Extended Forecast Discussion NWS Weather Prediction Center College Park MD 206 PM 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... During the medium range period Tuesday to Saturday, an upper level trough initially digging across the West will push eastward and expand from additional digging shortwave energy through the week in between eastern Pacific and western Atlantic ridging. Ahead of the trough axis, a potent cold front and widespread precipitation will track across the central and eastern U.S., with heavy rain in the warm sector and increasing potential for wintry weather on the backside of the system. ...Guidance Evaluation/Predictability Assessment... Recent guidance remains in fairly good agreement with the overall large scale pattern, but with some detail differences remaining, particularly later in the period. The 00Z/06Z model cycle continues to show a compact southern stream mid-upper low moving into the Gulf by early Tuesday and shearing out quickly after that. Northern stream shortwaves over the north-central U.S. and the western Atlantic also appear agreeable at the beginning of the period. Thus a multi-model deterministic blend of the 00Z ECMWF/CMC/UKMET and 06Z GFS was utilized for the early part of the WPC forecast. The trough deepening in the West on Tuesday-Wednesday shows a good consensus for axis and amplitude even as multiple shortwaves combine to create it. There are some slight timing differences with the eastern side of the trough as it shifts eastward by around Thursday, which causes some slight timing differences with the associated potent cold front an placement of waves of low pressure along it. Generally the 00Z ECMWF and its ensemble mean were a bit east compared to the 00Z/06Z GFS suite. Most guidance continues to show combined northern/southern stream troughing through early Thursday, with the exception of the UKMET with more separation. Meanwhile on the western side of the trough, additional shortwave energy will likely dive through around Thursday and then could create some northern/southern stream separation in the overall troughing by around Friday, by holding back southern stream energy in the Southwest. The 00Z GFS was strongest with this feature among the deterministic guidance and most ensemble members during the 00/06Z cycle and comparing to the new 12Z cycle as well. Meanwhile the 00Z CMC keeps the streams a little more joined and ends up faster especially by Saturday, while the 00Z ECMWF seemed to be the best middle ground position. The latter part of the forecast was based on a blend favoring the 00Z ECMWF for this reason, with lesser inclusion of the 06Z GFS (which was not quite as held back as the 00Z), as well as some ensemble mean incorporation, especially the 00Z GEFS mean as it displayed hints of the stream separation that is becoming the consensus late in the period. ...Weather Highlights/Threats... The deepening trough in the West will initially help cause light to moderate precipitation in the Intermountain West on Tuesday into Wednesday, particularly mountain snow in the Rockies. But as the trough and the cold front pushing ahead of it shift eastward, ample Gulf moisture will be drawn northward and cause widespread precipitation across much of the central and eastern U.S. beginning Tuesday and lasting through the workweek as it slowly tracks eastward. The best chance for heavy rainfall extends from the Southern Plains and Lower Mississippi Valley into parts of the Ohio/Tennessee Valleys to the Appalachians and the East. Flash flooding is possible in this pattern, but may be limited by lack of instability, and the location of heavy rainfall causing any flooding/flash flooding is also uncertain. Meanwhile in the cooler air on the backside of the system, wintry weather is likely, with potential for notable snow from central/south-central parts of the Plains and Mississippi Valley northeastward through the Great Lakes and the interior Northeast. Sleet and freezing rain are also possible in the transition zone between rain and snow, but at this point the details of the wintry precipitation remain in flux depending on lower-confidence details of ejecting shortwave energy and frontal waves. Above average temperatures by around 10-15F for highs will spread eastward Tuesday-Thursday across the eastern third of the country with daytime highs generally 15-20 degrees above normal along the East Coast on Thursday. 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 likely. These temperatures may moderate slightly as they shift east into the Ohio Valley/Gulf Coast states next Friday and the East on Saturday, though Texas remains below average through the end of the week. The West Coast states should be near normal through much of next week owing to amplified ridging across the East Pacific. 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, 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