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Climate Prediction Center

U.S. Hazards Outlook - Made Dec 26, 2014

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Day 3-7 OutlookDay 8-14 Outlook

Valid Monday, December 29, 2014 to Friday, January 09, 2015

Summary of Forecasts and Hazards

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST December 26 2014

Synopsis: Cold arctic air is expected to move southward across the Western and Central lower 48 states from the beginning of the 3-7 day period into the middle of week-2 in association with strong surface high pressure. Strong, southerly, onshore flow from the Gulf of Alaska is anticipated to bring unsettled weather and warmer temperatures for much of the southern half of Alaska.

Hazards
  • Much below normal temperatures across parts of the Great Plains and Rockies, Mon-Thu, Dec 29-Jan 1.
  • Freezing rain for west-central Texas, Tue-Wed, Dec 30-31.
  • Heavy snow for the mountains in southern California, Wed-Thu, Dec 31-Jan 1.
  • High winds for the south coast of Alaska, Mon, Dec 29.
  • Heavy precipitation for parts of the South Coast of Alaska, including Kodiak Island, Mon-Tue, Dec 29-30.
  • High winds for the Aleutians and the west coast of Alaska, Tue-Wed, Dec 30-31.
  • High winds for the northern Plains and the Upper Mississippi Valley, Wed-Thu, Dec 31-Jan 1.
  • Much above normal temperatures across much of the southern half of mainland Alaska, Mon-Wed, Dec 29-Dec 31.
  • Freezing rain for parts of west-central Alaska, Mon-Tue Dec 29-30.
  • Slight risk for much below normal temperatures across parts of the southern Plains, southern Rockies, and Southwest, Sat-Sun, Jan 3-4.
  • Moderate risk for much below normal temperatures for parts of the Southwest, Sat-Sun, Jan 3-4.
  • Flooding ongoing or likely for parts of southern Georgia, northern Florida, and western Oregon, Mon-Tue, Dec 29-30.
  • Severe drought for the Central and Southern Great Plains, Southwest, Southeast, Lower Mississippi Valley, Pacific Northwest, Great Basin, and California.
Detailed Summary

For Monday December 29 - Friday January 02: This forecast period is expected to begin with an amplified upper-level ridge in eastern Alaska and an amplified trough digging down to the southwestern states. At the surface, high pressure is expected to move down from western Canada to the southern Plains. As it does, strong upslope flow could lead to localized heavy mountain snow in parts of the central and southern Rockies. However, precipitation forecasts from recent numerical models do not indicate the presence of enough moisture to cause widespread hazardous snowfall totals. This area of high pressure is also expected to bring much below normal temperatures from the Pacific Northwest to Texas, with daily minimum temperature anomalies forecast up to 30 degrees below normal from the 29th through January 1. In addition, moist flow off the Gulf of Mexico riding on top of this cold air could set the stage for a period of freezing rain for parts of west-central Texas.

The western shortwave trough is expected to cut off over the southwestern states, while a progressive northern stream impacts the Great Lakes and New England. The cut-off low is forecast to bring in Pacific moisture and with the influx of moisture in the presence of cold air, heavy snow is possible in the mountains in southern California from the 31st to the 1st of January. Snowfall totals of 6-12 inches are possible in the higher terrain. In the northern stream, an increasing pressure gradient due to the approach of a storm in southeastern Canada is expected to lead to high winds for parts of the northern Plains and Upper Mississippi Valley for the 31st and 1st, with winds of 20-30 knots forecast.

The upper-level ridge in Alaska is expected to lead to a prolonged period of strong southerly flow into the state. This will set the stage for heavy precipitation along the southern coast from the 29th to the 30th, high winds along the southern coast for the 29th and for the Aleutians and west coast from the 30th to the 31st. In addition, the southerly winds will lead to most of the state seeing much above normal temperatures. However, the hazard denoted on the map is only for those locations expected to see daytime temperatures near or above freezing. This situation could lead to warm, moist air moving across cold, wet roads, which may lead to frosty, slick driving conditions. Additionally, enough moisture is expected to lead to freezing rain for west-central Alaska from the 29th through the 30th.

For Saturday January 03 - Friday January 09: The southwestern cut-off low is expected to still be present at the beginning of this period. This low is forecast to lead to a slight risk of much below normal temperatures for the central and southern Plains, Rockies and Southwest with a moderate risk of much below normal temperatures centered on Arizona and western New Mexico. In these states, daily minimum temperatures going below freezing are possible.

The most recent U.S. drought monitor, released on December 24, indicates a very slight decrease in the areal coverage of severe to exceptional drought (D2 to D4) from 17.27 to 17.18 percent across the continental U.S.

Forecaster: Kenneth Pelman

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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.


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