342 FXUS21 KWNC 311823 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT May 31 2026 SYNOPSIS: Increased potential of extreme heat continues across parts of the central and east-central contiguous U.S. (CONUS) associated with strong mid-level high pressure centered over the Upper Mississippi Valley. Increased moisture associated with a potential tropical wave may result in heavy precipitation for the Florida Peninsula through the middle of week-2. HAZARDS Slight risk of extreme heat for portions of the Northern and Central Plains, Upper and Middle Mississippi and Ohio Valleys, and Great Lakes region, Mon-Thur, June 8-11. Slight risk of heavy precipitation for the Florida peninsula, Mon-Fri, June 8-12. Possible Rapid Onset Drought for parts of the Upper and Middle Mississippi Valley and Great Lakes region. DETAILED SUMMARY FOR WEDNESDAY JUNE 03 - SUNDAY JUNE 07: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR MONDAY JUNE 08 - SUNDAY JUNE 14: Multiple model ensemble solutions for 500-hPa height anomalies depict amplified ridging over the Upper Mississippi Valley at the outset of week-2, which is then favored to weaken somewhat and widen to eventually span most of the U.S.-Canadian border by the end of week-2. This is likely to bring above-normal temperatures across much of the CONUS, particularly for the Upper Midwest, under the axis of the ridge. The Probabilistic Extremes Tools (PETs) from both the ECMWF and GEFS indicate at least a 20% chance of maximum temperatures to exceed the 85th climatological percentile and at least 90F from the Northern Plains eastward into the Ohio Valley through at least the middle of the forecast period. The GEFS indicates a long-lived event, meeting the above criteria for all of week-2, while the ECMWF has a weaker signal in the second half of week-2. Going with the best model consensus, a slight risk of extreme heat remains posted for portions of the Northern and Central Plains, Upper and Middle Mississippi and Ohio Valleys, and Great Lakes region, valid Jun 8-11. Following a very wet spring across the Great Lakes and Upper Mississippi Valley, precipitation has been limited over the past several weeks. The most recent release of the U.S. Drought Monitor shows expansion of abnormally dry conditions across parts of the region. WPC's week-1 forecast indicates below normal precipitation and above normal temperatures in this area. Above normal temperatures are forecast to continue into week-2 with only near normal precipitation favored. Therefore, a possible risk of ROD is posted for parts of the Upper and Middle Mississippi Valley and Great Lakes region. Multiple model ensembles depict increasing tropical moisture and convection over the Gulf of America during the forecast period, potentially associated with a tropical wave moving into the region. Model solutions keep much of this enhanced convection south of the CONUS, but a plume of this moisture is favored to move over Florida during week-2. The PETs from the ECMWF and GEFS both indicate at least a 20% chance of 3-day precipitation exceeding 1 inch throughout the forecast period. Uncalibrated probabilities from the GEFS and ECMWF reach the above thresholds as well, with a bullish ECMWF pushing probabilities of 3-day precipitation totals exceeding 1 inch over 50% for southern Florida. The signal weakens a little in both models towards the end of week-2 though, so a slight risk of heavy precipitation is posted for the Florida Peninsula valid Jun 8-12. Although a flooding hazard is not being issued at this time, localized urban and flash flooding is possible given Florida's flat topography and the potential for widespread heavy rain. In Alaska, river ice breakup season is ending, but many rivers north of the Brooks Range remain icebound. River breakup flooding can occur with little or no notice as conditions on frozen rivers can change quickly, so please check with the Alaska Pacific River Forecast Center for the latest conditions and advisories. FORECASTER: Danny Barandiaran $$