Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 PM EST Thu Jan 27 2022 Valid 12Z Sun Jan 30 2022 - 12Z Thu Feb 03 2022 ...Overview... By the start of the medium range period early Sunday, the deep system tracking just off the East Coast late this week into the weekend should reach a position east or northeast of Maine, still supporting some strong winds even if precipitation tapers off. This storm will continue moving rapidly away from New England during the day Sunday. For information on the storm's effects before early Sunday consult the WPC website for updated Key Messages and check your local forecast at weather.gov. Through the rest of the period, the dominant theme will be a significant pattern change as an upper trough strongly amplifies from the northeastern Pacific into the western/central U.S. while a strong ridge builds and then persists over the eastern Pacific, and another ridge crossing the East Coast Tuesday settles over the western Atlantic thereafter. This evolution will initially spread precipitation across the West and then likely produce significant precipitation farther eastward as a leading front interacts with a strong flow of Gulf moisture, with the possibility of wintry weather on the backside of the front. Ahead of the trough, a southern stream shortwave/upper low may generate some enhanced rainfall along/north of the Gulf Coast around Monday. ...Guidance Evaluation/Predictability Assessment... An operational model blend early in the period favoring the 00Z/06Z GFS and 00Z ECMWF and CMC followed by a transition toward about half the total weight of 06Z GEFS/00Z ECMWF means continued to provide a good representation of consensus ideas, with mainly just typical run-to-run detail changes versus previous cycle. For the storm producing lingering effects over New England, there are still meaningful differences in the short range due in part to fine-scale issues with the supporting upper low, so there is still a fair amount of uncertainty over the exact location/structure of the storm as of early Sunday. Overall the latest GFS/GEFS mean continue to be on the faster side and the ECMWF/ECMWF mean are slowest, conforming to long-historical tendencies. Meanwhile guidance continues to consolidate for the handling of the southern stream shortwave/upper low emerging from the Southwest, with the 00Z UKMET straying faster than most other solutions. This feature should rapidly shear out beyond the Plains. Farther west, there are still differences in how some energy pulls off from the southwestern part of the shortwave approaching the West Coast Sunday but now with less pronounced spread than in previous cycles. As the larger scale upper trough digs into the western/central U.S. Tuesday-Thursday, the ensemble means and a multi-run average of operational runs suggest above average predictability for the large-scale feature while individual members/model runs show embedded detail uncertainties. Examples of the latter include to what degree flow may separate near the Four Corners region around Wednesday and the character of upstream energy dropping into the mean trough by Thursday. GFS runs have been persistent with a stronger feature for the latter compared to the ECMWF runs, and these differences do affect the width of the troughing as well as the axis somewhat, and the timing of the surface cold front pushing ahead of the trough. The blend of deterministic and ensemble guidance used for the end of the period worked as a compromise at this point. ...Weather Highlights/Threats... Expect strong winds over New England at the start of Sunday to moderate over the course of the day as strong low pressure tracks rapidly away from the region. Otherwise the effects of the initial storm will be in the short range. See the WPC website for latest Key Messages on the system and additional information in the Probabilistic Heavy Snow and Icing Discussion, plus check your local forecast at weather.gov. The upper trough/low reaching the Southwest by early Sunday should produce little if any precipitation over that region. However, as the feature continues eastward, there will be some potential for locally moderate to heavy rainfall from eastern Texas across parts of the Gulf Coast region during the first half of the week. Best potential at this time appears to be over eastern Texas with lower confidence in details farther east. Some aspects of this event may hinge on small-scale details not easily resolved very far in advance. The northeastern Pacific upper trough digging into the West Sunday-Tuesday will spread moderate amounts of rain and mountain snow from the Pacific Northwest eastward and southeastward into much of the Rockies. Highest totals are likely to be in the Pacific Northwest but should not be too extreme. In general the forecast remains on track for a significant increase of coverage and intensity of precipitation over the east-central U.S. by Wednesday-Thursday as the upper trough emerges from the Rockies and the leading cold front interacts with a strong low level feed of Gulf moisture. At this time the best potential for heaviest rainfall extends across the lower half of the Mississippi Valley into parts of the Ohio/Tennessee Valleys. Wintry weather will be possible on the northwest side of the moisture shield, with at least some potential for meaningful snow from the central/south-central Plains northeastward through the Great Lakes. While confidence in a heavy rain area appears better than average, details with the wintry precipitation in the colder air may be more dependent on lower-confidence details of ejecting shortwave energy and frontal waves. Cold conditions near the East Coast will extend through Sunday with many areas 10-20F below normal. Subfreezing lows should extend into portions of Florida and parts of the Florida Peninsula may challenge daily records for both morning lows and daytime highs. Much of the Plains will see above normal temperatures Sunday into the first part of next work week, with some northern/central areas possibly seeing plus 20F or greater anomalies on one or two days. This warm air will progress into the eastern half of the country Tuesday-Thursday, bringing a broad area of temperatures 10-20F above normal and perhaps greater anomalies for lows over the Northeast by Thursday. Also during Tuesday-Thursday much of the West and then into the Plains will see an episode of chilly temperatures with the Rockies and Plains seeing the best potential for readings 10-20F below normal. Rausch/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