Valid Monday November 30, 2015 to Friday December 11, 2015
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EST November 27 2015Synopsis
: At the start of the period,
surface low pressure over the southern Plains will move slowly
east/northeastward to the Lower Mississippi Valley, and then northward to the
Great Lakes. Arctic high pressure is expected over the western and central
portions of the lower 48 states through the end of November. A frontal system
is forecast to approach the west coast Dec 2-3. Surface low pressure just south
of the Aleutians is anticipated to move slowly eastward Nov 30-Dec 2. An area
of upper-level low pressure is expected over western Alaska Dec 4-7.
Detailed Summary For Monday November
30 - Friday December 04:
- Heavy rain for parts of the Tennessee and Ohio
Valleys, southern Appalachians, Mid-Atlantic, and southeast, Mon-Tue, Nov
- Much below-normal temperatures for parts of the northern Intermountain west
and central Great Basin, Mon-Tue, Nov 30-Dec 1.
- High winds for coastal sections of Washington, Oregon, and northern
California, Tue-Thu, Dec 1-3.
- Heavy rain for western sections of Washington, Oregon, and Northern
- Wed-Thu, Dec 2-3.
- River flooding likely or possible over parts of the southern Plains,
Mississippi Valley, and southern Great Lakes.
- Slight chance of much below normal temperatures for parts of western
Alaska, Sat-Mon, Dec 5-7.
- Severe drought in the far western CONUS and Puerto Rico.
Low pressure and its associated frontal system
over the southern Plains/Lower Mississippi Valley are expected to act as a
focusing mechanism for precipitation. Heavy rain (in excess of 1 inches in 24
hours) is anticipated for parts of the Lower Mississippi Valley, and Tennessee
and Ohio Valleys Nov 29. Behind the front, a cold air mass will surge southward
along the Front Range into the southern High Plains and eastward toward the
Great Lakes. Wintry precipitation is possible for parts of the central and
northern Plains and western Great Lakes Sunday-Tuesday, but amounts are
expected to be light so a hazard area is not currently depicted.
The area of arctic high pressure expected over the western and central
CONUS leads to much below-normal temperatures for parts of the northern
Intermountain west and central Great Basin Nov 29-30. Minimum temperatures of
12-20 degrees F below normal are forecast for the central and northern parts of
the depicted hazard region.
A frontal system approaching the west coast leads to strong southwesterly
flow and high winds (in excess of 30 knots) for coastal sections of Washington,
Oregon, and northern California Dec 2-3. Heavy precipitation for these same
regions are possible, but model uncertainty on precipitation amounts precludes
the specification of a hazard shape at the current time.
The combination of snow melt and additional precipitation prior and during
the period leads to likely or possible river flooding over parts of the central
and southern Plains, Mississippi Valley, and southern Great Lakes.
Very active weather is forecast for southern Alaska this weekend, and the
latest guidance suggests that a heavy precipitation hazard is prudent for parts
of the Alaska Panhandle Nov 29. Liquid amounts in excess of 2 inches in 24
hours are likely within the depicted hazard. Snowfall in excess of 8 inches in
24 hours is possible at higher elevations. For Saturday December 05 -
Friday December 11:
During week-2, a zonal flow pattern is expected across
much of the CONUS. A trough forecast over western Alaska leads to a slight
chance of much below normal temperatures for parts of northern and western
Alaska and the Alaska Peninsula Dec 4-7.
The most recent U.S. drought monitor, released on November 24, indicates a
very slight decrease in the coverage of severe to exceptional drought (D2 to
D4), from 14.88 to 14.83.
Forecaster: Randy Schechter
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Please consult local NWS Forecast Offices for short range forecasts and region-specific information.