Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Mon Mar 07 2022 Valid 12Z Thu Mar 10 2022 - 12Z Mon Mar 14 2022 ...Winter storm threat for parts of the Midwest on Thursday-Friday, with heavy to excessive rainfall likely across the Southeast... ...Overview... A shortwave digging south through the interior West as the medium range period starts Thursday will amplify troughing across the central U.S. and shift east with time, exiting the East Coast by Sunday. This will push a strong arctic boundary south across the Plains and then the East as an area of low pressure develops and deepens through the Midwest and Northeast Friday and Saturday. A swath of snow is expected to the northwest of the surface low, potentially heavy rainfall across parts of the East ahead of the front, and a chilly arctic airmass engulfing much of the central and eastern U.S. to follow. By early next week, flow across the CONUS should become a little more zonal as weak systems move through the northern tier states, though the next trough may develop across the central U.S. by next Monday. ...Guidance Evaluation/Predictability Assessment... In general, the model guidance continues to show reasonable agreement for the large scale pattern across the CONUS, but with plenty of uncertainty in timing and details of features. The most impactful differences surround the amplified trough into the Plains and East Friday-Saturday. The 18z/Mar 6 (and todays new 00z) run of the GFS continues to be quite a bit faster with trough axis and frontal placement, although an ever so slight slower trend is noted with the last few runs. Meanwhile, the 12z/Mar 6 ECMWF (with support from its ensemble members) was the slowest of the solutions, however the 00z run today did come in a little faster. Both the CMC and UKMET were more in the middle of these two camps, and probably the best proxy for the overnight medium range progs which are a hair slower than previous WPC continuity. The next shortwave hits the Pacific Northwest by Sunday, and there's pretty good agreement on this, but the CMC is a little slower. Beyond day 5, preferred a solution closer to the ensemble means to help mitigate these later period differences which will take time to resolve anyways. ...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/push east with the strong cold front on Saturday, but not before several days of widespread rain. At least locally heavy rainfall is a concern, and flooding/flash flooding may be a threat with heavy downpours, especially where multiple rounds of convection track over the same areas during the period, despite the relatively dry antecedent conditions. Meanwhile, low pressure spinning up in the lee of the Rockies and lifting into the Upper Midwest Thursday-Friday brings a winter storm threat from the central Plains to the Upper Midwest, with less certain wintry impacts into the Ohio Valley and interior Northeast Friday and Saturday. The elongated upper trough should tap Gulf of Mexico moisture with widespread rain into much of the East ahead of the cold front on Friday. The next system coming into the Northwest next weekend is likely to increase rain and mountain snow chances across the Pacific Northwest and northern Rockies as well. Arctic sourced air will 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. 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 next weekend following the passage of the cold front. Meanwhile, parts of the West and central U.S. next Sunday-Monday may be moderately above normal as upper ridging slides overhead. 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