Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 AM EST Thu Mar 10 2022 Valid 12Z Sun Mar 13 2022 - 12Z Thu Mar 17 2022 ...Overview... An amplified trough and associated very deep cyclone will be exiting the East Coast early Sunday with a modified but chilly airmass behind. Meanwhile, an active pattern looks to return to the Pacific Northwest with a couple of shortwaves -- the first moving through on Sunday and the next one Monday into Tuesday. The first wave will dive southeast to the Gulf Coast and shift across the Southeast early to mid next week. The second, stronger wave, will bring a quick atmospheric river to the region before becoming more positively tilted and slowly make its way across the West Wednesday into Thursday. In between, upper ridging will build across the central U.S. and into the Midwest. ...Guidance Evaluation/Predictability Assessment... Plenty of uncertainty continues surrounding the initial shortwave into the Pacific Northwest early Sunday. Right off the bat, the 12z/Mar 9 CMC (most recent run at forecast issuance time) was much flatter than the consensus, resulting in a quicker wave through the central/eastern U.S., so it was excluded from the medium range blend tonight. However, the new 00z run did come in looking more amplified and usable. Models are beginning to come together on the idea that this wave may split, with northern stream energy moving into the Midwest/Northeast and amplifying southern stream energy with a possible closed low over the Gulf Coast/Southeast mid-next week. Despite this trend, there remains quite a bit of depth and timing issues, with the GFS consistently the deepest/slowest of the solutions (although also the first model to pick up on this idea) and also significantly faster with the northern stream energy. The ECMWF seems a little more reasonable and more in line with recent ensembles. The next trough into the West early next week continues to show ample run to run variability and timing, but at least decent agreement on the larger scale. The WPC blend tonight used a blend of the GFS and ECMWF, and smaller amounts of the UKMET, through day 5. After this, began increasing contributions from the ensemble means to help mitigate the details with both the system in the Southeast and the West. ...Weather Highlights/Threats... A departing and still rapidly deepening surface low out of the Northeast should continue to bring some gusty winds to northern New England into Sunday. An arctic airmass will still be in place across the East through Sunday, with daytime highs Sunday averaging 10-15 degrees below normal likely. Subfreezing temperatures are likely Sunday morning as far south as the Gulf Coast and northern Florida, with record lows possible in several locations. After Sunday, temperatures in the East should rebound back to more spring like weather with above normal temperatures persisting through much of next week. Meanwhile, rain and mountain snows will accompany the first shortwave passage this week across the West. As the southern stream energy amplifies into the Southeast next week, it should tap Gulf moisture to bring increasing rain and thunderstorms chances across the Gulf Coast and Southeast Monday-Tuesday, and maybe into Wednesday depending on the progression of the upper low/trough. Out West, the second trough early next week looks to direct an atmospheric river into the Pacific Northwest, bringing mostly beneficial rainfall and higher elevation snows to western Washington/Oregon and northern California. Upper level ridging between these troughs will build across the central U.S. with daytime highs 10 to 25 degrees above normal by next Tuesday-Wednesday for the northern/central Plains, which should be a welcome relief to the very chilly weather there currently. Santorelli 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