Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Thu Feb 02 2023 Valid 12Z Sun Feb 05 2023 - 12Z Thu Feb 09 2023 ...Overview... The medium range period begins Sunday with a wavy and fairly progressive upper-level pattern across the lower 48. An upper trough will shift across the central and eastern U.S. early in the week but with fairly dry conditions, while the bigger weather maker looks to be a trough entering the West Coast Sunday spreading some precipitation to the West. As that trough tracks into the central U.S. in some fashion by Tuesday-Wednesday, it should lead to a wetter pattern there. Much of the central and eastern U.S. looks to see above average temperatures through next week, with near normal conditions in the West. ...Guidance/Predictability Assessment... The early part of the medium range period remains in reasonably good agreement as one trough tracks into the East by Monday, another stronger trough digs into the West, with ridging in between. The WPC forecast used a blend of the 12/18Z deterministic guidance for days 3-4 given no notable outliers. Notably greater differences arise by late Monday with the Western trough's evolution. GFS runs have been persistent in showing stream separation leading to an upper low closing off in the Southwest/northern Mexico Tuesday-Wednesday and slowing down, with some ejection east by Thursday. The 18Z run was even farther west with the upper low than the 12Z run, and the newer 00Z run is close to the position of the 12Z. ECMWF runs on the other hand continue to indicate a trough with a bit of separation, but with relatively more phasing and a steadier trek eastward. The 12Z CMC seemed sort of like a compromise between the two--but the newer 00Z run shows more stream separation. Unfortunately all the 12Z ensemble suites appeared underdispersive, with ensemble members generally clustering with their own parent model. This was particularly true for the GEFS, as the EC and CMC ensemble members did have relatively more crossover with each other in cluster groups. While it seems reasonable to have some stream separation, the WPC forecast did not favor a solution as slow as the GFS runs, nor as fast as the ECMWF with the track of its trough east. Additional energy coming in northwest of the feature creates additional uncertainty with the evolution as well. The forecast blend quickly transitioned to favoring the ensemble means--particularly the EC mean and the NAEFS mean as a good compromise of the CMC/GEFS ensembles. ...Weather/Hazard Highlights... A couple of rounds of light precipitation are forecast across the Midwest/Great Lakes into the Northeast next week, and amounts could be enhanced downwind of the Great Lakes. 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. In the West, generally moderate precipitation is expected on Sunday in the form of lower elevation rain and higher elevation snow, with typical terrain enhancement across the coastal ranges and the Sierra Nevada. Snow is also forecast to spread into the Intermountain West and Rockies early next week, and then precipitation could overspread the central U.S. by Monday-Tuesday along and ahead of a low pressure/frontal system. 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 Lower Mississippi Valley and surrounding areas by Tuesday-Wednesday, with some potential for wintry weather across portions of the Plains to Midwest, but this is subject to change with future forecasts. Meanwhile, additional rounds of energy coming into the West will keep precipitation chances likely in the Pacific Northwest and the Northern Rockies through midweek. Another cold morning is expected Sunday across northern New England, but with temperatures below zero more limited in scope than in the short range period, and highs should warm up close to normal there during the day. Across the central U.S., the areal coverage of above average temperatures by 10-20F (15-25F above average for highs) will continue to grow through early next week, with some shift into the eastern half of the U.S. by Tuesday-Thursday. Underneath the upper troughing in the West, highs are forecast to be around 5-10F below normal, though with lows about average. Tate 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