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Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Friday April 26, 2024 to Thursday May 02, 2024

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT April 18, 2024

Synopsis: A multi-day risk of thunderstorms, high winds, and elevated wildfire danger is forecast across from the Great Plains east to the Mississippi Valley during late April through the beginning of May. A late-season snowfall is expected at the highest elevations of the Sierra Nevada Mountains along with the northern to central rockies. Although above-normal temperatures are favored across the central and eastern U.S. during week-2, hazardous heat is not anticipated at this time of year.

Hazards

• Moderate risk of heavy precipitation for parts of the Central and Southern Plains and Middle to Lower Mississippi Valley, Fri-Sun, Apr 26-28.
• Slight risk of heavy precipitation for parts of the Great Plains, Middle to Lower Mississippi Valley, and Lower Ohio Valley, Fri-Thu, Apr 26-May 2.
• Moderate risk of high winds for parts of the Southwest, Central and Southern Rockies, and Central and Southern Plains, Fri-Sun, Apr 26-28.
• Slight risk of high winds for parts of the Southwest, Rockies, and Great Plains, Fri-Thu, Apr 26-May 2.
• Flooding possible across eastern Texas and the Lower Mississippi Valley.

Detailed Summary

For Sunday April 21 - Thursday April 25: WPC Days 3-7 U.S. Hazards

For Friday April 26 - Thursday May 2: Later next week, a warm front is forecast to shift northward across the Great Plains and Mississippi Valley. For the second consecutive day, the GEFS and ECMWF ensemble means are in good agreement indicating an amplified 500-hPa trough progressing east to the Southwest from April 26 to 28. The upstream 500-hPa trough and climatology would favor a multi-day risk of thunderstorm initiation along the dry line. The large-scale environment is likely to result in periods of thunderstorms with locally heavy rainfall from the Southern to Central Great Plains east to the Mississippi Valley. Based on the 500-hPa height evolution, the GEFS would favor the highest chance to the north such as Kansas and Missouri while the ECMWF ensemble mean targets the Southern Great Plains. A model consensus of uncalibrated 24-hour precipitation amounts was used to define the moderate risk of heavy precipitation. Due to continued spread among the ensemble means on one or more surface low tracks, a broader slight risk of heavy precipitation is depicted and is valid through the entirety of week-2.

Along with the increased risk of thunderstorms with heavy rainfall, the longwave pattern is likely to lead to leeside cyclogenesis across the Central and Southern High Plains. Based on pattern recognition and wind speed forecasts from deterministic model runs, a moderate risk of high winds is posted for those areas along with parts of the Southwest Apr 26 to 28. Similar to the heavy precipitation hazard, model guidance supports the continuation of a slight risk of high winds through May 2. The gusty winds could cause blowing dust from southeastern Colorado and New Mexico east to Kansas, Oklahoma, and the Texas Panhandle. The amplified 500-hPa trough is expected to result in at least a brief period of heavy snowfall, initially over the Sierra Nevada Mountains and then overspreading the northern to central Rockies during late April. Since any heavy snowfall would likely be limited to the highest elevations, a snow hazard is not depicted.

The GFS ensemble mean depicts a persistent 500-hPa trough over the Aleutians and western Alaska during week-2. Although this would favor enhanced onshore flow into south-central and southeastern Alaska, precipitation amounts are expected to remain below hazards thresholds.

Forecaster: Brad Pugh

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

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts