Valid Sunday October 30, 2016 to Thursday November 10, 2016
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT October 27 2016Synopsis
: 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:
- Heavy precipitation (rain and high-elevation snow) for parts of
northern California, Sun, Oct 30.
- Heavy snow for parts of the northern Rockies, Sun-Mon, Oct 30-31.
- High winds for parts of the Great Plains, Sun-Mon, Oct 30-31.
- Significant waves for parts of the Aleutians and Alaska Peninsula, Sun-Mon,
- High winds across portions of western mainland Alaska, the Alaska
Peninsula, and the Aleutians, Sun-Mon, Oct 30-Oct 31.
- Heavy precipitation (rain and high-elevation snow) for the eastern Kenai
Peninsula and western Prince William Sound , Mon-Tue, Oct 31-Nov 1.
- Heavy precipitation (rain and high-elevation snow) for parts of the Pacific
Northwest, Fri-Sat, Nov 4-5.
- Flooding occurring along the Waccamaw River in northeast South Carolina.
- Severe drought across parts of the eastern U.S., Great Plains, Missouri
River Valley, Intermountain West, Arizona, California, Nevada, and Hawaii.
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
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
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.