Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Saturday February 22, 2025 to Friday February 28, 2025

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST February 14 2025

Synopsis: Surface high pressure is forecast across the eastern contiguous U.S. (CONUS) at the outset of week-2, with an Arctic air outbreak ongoing, but beginning to moderate relative to the late week-1 period. Mid level-high pressure is predicted over the West with increasing downslope flow across much of the central CONUS. This favors warming temperatures but also an increased risk for high winds, especially across the Northern Tier where pressure gradients are forecast to be strongest. Mid-level low pressure across the Northeast Pacific and Alaska favors intermittent rounds of enhanced precipitation across portions of Southeast Alaska and the Northwest CONUS, although hazards thresholds are unlikely to be reached.

Hazards

• Moderate risk for high winds across portions of the Northern and Central High Plains, Sat-Mon, Feb 22-24.
• Slight risk for high winds across portions of the Northern and Central Plains, Upper and Middle Mississippi Valley, and the Great Lakes, Sat-Wed, Feb 22-26.
• Slight risk of much below normal temperatures across portions of the Great Plains, Great Lakes, Upper and Middle Mississippi and Ohio Valleys, and Northeast, Sat, Feb 22.
• Slight risk of much below normal temperatures across portions of the Southern Plains, Lower Mississippi and Tennessee Valleys, Southeast, Appalachians, and Mid-Atlantic, Sat-Sun, Feb 22-23.
• Possible flooding for the Lower Mississippi and Tennessee Valleys, Southeast, and the Appalachians.

Detailed Summary

For Monday February 17 - Friday February 21: WPC Days 3-7 U.S. Hazards

For Saturday February 22 - Friday February 28: A major Arctic air outbreak is forecast to be ongoing across much of the eastern half of the CONUS at the outset of week-2. The GEFS (ECENS) Probabilistic Extremes Tool (PETs) depicts at least a 40 (60) percent chance minimum temperatures fall below the lowest 15th climatological percentile on day-8 (Feb 22) from the Ohio and Tennessee Valleys southward to the Gulf Coast. However, despite these higher probabilities, the uncalibrated 0z GEFS and ECENS indicate about a 5-10 deg F rise in minimum surface temperatures between days 7 and 8 (Feb 21 and 22) signaling that the most robust cold is favored late in week-1 and beginning to moderate heading into week-2. The percentile probabilities in the PETs are likely inflated due to the rising temperature climatology in late-February, and the chances for absolute temperatures reaching hazards cold thresholds continue to trend downward. Winds are also forecast to be lighter underneath the surface high, limiting the wind chill values. Therefore, only a slight risk for much below normal temperatures is posted from the Great Plains eastward to the Atlantic coast. The risk is discontinued after day-8 (Feb 22) across the Great Plains, Upper and Middle Mississippi and Ohio Valleys, Great Lakes, and Northeast, and continues through day-9 (Feb 23) across portions of the Southern Plains, Lower Mississippi and Tennessee Valleys, Great Lakes, Mid-Atlantic, and Southeast consistent with the pattern progression indicating weakening surface high pressure and increasing Pacific flow supporting a west to east warming trend.

During week-2, an area of mid-level low pressure across the Arctic is forecast to drop southward into northern Canada. This favors decreasing mid-level heights and lowering surface pressures across much of Canada, with a tightening pressure gradient extending into the north-central CONUS due to the surface high established over the Southeast. This set-up in combination with a ridge over the West favors increasing Pacific flow and downslope winds across the Northern Plains into the Upper Midwest. The ECENS PET depicts parts of the Northern High Plains having at least a 40 percent chance wind speeds exceed the 85th climatological percentile, with probabilities above 30 percent in the GEFS. There is also support in the uncalibrated guidance indicating increased chances for wind speeds exceeding 25-mph justifying a moderate risk for high winds across the Northern and Central High Plains, Feb 22-24. The slight risk is extended further east to the Great Lakes through Feb 26, consistent with where the ECENS PET depicts at least a 20 percent chance wind speeds exceed the 85th percentile and 20-mph.

Ridging and relatively drier conditions are favored across the western CONUS during week-2, especially over more southern areas. With the mean flow pattern looking to become more offshore, portions of California may see renewed risk of high winds. However, there remains insufficient support in the tools to issue any corresponding wind hazards, and given the heavy precipitation and flooding experienced over the region recently, this part of the country looks to be less susceptible to any wildfire risk. Elevated wind speeds remain possible across the Northeast on day-8 (Feb 22) in the wake of a departing surface low late in week-1, although the strongest winds are now favored prior to the start of week-2 allowing the related wind hazard from yesterday to be discontinued.

Although precipitation guidance has trended considerably drier for week-2 for much of the country, a flooding possible hazard remains posted for many parts of the southeastern CONUS. Many locations within the highlighted area have registered well above-normal precipitation since early February, with additional amounts upwards of 3 inches expected during week-1 (based on WPC QPF) as the area is expected to remain vulnerable for long duration flooding.

Troughing and associated enhanced onshore flow is likely to promote above-normal precipitation and above-normal temperatures across much of Alaska during week-2. This is reflected in both the GEFS and ECMWF PETs, depicting at least a 20 percent chance for 3-day amounts exceeding the 85th percentile, although actual amounts are unsupportive to post any corresponding hazard. However, it should be noted that warmer temperatures favored during week-2 could result in higher freezing levels (~4000 ft), which combined with any enhanced precipitation could lead to an increased risk of runoff with possible landslides. There are also increased signals in the PETs for enhanced precipitation extending into the Pacific Northwest, although daily totals are also marginal in terms of supporting a precipitation hazard.

Forecaster: Thomas Collow

$$ Please consult local NWS Forecast Offices for short range forecasts and region-specific information.

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts