Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 PM 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 latest runs of the GFS, UKMET, CMC and the ECWMF once again yielded an above average clustering during the beginning and middle periods of the extended forecast then returns to average agreement with more prevalent model differences. To help maintain forecast continuity and to reduce some of the differences for the latter periods, inclusion of the EC ensemble mean was utilized given recent history and long standing bias with closed lows in separated flow. ...Weather/Hazard Highlights... The leading upper trough will bring a significant coastal storm up the Southeast/Mid-Atlantic coast this weekend to off New England Monday. With this system there will be the 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. A wintry mix will be possible inland along the northwest periphery of the precipitation shield. There will be an upper-level trough/low amplification in splitting flow across the West that should lead to modest precipitation along the California coast and into the Southwest. The closed low is progged to track inland over northwest Mexico/Southwest Monday, across the Southern Plains and then pick up pace as it lifts northeast through the central and eastern states by Wednesday/Thursday. There will be a renewed possibility for areas of heavy rainfall across the Southern tier but the exact location and amounts are uncertain at this time. However, with moisture streaming northward from the Gulf ahead of this system there may be a renewed threat for enhanced rainfall and local areas of excessive rainfall. Downstream amounts will likely be more broad over the eastern states. Overtop, the progression of a northern stream upper trough and surface system with reasonable amplitude from the Northern Rockies through the Northeast through 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. Campbell/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