash flood opportunities with any rates >0.5"/hr. This is still feasible with PWATs remaining ~2 deviations above normal in this zone when assessing the latest NAEFS output. A MRGL risk remains in place over these areas of the central and southern Rockies as a result. Kleebauer 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