Extended Forecast Discussion NWS Weather Prediction Center College Park MD 126 PM EST Mon Mar 07 2022 Valid 12Z Thu Mar 10 2022 - 12Z Mon Mar 14 2022 ...Winter storm threats for parts of the Corn Belt/Great Lakes Thursday-Friday and from the Mid-South to the interior Northeast Friday-Saturday... ...Heavy rainfall likely across portions of the Southeast Thursday-Friday... ...Overview... A strong shortwave in the Great Basin/Southwest early Thursday will bring record cold to some areas of the interior West. This will move into the Mid-South by early Saturday as a northern stream shortwave digs through the Upper Midwest into the Great Lakes. These features will likely combine/interact to support strong cyclogenesis into the Appalachians in a classic spring system featuring snow and cold temperatures to the north/northwest of the surface low with warm/wet conditions ahead of the cold front. By next week, pattern may become quasi-zonal with quieter conditions in the East in the wake of the departing system, with weak/modest systems into the Pacific Northwest. ...Guidance Evaluation/Predictability Assessment... Trend in the guidance for the central/eastern system has been overall slower, favoring more interaction between the northern/southern stream, but with continued differences in how the surface low quickly evolves out of the Lower Mississippi Valley including its track to the northeast. The 06Z GFS was closer to the 00Z ECMWF than its 00Z run, and this agreement carried across to their ensemble means as well, forming the basis for the surface progs. The 00Z Canadian was close to this consensus as well, though it was a little slower with the southern trough and quicker with the northern trough, yielding a weaker system overall. The 00Z UKMET was most outside the consensus as a low probability solution. Overall pattern remains rather progressive despite the rapid deepening of the surface low (a bit characteristic of this winter pattern), but further refinements slower or faster are probable. For next week, deterministic models diverge (rather expectedly) in the quasi-zonal pattern. Trended toward a majority ensemble mean consensus with weaker systems out of the Pacific having lower predictability. ...Weather Highlights/Threats... Showers and thunderstorms should be ongoing by Thursday across the Southeast as a frontal boundary settles over the region with ample moisture and instability present. This boundary should finally become absorbed/pushed east/lift northward with the strong cold front on Saturday. Rainfall will come in waves over the Southeast, some of which could be heavy and flooding/flash flooding may be a threat especially where multiple rounds of convection track over the same areas during the period, despite the dry soil moisture currently that may abate starting just before the medium range period. Troughing in the West will support a multi-wave and dynamic storm system that will first spread snowfall across the Corn Belt Thursday ahead of the strong arctic front to the northwest. As the southern portion of the system develops, cold air will pour through the central Plains and could support rain changing to snow behind the front Friday evening with some accumulation even into the Lower Mississippi Valley. As the surface low rapidly deepens and moves into the interior Northeast, rainfall will surge northward through all of New England with snow, possibly heavy, over the eastern Great Lakes that will move eastward as cold air wraps around the low. Precipitation will be much lighter next week in the Pacific Northwest as well as into the Great Lakes as a clipper system moves through. Arctic-sourced air will bleed through the interior West and spill into the Plains on the backside of the front, with daytime highs 20-30+ degrees below normal as far south as Texas through Friday. Overnight lows across the northern Plains and in higher elevations of the Rockies are likely to be near or below zero for many locations with record lows possible in some locations. Ahead of the cold front, above normal temperatures should spread across the eastern third of the country Thursday and Friday before being replaced by below normal temperatures this coming weekend following the passage of the cold front. Meanwhile, by next week parts of the West and central U.S. may see moderately above normal temperatures as periodic upper ridging slides through. Fracasso/Santorelli 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 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