Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Mon Feb 05 2024 Valid 12Z Thu Feb 08 2024 - 12Z Mon Feb 12 2024 ...Overview... Broad and renewed troughing will hold over the West through about Saturday, before beginning to slowly shift eastward as upper ridging tries to build in next Sunday-Monday. This will keep this region quite active with rounds of lower elevation rains and mountain snow, including possibly a couple of weak atmospheric rivers into California. Precipitation is certainly forecast to be lower than in the short range though. Meanwhile, a strong upper ridge shifting out of the Central U.S. will continue to support well above normal temperatures that could be record-setting across the parts of the Upper Midwest on Thursday-Friday before it becomes suppressed and shifts eastward with time. Shortwaves/energy from the mean upper trough over the West will periodically eject into the central U.S., with a couple of modestly deep surface lows moving into the Upper Midwest/Great Lakes. This should increase precipitation chances across the Mid-South/Southeast late period, with some snow chances in the beginning of the period over the northern Plains. ...Guidance/Predictability Assessment... Model guidance continues to be reasonably agreeable on the overall large-scale pattern during the medium range period, but there are some notable key differences that have sensible weather impacts. These differences mainly focus out West involving integration of multiple pieces of energy into the Western trough, particularly a potent shortwave which shows better agreement to dig down the western side of the trough with potential compact closed low developing over the Southwest by Saturday. Initially, the GFS seemed to be on its own in being so amplified with this system, but recently other guidance has trended towards the stronger solution. There's still plenty of uncertainty in the details/sensible weather impacts, but overall better consensus for a digging shortwave/amplified trough which eventually shifts eastward Sunday-Monday. By this time though, there are considerable differences in the timing with the ECMWF being significantly faster with the shortwave, and the CMC slower/flatter. Interestingly, the GFS was a preferred deterministic solution for tonight, which was also closest to the fairly agreeable ensemble means. Behind this trough, the models suggest upper ridging should try to build back into the West, but with some uncertainties on possible disruption from another shortwave. The WPC forecast utilized a blend of deterministic guidance early in the forecast period, with a gradual shift toward more GEFS and EC ensemble guidance with the GFS by late period given increasing model spread. Overall, this approach maintained good continuity with the previous WPC forecast. ...Weather/Hazards Highlights... General broad troughing over the Southwest should keep the Western U.S. periodically active with widespread lower elevation rain/mountain snows into next weekend. Additional rounds of rain and mountain snows could come into California Thursday-Friday, but models vary still on exact amounts and locations of heaviest precipitation. Given extreme rainfall across much of California recently, the area is more sensitive than usual to additional rainfall, but there isn't enough support for even a marginal risk on the ERO at this point still. Precipitation looks to clear out of much of the Intermountain West by Saturday, but may focus again in the Pacific Northwest. A leading shortwave and surface front out of the West on Thursday should focus moisture and some weak instability to fuel rain ahead of the cold front across the Mid-South. Rain rates and amounts do not look high enough to cause flooding issues given fairly progressive movement. Showers and thunderstorms should then settle across the Gulf Coast/Southeast next weekend, mainly in areas that have low antecedent soil moisture limiting any flooding threat, except farther west across Louisiana/Arkansas and eastern Texas. Some increasing support in the guidance for locally heavy multi-day amounts for this region, but lots of uncertainty and highly dependent on exact evolution of Western U.S. troughing. There is also some snowfall potential on the north side of the surface cyclone across the north-central U.S. into Thursday. The upper ridge initially from the Lower Mississippi Valley through Great Lakes will support a broad area of unseasonably warm temperatures which will shift from the Upper Midwest/Great Lakes Thursday-Friday into the Northeast by Saturday. Daytime highs in this region could be 20-30F above normal, with potential for widespread daily temperature records. In contrast, the Southwest U.S./California should see cool but moderating with time daytime highs through the period with some areas around 10-15F below normal on multiple days. Clouds/precipitation over the West should keep morning lows near to above normal though later this week. Temperatures across the entire Eastern U.S. will trend warmer as the period progresses, while moderating a bit closer to normal in the Midwest by next weekend. Santorelli 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw