Extended Forecast Discussion NWS Weather Prediction Center College Park MD 145 PM EST Fri Feb 03 2023 Valid 12Z Mon Feb 06 2023 - 12Z Fri Feb 10 2023 ...Guidance/Predictability Assessment... The latest suite of guidance continues to have multiple solutions to how this pattern will evolve thus the confidence in this forecast remains below average. The initial starting point of the extended had fair agreement on the upper level pattern so a mix of deterministic models and the ensemble means were used but transitioned heavily to the means by the start of Day 4 and then 100 blend of the ensemble means for the rest of the extended period. Two general forecast scenarios seem to exist in guidance with recent GFS/Canadian runs showing run to run stream separation leading to an upper low closing off in the Southwest/northern Mexico Tuesday-Wednesday that is stronger then slower to eject downstream through the east-central U.S. next week compared to the ECMWF/UKMET. Ensemble members by and large showed similar progression trends as their parent models with the GEFS/Canadian/NAEFS ensemble means less progressive than the ECMWF ensemble mean. This remains a difficult emerging split flow forecast with low predictability, but still suspect that a solution on the less progressive side of the full envelope of guidance makes more sense given much guidance does develop a separated southern stream system of which often are on the slow side to eject. ...Weather/Hazard Highlights... Near the start of the week a couple rounds of light precipitation will pass over portions of the Midwest, Great lakes and the Northeast region with shortwave passages and the approach of a lead low/frontal system. There may be lake enhancement of the snowfall for the favored areas downwind of the Great Lakes which could result in higher amounts than surrounding locations. Showers are possible along the Eastern Seaboard with some moisture return by Sunday from Florida into the eastern Carolinas and eastern parts of New England, but any heavier amounts look to remain offshore. Moderate precipitation is expected to overspread the West Coast and inland to the Intermountain West and Rockies region early by next week. For most of lower coastal areas the precipitation will likely fall as rain and then transition to snow for the mid-base to highest elevations; with typical terrain enhancement across the coastal ranges and the Sierra Nevada. As the low pressure system advances eastward the precipitation ahead of it could overspread the central U.S. The details of this precipitation including placement and precipitation type remain uncertain given the model differences. The current forecast shows enhanced rainfall amounts centered across the Southern Plains and Lower Mississippi Valley and surrounding areas by Tuesday-Wednesday with enhanced low/frontal system induced return Gulf of Mexico moisture inflow. WPC has identified an area across the Southern Plains and parts of the Lower Mississippi Valley as having the potential for excessive rainfall. An experimental Marginal Risk is in effect for that area Tuesday into Wednesday. The northern edge of the precipitation shield has the potential for snow/ice across portions of the Southern Plains to Midwest and interior Northeast next week, but this is subject to change with future forecasts. Subsequent eastern Pacific system approach Tuesday/Wednesday should offer modest system amplitude and associated moisture/rainfall potential across the Pacific Northwest along with terrain/mountain snows inland from the Northwest through the northern Great Basin/Rockies. 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