Extended Forecast Discussion NWS Weather Prediction Center College Park MD 205 AM EST Sat Feb 12 2022 Valid 12Z Tue Feb 15 2022 - 12Z Sat Feb 19 2022 ...Mid-late week system to bring potential for heavy rain and severe weather from the south-central to east-central U.S. and wintry weather from the Midwest through Great Lakes and interior Northeast... ...Overview... The dominant focus of the medium range forecast will be on a potent upper low/trough likely centered over northern California/Nevada to begin the period Tuesday, which will track eastward as the week progresses and become incorporated into a Plains/east-central U.S. mean trough by the latter half of the week. This evolution aloft 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. Expect rain and thunderstorms in southern areas, while snow and wintry weather are likely on the northern and western side of the precipitation shield across the central Rockies/Plains and through the Midwest, Great Lakes, and interior Northeast. ...Guidance Evaluation/Predictability Assessment... For the most part, recent guidance remains more agreeable and consistent than average for the medium range period, especially for the early part of the forecast. Consensus has been steady in showing the upper low moving southeastward over the southwest quadrant of the U.S. Tuesday and Wednesday, while downstream, low amplitude ridging broadens and shifts from the central to eastern U.S. The CMC was the main outlier among the deterministic guidance for the 12/18Z cycle, with a weaker and slower upper low system indicated by Wednesday that then affects its forecast downstream for the latter part of the week. This has persisted in the new 00Z cycle for the CMC; it may be notable that the new 00Z ECMWF shows a bit of a pull to the southwest with the center of the upper low early Wednesday as well, but not to the extent of the CMC runs. But for the early part of the WPC forecast, a blend of the 12/18Z GFS, 12Z ECMWF, and 12Z UKMET represented the prevailing themes of the forecast well. Uncertainty and guidance spread/run-to-run variability increase somewhat during the latter half of the period. Contributors to the differences include upstream shortwave energy forecast to drop into and through the West during mid-late week as well as important specifics of northern stream flow that may interact with the leading upper low as it ejects beyond the Rockies/Plains, with some phasing differences. These issues will affect the timing, strength, and track of low pressure as it progresses from near the south-central Plains northeastward after midweek. However, ECMWF and GFS runs have matched fairly well particularly in the upper levels considering it is a day 5-7 forecast. 12/18Z GFS runs were a bit northwest of the preferred solution of the ECMWF and ensemble means with the surface low track Thursday-Friday, but the 00Z run appears to have come into better agreement with the low track. Including some GEFS and EC ensemble mean input by days 6-7 Friday-Saturday accounted for the gradual increase of uncertainty and provided good continuity from the previous forecast, with perhaps just a slightly faster track of the main cold front and precipitation forecast and a slightly stronger low indicated over the Northeast early Friday. ...Weather Highlights/Threats... Underneath the upper low/trough over the West early in the week, some light to moderate precipitation in the form of lower elevation rain and mountain snow is expected for California into the Great Basin and into the Northern Rockies, increasing in the Central Rockies on Wednesday. Showers and thunderstorms will become more widespread over the central U.S. by Wednesday into Thursday as surface low pressure 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 Appalachians and Eastern Seaboard. Strong storms are possible, with the Storm Prediction Center outlook showing some severe threat for parts of the southern Plains into the Lower Mississippi and Tennessee Valleys and vicinity on Wednesday and Thursday. There could also be flash flooding concerns where heavy rainfall occurs, possibly in similar regions and into the Southern Appalachians. Continue to monitor forecasts as uncertain details of these potential threats become better refined. At the same time, expect a band of snow in the colder air on the northwestern periphery of the system. The best potential for meaningful accumulations currently extends 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. Totals/location of any snow will be very sensitive to precise strength and track of the system. Strong winds may be possible in the gradient between the surface low and high pressure to the northwest, and then possibly along parts of the East Coast within the southerly flow ahead of the storm. The change and progression of the overall pattern will be evident in temperatures over the course of next week, as warmer than average temperatures push eastward through the workweek ahead of the trough/frontal system and cooler temperatures spread behind the cold front. Highs of 10-20F above average and lows 15-30F above normal will be shunted from the Plains on Tuesday into the Mid-Mississippi and Ohio Valleys (while persisting in the Southern Plains) on Wednesday, then into the Eastern Seaboard on Thursday. On the backside of the front, temperatures should flip to near to below average, first over the West and spreading to the Rockies, Plains, and Midwest Wednesday and Thursday before tracking into the eastern third of the country for the latter part of the week while moderating. Parts of the West and into the Plains are expected to warm up above average once again by the end of the week. Tate/Rausch 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