799 FXUS21 KWNC 301812 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT May 30 2025 SYNOPSIS: Mid-level low pressure is forecast across western and central Canada during the first half of the period. While models differ in the amplitude of this feature, it is likely that an associated frontal boundary will exist across the central and east-central contiguous U.S. (CONUS) serving as a focus for episodes of heavy, convective precipitation, although confidence is low regarding the exact areas that receive heavy precipitation. There are also continued signals for increasing tropical moisture across Florida and the Southeast, particularly in the middle and later parts of week-2. As the aforementioned mid-level low shifts eastward, mid-level high pressure is forecast to expand across the northeastern Pacific into the northwestern CONUS which could renew heat concerns across portions of the West. HAZARDS Slight risk of heavy precipitation across much of the central and eastern CONUS (excluding portions of the Northeast, northern Mid-Atlantic, and Upper Midwest), Sat-Fri, Jun 7-13. DETAILED SUMMARY FOR MONDAY JUNE 02 - FRIDAY JUNE 06: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SATURDAY JUNE 07 - FRIDAY JUNE 13: Early in week-2, troughing is forecast across western and central Canada, with the 0z ECENS and 0z CMCE being more amplified with this feature compared to the 0z GEFS. The trough favors a frontal zone setting up across the central and east-central CONUS, with potentially multiple episodes of heavy precipitation tied to enhanced convective activity. The ECENS Probabilistic Extremes Tool (PET) depicts at least a 20 percent chance 3-day precipitation totals exceed the 85th climatological percentile and 1-inch extending as far north as the Upper Mississippi Valley at the start of the period, likely due to the stronger upstream troughing. The GEFS PET confines these elevated probabilities to the Central and Southern Plains eastward to the Lower Mississippi and Tennessee Valleys. The uncalibrated 0z ECENS depicts a broad region extending from the eastern Plains to the Ohio and Tennessee Valleys and Southeast with a 20-40 percent chance week-2 total precipitation exceeds 2-inches, with localized high daily totals depicted in the recent ECMWF and GFS deterministic guidance. While confidence is fairly high regarding heavy precipitation somewhere within the eastern half of the CONUS, confidence is much lower regarding the exact location due to the convective nature of the precipitation and uncertainty regarding the strength of the trough. Further complicating the forecast is the added potential for tropical moisture to move into Florida or the Southeast by the second half of the period. This is more evident in the 0z GEFS and 0z CMCE solutions, but not as robust in the 0z ECENS. It should also be considered that the Madden Julian Oscillation (MJO) is forecast to reach phase 8 which can correlate with a more active tropical activity across the Gulf. All things considered, a large slight risk for heavy precipitation is designated across most of the central and eastern CONUS, excluding the northern Great Lakes, Northeast, and northern mid-Atlantic for all of week-2 (Jun 7-13). Localized flooding is a concern for any areas that do receive heavy rainfall. Ridging is forecast across the northeastern Pacific, and associated positive height anomalies are predicted to expand into the western CONUS as the downstream troughing shifts further east and weakens. This favors a gradual increase in temperatures, and is borderline for an extreme heat risk over some areas. At the start of the period, the largest positive temperature anomalies are favored further to the south, with the uncalibrated 0z ECENS and 0z GEFS depicting daily maximum temperatures in the upper 90s deg F to low 100s deg F over the California Central Valley. Closer to normal or even slightly below-normal temperatures are possible across the Northwest at the start of the period due to influence from the trough, but heat signals in the PETs increase by day-10 (Jun 9), with probabilities for maximum temperatures exceeding the 85th climatological percentile rising above 40 percent in the ECENS PET and at least a 20 percent chance high temperatures in low elevation areas reach the 90s deg F. Despite these warm temperatures across the Northwest and California Central Valley, an extreme heat risk is not posted due to increasing heat hazard thresholds during the month of June, and the heat not predicted to peak until the middle of week-2. These areas will continue to be closely monitored for a possible heat risk designation in future outlooks. Weak troughing is predicted across the Bering Sea and western Alaska during week-2. This generally favors enhanced probabilities of below-normal temperatures across Alaska, and some increased potential for heavy precipitation over southeastern Alaska early in the period tied to enhanced onshore flow. However, precipitation amounts are predicted to remain below hazards criteria. Increasing mid-level heights later in the period tied to expanding ridging over the northeastern Pacific favor a drying trend over southern Alaska. FORECASTER: Thomas Collow $$