Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Thu Feb 09 2023 Valid 12Z Sun Feb 12 2023 - 12Z Thu Feb 16 2023 ...Stormy flow with a series of deepened closed lows in split southern stream flow from the West to East Coast... ...Guidance/Predictability Assessment... The GFS/ECMWF/UKMET/Canadian solutions now seem better clustered than normal Sunday-Tuesday and a composite offers a fairly detailed and energetic depiction of the main features. Model and ensemble forecast predictability remains above average into next Wednesday/Thursday, but slowly growing forecast spread likely suggests that minority inclusion of ensemble mean guidance may smooth out some detail consistent with individual uncertainty. Leaned the blend at these loner time frames toward the slower and more amplified southern stream flow depiction of the ECMWF/Canadian and ECMWF ensembles given recent history and long standing bias with closed lows in separated flow. ...Weather/Hazard Highlights... The recent lead upper trough trend to become deeper and with a slower track seems to have reached a crescendo, but the resultant solution continues to favor a significant coastal storm up the Southeast/Mid-Atlantic coast this weekend to off New England Monday. This system will usher in significant wind and wave threats, along with potential for heavier precipitation as moisture wraps in around the central low pressure. The enhanced rains over portions of the southeastern Mid-Atlantic offers some potential for localized areas of flash flooding/ponding, so the WPC medium range experimental Excessive Rainfall Outlook (ERO) maintained a Day 4 "Marginal" Risk. There also remains potential for some wintry weather on the far inland northwest periphery of the amply wrapped back precipitation shield. Across the eastern Pacific and West Coast an upper-level trough/low amplification in splitting flow should lead to modest precipitation along the California coast and into the Southwest. The closed trough/upper low track from southern California Sunday to over the Southwest/northwest Mexico Monday is then forecast to trek across the Southern Plains Tuesday before ejecting more rapidly northeastward over the east-central U.S. and out through the Northeast Wednesday/Thursday. With moisture streaming northward from the Gulf ahead of this system there may be a renewed threat for enhanced rainfall over the Southern Plains/The South early next week, with broader amounts then downstream over the east-central to eastern states. Overtop, the progression of a northern stream upper trough and surface system with reasonable amplitude from the northern Rockies through the Northeast Sunday-Tuesday offers limited wintry precipitation potential across the northern tier and seems mostly out of sync for phasing with the much more energetic and separated southern stream flow. Upstream, there is a strong guidance signal for dynamic system digging sharply into an unsettled West by early next week within a renewed southern stream. This still seems likely to support widespread precipitation across the Northwest next early week and spreading more earnestly across the Intermountain West/Southwest and Rockies through next midweek to include rapid cooling with enhanced interior/mountain snows with closed low development. Expected system emergence over the south-central U.S. starting next midweek will likely renew a heavy rainfall pattern over the region and then into the east-central U.S. with increasing lead Gulf inflow and cyclo/frontogenesis. Cold Canadian air digging southward on the backside of this system could meanwhile offer a pattern favorable for heavy snow focus on the northwest periphery of the expanding precipitation shield out from the Rockies to across the central Plains and vicinity toward perhaps the Upper Midwest. 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