Extended Forecast Discussion NWS Weather Prediction Center College Park MD 217 AM EST Sun Feb 05 2023 Valid 12Z Wed Feb 08 2023 - 12Z Sun Feb 12 2023 ...Guidance/Predictability Assessment... Latest model and ensemble solutions now seem better clustered valid Wednesday-Thursday, bolstering forecast confidence compared to less than stellar runs over the past few days. Prefer a composite of the GFS/ECMWF/UKMET/Canadian to mitigate consistent with uncertainty ample lingering smaller scale system differences. The GFS/ECMWF solutions seems to cluster best with ensembles heading into/through next weekend and a composite seems to offer a reasonable forecast basis amid growing forecast spread in highly amplifying/slowing flow with likely development of strong upper troughs over the east-central U.S. and off the West Coast along with ample upper ridges over the west-central U.S. and western Atlantic. There remains some stream phasing uncertainties as a more progressive northern stream periodically digs shortwave energy/cold air deeper southward into the lower 48. ...Weather/Hazard Highlights... An initially closed southern stream upper trough/low will eject into the southern Plains by midweek as a kicker shortwave trough digs southeastward through the Great Basin to support some potential for snow there into the Rockies. Downstream, a surface frontal wave over Texas with the lead system will organize, deepen and occlude while lifting northeast into the Midwest/OH Valley Thursday before exiting through the Northeast Friday. Gulf moisture inflow/instability and supportive upper jet/height falls will combine with the associated frontal system to produce a swath of heavy rain/convection this period across the Lower/Mid MS and TN/OH Valleys, with widespread moderate rains then shearing across the Appalachians and Eastern Seaboard. The WPC experimental Day 4 Excessive Rainfall Outlook (ERO) will show a "marginal" threat area over the mid-lower MS Valley and vicinity through Wedensday, extending from a Day 3 marginal and slight risk area just upstream. Cold air draped to the north of the system and several potent shots of Canadian air in the wake of system passage will also offer a threat for heavy snow/ice on the northern periphery of the expanding precipitation shield this period from the central Plains through the Great Lakes and interior Northeast and southern Canada. Expect lake effect snows into the weekend given lingering cold/windy flow. Upstream, there is a growing guidance signal for the amplification of the overall flow significantly into later week across the nation and adjoining oceans, but with limited precipitation re-emergence overall at this point. Organized rains stay mainly off the West Coast this period, with significant eastern Pacific storm development held just offshore. Renewed shortwave approach out from the West and potentially the northern stream will meanwhile help carve out an amplified central to east-central upper trough position later week into next weekend, but responding surface system development does not seem to have deep moisture inflow in the wake of the aforementioned lead main system, so expect an expanding area of overall moderate rainfall signature with a main focus likely to lift from the Southeast to up the East Coast next weekend with modest coastal low genesis and Atlantic inflow that could offer a late period interior snow threat over the Northeast to monitor. Schichtel 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, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml