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Climate Prediction Center

U.S. Hazards Outlook - Made Nov 21, 2014

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Day 3-7 OutlookDay 8-14 Outlook

Valid Monday, November 24, 2014 to Friday, December 05, 2014

Summary of Forecasts and Hazards

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST November 21 2014

Synopsis: A strong storm system is predicted to reach the Great Lakes by Monday. Surface high pressure is anticipated to build across much of the rest of the lower 48 states during the first half of the period. A cold front is forecast to sink southward from Canada by Wednesday, bringing cold, arctic air to northern portions of the eastern and central Contiguous U.S. Another cold, surface high is predicted to spread southward from Canada during the beginning and middle of week-2. A series of surface lows are anticipated to develop over the Bering Sea, Aleutians, and Gulf of Alaska during days 3-7.

Hazards
  • Localized heavy lake effect snow for parts of Michigan and Wisconsin, Mon-Wed, Nov 24-26.
  • Localized heavy lake effect snow for parts of the Lower Great Lakes, Tue-Wed, Nov 25-26.
  • Possible localized flooding for parts of the Great Lakes, Mon, Nov 24.
  • High winds for parts of the Upper Mississippi Valley and Great Lakes, Mon-Tue, Nov 24-25.
  • Much below normal temperatures for parts of the Northern Plains, Upper Mississippi Valley, and Upper Great Lakes, Wed-Fri, Nov 26-28.
  • Heavy snow for parts of the Cascade Mountains, Mon-Tue, Nov 24-25.
  • Heavy snow for parts of the Northern and Central Rockies and Northern and Central Great Basin, Mon-Wed, Nov 24-26.
  • Much below normal temperatures for parts of the Central Rockies, Mon-Tue, Nov 24-25.
  • Slight chance for much below normal daily minimum temperatures across much of the central and eastern Northern Tier of the CONUS, Sat-Mon, Nov 29-Dec 1.
  • Severe drought for the Central and Southern Great Plains, Southwest, Southeast, Tennessee Valley, Pacific Northwest, Great Basin, and California.
Detailed Summary

For Monday November 24 - Friday November 28: A strong storm system is predicted to reach the Great Lakes at the beginning of the period, bringing localized heavy lake effect snow to parts of Michigan and Wisconsin, Monday to Tuesday and the Lower Great Lakes on Tuesday. This storm may also bring high winds to parts of the Upper Mississippi Valley and Great Lakes Monday to Tuesday, with sustained wind speeds possibly reaching 30-40 knots or greater. As this storm exits the U.S. into Canada, a surface low is expected to develop over the Upper Great Lakes along a cold front draped across the Northern Tier on Wednesday, leading to enhanced chances for another bout of lake effect snow across parts of these Great Lakes areas on Wednesday. The greatest likelihood for significant snowfall is over Michigan and Wisconsin, with the potential for half an inch of liquid equivalent or greater in a 24-hour period. Currently, lower snow accumulations are expected for areas east of Lakes Erie and Ontario. This cold front is anticipated to move southward across the central and eastern CONUS, bringing much below normal temperatures to parts of the Northern Plains, Upper Mississippi Valley, and Upper Great Lakes, Wednesday to Friday. These areas may experience daily temperatures 16 degrees or greater below normal, with minimum temperatures reaching the negative single digits in some locations.

A moderation of temperatures is anticipated for parts of the Great Lakes on Monday. Above freezing temperatures, in addition to expected rain showers, may lead to localized flooding of creeks and lakes from melting of antecedent Lake Effect snow in the Great Lakes region on Monday. The greatest chances for significant flooding are east of Lakes Erie and Ontario. Urban sections of Buffalo may experience ponding and flooding due to the large volume of melt water overloading drainage systems. The area south of Lake Michigan is expected to have minor flooding. The aforementioned cold front sinking southward from Canada is anticipated to provide flood relief in these areas by Tuesday due to the expectation that temperatures will go below freezing.

A series of surface lows are expected to develop over the northeast Pacific Ocean. Strong onshore flow associated with this pattern is anticipated to bring localized heavy snow to parts of the Cascade Mountains Monday to Tuesday. This area may receive an inch or greater of liquid equivalent in a 24-hour period. In general, snow elevation levels are expected to rise to between 7000 to 8000 feet by Tuesday, with the exception of snow levels potentially remaining at 3000 feet near the Canadian border.

Surface high pressure is forecast to build across the western half of the CONUS during this period, leading to strong, upslope flow across the Rockies for much of this period. This pattern is expected to bring episodes of localized heavy snow to higher elevation areas of the Northern and Central Rockies and Northern and Central Great Basin Monday to Wednesday. Some areas may receive an inch of liquid equivalent or greater in a 24-hour period. This northwesterly, upslope flow is also expected to bring much below normal temperatures to parts of the Central Rockies on Monday and Tuesday. Daily minimum temperatures may reach the negative single digits in some areas.

For Saturday November 29 - Friday December 05: There is much more consensus amongst models today compared to yesterday, regarding the potential for another surge of cold, arctic air from Canada into northern parts of the CONUS from the beginning to middle of week-2. An area for slight risk of much below normal temperatures is highlighted across much of the central and eastern Northern Tier of the CONUS next Saturday to the following Monday. These areas may experience daily minimum temperatures below the 10th percentile compared to climatology.

In general, a relatively zonal pattern is predicted for week-2, favoring above-normal temperatures for much of the western two-thirds of the CONUS, and normal temperatures for the eastern third of the CONUS, excluding the area of below normal temperatures across the Great Lakes mentioned above. Normal to above normal 500-hPa heights are forecast for Alaska, bringing normal to above normal temperatures to the state.

The most recent U.S. drought monitor, released on November 20, indicates a slight decrease in the areal coverage of severe to exceptional drought (D2 to D4) from 17.27 percent to 17.13 percent across the Continental U.S.

Forecaster: Melissa Ou

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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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