Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Saturday May 31, 2025 to Friday June 06, 2025

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT May 23 2025

Synopsis: Mid-level high pressure is forecast to strengthen over the West leading to anomalous warmth to end May and start June. Multiple models have increased signals compared to yesterday for extreme heat especially across the Central Valley of California on May 31, thus a moderate risk of extreme heat is designated for this day. A stationary front may bring locally heavy rainfall from the Central to Southern High Plains southeastward to the western Gulf Coast through early week-2, although there is significant model uncertainty regarding this hazard. During the first week of June, there is an increasing risk of heavy rainfall across Florida and the northern Gulf Coast. A tight pressure gradient along parts of the West Coast may bring periods of high winds to parts of the northern coast of California.

Hazards

• Moderate risk of extreme heat for the Central Valley of California, Sat, May 31.
• Slight risk of extreme heat for the Central Valley of California, Sat-Sun, May 31-Jun 1.
• Slight risk of heavy precipitation for parts of the Central to Southern Great Plains, western Gulf Coast, and Lower Mississippi Valley, Sat-Mon, May 31-Jun 2.
• Slight risk of heavy precipitation for parts of the Southeast, Wed-Fri, Jun 4-6.
• Slight risk of episodic high winds for coastal portions of northern California, Sat-Mon, May 31-Jun 2.

Detailed Summary

For Monday May 26 - Friday May 30: WPC Days 3-7 U.S. Hazards

For Saturday May 31 - Friday June 06: Multiple model ensemble means indicate stronger mid-level ridging over the western contiguous U.S. (CONUS) compared to yesterday, at the onset of week-2. Peak ridging is anticipated for the end of week 1 (May 30) to the onset of week-2 (May 31), with noticeable weakening by the middle of the period. Model guidance and temperature tools reflect this change in the increase in heat signals. The GEFS and ECENS Probabilistic Extremes Tools (PETs) show higher probabilities of maximum temperatures exceeding the 85th percentile climatologically and 100 deg F. Thus a moderate risk of extreme heat is designated across the Central Valley of California for May 31, where the GEFS and ECENS indicate greater than 50% chances of exceeding these thresholds. Recent deterministic guidance shows the potential for some areas experiencing temperatures greater than 110 deg F across some of the extreme risk areas. The combination of high temperatures, low relative humidity, and drying vegetation may result in elevated wildfire risk for that part of California.

Surface high pressure predicted over the Northeastern Pacific combined with adjacent surface low pressure across parts of California may result in a tight pressure gradient along the coast of California. This pattern may support episodes of high winds in the area at the beginning of week-2. A slight risk of episodic high winds is designated for coastal portions of northern California, where PETs indicate at least a 30% chance of wind speeds exceeding the 85th percentile and 35 mph. Anticipated dry, hot conditions combined with gusty winds could increase wildfire potential across portions of coastal California.

A front may linger across the Central and Southern High Plains southeastward to the western Gulf Coast and Lower Mississippi Valley at the beginning of the period. This front is expected to be a focus for convection with locally heavy rainfall. There is more uncertainty in today’s models compared to yesterday regarding anticipated rainfall amounts, with the ECENS especially decreasing the signal for enhanced amounts compared to yesterday. As of 5am PDT on May 23, the NHC states that there is a 60 percent chance of tropical cyclone (TC) development across the East Pacific during the next seven days. Despite uncertainty among models regarding rainfall totals, if this TC forms and tracks more northward, then enhanced mid-level moisture may shift northward into the south-central CONUS which was another factor supporting at least a slight risk of heavy precipitation for this region.

Locally heavy rainfall could trigger flash flooding or renewed river flooding especially for northeastern Texas and western Louisiana, but uncertainty regarding where the heaviest rainfall may occur during early week-2 precludes designating a flooding shape on the map but will continue to be monitored.

Multi-model ensemble means continue to depict a surge of tropical moisture spreading northward from the western Caribbean to Florida and the northern Gulf Coast during the first week of June. The GEFS and ECENS PETs continue to show at least a 20% chance of 3-day rainfall amounts exceeding the 85th percentile (and 1 inch?)across Florida, the northern Gulf Coast, and Coastal Plain of the Southeast, supporting a slight risk of heavy precipitation for June 4-6. According to the U.S. Drought Monitor, severe to extreme drought covers south Florida including the Everglades. The wetter pattern forecast to start June would be welcome drought relief for these areas.

The GEFS, ECENS, and CMCE depict an amplified 500-hPa trough over Alaska early in week-2 which favors below-normal temperatures and above-normal precipitation. Although the GEFS and ECENS PETs indicate at least a 20% chance of 3-day precipitation amounts exceeding the 85th percentile across southeastern Alaska through June 2, totals are not anticipated to reach hazardous criteria.

Forecaster: Melissa Ou

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

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts