Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Sat Jan 29 2022 Valid 12Z Tue Feb 01 2022 - 12Z Sat Feb 05 2022 ...Next week to bring heavy precipitation to the central and eastern U.S., including winter weather from the Central Plains to Great Lakes and interior Northeast around midweek... ...Overview... Upper level ridging over both the western Atlantic and East Pacific will allow for a shortwave to dig into the western U.S. Tuesday-Wednesday, shifting east into the Plains on Thursday. Another shortwave should drop into the base of the trough on Thursday across the Southwest which will help to reinforce/amplify the trough as it tracks into the Midwest/East Friday and Saturday. This evolution is expected to bring widespread precipitation along and ahead of a leading frontal boundary into much of the eastern half of the country mid-late next week, with increasing potential for wintry weather on the backside of the system. ...Guidance Evaluation/Predictability Assessment... Recent model guidance remains in generally good agreement for the overall large scale pattern, but with continuing uncertainty in the smaller scale details. Models remain pretty consistent with the track of the initial compact southern stream upper low over the Gulf on Tuesday before shearing out with somewhat variable timing as upper ridging builds off the East Coast. Meanwhile, in the northern stream, a shortwave moving across the Great Lakes and Northeast early in the workweek also shows good agreement in the deterministic models. There continues to be increasing consensus with energy diving south through the Intermountain West Tuesday-Wednesday, serving to deepen the trough into the Central U.S.. A trend towards less separation of streams with the trough has remained, but models are showing timing differences into the southern Plains/Midwest which affects frontal and surface low position by Friday. The ECMWF and CMC are faster than the GFS and UKMET (through day 5 at least), but the ensemble means tend to fall somewhere in between. There also seems to be a trend towards a stronger shortwave diving into the Southwest around Friday but with a lot of uncertainty by Saturday/day 7 regarding strength and timing, as exhibited by the latest ensemble spaghetti plots. The WPC forecast for tonight used a purely multi-model deterministic blend for days 3-5. After that, increased weighting of the GEFS/ECENS ensemble means to help mitigate some of the late period differences. Given better than average agreement on the large scale though, was still able to maintain 50 percent of the deterministic GFS/ECMWF (and smaller parts CMC) through day 7/Saturday. Overall, this maintained good continuity with the previous WPC forecast for days 3-6. ...Weather Highlights/Threats... Some moderate rain may be possible along the central Gulf Coast on Tuesday associated with weakening southern stream energy out over the Gulf and increasing moisture ahead of the next system into the West. The bigger threat during the medium range period though is a developing trough over the West and into the Central U.S. by Wednesday. Initially on Tuesday, this feature should spread mainly light to moderate lower elevation rain and mountain snow across the Rockies. The forecast however remains on track for a significant increase of coverage and intensity of precipitation over the east-central U.S. by Wednesday and beyond as the upper trough emerges from the Rockies and the leading cold front interacts with a strong low level feed of Gulf moisture. The best chance for heaviest rainfall extends across the lower half of the Mississippi Valley into parts of the Ohio/Tennessee Valleys to the Appalachians and the East. The pattern certainly favors a heavy to excessive rainfall threat, but the exact location of where this sets up any flooding/flash flooding impacts remains quite uncertain still. Wintry weather will be possible on the northwest side of the moisture shield, with increasing potential for meaningful snow from central parts of the Plains and Mississippi Valley northeastward through the Great Lakes and into the interior Northeast. While heavy rainfall to the south seems fairly certain, the details with the wintry precipitation in the colder air may be more dependent on lower-confidence details of ejecting shortwave energy and frontal waves. Above average temperatures will spread eastward Tuesday-Thursday across the Eastern third of the country with daytime highs as much as 15-20 degrees above normal along the East Coast on Friday. At the same time, arctic high pressure dives into the Central U.S. behind the cold front midweek, bringing chilly and much below normal temperatures all the way from the northern Rockies/High Plains southward into Texas. Widespread daytime highs (and slightly less extreme overnight lows) as much as 10-25 degrees below average are possible. The below normal temps may moderate slightly as they shift east into the Ohio Valley/Gulf Coast states next Friday and the East on Saturday. The West Coast states should be near normal through much of next week owing to amplified ridging across the East Pacific. 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, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml