959 FXUS07 KWBC 301900 PMD30D Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 300 PM EDT Thu Apr 30 2026 30-DAY OUTLOOK DISCUSSION FOR MAY 2026 The updated May Temperature and Precipitation outlooks are based on the latest dynamical models, WPC temperature and precipitation forecasts during the first week of the month, the CPC 8-14 day temperature and precipitation outlooks, and the week 3-4 model output (valid May 15-28). Soil moisture was also a factor in the updated May outlooks. The Madden-Julian Oscillation (MJO) strengthened during early April with an eastward propagation over the Western Hemisphere. By late April, the MJO shifted east to Africa and the western Indian Ocean. A robust MJO overspreading the Indian Ocean and its potential influence later in May was a consideration in the updated temperature outlook. ENSO-neutral conditions are present with El Nino likely to emerge during May-June-July. Following an unusually warm early spring for the south-central and eastern contiguous U.S. (CONUS), a major pattern change was well underway by the end of April as a highly amplified 500-hPa trough has developed over eastern North America. A couple of strong cold fronts for this time of year are forecast to usher in cooler-than-normal temperatures from the Great Plains to the East Coast through the first ten days of the month. Unseasonably cool temperatures through at least early May results in the updated outlook leaning towards below-normal temperatures across parts of the Eastern Corn Belt, Great Lakes, and Northeast. The GEFS and ECENS depict the eastern North America trough deamplifying and progressing to the east by mid-May with anomalous mid-level ridging expanding to the Great Plains. The Week 3-4 GEFS and ECENS, valid from May 15-28, are in good agreement with a broad 500-hPa ridge and positive height anomalies throughout the lower 48 states. These model solutions also favor a flip from below to above-normal temperatures across much of the east-central CONUS during mid-May which would be consistent with the MJO currently entering the Indian Ocean. This predicted variable temperature pattern during May supports smaller probabilities (< 50%) for below and above-normal temperatures along with equal chances (EC) of below, near, or above-normal temperatures across the eastern third of the CONUS. Farther to the west, above-normal temperatures are more likely to prevail during most if not all of the month. The largest above-normal temperature probabilities (> 60%) are forecast for the Pacific Northwest with temperatures averaging 10 to 15 degrees F above normal during the first week of May. Probabilities are lower across the Desert Southwest as model solutions remain consistent that a couple of southern stream shortwave troughs cross this region early in the month. In addition to the predicted longwave pattern and dynamical model temperature tools, dry topsoil supports the increased chance of above-normal temperatures from the Oklahoma and Texas Panhandles north through western Kansas and Nebraska. Due in part to nearby below-normal sea surface temperature anomalies, the May outlook continues to slightly favor below-normal temperatures for southwestern Alaska and the Alaska Peninsula. Based on a model consensus, above-normal temperatures are slightly favored across northern to eastern Alaska. The updated May precipitation outlook relies primarily on the model precipitation forecasts through the first two weeks of the month. During the latter half of May, the GEFS and ECENS either diverge or depict weak signals for precipitation. A stationary front along with at least two shortwave troughs within the southern stream favor above-normal precipitation from Texas east to the Western Gulf Coast, Lower Mississippi Valley, and parts of the Southeast. Probabilities exceed 40% in portions of southeastern Texas, Louisiana, and southwestern Mississippi where the WPC 7-day qpf has around 2 inches of precipitation. Downstream of a 500-hPa trough axis that is forecast to persist through mid-May and consistent with the 8-14 day outlook, above-normal precipitation is slightly favored for eastern Maine. Although a number of tools lean on the wetter side for more of the Southeast and New England early in the month, high uncertainty during the later half of May precludes favoring above-normal precipitation. The large above-normal precipitation probabilities (> 60%) across southern New Mexico and the El Paso area are related to the likelihood that precipitation during the first week of May reaches the upper tercile for the month in a climatologically drier area. A dry start to the month and the expectation that anomalous 500-hPa ridging expands eastward to the north-central CONUS by mid-May favors below-normal precipitation across the Pacific Northwest, much of the Northern Rockies, Northern to Central Great Plains, and Upper Mississippi Valley. Due to weak and conflicting model guidance, EC is forecast throughout Alaska. ***************************************************************************** Previous discussion released on April 16 below ***************************************************************************** The May 2026 Temperature and Precipitation Outlooks are based on the: North American Multi-Model Ensemble (NMME) and International Multi-Model Ensemble (IMME), consolidation (combination of statistical and dynamical model tools), soil moisture influence and its constructed analog, and decadal trends. The Madden-Julian Oscillation (MJO) strengthened during early April and dynamical models have remained consistent since last week that a robust MJO propagates eastward from the West Pacific to the Indian Ocean during the latter half of April. This MJO evolution and its potential influence on the mid-latitude circulation pattern was considered in the temperature outlook. ENSO-neutral conditions are present with El Nino likely to emerge during May-June-July. The NMME and IMME support an increased chance of above-normal temperatures for the western contiguous U.S. (CONUS), much of the Great Plains, and Southeast. The largest above-normal temperature probabilities (greater than 50%) are forecast for the Pacific Northwest where the calibrated NMME and IMME have the strongest warm signal and there is also support from the statistical tools. In addition, the larger probabilities are consistent with the expectation for a drier-than-normal May. Recent heavy precipitation has moistened topsoil from eastern Oklahoma southward into central Texas. The GEFS and ECENS favor a continuation of the wet pattern for these areas with an expansion eastward into the Lower Mississippi Valley by the end of April. Due to the likelihood that topsoil is neutral to wet heading into May and tools favor above-normal precipitation for the month, above-normal temperature probabilities from the dynamical models are reduced across much of the south-central CONUS. Farther to the east, drier topsoil and the consolidation tool lead to an increased chance of above-normal temperatures for the Southeast. The current West Pacific MJO (phase 7) would favor an amplified 500-hPa trough developing over the eastern CONUS by the end of April which may result in a relatively cool start to May for the Midwest, Northeast, and Mid-Atlantic. However, if the MJO propagates back to the Indian Ocean, then above-normal temperatures could return to these areas later in May. Due to this expected variable temperature pattern during the month and a weaker warm signal among the dynamical models, equal chances (EC) of below, near, or above-normal temperatures are forecast from the Middle and Upper Mississippi Valley east to the Mid-Atlantic and Northeast. Elevated above-normal temperature probabilities are forecast for eastern Alaska. However, the outlook hedged colder across southwestern Alaska with EC forecast due to the Week 3-4 GEFS and ECENS favoring near to below normal early in the month. Large negative SST anomalies led to the outlook leaning slightly on the colder side along coastal southwestern Alaska and the Alaska Peninsula. Based on the NMME, IMME, and consolidation, below-normal precipitation is favored for parts of southeastern Alaska, the Pacific Northwest, and the Great Basin. Conversely, these forecast tools support the outlook leaning on the wetter side across southwestern Arkansas, southeastern Oklahoma, central to eastern Texas, and most of Louisiana. Many of the dynamical models, especially the ECMWF, along with trends favor a wetter May across the Southeast. However, equal chances (EC) of below, near, or above-normal precipitation are forecast for this region as the wet model signal was offset by a correlation between dry April soil moisture and below-normal precipitation during May. As of mid-April, soil moisture is below the 5th percentile throughout the Southeast and will likely decline further during the next week with summerlike heat and an increasing water demand. A large coverage of EC is also forecast across a majority of Alaska and the lower 48 states due to high uncertainty at this time lead with a monthly precipitation outlook along with low predictability in forecasting anomalous convective precipitation throughout the central and eastern CONUS. FORECASTER: Brad Pugh 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 Jun ... will be issued on Thu May 21 2026 These outlooks are based on departures from the 1991-2020 base period. $$