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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made February 22, 2017

 Days 3-7Days 8-14Prob. Days 8-14
Precipitation No HazardsNot Available
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Categorical Outlooks
Experimental Probabilistic Outlooks (Information)

Valid Saturday February 25, 2017 to Wednesday March 08, 2017

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST February 22 2017

Synopsis: A strong surface low is forecast to exit the Great Lakes on Saturday, Feb 25. Another vigorous low pressure system is expected to move inland into the western U.S. by early next week. Surface low development is forecast to develop across the central Great Plains on Tuesday, Feb 28 with a subsequent track northeast to the Great Lakes. A low pressure system is forecast to cross the Bering Sea early in the period. During Week-2, an area of upper-level low pressure is favored over the western U.S. while an unseasonably strong area of upper-level high pressure remains anchored over the southwest Atlantic.

Hazards Detailed Summary

For Saturday February 25 - Wednesday March 01: A potent shortwave trough with enhanced Pacific moisture is forecast to enter California where heavy precipitation (rain and high-elevation snow) is most likely across the Sierra Mountains along with central and southern California. Model guidance indicates precipitation amounts ranging from 1 to 3 inches, liquid equivalent, in the outlined hazard area on February 26 and 27. Snow levels are expected to be relatively low over the Sierra Mountains. As the shortwave trough progresses inland over the western U.S., heavy snow (6 inches or more) is forecast for the higher elevations of Arizona and the Colorado Rockies on February 27 and 28. Snow levels are expected to fall below 6,000 feet across Arizona by Tuesday, Feb 28 with lowering 500-hpa heights. High winds (speeds above 35 knots) are forecast to accompany the upper-level trough over the southwestern U.S. on Feb 27 and extend to the central and southern high Plains on Feb 28. The risk of critical fire weather conditions returns to the central and southern high Plains early next week and are expected to be posted on the hazards map later this week.

Deterministic model solutions feature surface low development across the central Great Plains by Feb 28. Although there remains model spread on the strength and track of this surface low as it moves to the Great Lakes, forecast confidence is increasing for a swath of heavy snow (4 to 8 inches, potentially more) over the upper Mississippi Valley on Feb 28 and Mar 1. The deterministic ECMWF model is the most bullish with the strength of the surface low. Meanwhile, in the warm sector, robust Gulf inflow sets the stage for heavy rain (more than 1 inch per 24 hours) ahead and along a cold front across the Ohio and Tennessee Valleys and central Appalachians on Feb 28 and Mar 1. Severe weather is also possible for these same areas, but model variability precludes designation of a severe weather hazard at this time.

A deep low pressure system is forecast in the Bering Sea at the beginning of Week-1 with heavy snow predicted for northwest interior Alaska. Sustained winds do not appear likely to meet the region's hazard criteria (35 kt), but periodic blizzard conditions (frequent gusts to 35 mph for 3 consecutive hours) are possible with this system. A second area of heavy snow (total amounts greater than 12 inches) is forecast for the western and northern slopes of the Alaska Range on Feb 25 and 26.

For Thursday March 02 - Wednesday March 08: The predicted longwave pattern during Week-2 continues to feature a highly amplified ridge over the north Pacific with a downstream trough over western North America. This upper-level pattern favors below-normal temperatures across Alaska and the western U.S. Early in Week-2, the highest odds for much below-normal temperatures exists across southeast mainland Alaska, the Alaska Panhandle, and the northwestern U.S. where the GEFS probabilistic extremes tool indicates a 40 percent or higher chance of minimum temperatures below the 15th percentile compared to climatology.

The amplified ridge upstream across the north Pacific is expected to result in a major pattern change with below-median precipitation favored for California during early March.

Severe drought is currently noted over portions of the Central Plains, the Mid-Atlantic, the Lower Mississippi Valley, the Tennessee Valley, the Northeast, California, the Southeast, the Southern Appalachians, the Southern Plains, and the Southwest. Coverage of severe, or greater intensity, drought decreased to 3.17 percent of the CONUS. This is the lowest coverage of severe to exceptional drought since October 2010.

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.