Extended Forecast Discussion NWS Weather Prediction Center College Park MD 330 PM EST Tue Feb 04 2020 Valid 12Z Fri Feb 07 2020 - 12Z Tue Feb 11 2020 ...Heavy snow risk exiting New England Friday... ...Overview and Guidance/Predictability Assessment... Upper pattern will flip between the end of this week and early next week as troughing in the east exits into the Atlantic and ridging along the West coast retrogrades offshore. Troughing from south of the Gulf of Alaska will dig down through the Great Basin and into the Southwest Sun-Tue with broad southwesterly flow east of the Rockies. This could set up a heavy rain threat for the end of the period (next Tue into Wed) over the Lower Mississippi Valley/Southeast. A multi-model deterministic blend sufficed to start the period with the exiting Northeast system (mostly timing differences) with a trend toward favoring the 06Z GFS and 00Z ECMWF. By next Mon/Tue, used a majority ensemble weighting (both 06Z GEFS and 00Z ECMWF ensemble mean) as spread increased in system track and timing, though confidence was above average in the overall pattern. Details remain less clear, as is typical, and still need to be worked out especially toward the end of the period. ...Weather/Hazard Highlights... Lingering heavy snow will continue across parts of the interior northeast and northern New England Friday and dissipate early Saturday over Maine. A second shortwave, crossing the Appalachians this weekend, may bring a period of light rain and/or minor accumulating snows to parts of the southern/central Appalachians late Saturday into early Sunday. This may skirt close enough to New England later on Sunday to bring some light rain/snow to the region. Several frontal systems out of the Northeast Pacific will bring modest to possibly heavy snowfall to the higher terrain of the Pacific Northwest into the northern/central Rockies Friday and Saturday. As the front sinks southward through the West, rainfall and mountain snow will push through California and the Great Basin with some lighter rain for coastal areas. As the upper low slowly moves through the Southwest, Gulf moisture will increase into the southern Plains/Lower Mississippi Valley next Mon/Tue. Convectively-enhanced rainfall may support locally heavy rain amid a widespread area of at least light precipitation (nearly all rain). Temperatures across the CONUS through the medium range period should be fairly close to average (within 5-10 degrees). Areas with the higher temperature anomalies will be over the Mid-Atlantic and coastal Texas. A general warming trend is expected across the Eastern U.S., while temperatures should trend cooler out west as troughing moves through. The central U.S. should be near average through the entire period. Fracasso Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Fri-Sat, Feb 7-Feb 8. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Mon-Tue, Feb 10-Feb 11. - Heavy snow across portions of the Central Plains, the Central Great Basin, the Northern Plains, the Northern Rockies, the Central Rockies, and the Northern Great Basin, Fri-Sat, Feb 7-Feb 8. - Heavy snow across portions of the Central Rockies, the Central Plains, the Northeast, and the Great Lakes, Fri, Feb 7. - Flooding possible across portions of the Northeast, the Central Appalachians, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Pacific Northwest. - Flooding occurring or imminent across portions of the Lower Mississippi Valley and the Northern Plains. - Flooding likely across portions of the Southeast, the Mid-Atlantic, and the Pacific Northwest. - High winds across portions of mainland Alaska and the Aleutians, Fri-Mon, Feb 7-Feb 10. - Much below normal temperatures across portions of mainland Alaska, Fri-Sat, Feb 7-Feb 8. WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml