FOUS30 KWBC 230044 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 844 PM EDT Thu Oct 22 2026 Day 1 Valid 01Z Fri Oct 23 2026 - 12Z Fri Oct 23 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF SOUTHWEST COLORADO, SOUTHERN UTAH, AND NORTHWESTERN NEW MEXICO... ...Southwest and Great Basin... 01Z Update: Current WV satellite depicts our upper level low (ULL) positioned over west-central CA with a prevailing south to southwest flow over the Southwest U.S. Jet streak downstream of the mean trough is providing ascent within the RER of the jet which coupled with anomalous deep layer moisture downstream is providing significant convective coverage across eastern AZ up into western NM into southern CO/UT. Height fields depict a textbook diffluent flow between 700-200mb over much of the Southwest with limited deviation in its depiction the past several hours thanks to a slow evolution of the upstream pattern back towards the west coast. Scattered bouts of heavy rainfall with some training due to deep layer flow remaining fairly uni-directional has aided in several flash flood occurrences across the high deserts in UT/AZ/NM this afternoon and will continue for several more hours into the early evening. The San Juans in CO continue to see prevailing upslope flow with locally enhanced rainfall providing a steady rise in the total rainfall in the region. We have fortunately remained away from the stronger cell cores at this juncture with the best instability located further south into western NM and eastern AZ where thunderstorm clusters and stronger individual mesocyclones have materialized causing rain rates to top 1"/hr in some areas. Considering the environment in place and the antecedent ground conditions leftover from the rainfall prior, flash flood chances will remain elevated through at the least the first half of the overnight period before the threat settles. Given the state of the radar and observation trends across NM, have elected to expand the MDT risk southward to encompass the northwest quadrant of the state which will see convection funnel into the area with hours of overlap into areas already experiencing flash flooding. The high-end MDT remains for the San Juans with the MDT risk expanding through the Four Corners into southeastern UT. Expectation is for 1-2", locally higher, of additional rainfall in the area encompassed by the MDT risk with more scattered instances of 1" or more within the SLGT risk area that extends around the current higher risk (MDT). Across the northern sections of the Great Basin, a targeted area of northwestern NV into southern OR will be under the defined axis of deformation as the upper pattern evolves leading to some enhancement of the precipitation field overnight. Trends among guidance have signaled a bit less vigor in terms of hourly rate expectancy for the setup as the latest HRRR/RRFS tandem limit the instability in the region, thus limiting the upper end potential for heavier rainfall. Despite some of the signatures for 1-1.5" of rainfall overnight in pockets of the above area, much of the rain will come over the span of several hours which would preclude a lot of flash flooding potential, even for this area of historically lower FFG's. An isolated flash flood threat still exists, however, so the chances remain within the MRGL risk category, but the previous SLGT was removed given the lowered threat overall. ...Southeast Florida... Easterly low level flow will continue across South FL with the threat for convection to motion out of the nearby Atlantic waters still prevalent through the overnight hours as noted via several of the CAMs. A cluster of activity is currently migrating parallel to the land with the fringe of the convection reaching parts of the Upper Keys. This will likely not move the needle with regards to flash flood prospects, but is a defined look to what is plausible a bit further north as we maintained the prevailing east to northeast flow into the southern tip of the Peninsula. HRRR/RRFS are not as enthusiastic with the potential, but other CAMs noted some potential overnight, albeit fairly isolated overall. Decided with the current presentation and some guidance still offering the low- end threat, maintained continuity and kept the MRGL in place to account for any cells moving onshore during the overnight period. Threat remains at the lower end of the risk threshold with a greater potential spurring up over the coming days. Kleebauer Day 2 Valid 12Z Fri Oct 23 2026 - 12Z Sat Oct 24 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE SACRAMENTO MOUNTAINS SOUTH THROUGH THE EL PASO METRO... ...21Z update... ...NM and southern CO... Model agreement remains good concerning the track and timing of a mid to upper-level trough axis moving east across the Southwest through Saturday morning. As the main energy over Arizona/Utah from Thursday night lifts northeastward, the trough is reinforced on Friday over California/Nevada/Arizona, resulting in the formation of a new closed low. The net result downstream is only a minor eastward push of heights into New Mexico and Colorado which will be a hindrance for forcing. However, precipitable water values are forecast to remain anomalous (2 to 4+ standardized anomalies from the 12Z GFS) from far western Texas into central/eastern New Mexico and southeastern Colorado including a middle and upper level connection to moisture related to remnant tropical systems west of the central Mexican coast. The mean steering flow will be from the SSW, ranging from 20 to 40 kt and 850-700 mb winds remain fairly strong