Extended Forecast Discussion NWS Weather Prediction Center College Park MD 147 PM EST Wed Mar 03 2021 Valid 12Z Sat Mar 06 2021 - 12Z Wed Mar 10 2021 ...Overview and Guidance Evaluation... The synoptic pattern across the CONUS during the period is expected to feature quasi-persistent troughing over the eastern Pacific / West Coast while deep troughing over the East Coast this weekend quickly is replaced by zonal flow to ridging by early to mid next week. The troughing over the West Coast is expected to bring an unsettled to active period of sensible weather with several episodes of precipitation. By Tuesday/Wednesday next week, a more significant shortwave could track across the Rockies and result in a deepening low over the Plains with more widespread precipitation across portions of the north-central/east U.S. Downstream ridging over the East Coast could bring a few days of above normal temperatures by day 7. Model guidance spread has lessened somewhat this cycle with respect to the overall pattern. Earlier timing issues between the GFS and other global models have lessened and more or less, an agreeable progression has set up. The East Coast trough and associated sprawling high pressure shows high agreement between the various models and should exit offshore late in the weekend/Monday. A shortwave trough moving onshore the West Coast on day 3 /Saturday/ will ripple through the flow and weaken as it opens up over the Plains on day 5 /Monday/. Here, there remain some timing/strength differences where the GFS is still flatter/faster, but the spread is fairly minimal for being day 3-5. Finally, persistent closed low wobbling over the eastern Pacific offshore Washington will bring several shortwave troughs the flow in fast progression early to mid week. There is fairly good agreement in the large scale pattern between the GFS/ECMWF/CMC. Overall, the WPC blend had average to slightly above average forecast confidence and primarily was made up of the latest ECMWF/GFS/GFSP/CMC with higher weights toward the ECMWF and ECENS (in latter periods). ...Weather/Threats Highlights... The sensible weather highlights include the unsettled weather pattern expected for the West Coast with a parade of weather systems bringing rain and higher elevation snow mainly from northern California to the Pacific Northwest. Precipitation could be moderate to locally heavy at times with highest five-day totals (perhaps reaching several inches) most likely over southwest Oregon into northern California. This unsettled weather then is forecast to spread to the Interior West and Rockies though with less intensity. This system will eject into the Plains by the middle of next week and could spawn a deepening/significant low pressure. With an open source/return flow from the Gulf of Mexico, widespread precipitation, rain, thunderstorms will be possible across the warm sector while colder/northern areas could see a round of wintry weather. Much above normal temperatures over the Northern Plains this weekend, reaching 10-25F above normal, will gradually extend eastward into the Upper Midwest and Great Lakes with less extreme warmth also reaching into the Northeast by late in the period. Some daily records for highs and/or warm lows will be possible. By next Tuesday-Wednesday well above normal readings for morning lows in particular will extend well southward over the Plains and Mississippi Valley as Gulf inflow increases. Elsewhere, a cooling trend toward moderately below normal readings will spread across the western U.S. during the period. East Coast states will be chilly during the weekend with highs 5-10F or so below normal and then trend warmer. Rausch/Taylor 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 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