Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EST Fri Feb 14 2025 Valid 00Z Sat Feb 15 2025 - 00Z Mon Feb 17 2025 ...A life-threatening flash flooding event emerges over the Lower Mississippi, Tennessee, and Ohio Valleys as well as parts of the Appalachians this weekend with severe thunderstorms across the Lower Mississippi Valley... ...Widespread moderate to locally heavy snowfall expected across the Upper Midwest tonight, then through the Great Lakes into New England this weekend with a swath of sleet/ice just to the south... ...A cold front will usher in another round of Arctic air spreading southward across the Plains, Midwest, and Mississippi Valley this weekend... ...Pacific system will bring renewed round of lower elevation coastal/valley rain and higher elevation snow to the Pacific Northwest by Sunday... A very active weather pattern will continue across the country heading into the weekend as a potent upper-level trough and accompanying surface low pressure/frontal system bring the threat of flash flooding, severe weather, and heavy snow from Intermountain West to the East Coast this weekend. For today, moderate to locally heavy higher elevation mountain snow and a wintry mix at lower elevations will continue across the Intermountain West into Friday night as the upper-level trough/frontal system move through the region. Much of this precipitation should begin to taper off into the day Saturday, with snow showers lingering longest over the central Rockies. The system will begin intensifying as it approaches the Mississippi Valley overnight Friday and through Saturday night, with both strengthening low and upper-level wind fields and a significant flow of moisture northward from the Gulf. The combination of favorably strong dynamics, flow parallel to the approaching front, and plentiful moisture will contribute to widespread intense thunderstorms increasing in coverage across the Lower Mississippi, Tennessee, and Ohio Valleys through the day. Repeated rounds of intense storms as they move parallel to and back build along the front will lead to rainfall rates of 1-2" per hour and totals of 3-6", with isolated amounts up to 8". The greatest risk for this intense rainfall leading to life-threatening flash flooding will be across portions of northwestern Tennessee and western Kentucky, where a High Risk of Excessive Rainfall (level 4/4) is in effect. A broader Moderate Risk (level 3/4) covers portions of the Mid-South to Ohio Valley, with a Slight Risk (level 2/4) encompassing the general region east to the Appalachians. Still potentially significant, but more scattered instances of flash flooding will be possible in these areas. In addition to the flood risk, severe weather is also expected, with an Enhanced Risk (level 3/5) issued by the Storm Prediction Center for portions of the Lower Mississippi Valley. Supercell thunderstorms ahead of the front will be capable of all severe hazards through the day Saturday, including the risk for strong tornadoes. The progress of the cold front will speed up into Saturday evening, transitioning the threat to damaging winds and QLCS tornadoes, which may continue further east into the Southeast overnight Saturday. The system will continue eastward on Sunday, with a broad area of showers and thunderstorms spreading across the Mid-Atlantic and Southeast producing moderate to locally heavy rainfall, with some isolated flash flooding possible in the southern Mid-Atlantic. To the north, a band of moderate to locally heavy snow is expected in the colder air northwest of the system track, spreading across the Upper Midwest Friday night into early Saturday and the Great Lakes through the day Saturday. Winter Weather Advisories are in place for totals generally in the 3-6" range. A wintry mix will be possible in the transition zone along the storm track through portions of the Midwest. As the storm intensifies, a more significant winter storm is becoming more likely for Upstate New York and northern New England late Saturday into Sunday. Winter Storm Watches have been issued for portions of the region for snow totals of 5-10", locally higher, especially for higher mountain elevations and across northern Maine. Gusty winds as the intensifying area of low pressure passes through may also lead to periods of blowing snow and very difficult travel conditions. Some moderate snow totals will also be possible further south across higher elevations of the Appalachians. Daytime high temperatures will be above average and rather mild for regions ahead of the storm system from the central to eastern U.S. this weekend. Forecast highs in the 50s to 70s are expected from the Ohio Valley southward to the Lower Mississippi Valley/Texas/Gulf Coast on Saturday. After a cold Saturday, much warmer temperatures are forecast Sunday across the Mid-Atlantic and Carolinas as temperatures reach into the 50s and 60s here as well, with 60s and 70s in the Southeast ahead of the front. A much colder, Canadian airmass will spread southward behind the front, bringing well below average, bitterly cold temperatures to areas of the northern and central Plains on Saturday, with highs in the single digits and teens for many locations. Some highs may not even reach above zero by Sunday. Blustery winds will lead to wind chills below zero, particularly across the northern Plains. These colder temperatures will expand into the Mississippi Valley and southern Plains by Sunday with highs dropping into the 30s and 40s for most locations. Back to the West, an upper-level trough/Pacific storm system will bring a renewed round of precipitation to the Pacific Northwest beginning late Saturday which will spread inland across the northern Great Basin/Rockies into Sunday. This will include periods of moderate rainfall for coastal locations, a mix of rain and snow for interior valleys, and moderate to locally heavy snow accumulations for higher mountain elevations, particularly across the Cascades and northern Rockies. Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php