249 FXUS07 KWBC 301901 PMD30D Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 300 PM EDT Wed Sep 30 2026 30-DAY OUTLOOK DISCUSSION FOR OCT 2026 The updated set of temperature and precipitation outlooks for October 2026 are based primarily on the latest WPC Week-1 and CPC Week-2 and Weeks 3-4 guidance, along with the latest dynamical model input from the ECENS and GEFS ensemble systems. Other considerations include the very active tropical cyclone season in the eastern and central Pacific, the current El Nino, climatology, and precipitation 7-day and 30-day departures from normal. Experimental GEFS and CFS Period-Weighted temperature and precipitation forecasts were also considered, as well as experimental AIMS2S model guidance. The updated temperature outlook for October favors above normal monthly mean temperatures for nearly all areas west of the Continental Divide. East of the Divide, anomalous warmth is favored for the northern and central Plains, the Upper Mississippi Valley, and in the vicinity of the Gulf coast. The highest chances of above normal temperatures are indicated over California and parts of western Nevada and southern Oregon, as well as over most of the Florida Peninsula. The broad coverage of favored above normal temperatures is generally consistent with official WPC week-1 and CPC week-2 and weeks 3-4 temperature guidance, as well as an extended period of mid-level ridging and 500-hPa positive height anomalies for the West. AIMS2S subseasonal-to-seasonal temperature guidance also lends support to this outlook, though it differs by predicting a cool-down relative to normal during the latter half of October across the Gulf Coast region and Southeast. In Alaska, experimental GEFS and CFS Period-Weighted guidance, in addition to CPCs extended-range temperature outlooks, favors above normal temperatures over the eastern Interior, southcentral and southeastern Alaska. Elsewhere, which includes a sizable portion of the Lower 48 states, and western and northern Alaska, Equal Chances (EC) of above, near, and below normal temperatures is favored. The updated precipitation outlook for October favors above normal precipitation for most of the southern tier of the Contiguous U.S. (CONUS), from southern Arizona eastward across the Southern Plains, Lower Mississippi and Tennessee Valleys, and the Southeast. Maximum probabilities ranging from 50 to as much as 80-percent are concentrated closer to the Gulf Coast and the Texas Hill Country. This wet pattern is heavily front-loaded (within the first 7-10 days of October) and is associated with several high pressure systems and their accompanying surges of cooler Canadian air moving southward to near the Gulf Coast. The respective cold fronts representing the leading edges of these cooler surges are forecast to stall across the deep South, accompanied by easterly surface flow and increasingly moist conditions. In addition, many of the models and tools used support this anomalously wet outcome. Despite this being early in the fall season, the southern storm track commonly observed with strong El Ninos is already beginning to take shape. Below normal precipitation is favored from the Upper Mississippi Valley/western Great Lakes region west-southwestward across the Northern and Central Rockies, and the Northern and Central Great Basin to nearly all of the West Coast. This is associated with extensive and prolonged mid-level high pressure and the expectation of widespread positive 500-hPa height anomalies. In the Pacific Northwest, conditions look abnormally dry at least through the first half of October, according to WPCs official week-1 precipitation outlook and CPCs official week-2 precipitation outlook. Later in October, the possibility of a persistent northeast Pacific mid-level trough shifting eastward warrants at least a non-dry (i.e. EC) outlook for the westernmost reaches of Washington state. Across the Southwest, the monsoon is typically winding down in October. However, there is always the tropical cyclone wildcard to consider, where a late season tropical cyclone over the eastern Pacific and/or related gulf surge from the Gulf of California brings abundant moisture into the American Southwest. This fall, given the current strength of El Nino and the very active tropical cyclone season thus far, the possibility of a tropical system affecting the Southwest extends into the autumn season even later than usual. The precipitation outlook for Alaska seems relatively straightforward given the increased likelihood of a mid-level trough positioned from about the Bering Sea to the central Gulf of Alaska, which is a highly favorable pattern that promotes increased precipitation over the southern portion of the state. This widespread onshore flow pattern is clearly indicated by the AIMS2S tool, and the GEFS/ECENS Week-2 precipitation departure forecasts which takes us at least into mid-October. Elsewhere, which includes a large portion of the CONUS, western and northern Alaska, and the Aleutians, Equal Chances (EC) of above, near, and below normal precipitation is favored. **************************************************************************** Previous mid-month discussion below **************************************************************************** The October 2026 Temperature and Precipitation Outlooks are based on the: North American Multi-Model Ensemble (NMME) and International Multi-Model Ensemble (IMME), consolidation (dynamical and statistical tools), and El Nino composites. Due to the strong and dominant El Nino, the Madden-Julian Oscillation (MJO) was not a factor in the October forecast. The West Pacific is likely to remain active with a number of tropical cyclones (TCs) heading into October. If a TC recurves northeastward into the higher latitudes of the North Pacific, it could disrupt the downstream longwave pattern which increases forecast uncertainty. Although soil moisture has a declining influence on surface temperatures during the fall, the intensifying drought conditions with low soil moisture will have a warming effect on surface temperatures across the Southern Great Plains, Ozarks region, Lower Mississippi Valley, and parts of the Southeast. The October Temperature Outlook generally used the consolidation tool as a guide, which represents a combination of dynamical model output and statistical tools which include impacts from the phase of the El Nino Southern Oscillation (ENSO) and long-term trend. Above-normal temperatures are favored along the West Coast and for much of the central and eastern Contiguous U.S. (CONUS). The equal chances (EC) of below, near, or above-normal temperatures across the interior West is due to conflicting signals between the cooler El Nino composites and warmer dynamical models. The outlook leans slightly towards above normal (33-40% chance) across parts of Arizona and New Mexico based on the long-term trend. Above-normal temperature probabilities are increased to more than 50% for the Lower Mississippi Valley given the intensifying drought and low soil moisture having a warming effect heading into October. The other area with higher forecast confidence is southeastern Alaska with the calibrated NMME and IMME depicting greater than a 50% chance of above-normal temperatures. The lack of sea ice supports above-normal temperatures for the North Slope of Alaska. The increased chance that a recurving TC in the West Pacific affects the longwave pattern downstream over North America is a source of forecast uncertainty, limiting the coverage of above-normal temperature probabilities exceeding 50 percent. During the first half of October, the GEFS and ECMWF models are in good agreement with a 500-hPa trough near the West Coast and anomalous mid-level ridging over the eastern two-thirds of the CONUS. This longwave pattern would yield a relatively wet start to the month for the Southwest. On the monthly time scale, the CFS model along with the NMME and IMME support elevated above-normal precipitation probabilities from the Southwest eastward to the Central to Southern Great Plains and parts of the Gulf Coast. This favored wetness also extends west to include southern California due to good model consistency from past daily CFS model runs and the likelihood of a continued active East Pacific hurricane season. Although El Nino composites would support the October outlook leaning on the drier side for the Pacific Northwest and Northern Intermountain West, EC is forecast for these areas due to a lack of support from the calibrated dynamical model output and the ENSO-OCN tool. Elsewhere across the lower 48 states, EC is also forecast with generally weak signals among the tools at this time lead. Based on model guidance favoring above-normal precipitation during the first half of the month along with the IMME on the monthly time scale, elevated above-normal precipitation probabilities (33-40%) are forecast across parts of southeastern Alaska and coastal southern Alaska. FORECASTER: Anthony Artusa The climatic normals are based on conditions between 1991 and 2020, following the World Meteorological Organization convention of using the most recent 3 complete decades as the climate reference period. The probability anomalies for temperature and precipitation based on these new normals better represent shorter term climatic anomalies than the forecasts based on older normals. The next monthly outlook...for Nov ... will be issued on Thu Oct 15 2026 These outlooks are based on departures from the 1991-2020 base period. $$