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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made November 27, 2014

 Days 3-7Days 8-14Prob. Days 8-14
Precipitation No HazardsNot Available
TemperatureNo HazardsNo Hazards
SoilsNot Available

Categorical OutlooksDay 3-7Day 8-14
8-14 Day Probabilistic OutlooksTemperature HazardsPrecipitation Hazards

Valid Sunday November 30, 2014 to Thursday December 11, 2014

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST November 27 2014

Synopsis: An area of upper-level low pressure is expected to slowly progress inland from the East Pacific next week. A strong surface high is forecast to shift southeast from the Pacific Northwest and northern Rockies on Sunday to the Midwest on Monday. Meanwhile, an upper-level ridge of high pressure is forecast to build across the southeastern U.S. in the beginning of December. A surface high is expected to persist across northeast Alaska during the next week, while a low pressure system strengthens as it moves into the Bering Sea this weekend.

Hazards Detailed Summary

For Sunday November 30 - Thursday December 04: An upper-level trough is forecast to separate from westerly flow across the northeast Pacific this weekend. The evolution of this trough remains uncertain as model differences increase next week. The high-resolution GFS model continues to be much more progressive with this upper-level trough and is also a wetter solution compared to the high-resolution ECMWF model. Due to large differences among the high-resolution models, the location and timing of heavy precipitation hazards for California are based primarily on the 0Z and 6Z GFS ensemble means. Several inches of precipitation (liquid equivalent) are expected across the coastal ranges of northern California and the Sierras from Sunday through at least Tuesday. Snow levels around 7,000 feet are expected for the Sierras. Onshore flow and the potential for tropical moisture to become entrained into the upper-level trough increase prospects for locally heavy rain (more than 1 inch) across southern California on December 2 and/or 3.

The 12Z GFS model indicates light precipitation spreading north into the Pacific Northwest on Sunday and Monday ahead of the East Pacific trough. If precipitation occurs, surface temperatures are expected to support freezing rain across the Willamette Valley and Columbia River Gorge. Large model differences on precipitation amounts preclude designation of a freezing rain hazard at this time.

Forecast confidence for heavy precipitation across Arizona is lower today due to large model differences upstream over the East Pacific. The past few runs of the high-resolution GFS model indicate less precipitation for Arizona with the shortwave trough becoming less amplified as it moves inland.

Meanwhile, a strong surface high building south from western Canada is expected to enhance easterly winds through the Columbia River Gorge where a high wind hazard is depicted. Heavy rainfall this week may trigger flooding along the most flood-prone rivers along the western slopes of the northern Washington Cascades.

A 1036-ha surface high building south from Canada is likely to result in much below-normal temperatures across parts of the Pacific Northwest, northern Rockies, and northern/central Great Plains on Sunday. The much-below normal temperatures are then expected to expand east into the Upper Mississippi Valley on Monday. Subzero minimum temperatures could extend as far south as Nebraska and Iowa by Monday morning.

A low pressure system is forecast to strengthen as it tracks into the Bering Sea during the weekend. The high resolution 0/6Z GFS and 0Z ECMWF models indicate a 968-hpa low across the Bering Sea later in the weekend. On Sunday, high winds across the Aleutians are expected to accompany this low pressure system.

For Friday December 05 - Thursday December 11: Since model differences are large as early as Day 5, no specific hazards can be defined during Week-2 except for the areas of ongoing severe to exceptional drought.

The most recent U.S. drought monitor, released on November 27, indicates a slight decrease in the areal coverage of severe to exceptional drought (D2 to D4) from 17.13 percent to 16.81 percent across the continental U.S. This this the lowest coverage of severe to exceptional drought since December 2013.

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.