940 FXUS21 KWNC 261850 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT April 26 2026 SYNOPSIS: Mid-level low pressure favored over the northeastern contiguous U.S. (CONUS), is expected to bring anomalously cold air and gusty winds into parts of the Midwest and eastern U.S. next weekend into early next week. While much of the strongest cold anomalies have timed off into week-1, much below normal temperatures with freezing and near freezing conditions are possible in some areas, potentially damaging early spring blooms. Later in week-2, a restrengthening of mid-level low pressure over the northeastern CONUS may bring the return of unseasonable cold air to portions of the Midwest, but there is too much uncertainty to post any additional hazards at this time. HAZARDS Slight risk of much below normal temperatures from much of the eastern Ohio Valley, lower Great Lakes, Appalachians, and Mid-Atlantic, Mon, May 4. Slight risk of high winds for much of the eastern U.S., Mon-Tue, May 4-5. DETAILED SUMMARY FOR WEDNESDAY APRIL 29 - SUNDAY MAY 03: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR MONDAY MAY 04 - SUNDAY MAY 10: By next weekend, dynamical model 500-hPa height anomaly forecasts favor amplified troughing over the northeastern CONUS, with a strong anomalous ridge center to the south of Greenland. The predominance of these two mid-level height features over North America well aligns with a negative North America Oscillation (-NAO) pattern, which dynamically (and historically) supports the advection of anomalous cold air into many parts of the central and eastern CONUS. Relative to yesterday, the GEFS and ECMWF ensembles have become much more varied on the evolution of the height pattern, leading to significant uncertainty in the updated hazard outlook. While both models are beginning to favor more southern stream energy heading into week-2, the ECMWF is stronger with the shortwave activity with a broader coverage of negative height departures over the southern tier of the U.S. than the GEFS. The ECMWF also features a succinct northern stream shortwave trough over south-central Canada that is virtually absent in the GEFS. Taken together, this results in three minima in the ECMWF ensemble mean anomaly height field east of the Rockies, with a busier surface reflection in regards to potentially hazardous temperatures and precipitation compared to the GEFS early in week-2. Later in the period, the ECWMF has been consistent in developing an amplified ridge over southwestern Canada and the northwestern CONUS. Although the GEFS has fallen more in line in building heights upstream of the persistent troughing over the northeastern CONUS, it places anomalous ridging over the Interior West and Great Plains, out of phase with the ECMWF. In the wake of a large frontal boundary late in week-1, surface high pressure and accompanying anomalous cold air looks to be established across parts of the central and eastern U.S., with the largest negative temperature departures centered along an axis from the Southern Plains to the Mid-Atlantic. With the mean surface high weakening by the outset of the period, a moderation of temperatures is favored and the strongest cold anomalies are expected to be timed off into week-1. Therefore, a moderate risk of much below normal temperatures is discontinued. However, a corresponding slight risk area remains posted for day 8 (May 4) over portions of the Ohio Valley, Appalachians, Great Lakes, and Mid-Atlantic where both the GEFS and ECMWF Probabilistic Extreme Tools (PETs) maintain increased chances for minimum temperatures falling below the 15th percentile and 40 degrees F. Any residual cold with freezing or near freezing temperatures may threaten vulnerable springtime vegetation, particularly in areas that have experienced early growth due to antecedent warmth during April. Tied to the aforementioned northern stream shortwave trough, ECMWF temperature tools favor a reemergence of anomalous cold air over the Upper Midwest, with the PET depicting increased chances for minimum temperatures falling below the 15th percentile overspreading much of the Plains and Mississippi Valley by day 10 (May 6). However, the GEFS maintains near to above-normal temperatures for this part of the country, and the opposing temperature signals precludes any additional temperature hazards being posted. It should be noted that given the favored persistence of a -NAO circulation to predominately keep temperatures below normal mainly east of the Mississippi throughout week-2, any renewed cold signals will continue to be closely monitored in the upcoming hazard outlooks. Despite the surface high weakening over the eastern U.S early in the period, ensembles continue to favor a mean surface low to the south of the Canadian Maritimes to potentially bring periods of high winds over the northeastern U.S. With the ECMWF favoring stronger southern stream energy aloft, additional surface low formation is featured offshore of the Southeast. This is a novel development from the ECMWF, and though there is modest support in the GEFS for additional surface low activity in the western Atlantic, elevated wind speeds nonetheless remain possible at the base and ahead of the trough axis favored aloft. Therefore, a slight risk of high winds remains issued over the eastern U.S. for May 4-5 where there continues to be increased wind signals in the ECMWF PET along with increased chances for strong gusts in the calibrated tools. This secondary surface low in ECMWF also translates into higher precipitation amounts favored over the southeastern U.S. late in week-1 and into early week-2. The uncalibrated ECMWF shows at least 20% chances for 3-day amounts exceeding an inch from the Southern Plains to the lower eastern Seaboard, however both the GEFS and ECMWF PET are considerably more limited with any heavy precipitation threat. Given this, and differences in the surface pattern among these models, no precipitation hazards are posted. 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. Conditions are expected to remain below hazard thresholds, and no corresponding wind or precipitation shapes are posted. Additionally, 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 $$