Valid Thursday, February 28, 2019 to Monday, March 11, 2019
Summary of Forecasts and Hazards
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT August 10 2020Synopsis
: Upper-level high pressure is
forecast to strengthen over the West during the next week, with an increasing
risk of a long duration heat wave across the Desert Southwest. During the next
two weeks, multiple tropical cyclones (TCs) are expected to develop over the
East Pacific. Despite this increase in TCs, intensifying drought is likely
across the Southwest through at least the early part of week-2. The favorable
large-scale environment for TC development is expected to overspread the
Atlantic basin during late August. Hazards
- High risk of
excessive heat for the lower deserts of the Southwest, Tue, Aug 18.
- Moderate risk of excessive heat for parts of the Southwest, Great Basin,
and California, Tue-Fri, Aug 18-21.
- Slight risk of excessive heat for parts of the western U.S. and southern
high Plains, Tue-Mon, Aug 18-24.
Thursday August 13 - Monday August 17: WPC Days 3-7 U.S.
Hazards For Tuesday August 18 - Monday
A multi-day heat wave is becoming more likely across the Desert
Southwest, beginning later this week and persisting into week-2. The ECMWF
ensemble mean depicts an amplifying 500-hPa ridge over the western U.S. during
the next week with heights near or above 594-dm across the Four Corners region
early in week-2. Although the GFS ensemble mean is slightly lower with 500-hPa
heights, its model guidance would also support anomalous heat during week-2. On
August 18, a high risk of excessive heat is posted for the lower deserts of the
Southwest where the ECMWF reforecast tool indicates that maximum temperatures
have more than a 60 percent chance of exceeding the 85th percentile. This tool
also shows that maximum temperatures have around a 20 percent chance of
exceeding the 98th percentile across much of the Southwest, implying the
potential for record high temperatures early next week. A moderate risk of
excessive heat extends through August 21 across a broader region of the
Southwest, Great Basin, and California since the ECMWF reforecast tool depicts
maximum temperatures having at least a 40 percent chance of exceeding the 85th
percentile for a few more days. An even larger spatial area with a slight risk
of excessive heat covers the West and extends through the entirety of week-2,
supported by both the GEFS and ECMWF reforecast tools and the anomalous ridge
aloft. The heat wave across the Desert Southwest is expected to peak this
weekend into early next week when maximum temperatures are near or above 115
degrees F across the lower desserts.
A major climate-related hazard is the expanding and intensifying drought
across the Southwest due to a weak North American Monsoon. Since early July,
precipitation has averaged less than 25 percent of normal across southern and
western Arizona along with southwestern Utah. According to the U.S. Drought
Monitor valid on August 4, moderate to severe drought covers 81.68 percent of
Arizona. Based on the 500-hPa height pattern, below normal precipitation is
favored to continue during the next week to ten days. A predicted increase in
the number of tropical cyclones across the East Pacific will have to be closely
monitored for northward surges of enhanced moisture. If this occurs, then
monsoon rainfall may begin to increase across the Desert Southwest during late
A weakness in the subtropical ridge is expected to contribute to enhanced
daily convection across the Gulf Coast States during week-2. However, a heavy
rain hazard is not posted since scattered convection with locally heavy rain is
not expected to be hazardous and trigger flooding at this time.
Model solutions feature an upper-level ridge persisting over the Aleutians
and Bering Sea through week-2. The presence of this ridge aloft favors near to
below normal precipitation for much of Alaska. Therefore, no hazardous
precipitation is anticipated for Alaska.
Forecaster: Brad Pugh
Click here to see a display of the GFS Ensemble Forecasts
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.