![\"Moderate](\"https:\/\/ialert.com\/blog\/wp-content\/uploads\/2026\/09\/ialert-moderate-risk-flash-flooding-southwest-september-28-2026.jpg\")
\n 11:33 am EDT Monday, September 28, 2026. Red marks the Moderate Risk flash flooding area (level 3 of 4) across the Four Corners, yellow the Slight Risk
\n (level 2), and green the Marginal Risk (level 1). A second Slight Risk covers eastern North Dakota and northwest Minnesota. Data: NOAA Weather
\n Prediction Center.<\/figcaption><\/figure>\n
Moderate Risk flash flooding covers much of the Four Corners region under the NOAA Weather Prediction Center’s Day 1 Excessive Rainfall Outlook for
\n Monday, September 28, 2026. The outlook is valid through 6:00 am MDT (5:00 am MST in Arizona) Tuesday, September 29. Moderate is level 3 of 4 on the WPC
\n scale, and forecasters expect a widespread 1\u20133 inches of rain on soils that are already at or near saturation from recent heavy rainfall.<\/p>\n
Key points:<\/strong><\/p>\n Get Severe Weather Alerts for Your Location<\/p>\n When any NWS watch, warning, or advisory is issued for your area, iAlert sends you an immediate notification by email, text message, or phone call, 24 hours a day, 7 days a week.<\/p>\n Sign Up for Severe Weather Alerts →<\/a>\n<\/div>\n The Moderate Risk area is a broad oval centered on the Four Corners. It runs from the Colorado River near the California, Arizona, and Nevada WPC names the terrain most likely to see the heaviest totals: the south- and west-facing slopes of the Mogollon Rim in Arizona and the San Juan Phoenix, Tucson, El Paso, and Las Vegas sit just outside the Moderate area in the surrounding Slight Risk (level 2 of 4). A Marginal Risk (level 1 of WPC describes the setup as a predecessor rainfall event (PRE), a band of heavy rain that forms well ahead of a tropical system along a plume of its Strong upper-level divergence and southwest flow striking the terrain head-on add lift from both the large-scale pattern and the mountains. That One mitigating factor: WPC’s 16Z discussion notes that much of the rain falling in Arizona Monday morning is steady stratiform rain rather than The Excessive Rainfall Outlook, or ERO, is WPC’s national flash flood forecast. It gives the probability that rainfall will exceed flash flood A Moderate Risk flash flooding outlook means at least a 40 percent chance that flash flood guidance is exceeded within about 25 miles of any point in It is a statement of likelihood, not a report that flooding is underway. Flash Flood Warnings from local National Weather Service offices identify The Day 1 outlook covers 12Z Monday to 12Z Tuesday. In local time that is 6:00 am MDT in New Mexico, Colorado, and Utah, 5:00 am MST in Arizona, 5:00 Afternoon heating is the main trigger for the slow-moving storms WPC expects near the Colorado River, but steady rain on saturated soil can keep A second outlook area covers the northern Plains. Upper-level jet forcing and deepening moisture, with precipitable water near 1.5 inches, are The Slight Risk includes Fargo and Grand Forks and was expanded southwest toward southern North Dakota. WPC made no changes at 16Z because the event This Moderate Risk flash flooding day is a textbook late-season Southwest flood setup. Tropical moisture arriving after recent heavy rain finds The terrain is the multiplier. A slot canyon can flood from a storm that never reaches the hikers inside it, and a burn scar can send debris flows This is also the first day of a multi-day event, not a one-day spike. WPC’s Day 2 outlook keeps a Moderate Risk from south-central Arizona to the More than half of flood drownings in the United States happen when a vehicle is driven into flood water, often on roads that looked passable. During More than half of flood drownings in the United States happen when a vehicle is driven into flood water, often on roads that looked passable. During You can check conditions for your area on the local weather forecast page<\/a>. WPC’s four-tier rainfall Across the Four Corners: northern and eastern Arizona, southern Utah, southwest Colorado, and much of New Mexico, including Albuquerque, Lordsburg, Level 3 of 4, the second-highest WPC category. It means at least a 40 percent chance that rainfall exceeds flash flood guidance within about 25 miles WPC attributes the rain to a predecessor rainfall event fed by moisture from Odalys and the approach of Tropical Cyclone Polo. Moisture levels are 2 The Day 1 outlook runs through 6:00 am MDT (5:00 am MST in Arizona) Tuesday, September 29, 2026. WPC’s Day 2 outlook keeps a Moderate Risk over the No. Moderate Risk flash flooding is a probability, not a certainty, and most of the outlined area will not flood. Flash Flood Warnings issued during Sources:<\/strong><\/p>\n Get Severe Weather Alerts for Your Location<\/p>\n When any NWS watch, warning, or advisory is issued for your area, iAlert sends you an Sign Up for Severe Weather Alerts →<\/a>\n <\/div>\n","protected":false},"excerpt":{"rendered":"\n
Where the Moderate Risk flash flooding is outlined<\/h2>\n
\n tripoint east across northern Arizona and southern Utah into southwest Colorado and New Mexico. In New Mexico it forks south to include the Lordsburg
\n area and the Sacramento Mountains, two places WPC singles out for their burn scars.<\/p>\n
\n Mountains of Colorado, both of which sit square to the southwest flow. Southern Utah is flagged for its slot canyons and burn scars, and much of New
\n Mexico for saturated ground.<\/p>\n
\n 4) rims the whole region from southern Nevada to eastern Colorado. With this update WPC also pushed the Marginal and Slight areas north along the
\n Nevada and Utah border, where morning showers could organize into nearly stationary lines by afternoon.<\/p>\nWhat is driving the Southwest flood threat<\/h2>\n
\n moisture. Here the plume comes from the combination of Odalys and the approaching Tropical Cyclone Polo. Precipitable water, the total moisture in the
\n air column, is running 2 to 3.5 standard deviations above normal across much of the region.<\/p>\n
\n combination is what turns a moist airmass into repeated heavy rain over the same slopes.<\/p>\n
\n intense thunderstorms, because instability is limited. WPC calls the day “on the low end of the MDT risk category,” but kept the Moderate Risk in place
\n because of the moisture levels and flash-flood-prone ground. It expects a small cluster or line of slow-moving storms to develop near the Colorado River
\n this afternoon as skies clear and heating builds.<\/p>\nWhat a Moderate Risk flash flooding outlook means<\/h2>\n
\n guidance, the amount of rain an area can absorb before small streams and drainage systems overflow.<\/p>\n
\n the outlined area. Slight corresponds to at least 15 percent and Marginal to at least 5 percent. Only the High Risk, level 4 of 4, ranks above
\n Moderate.<\/p>\n
\n the specific communities at immediate risk.<\/p>\nModerate Risk flash flooding timing: 6 am MDT Monday to 6 am MDT Tuesday<\/h2>\n
\n am PDT in southern Nevada and California, and 7:00 am CDT in North Dakota and Minnesota.<\/p>\n
\n streams rising well into the night. For current warnings, check the live radar and alerts page<\/a>
\n and the list of active weather alerts<\/a>, both updated continuously.<\/p>\nSlight Risk in North Dakota and northwest Minnesota<\/h2>\n
\n feeding training showers and storms across eastern North Dakota into northwest Minnesota. Training means cells repeatedly crossing the same ground.<\/p>\n
\n is already ongoing. Bismarck is in the surrounding Marginal Risk, which extends from northern South Dakota across North Dakota to far northwest
\n Minnesota.<\/p>\nMeteorologist’s take<\/h2>\n
\n ground that cannot absorb more water, and flash flood guidance values drop to fractions of an inch. The steady rain in Arizona this morning is the good
\n news; the saturated soils mean it does not take thunderstorm rainfall rates to cause problems.<\/p>\n
\n downhill from as little as half an inch of rain in an hour. WPC singles out the Lordsburg area, the Sacramento Mountains, southern Utah’s canyons, and
\n the San Juans for exactly these reasons.<\/p>\n
\n Texas Panhandle and western Kansas on Tuesday as Polo’s remnant energy is absorbed into an upper trough, and the Day 3 outlook holds Moderate Risks over
\n the central and southern High Plains on Wednesday. Track Polo on the iAlert hurricane tracker<\/a>.<\/p>\nHow to stay safe during Moderate Risk flash flooding<\/h2>\n
\n Moderate Risk flash flooding in the desert Southwest, dry washes and low-water crossings can go from empty to impassable in minutes.<\/p>\n
\n Moderate Risk flash flooding in the desert Southwest, dry washes and low-water crossings can go from empty to impassable in minutes.<\/p>\n\n
\n scale follows the same logic as the Storm Prediction Center’s five-tier severe storm scale, explained in our guide to SPC outlook risk categories<\/a>.<\/p>\nModerate Risk flash flooding FAQ<\/h2>\n
Where is the Moderate Risk flash flooding area?<\/h3>\n
\n and the Sacramento Mountains. It extends west along the Colorado River to the California, Arizona, and Nevada tripoint.<\/p>\nWhat does a Moderate Risk mean on the Excessive Rainfall Outlook?<\/h3>\n
\n of any point in the outlined area.<\/p>\nWhy is the Southwest flooding in late September?<\/h3>\n
\n to 3.5 standard deviations above normal, and soils are already saturated from recent heavy rain.<\/p>\nWhen does this outlook expire?<\/h3>\n
\n Southwest and southern High Plains through Wednesday morning.<\/p>\nDoes a Moderate Risk mean flooding is guaranteed?<\/h3>\n
\n the event identify the specific communities at immediate risk.<\/p>\n\n
\n 11:33 am EDT September 28, 2026<\/a><\/li>\n<\/ul>\n
\n immediate notification by email, text message, or phone call, 24 hours a day, 7 days a week.<\/p>\n