at 15 to 30+ kt. Therefore, while individual cells should remain progressive, there will be high potential for repeating and training of heavy rain. The 12Z HREF/REFS showed that the probabilities for 0.5 to 1.0+ in/hr rainfall ramp up in the 18-21Z time frame and diminish after 06Z Saturday. Total rainfall of 1 to 2 inches is likely across portions of central/eastern New Mexico into southern Colorado for the 24 hour period with localized totals between 2 to 3 inches. Thinking from the previous shift remains valid (see below), including the higher potential for higher rates/instability across far western Texas into southern New Mexico despite the QPF signal in the models lowering the existing Slight Risk area. ...East Coast of Florida... A Marginal Risk remains in place across southeastern Florida but was expanded northward to include Cape Canaveral where similar potential for slow moving cells will exist. Some of the 12Z model guidance showed the potential for higher instability farther north with 500 to 1000 J/kg in place at times throughout the 24 hour period near the Cape Canaveral region. While precipitable water values are lower into the Space Coast (at or less than 1 inch), there are some modest probabilities for 3, 5 and 8 inches over the 24 hour period ending Saturday morning near or just offshore of the coast according to the 12Z HREF/REFS. Otto ...previous discussion follows... ...NM and southern CO... Scattered convection is expected to develop across portions of NM into southern CO downstream of a mid to upper level trough tracking eastward from CA into AZ. In the broader evolution of the system, day 2 (Friday) appears to represent a relative minimum in convective coverage and overall intensity compared to more active periods expected on both Thursday and Saturday. Nonetheless, PWs will remain anomalous and collocated with 500-1500 J/kg of CAPE. This environment will support scattered convection capable of locally high rainfall rates and an isolated flash flood threat. While the latest QPF guidance remains modest and generally supportive of a Marginal risk, the presence of better instability over southern NM could yield an uptick in convective rainfall as we get more into the high res model timeframe. Considering the hydrologic vulnerability, the inherited Slight risk was maintained across the terrain and burn scars of the Sacramento Mountains into adjacent urban corridors. ...Southeast FL... A setup similar to day 1 will persist across southeast FL, where low level northeasterly flow and coastal convergence could focus slow moving cells along the immediate coast. The heavy rainfall threat remains conditional, with a possibility the heaviest cores remain just offshore. Model differences also introduce some uncertainty regarding the moisture profile, with the GFS showing notably higher PW values than the ECMWF. Given the lingering uncertainty with these details the inherited Marginal risk was left unchanged. Chenard Day 3 Valid 12Z Sat Oct 24 2026 - 12Z Sun Oct 25 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN NEW MEXICO INTO SOUTHEASTERN COLORADO, AND OVER SOUTHEAST FLORIDA... ...21Z update... ...Eastern NM into southeast CO... Minor timing differences existed in the 12Z models regarding the eastward progression of a mid to upper-level closed low over the Southwest with the 12Z GFS a bit faster than the consensus by Sunday morning. Despite these differences, the models are unanimous with the potential for heavy rainfall, especially over eastern New Mexico, with broad support for 1 to 3 inches over the 24 hour period. Anomalous precipitable water values from Friday will remain over eastern New Mexico/eastern Colorado into the adjacent High Plains containing 2 to 4+ standardized anomalies in the 12Z GFS. The increased forcing/instability mentioned in the previous discussion continues to look valid which will likely support higher potential for heavy rain. Hourly rainfall locally exceeding 1 inch appears likely and when combining with antecedent heavy rainfall from the previous couple of days, a higher end Slight Risk remains focused from the southern Sacramento Mountains into far southeastern Colorado. ...Four Corners Region While better moisture will have shifted well east of the Four Corners region by Saturday morning, there will continue a localized concern for heavy rainfall near and just east of the approaching closed low aloft over Arizona/Utah. Snow levels should remain high enough (9000+ feet above MSL) across the region to allow for heavy rainfall from slow moving or repeating cells. Model forecast instability is weak across the region but where pockets of at least a few hundred J/kg are expected to set up, there will be support for localized rainfall of 0.5 to 1.0+ inches in 3 hours. Given the preceding days of heavy rainfall leading up to Saturday, the region will be more hydrologically sensitive than average to additional, albiet localized, heavy rainfall. ...East Coast of Florida... Similar to Friday/Friday night, the previous Marginal Risk was extended northward to include the Space Coast given similar potential for instability and heavy rain from slow moving cells. There is better model agreement today, regarding a mid-level low that is forecast to drop southward near the east coast of Florida late Saturday into Sunday, associated with a surge in moisture and low level easterly flow into the central and southern Peninsula. While model QPF for southeastern Florida are mixed, cannot rule out some locally enhanced threat for flash flooding across the urban southeastern