Extended Forecast Discussion NWS Weather Prediction Center College Park MD 216 PM EST Sat Jan 08 2022 Valid 12Z Tue Jan 11 2022 - 12Z Sat Jan 15 2022 ...Overview... Model guidance indicates that general ridging will prevail over the western U.S. as broad troughing tends to eject disturbances eastward across the northern tiers as well as the Deep South under a split flow pattern. Meanwhile, a closed upper low lingering just off the Southwest will likely play a role in bringing Gulf moisture into the South late next week. Heavy precipitation will edge closer toward the Pacific Northwest Tue/Wed but with the heaviest activities likely over Vancouver Island. ...Guidance/Predictability Assessment... Overall, models show reasonably good agreement in predicting the pattern evolution across the U.S. for the medium-range period, with expected larger spread toward the end of the period. The main issues are with regard to how the lingering upper low off the Southwest should be handled, as well as the speed and amplitude of the next Pacific trough/upper low should approach the West Coast during the latter half of next week. Farther east, there is uncertainty with regard to the speed of the northern stream disturbances as well as how much they phase with the southern stream energy. It appears that the latest ensemble means favor more phasing of the two streams with a pair of low pressure systems tracking through the northern tier states and the Deep South by next weekend. A multi-model/ensemble blend was used to compose this morning's WPC medium-range forecasts. The 06Z GFS was noted to dive too much shortwave energy across the Midwest toward the Southeast next Thu-Fri. It was also too slow bringing in the upper low across the Southwest late next week compared with the rest of the guidance. The 00Z and 12Z GFS were more agreeable in this regard. The 00Z CMC was too aggressive in tracking a frontal wave near/north of the Great Lakes by Day 5 in contradiction with its ensemble mean. The ECMWF remains quite reasonable with its ensemble means through Day 7. Therefore, little to none of the 06Z GFS and 00Z CMC were included in the blend beyond Day 5, with the remaining portion from the 00Z ECMWF/00Z EC mean, the 06Z GEFS, and the 00Z CMC mean. ...Weather Highlights... The Pacific Northwest should see heavy precipitation edging closer ahead of a warm front Tue/Wed. Higher totals are expected over typical upslope areas of the Olympics and Cascades but the heaviest activities will likely be north of the border over Vancouver Island. In contrast, dry conditions with a continued warming trend will likely engulf much of the central and northern Plains. A large surface high will also maintain dry conditions over the Intermountain West. Meanwhile, a closed upper low lingering just off the Southwest will likely move inland and play a role in bringing Gulf moisture into the South late next week. It appears that a swath of wintry precipitation will track across the Great Lakes toward New England by the weekend in association with the northern stream system. Meanwhile, the rain in the South should then spread toward the eastern U.S. where the split flow tends to phase next weekend. Cold air will be in place over the Upper Midwest and into the Northeast on Tuesday, with high temperatures 10-30F below average for one of the coldest days of the season thus far. Then the central U.S. will see a pronounced warming trend next week with expanding coverage of max/min temperatures 10-20F above normal Tuesday onward. Some locations in the northern two-thirds of the Plains may see even warmer readings mid-late week. Across the West expect to see daytime highs within 10F on either side of normal through the period, while above normal lows should become more prevalent with time. By the end of the week temperatures are currently forecast to moderate close to normal. Kong 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