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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made February 27, 2015

 Days 3-7Days 8-14Prob. Days 8-14
Precipitation No HazardsNot Available
Temperature
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Categorical OutlooksDay 3-7Day 8-14
8-14 Day Probabilistic OutlooksTemperature HazardsPrecipitation Hazards

Valid Monday March 02, 2015 to Friday March 13, 2015

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST February 27 2015

Synopsis: An arctic air mass is forecast to move southward and eastward out of western Canada early in the period. Unseasonably cold air is expected to overspread most of the lower 48 states, reaching the Eastern Seaboard by the end of next week. Several precipitation events are predicted across much of the central and eastern lower 48 states during the first half of the Outlook period, with a range of precipitation types expected. In the higher elevations of the Southwest, an extended period of snowy conditions is anticipated. Relatively mild and wet conditions are predicted for a large portion of Alaska, as a series of Pacific storm systems moves across the state. In Hawaii, an upper-air disturbance is forecast to bring heavy precipitation, especially for the southern islands of the archipelago.

Hazards Detailed Summary

For Monday March 02 - Friday March 06: An arctic air mass is forecast to move southward and eastward out of western Canada early in the period. Unseasonably cold air is expected to overspread most of the lower 48 states, reaching the Eastern Seaboard by the end of next week. Temperatures are predicted to range between 12 and 32 degrees F below normal, with the largest departures in the Central CONUS.

As this arctic air mass moves across the northern Great Plains on Tuesday, it is expected to be accompanied by gusty winds of 20-25 knots, which doesn't quite reach the hazardous wind speed criterion (30 knots). Therefore, no wind hazard has been placed on the map in this region.

Periods of heavy snow are predicted for the Four Corners region from Mar 2-4, 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.

Southerly flow is predicted to briefly develop across the southeastern quarter of the CONUS, prior to the next southward push of arctic air. Current thinking is that the boundary separating the warm, moist air from the cold, dry air (initially stretching from the central Plains to the Carolinas) 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 central Plains northeastward towards the Great Lakes 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 receive heavy winter precipitation (snow, sleet, freezing rain) is from the north-central Mississippi Valley eastward across the Great Lakes region, northern Ohio Valley, and Northeast, Mon-Thu, Mar 2-5. The area most likely to receive heavy rainfall is the central and southern Mississippi Valley, the southern Great Lakes region, the Ohio and Tennessee Valleys, much of the interior Southeast, most of the Appalachians, and from Virginia to southern Maine, Mon-Thu, Mar 2-5. There is a fairly large area of overlap between these two shapes. This overlap area depicts several things. First, this is the forecasted area most likely to receive freezing rain and sleet. Second, this area also depicts a transition zone where the precipitation types are expected to change several times during this period.

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 currently 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 either imminent or occurring in central Mississippi from Monday 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.

A 500-hPa trough over the east-central Pacific is predicted to shift west of Hawaii, before resuming its eastward motion. As a result, several models predict rainfall amounts of 2-5 inches for the Islands in general, and locally up to a foot of rain is possible in Maui and the Big Island during this period.

In Alaska, relatively fast zonal flow is forecast during this period, which reduces the possibility of extremes for both temperature and precipitation. Near to above-normal temperatures, and above-median precipitation, are anticipated for Alaska during this period.

For Saturday March 07 - Friday March 13: There is a slight risk of much below-normal temperatures for the southern Plains, Mississippi Valley, Great Lakes region, Northeast, mid-Atlantic, Ohio and Tennessee Valleys, and the central Gulf Coast states, Sat-Mon, Mar 7-9. A moderate risk of much below-normal minimum temperatures is indicated for much of the southern Plains, Mississippi Valley, the Great Lakes region, the Ohio Valley and lower Tennessee Valley, and from northern West Virginia and northern Maryland northeastward to Maine, Sat-Mon, Mar 7-9.

The most recent U.S. drought monitor, released 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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