Extended Forecast Discussion NWS Weather Prediction Center College Park MD 119 PM EST Thu Mar 10 2022 Valid 12Z Sun Mar 13 2022 - 12Z Thu Mar 17 2022 ...Overview... Two main waves affect the CONUS next week. The first wave will dive southeast from the northern Rockies to the Gulf Coast Sunday night through Tuesday before shifting across the Southeast into or through the middle of next week. The second, stronger wave, will bring a quick atmospheric river to the Pacific Northwest before slowly making its way across The West through Thursday Wednesday into Thursday. In between, upper ridging will shift from the western through the central U.S.. ...Guidance Evaluation/Predictability Assessment... Excellent agreement among the 00Z ECMWF/UKMET and the 06Z GFS (and now the 12Z GFS) on the low that opens into a wave over the Pacific Northwest Sunday before shifting southeast down the Rockies through Monday before turning east over the Deep South Tuesday (which is a slower solution than prior model consensus). The 00Z CMC, however, was more open with the wave to begin, making for a more progressive/positively-tilted trough over The West that lays over the northern Gulf of Mexico Tuesday. Therefore, a blend of three deterministic models were used for the WPC forecast Days 3-5. Uncertainty with amplitude and timing of the next wave into the Northwest Monday night as well as the track of the low over the Southeast starting Tuesday night does warrant incorporation of the more agreeable 00Z ECENS and 06Z GEFS ensemble means for Days 6/7. Out west, the 00Z ECMWF was much more amplified with the trough, bringing it into central CA on Tuesday while the 06Z GFS (and now the 12Z GFS) features two waves that reach the Pacific Northwest Monday night and Wednesday night. In the Southeast, the 06Z GFS takes a much more northerly track (with the 12Z GFS now more northerly and faster), moving into the Mid-Atlantic Wednesday while the 00Z ECWMF maintains an easterly track over the Deep South before turning up the Carolina Coast Thursday. ...Weather Highlights/Threats... The Arctic airmass behind a departing powerful low moving from New England Saturday night will linger into Monday over the Southeast with Monday morning lows generally 10 to 15 degrees below normal over the Deep South with min temps around freezing over interior portions of the Southeast, but not as cold as Sunday morning which will feature a hard freeze over much of the Southeast into north Florida. After Monday morning, temperatures in the Central and East will rebound to more spring like weather with above normal temperatures persisting through much of next week. Meanwhile, mountain snows weaken as they cross the central/southern Rockies Sunday night ahead of the first wave. However, as this wave encounters strengthening southern stream energy, amplification occurs over the southern Plains Monday night and with the addition of Gulf moisture, rapidly increasing rain and thunderstorms can be expected across the lower MS Valley Monday night and across the Deep South Tuesday through Wednesday. Uncertainty exists with the track later Wednesday through Thursday. There was fair agreement with the 06Z GEFS mean and the 00Z ECMWF which were used to enhance rainfall over the southeast through Thursday. Out West, the second trough will direct an atmospheric river into the Pacific Northwest Sunday night, bringing mostly beneficial rainfall and higher elevation snows to western Washington/Oregon before spreading south through northern California through Monday night. Upper level ridging between these troughs will build across the central U.S. with daytime highs 15 to 25 degrees above normal by next Tuesday-Wednesday for the northern/central Plains/Midwest before spreading into the northeast Thursday, which should be a welcome relief to the wintry weather currently over these areas. Jackson Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php 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