corridor given the setup, so the Slight Risk was left in place for now. Once the forecast is more within the hires window, a better depiction of the flash flood potential should hopefully emerge with possible changes to the ERO. Otto ...previous discussion follows... ...Eastern NM into southeast CO... An uptick in the flash flood threat compared to day 2 is anticipated across eastern NM into southeastern CO on Saturday. Synoptic scale ascent will strengthen as the mid to upper level trough and associated jet streak approach the region, which will also help amplify the low level moisture transport axis. PWs will remain anomalous, holding well above normal and near climatological max values for late October. Model guidance also indicates upwards of 500-1500 J/kg of CAPE within this moisture plume. Deep unidirectional southerly flow will favor some cell training and backbuilding potential. Given the favorable ingredients, not surprising that model QPF values are notably higher compared to day 2. The combination of strong forcing, deep and anomalous moisture, and sufficient instability, will support convective rain rates locally as high as 1-2"/hr. Overall model agreement on the axis of heaviest rainfall is above average for a day 3 forecast. Higher end Slight risk probabilities are justified across much of eastern NM with scattered flash flooding expected. ...Southeast FL... The Slight risk has been maintained across the southeast FL urban corridor. The mesoscale setup remains similar to days 1 and 2, with northeasterly low level flow promoting coastal convergence and possible slow moving convection. By this time, dynamic ascent may be aided by a distinct mid level shortwave dropping southward into the area. While model guidance is in relatively good agreement synoptically, model spread persists regarding the magnitude of moisture present. The ECMWF and AIFS remain noticeably drier overall, depicting an environment less conducive for heavy rainfall. Conversely, the GFS/AIGFS/UKMET/CMC all depict a deeper moisture profile and consistently produce a coastal heavy rain signal. Given this lingering uncertainty and the conditional probability for slow moving convection to anchor along the sensitive coastal corridor, there is no reason to deviate from the inherited Slight risk. Trends will continue to be monitored in subsequent forecast cycles. Chenard Day 4 and Day 5 Valid 12Z Sun Oct 25 2026 - 12Z Tue Oct 27 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS, AS WELL AS SOUTHEAST FLORIDA ON SUNDAY... ...Central to Southern High Plains... Our western disturbance will continue to eject eastward, albeit relatively slowly, over the course of Sunday leading to enhanced ascent downstream of the mean trough. Elevated moisture positioned over the Central and Southern High Plains in tandem with the increased ascent within a defined jet coupling over the area will allow for scattered to widespread convective development during the course of Sunday into early Monday morning before we finally see the pattern settle heading into the D5 time frame. Current ensemble means remain steady with a broad axis of 1-2" of rainfall with the individual global deterministic output showing some of the embedded 3-4" higher amounts during the D4 period across the region between southern NE down into the TX Panhandle and adjacent northeastern NM. The overall pattern has been fairly consistent run-to-run in the evolution of the upper level disturbance with closed upper level reflection finally opening up and ejecting northeast into the Northern Plains by the D5 time frame which will subsequently put an end to the more prolific heavy rainfall posture we've experienced from the Southwest to the eventual impact across parts of the High Plains. The previous SLGT risk on D4 was adjusted a bit to reflect the, again, slower trends in the forward propagation of the upper low across the Four Corners which allowed for a small shift westward in the overall threat. The main area of interest has not changed, however, so the forecast remains in good standing with the greatest threat likely over eastern NM up through the TX/OK Panhandles, and into western KS. By D5, the threat begins wind down as the primary ascent shifts northward and the lingering elevated moisture and instability is offset from the primary forcing. Maintained the MRGL risk across the Southern High Plains to reflect the potential lingering into Monday and will need to monitor a potential risk addition over the Midwest as the main energy lifts into the area. That said, instability to the north is meager, comparatively, so the threat is not as prevalent over areas of SD/MN to areas south into TX/OK. ...Southeast Florida... A relatively stagnant synoptic pattern will lead to a continuation of heavy convective threats anchored to the immediate coast of southeastern FL. This is likely the final day of the heavy rain potential, although a few models do want to linger a bit into early next week. Regardless, a bit of a hold over from what will likely be an active D3 period leading to the threat for D4 (Sunday) before things finally settle. Expectation is for local totals of 3-5" additional on top of any heavy rain the previous periods will only add to the prospects of flash flooding within the urban corridor. Given the expected antecedent conditions and the threat of heavy rain from any convective development, a SLGT risk remains in place for the D4 time frame before we finally fall to a nil ERO for D5 (Monday) as the threat begins to fade. 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 $$