Extended Forecast Discussion NWS Weather Prediction Center College Park MD 201 AM EST Sun Mar 06 2022 Valid 12Z Wed Mar 09 2022 - 12Z Sun Mar 13 2022 ...Overview... Strong ridge axes off both the East and West coast should keep much of the CONUS within broad and reinforced troughing next week. A shortwave diving into the Pacific Northwest on Wednesday will shift south and east into the central and eventually the eastern U.S. next weekend. This will push an Arctic cold front down the Great Plains through Friday while a low develops along the front and deepens as it lifts into the Upper Great Lakes on Friday. Expect wintry weather to the northwest of the low from the central Rockies/Plains to the upper Midwest, with rounds of showers and storms ahead of the system across the Southeast/Mid-Atlantic. As the low lifts quickly into eastern Canada next Saturday, the cold front should clear the East Coast ushering in a much chillier air mass. By next Sunday/day 7, flow across the CONUS should become more zonal with weak systems through the northern tier states. ...Guidance Evaluation/Predictability Assessment... Fairly good agreement on the advancement of amplified troughing across the interior West and into the central states Wednesday-Thursday. By Friday and beyond, more differences in the details of possible stream splitting begins to emerge. Notable outlier amongst the 12z/18z guidance from yesterday is the CMC which is slower and much more amplified late week, closing off an upper low over the Midwest on Saturday (00z CMC came in generally the same). This also gets it out of sync with the next shortwave entering the Pacific Northwest on Sunday. The GFS and ECMWF show much better consistency with the ensemble means but there are some timing differences next weekend with the northern stream shortwave into the Northeast (GFS faster). Also some lingering uncertainties with regards to amplitude and timing of the Pacific Northwest shortwave next Sunday, though there is plenty of time for those details to be worked out. The WPC blend for tonight used a multi deterministic model consensus days 3-5. For 6-7, removed the CMC due to issues outlined above and increased contributions from the GEFS/ECENS ensemble means to mitigate the detail differences. Was able to maintain at least 50 percent deterministic GFS and ECMWF which helped give some added definition to individual systems. ...Weather Highlights/Threats... A stationary boundary settling across the Southeast should keep showers and storms in the forecast Wednesday-Friday. Even though amounts don't seem overly high for any given day at this point, multiple days of rain may increase concerns for flooding. Meanwhile, a shortwave through the West on Wednesday will continue a threat for heavy mountain snows for parts of the interior West and central Rockies. A low pressure spinning up in the lee of the Rockies and lifting into the Upper Midwest Thursday-Friday brings a winter storm threat from the central Plains to the Upper Midwest. The elongated upper trough should tap Gulf of Mexico moisture with widespread rain into the East ahead of the cold front on Friday. The next system into the Northwest next weekend should increase rain and mountain snow chances across the Pacific Northwest and northern Rockies. Arctic sourced air spills into the Plains, with daytime highs 20-30+ degrees below normal as far south as Texas through Friday. Overnight lows across the northern Plains will likely be near or below zero for many locations. Ahead of the cold front, above normal temperatures will spread across the Eastern third of the country Thursday and Friday before being replaced by below normal temps by Saturday following the passage of the cold front. By next Sunday, most of the country should modify closer to normal as upper flow become less amplified. 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