Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 PM EST Wed Feb 08 2023 Valid 12Z Sat Feb 11 2023 - 12Z Wed Feb 15 2023 ...Guidance/Predictability Assessment... The trend continues for a less progressive and deeper main lead closed low/trough set to form over the South/Southeast over the weekend before it lifts up/near the East Coast, now along with a deepening and coastal low/storm. By and large, the upper level pattern is fairly well clustered but differences remain that lead to challenges with the forecast. The UKMET is persistently slow with the latest runs and therefore were not utilized with this issuance. The GFS, ECWMF and the CMC maintain a separated southern stream flow progression thus were the preferred solutions. The GEFS and ECWMF ensemble means reduce some of noise, especially beyond 5, and compliment the pattern evolution as their parent models. Their weighting increased to around 40% for the middle and latter periods. ...Weather/Hazard Highlights... There is still a trend for the lead upper trough to become deeper with a slower track; which favors a more significant coastal storm up the Southeast/Mid-Atlantic coast to off New England early next week. This system will usher in significant wind and wave threats, along with the potential for heavier precipitation as moisture wraps in around the central low pressure. The enhanced rains over portions of the Southeast and Mid-Atlantic during the Day 4-5 period may lead to local areas of flash flooding/ponding so the WPC experimental Marginal Risks for excessive rainfall remain warranted.There is also an uncertain potential for some snow on the far northwest periphery of the precipitation shield to monitor. Across the eastern Pacific and West Coast an upper-level 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 forecast to trek across the Southern Plains Tuesday before ejecting more rapidly northeastward over the east-central U.S. midweek. With moisture streaming northward from the Gulf ahead of this system there may be a renewed threat for a broad area of rainfall over the Southern Plains that shifts to the east-central states. The passage of a series of smaller wavelength northern stream shortwaves should support several shots for modest precipitation with modest 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 and Wednesday that seems increasingly likely to support widespread precipitation including enhanced interior/mountain snows along with a rapid cooling trend. Campbell 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