Extended Forecast Discussion NWS Weather Prediction Center College Park MD 157 AM EST Fri Feb 11 2022 Valid 12Z Mon Feb 14 2022 - 12Z Fri Feb 18 2022 ...Precipitation chances increase mid- to late next week, with heavy rain from the south-central to east-central U.S. and wintry weather possible in the Midwest to interior Northeast... ...Overview... Expect a significant pattern change next week, as a potent upper low drops southeastward along the West Coast early in the workweek and develops into a trough pushing into the central U.S. by the latter half of the week. This upper pattern will lead to surface cyclogenesis and strong frontal systems in the central U.S., drawing moisture northward from the Gulf of Mexico and producing notable precipitation from the Plains eastward next Wednesday into Friday. Rain and thunderstorms are forecast in southern areas, while snow and wintry weather are likely on the northern and western side of the precipitation shield across central parts of the Plains to Midwest/Great Lakes and interior Northeast. ...Guidance Evaluation/Predictability Assessment... Model guidance from the 12/18Z cycle is quite agreeable with the large scale pattern early in the week with the aforementioned upper low moving through the West, especially considering its origins over the Gulf of Alaska. Additionally, models agree in principle that troughing in the East will lift and the ridging across the West during the short range period should get pushed eastward into the central U.S. around Tuesday and the East on Wednesday while flattening somewhat. Thus a multi-model blend of the 12Z ECMWF, CMC, UKMET, and 12/18Z GFS was utilized early in the medium range period for the WPC forecast. Around Wednesday into Thursday of next week is when greater differences appear to arise, as additional shortwave energy rounds a Pacific ridge earlier in the week and then enters the Northwest around Wednesday. This shortwave and those farther north into Canada show more variability from run to run and between models in their evolution. The 12/18Z GFS and 12Z ECMWF runs showed reasonably similar solutions as each other, with shortwaves in the Southwest and in the southern High Plains within the broader trough early Thursday, while the 12Z CMC indicated a more phased solution with the shortwave tracking east joined with the northern stream. Individual ensemble members show considerable variability with the details, and 00Z guidance still demonstrates these shortwave differences. The exact track and timing of the trough and shortwaves within it will also affect the position of the cold front and associated surface lows. However, the overall pattern is still reasonably agreeable for a day 6-7 forecast. The WPC forecast introduced and increased the proportion of the GEFS and EC ensemble means for days 6-7 of the forecast to minimize individual model differences. ...Weather Highlights/Threats... As the upper low/trough enters the western U.S. Monday, precipitation chances will increase across the West, with coastal/lower elevation rain and mountain snow, but totals should remain light to moderate there. However, widespread showers and thunderstorms are likely to develop by Wednesday into Thursday as the surface low consolidates in the High Plains and advects substantial moisture from the Gulf of Mexico northward into the Plains, Mississippi/Tennessee/Ohio Valleys, and eventually the Eastern Seaboard. Strong storms could be possible along with flash flooding concerns where heavy rainfall occurs, but with uncertainty in the details of these potential threats at this point. In the colder air on the northwestern periphery of the system, accumulating snow is currently expected from central parts of the Plains into the Middle Mississippi Valley and Midwest/Great Lakes region into interior New England, while mixed precipitation/ice cannot be ruled out in the transition zone between the snow and rain. The overall pattern change will be evident in temperatures next week as well. Warmer than average temperatures across the Central Great Basin and Southwest Monday will moderate to near normal Tuesday and Wednesday underneath the incoming trough. Meanwhile the central U.S. should see high temperatures 10-20F above normal with lows 15-25F above normal Wednesday before these anomalies shift east ahead of the trough and cold front into the Tennessee and Ohio Valleys Thursday. The Eastern Seaboard can expect colder than average temperatures by 10-20 degrees on Monday before moderating as the week progresses to much above normal by Friday. 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