978 FXUS21 KWNC 241800 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT April 24 2026 SYNOPSIS: A potentially strong surface high pressure system and accompanying anomalously cold air is expected to settle into the central and eastern contiguous United States (CONUS), resulting in an elevated risk of much below normal, near freezing temperatures to damage to early spring blooms early in week-2. Later in week-2, southerly return flow could trigger heavy precipitation across portions of the Plains and Mississippi Valley, but there is too much uncertainty to post any additional hazards at this time. HAZARDS Moderate risk of much below normal temperatures for portions of the Central Plains, Middle and Upper Mississippi and Ohio Valleys, Great Lakes, and Appalachians, Sat-Sun, May 2-3. Slight risk of much below normal temperatures from portions of the Great Plains eastward through the mid-Atlantic and Northeast, Sat-Mon, May 2-4. DETAILED SUMMARY FOR MONDAY APRIL 27 - FRIDAY MAY 01: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SATURDAY MAY 02 - FRIDAY MAY 08: Towards the end of next week (late week-1), dynamical models have been consistent featuring an amplifying mean 500-hPa trough over the upper-Midwest, where the phasing with a southern stream shortwave looks to result in expanding coverage of negative height departures mainly east of the Rockies early in week-2. Coupled with a potentially strong mid-level ridge center near southern Greenland, the pattern continues to align with a negative North American Oscillation (-NAO) as this high latitude feature also supports the advection of anomalously cold air into many parts of the central and eastern CONUS during early May. Over time, ensembles generally maintain a -NAO circulation over eastern North America to keep cooler temperatures over the eastern U.S., however the latest GEFS and ECMWF significantly disagree in regards to the evolution of the mid-level pattern upstream over western North America. The ECMWF favors an amplifying trough shifting eastward from the Gulf of Alaska to force rising heights across the western CONUS by the middle of the period. In contrast, the GEFS lacks any development of this mid-level feature upstream, resulting in more of a zonal pattern over the Interior West with a tilt towards below-normal heights situated just offshore of the lower West Coast. Any sign of anomalous troughing points to additional southern stream energy to promote more unsettled weather into the western and central CONUS compared to the ECMWF. Tied to the amplifying 500-hPa trough late next week, the Weather Prediction Center (WPC) day 7 surface analysis features a large area of surface high pressure becoming established over the Plains and Mississippi Valley, with a large cold front extending from the Southern Plains to the Northeast. Over the past few days, ensemble guidance has trended towards developing a more southerly and stronger solution of this mean surface high, which is well reflected in the raw temperature tools indicating increasing chances (now >50%) for negative temperature departures from the southern Plains into parts of the Northeast. Likewise, Probabilistic Extreme Tools (PETs) from the GEFS and ECMWF have also trended colder, and now feature 30-50% chances for minimum temperatures falling below the 15th percentile with these cold signals shifting eastward and gradually decaying with time over the southeastern CONUS through day 11 (May 5). While subfreezing temperatures are mostly likely to be confined to the Northern Plains, Upper Midwest, and Northeast, there continues to be increased chances in both the raw and calibrated tools for minimum temperatures falling below 38 and 40 deg F reaching into northern portions of the Southern Plains, Lower Mississippi and Tennessee Valleys, and lower Mid-Atlantic. Spring leaf index anomalies from the National Phenology Network show a very early (10-20 days) emergence of growth focused over parts of the Central Plains, Middle and Upper Mississippi and Ohio Valleys and Great Lakes due to antecedent warmth this spring. Based on the cold trends in the temperature tools, and 30-40% chances of minimum temperatures approaching near-freezing temperatures to adversely impact early and sensitive springtime vegetation over this region in central and eastern U.S., a moderate risk of much below normal temperatures is introduced in the updated outlook for May 2-3. According to the U.S. Department of Agriculture, there is also the potential for freeze damage to early-maturing fruit crops primarily in parts of Michigan and New York, despite freezing conditions not being too unusual in early May. A broader slight risk area of much below normal temperatures remains posted, and is expanded southward in coverage to account for increased chances for low temperatures dipping below 40 degrees F in the PETs early in the period. The high pressure system remains favored to move steadily eastward, allowing return warm, southerly flow to develop over the central CONUS fairly quickly. With time, the warming trend will progress eastward, reducing and ending the cold risk by days 10-11. The surface high pressure could be accompanied by breezy conditions as it pulls colder air southward into the central and eastern CONUS. Winds are not expected to reach hazards thresholds, but large portions of this region are entrenched in some degree of drought. The combination of dry and breezy conditions over parts of the central and eastern CONUS where there is antecedent dryness significantly increases the risk of wildfire activity, which could spread rapidly. Caution should be exercised to minimize the chances of wildfire ignition. The aforementioned surface return flow favored is expected to bring increased moisture into the Plains and Mississippi Valley where multi-model based tools depict some precipitation responses by the middle of week-2. However, both raw and calibrated tools are mostly unsupportive of any heavy precipitation risk, and given uncertainty in the evolving pattern aloft and at the surface upstream over the western CONUS, no precipitation related hazards are issued at this time. Over Alaska, models continue to favor mid-level troughing over the Bering Strait with ridging over the Mainland. An associated mean surface low centered over the Aleutians is expected to bring potentially strong winds and stormy conditions along the southern tier of the state early in week-2 before the pattern aloft deamplifies. At this time, conditions are expected to remain below hazard thresholds, and no corresponding wind or precipitation shapes are posted. The typical peak of the river ice breakup season is approaching, and ice jam flooding can occur this time of year with little or no notice as conditions on frozen rivers can change quickly. Please check with the Alaska Pacific River Forecast Center for the latest conditions and advisories. FORECASTER: Nick Novella $$