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Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Thursday June 02, 2022 to Wednesday June 08, 2022

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT May 25 2022

Synopsis: Early in week-2, an amplified 500-hPa height pattern is forecast across the contiguous U.S. (CONUS), with mid-level high (low) pressure forecast over the East (West). The axis of mid-level low pressure is forecast to retrograde closer to the Pacific Coast, resulting in increased chances for high winds across the southwestern CONUS, along with the potential for below normal temperatures continuing across parts of the Intermountain Region, extending into the Northern and Central Plains. By the middle of the period, the pattern is forecast to become less amplified, although there are indications of increased broad mid-level high pressure developing over the south-central CONUS, with excessive heat concerns increasing across parts of Texas during the second half of the period. Flooding risks remain elevated across the Red River of the North, northern Minnesota, and eastern parts of the Central and Southern Plains.

Hazards

• Slight risk of excessive heat across the San Joaquin Valley in California, Thu, Jun 2.
• Slight risk of excessive heat across parts of Texas, Sun-Wed, Jun 5-8.
• Slight risk of much below-normal minimum temperatures across eastern parts of the Intermountain West, extending into parts of the Central and Northern Plains, Thu-Fri, Jun 2-3.
• Slight risk of heavy precipitation across parts of the Southeast, Thu-Mon, Jun 2-6.
• Slight risk of high winds across the parts of the southwestern CONUS, Thu-Mon, Jun 2-6.
• Flooding possible along parts of the Red River of the North and northern Minnesota.
• Flooding possible across eastern parts of the Central and Southern Plains.

Detailed Summary

For Saturday May 28 - Wednesday June 01: WPC Days 3-7 U.S. Hazards

For Thursday June 02 - Wednesday June 08: The 0z ECMWF, GEFS, and Canadian ensembles depict troughing across the interior West late in week-1, retrograding toward the Pacific Coast at the outset of week-2. A slight risk of excessive heat remains posted for the San Joaquin Valley in California on day-8 (Jun 2) only as surface low pressure over the Desert Southwest promotes downslope flow into the region, and the ECMWF and GEFS reforecast tools depict at least a 20 percent chance of maximum temperatures exceeding the 85th percentile and 95 deg F. The signal diminishes thereafter, with the aforementioned troughing favoring temperatures closer to or even slightly below normal across California for the remainder of the period.

The troughing in the West late in week-1 favors an associated surface low pressure system to track across the Great Plains, with a cold front forecast to move through the region prior to the start of week-2 and usher in a period of below normal temperatures across parts of the west-central CONUS. Therefore, a slight risk of much below-normal temperatures is posted Jun 2-3 across eastern parts of the Intermountain West, extending into parts of the Central and Northern Plains. The GEFS reforecast tool indicates at least a 20 percent chance of minimum temperatures falling below the 15th percentile of the climatological distribution and 40 deg F, with the potential for some high elevation areas to fall below freezing. The ECMWF is much more robust compared to the GEFS, indicating probabilities as high as 60 percent for temperatures falling below the 15th percentile, and a more expansive area of subfreezing temperatures in the higher elevations. While some consideration was given for a moderate risk, the weaker signal in the GEFS combined with the fact that temperatures in early June will not be as cold as during the winter, supports only a slight risk. The slight risk includes parts of the Northern and Central Plains, and parts of northern Minnesota, where the GEFS and ECMWF reforecast tools indicate at least a 20 percent chance overnight lows fall below 40 deg F, which could result in some isolated frost.

The retrogression of the trough toward the Pacific Coast early in week-2 favors a westward shift in the elevated risk area for high winds compared to yesterday. The ECMWF reforecast tool now depicts at least a 20 percent chance wind speeds exceed the 85th percentile and 20-mph across portions of California, the Southwest, Four Corners Region, and the Central and Southern High Plains. A slight risk of high winds is posted across these areas from Jun 2-6. Increased wind speeds over regions with severe to, in some cases, exceptional drought favors increased potential for wildfires.

Downstream of the troughing, broad ridging may develop across the south-central CONUS toward the middle of the period. The GEFS reforecast tool indicates at least a 20 percent chance maximum temperatures exceed the 85th percentile and 95 deg F starting on day-10 (Jun 4), with the ECMWF reforecast tool indicating these elevated probabilities beginning a day later (Jun 5). Additionally, the composite ECMWF/GEFS heat probabilistic tool depicts areas of Texas having increased potential (20-40 percent chance) for heat indices of 105-110 deg F late in week-2, supporting the slight risk of excessive heat during the second half of week-2 (Jun 5-8). This could exacerbate and expand the ongoing drought, but will wait to see if this heat signal persists in the model guidance before considering a rapid onset drought hazard given the long lead time.

Across the East, anomalous ridging late in week-1 and early week-2 favors anomalously warm temperatures with some locations along the Eastern Seaboard potentially topping 90 deg F on day-8 (Jun 2), with the ECMWF ensemble depicting a warmer solution compared to the GEFS. However, heat indices are not forecast to reach the 100 (105) deg F threshold over the Northeast (Mid-Atlantic), precluding a related excessive heat hazard. Temperatures are forecast to moderate by the middle of the period as a frontal system traverses the eastern U.S., and more troughing develops over the region.

This troughing is forecast to subsequently increase tropical moisture flow across the southeastern CONUS. The uncalibrated 0z ECMWF and GEFS ensembles depict at least 2-3 inches of rain across parts of the Florida Peninsula during the week-2 period, with the 0z GEFS even indicating 4 inch totals across south Florida. Both the GEFS and ECMWF reforecast tools indicate at least a 20 percent chance 3-day precipitation totals exceed the 85th climatological percentile and 1 inch through the middle of the period over the area, and therefore, a slight risk of heavy precipitation is highlighted across parts of the Southeast, particularly the Florida Peninsula, from Jun 2-6.

River flooding is ongoing across areas along the Red River of the North, Northern Minnesota, and eastern parts of the Central and Southern Plains. Heavy rain is forecast over these areas late in the week-1 period, which favors the flooding risks to persist into week-2. The flooding possible shape is removed from Mainland Alaska due to the decline in available snow melt water.

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