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U.S. Hazards Outlook - Made February 26, 2015
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| 8-14 Day Probabilistic Outlooks | Temperature Hazards | Precipitation Hazards |
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Valid Sunday March 01, 2015 to Thursday March 12, 2015
US Hazards OutlookNWS Climate Prediction Center College Park MD
300 PM EST February 26 2015
Synopsis: Several arctic Highs are predicted to bring unseasonably cold temperatures to much of the contiguous U.S. during the first half of the Outlook period. The coldest temperatures, relative to normal, are expected to be in the Great Plains and Mississippi Valley. For the 6-10 day period, warmer than normal temperatures are anticipated in parts of the Southeast, and perhaps coastal portions of California and Oregon. Several precipitation events are forecast across much of the central and eastern lower 48 states by the early and middle portions of the Outlook period, with a range of precipitation types expected. Relatively mild and wet conditions are predicted for a large portion of Alaska, as a series of Pacific storm systems moves across the state.
Hazards
- Much below-normal temperatures for most of the central and eastern CONUS, Sun-Thu, Mar 1-5.
- Periods of heavy snow for the Four Corners region, Sun-Wed, Mar 1-4.
- Periods of heavy snow in a swath from western Kansas east-northeastward across the middle Mississippi Valley, northern Ohio Valley, lower Great Lakes region, and much of the Northeast, Sun-Wed, Mar 1-4.
- Periods of freezing rain/sleet in a band stretching from the Texas Panhandle and Oklahoma east-northeastward across southern portions of both Missouri and Illinois, the southern Ohio Valley, most of the interior mid-Atlantic, Long Island, and extreme southern New England, Sun-Wed, Mar 1-4.
- Periods of heavy rain for far eastern Texas, the lower Mississippi and Tennessee Valleys, northern Alabama, northern Georgia, portions of the Carolinas, and from most of Virginia northeastward into New Jersey, Sun-Thu, Mar 1-5.
- High Waves for the western Aleutians, Sun, Mar 1.
- Flooding possible in central Mississippi, Sun-Tue, Mar 1-3.
- A slight risk of much below-normal minimum temperatures from the eastern Intermountain region eastward across the Rockies, Great Plains, Mississippi Valley, the Great Lakes region, Ohio and Tennessee Valleys, the Appalachians, and the Atlantic Coast states from Virginia to Maine, Fri-Sat, Mar 6-7.
- A moderate risk of much below-normal minimum temperatures for much of the central and southern Plains, the upper and middle Mississippi Valley, the Great Lakes region, Ohio Valley, and from northern West Virginia and northern Maryland northeastward to western New England, Fri-Sat, Mar 6-7.
- A high risk of much below-normal minimum temperatures from the central Plains northeastward across the Midwestern states to lower Michigan, Fri-Sat, Mar 6-7.
- Severe drought for the Central and Southern Great Plains, Southwest, Great Basin, California, the Pacific Northwest, and Tennessee Valley.
For Sunday March 01 - Thursday March 05: At the start of this period, an arctic air mass is forecast to be in place across the central and eastern CONUS. Some of this colder air is expected to spill west of the Continental Divide, reducing daytime high temperatures by as much as 8-12 degrees F. However, the largest departures from normal are anticipated east of the Divide, ranging from 12 to as much as 28 degrees F below-normal across portions of the Great Plains.
Periods of heavy snow are predicted for the Four Corners region from Mar 1-4, as a surface low pressure system traverses the area and interacts with arctic air. A positively tilted 500-hPa trough, expected to be just west of this region, will help provide a favorable environment for precipitation with its associated large-scale ascent of air.
Significant wave heights of 23-26 feet are forecast by the NOAA Wavewatch Model for the western Aleutians on March 1, as a storm approaches from the southwest.
As an arctic high pressure center (1040 hPa) moves off the mid-Atlantic Coast, southeasterly surface flow is predicted to briefly develop across the southern Plains and lower Mississippi Valley prior to the next southward push of cold air. Current thinking is that the boundary separating the warm, moist air from the cold, dry air (initially stretching from the southern Rockies to the middle Mississippi Valley to the central Appalachians) will advance and retreat several times during this period. Rather than have a single, major storm system to contend with, it appears the associated precipitation will be distributed among two, weaker storm systems, which generally track from the southern Plains northeastward towards the mid Atlantic region. This complex and very dynamic setup makes it extremely difficult to accurately determine where the swaths of rain, snow, freezing rain, and sleet will be, and how they will shift with time. At this time, the area most likely to experience significant snowfall with these back-to-back storm systems is from western Kansas east-northeastward across the middle Mississippi Valley and northern Ohio Valley to New England. The area most likely to experience heavy rainfall is from far eastern Texas and the lower Mississippi and Tennessee Valleys eastward across portions of the Carolinas, and from most of Virginia into New Jersey. In-between these predicted snow and rain areas is where a transition zone of freezing rain and ice pellets is expected to set up. However, what the map cannot show is how these three bands of precipitation are expected to shift northward or southward with time, so these depicted areas should be interpreted only as a general guide. Icy precipitation events are common in winter on the northern and western sides of an upper-air ridge forecast to be located across the Southeast U.S.
Another consideration associated with the anticipated precipitation events over the central and eastern CONUS is severe weather. With so much uncertainty as to whether arctic air or maritime tropical air dominates the southern Plains, the lower Mississippi Valley, and the Ohio and Tennessee Valleys, no area of severe weather is indicated on the map. If warm advection of moist, unstable Gulf air dominates, the chances for severe weather will increase in this area. However, if cold, dry arctic air dominates, the boundary layer will be very stable, with winds blowing offshore, effectively shutting down the potential for severe thunderstorm activity.
Flooding is possible in central Mississippi from Sunday to Tuesday, especially in regards to the Big Black River at Bentonia and West. Several hydrographs (U.S. Army Corps of Engineers) indicate this river will remain above flood stage at least into Tuesday. According to the Advanced Hydrologic Prediction System (AHPS), 3-5 inches of rain has fallen in this area during the past 7-days.
For Friday March 06 - Thursday March 12: There is a slight risk of much below-normal temperatures from the eastern Intermountain region eastward across the Rockies, Great Plains, Mississippi Valley, the Great Lakes region, Ohio and Tennessee Valleys, the Appalachians, and the Atlantic Coast states from Virginia to Maine, Fri-Sat, Mar 6-7. A moderate risk of much below-normal minimum temperatures is indicated for much of the central and southern Plains, the upper and middle Mississippi Valley, the Great Lakes region, Ohio Valley, and from northern West Virginia and northern Maryland northeastward to western New England, Fri-Sat, Mar 6-7. A high risk of much below-normal minimum temperatures is depicted from the central Plains northeastward across the Midwestern states to lower Michigan, Fri-Sat, Mar 6-7.
The most recent U.S. drought monitor, released today, February 26, 2015, indicates a slight decrease in the areal coverage of severe to exceptional drought (D2 to D4) in the past week from 16.44 to 16.42 percent across the continental U.S. Forty percent of California remains designated in the exceptional drought (D4) category. Although most revisions made to the Monitor this week are fairly small, the more notable changes include a general 1-category improvement in Kentucky and western Tennessee, and a 1-category degradation across the central Gulf Coast area.
Forecaster: Anthony Artusa
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