Extended Forecast Discussion NWS Weather Prediction Center College Park MD 218 AM EST Wed Feb 08 2023 Valid 12Z Sat Feb 11 2023 - 12Z Wed Feb 15 2023 ...Guidance/Predictability Assessment... Recent GFS/ECMWF/Canadian runs have certainty trended less progressive and deeper with a main lead closed low/trough set to form over The South/Southeast this weekend before lifting up/off the East Coast, now along with a deepening and coastal low/storm. Upper flow depiction is decently clustered, but intracacies of the coastal low/weather focus still offer some challenges. The UKMET offers an even slower solution. While plausible, with the big change a composite of the GFS/ECMWF/Canadian, including now with the newer 00 UTC cycle, seems reasonable and compatible with separted southern stream flow progresion bias known in guidance. Modest input from the compatible GEFS/ECMWF ensemble means also seems viable to mitigate, consistent with predictability, lingering smaller scale variances. Even without UKMET, product continuity takes a needed hit with this significant slowed trend and coastal low. Otherwise across much of the lower 48 and adjoining areas, models and ensembles have overall converged upon a better clustered solution through medium range time scales, bolstering forecast confidence with a GFS/ECMWF/Canadian and GEFS/ECMWF ensemble means composite along with guidance from the National Blend of Models. ...Weather/Hazard Highlights... A lead deep upper trough closing off over The South/Southeast this weekend in increasingly separated southern stream flow is now likely to become deeper and less progressive than continuity across the region and to spawn more significant coastal storm up the Southeast/Mid-Atlantic coast to off New England early next week. While a potent maritime wind/wave threat, moisture wrapping around the well developed low now has potential to produce wrapback heavier weekend rains and enhanced winds from the Southeast to at least the eastern Mid-Atlantic and coastal New England. There is also uncertain potential for some snow on the far northwest periphery of the precipitation shield. Meanwhile well upstream, eastern Pacific/West Coast upper trough/low amplification in splitting flow should lead to modest precipitation southward along the California coast and eventually into the Southwest. Guidance then reasonably develops of an closed trough/upper low over the Southwest/northwest Mexico by Monday that is expected to work across the southern Plains Tuesday before ejecting more rapidly northeastward over the east-central U.S. midweek. Gulf moisture streaming ahead of it could renew an emerging/expanding rainfall threat from the Southern Plains to broadly across the east-central states. Meanwhile overtop, the passage of a series of smaller wavelength northern stream shortwaves should support several shots for modest precipitation wit hmodest amplification, mainly for the Pacific Northwest and inland to the northern Rockies. There is a growing signal for later period dynamic system digging more sharply into an unsettled West by next Tuesday amd Wednesday that seems increasingly likely to support widespread precipitation including enhanced interior/mountain snows along with a rapid cooling trend. 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