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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made October 27, 2016

 Days 3-7Days 8-14Prob. Days 8-14
TemperatureNo HazardsNo Hazards
SoilsNot Available

Categorical Outlooks
Experimental Probabilistic Outlooks (Information)

Valid Sunday October 30, 2016 to Thursday November 10, 2016

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT October 27 2016

Synopsis: A strong area of upper-level low pressure is likely to persist across the east Pacific through early November. An unseasonably strong area of upper-level high pressure is expected to expand north from the Gulf Coast to the mid-Atlantic next week. Surface low development is forecast across northern high Plains by Mon, Oct 31 with a subsequent track northeast into Ontario. An intensifying low pressure system is expected to cross the Aleutians early in the period.

Hazards Detailed Summary

For Sunday October 30 - Thursday November 03: A vigorous shortwave trough is forecast to move inland into the western U.S. this weekend. Heavy precipitation (1 to 3 inches, liquid equivalent) is expected on Oct 30 across parts of northern California. Snowfall amounts of more than 1 foot are possible across the Sierras in elevations above 7,000 feet. As the potent shortwave trough progresses east, rain and high-elevation snow is forecast to spread across the Great Basin and north-central Rockies on Sunday night and Monday. Heavy snow (more than 6 inches per 24 hours) is most likely across parts of the northern Rockies on Oct 30 and 31.

Model guidance remains consistent regarding lee side cyclogenesis across the northern high Plains early in the period. High winds are expected to develop on Sun, Oct 30 across parts of the Great Plains and persist through Oct 31, in the wake of the dryline. The increased surface winds along with drying soils are likely to elevate wildfire danger.

An unseasonably strong ridge aloft is likely to result in much-above normal temperatures (15 degrees F or more) across much of the central and eastern U.S. during this period. Although the maximum temperatures are forecast to range from the mid 80s to around 90 degrees F across the central/southern Great Plains, lower Mississippi Valley, and Southeast, these temperatures are not expected to be threatening to life, so no hazard is depicted. The abnormal heat is likely to intensify ongoing drought conditions across these areas.

Excessive rainfall, associated with Hurricane Matthew, triggered river flooding throughout the eastern Carolinas. Flooding continues along the Waccamaw River in northeast South Carolina, but it is expected to slowly recede next week.

The latest deterministic GFS and ECMWF model runs continue to depict an intensifying low pressure system (950 to 956 hpa) across the western Aleutians on Oct 30 and 31. This low pressure system is likely to cause periods of high significant waves (wave heights of at least 30 feet) Oct 30 and 31 for parts of the Aleutians and Alaska Peninsula. Coastal flooding due to ocean encroachment across these areas is possible, and the risk to life and property is high. High winds (sustained wind speeds in excess of 40 knots) are also likely to affect western mainland Alaska, the Aleutians, and Alaska Peninsula on Oct 30 and 31. Ahead of the low pressure system, heavy precipitation (rainfall exceeding 2 inches per 24 hours near the coast and snowfall in excess of 8 inches per 24 hours at higher elevations) is forecast for the eastern Kenai Peninsula and western Prince William Sound on Oct 31 and Nov 1.

Hurricane Seymour currently southwest of Baja California is expected to weaken as it moves north of 20 degrees latitude during the next 24 hours. However, moisture associated with this system may become entrained with the upper-level trough approaching the West Coast and enhance precipitation amounts across California.

For Friday November 04 - Thursday November 10: The amplified upper-level trough over the east Pacific is likely to maintain a wet pattern across the Pacific Northwest through early November. During Week-2, the 6Z GFS and 0Z ECMWF ensemble means are in good agreement with a total precipitation max of 10 inches located at Vancouver Island. Early in Week-2, heavy precipitation (rain and high-elevation snow) is posted for the Pacific Northwest due to a consistent signal among model solutions and the anomalous wetness this month. During the past 30 days, precipitation has averaged 8 inches or more above normal across the coastal Pacific Northwest.

The 0Z GFS ensemble mean indicates a negative Arctic Oscillation (AO) index persisting during Week-2. Despite this negative AO index, enhanced Pacific flow is expected to prevail and result in a continuation of mild temperatures throughout North America.

According to the latest U.S. Drought Monitor (USDM) valid on October 25, the coverage of severe or greater drought (for the CONUS) increased from 9.66 to 10.25 percent during the past week, which is the highest coverage during 2016. Severe or greater drought continues to expand from the Southeast west into the lower Mississippi Valley and southern Great Plains. Less than 1 percent of the Hawaiian Islands is designated with severe drought.

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.