Extended Forecast Discussion NWS Weather Prediction Center College Park MD 225 AM EST Tue Nov 08 2022 Valid 12Z Fri Nov 11 2022 - 12Z Tue Nov 15 2022 ...Nicole to impact Florida and the East Coast the second half of this week... ...Overview... A deep closed upper low will be in place across the Upper Mississippi Valley by the start of the period on Friday. This system will be responsible for a potentially significant winter storm affecting parts of the Northern Plains but should be coming to an end largely by Friday. Meanwhile, what is now Subtropical Storm Nicole should be starting to get picked up ahead of the approaching Plains trough by Friday, likely spreading heavy rain up the Eastern Seaboard through Saturday. A rebuilding upper ridge over the Northeast Pacific/northwestern North America will likely yield mean troughing over much of Canada into the lower 48 by the weekend and early next week, along with below normal temperatures over much of the country. ...Guidance and Predictability Assessment... There is good agreement in the overall upper pattern regarding the closed low and surrounding troughing pushing East, but differences in the details pertains to more noticeable concerns on exact low placement by early Friday across the Upper Midwest. The CMC has consistently been weaker and faster with the surface low through the Upper Midwest late week, and was not preferred in tonights blend. However, some of the new 00z guidance also trended towards the CMC. It is too early to tell if this is a new trend or not, but it certainly will need to be monitored. Ahead of this system, guidance continues to show a lot of uncertainty as Nicole enters the medium range period (likely with a more tropical character by this point), with a notable trend west and somewhat faster compared to prior runs (and especially with the new 00z guidance not available at the time of forecast generation). There is good agreement this system will get swept up by the trough from the Plains, but a lot of uncertainty still on timing. Much of the guidance is suggesting a quicker transition up the East Coast, and the previously much slower 18z/Nov 7th GFS has trended faster with its 00z run and closer to the consensus. The WPC QPF for Friday stuck pretty close to the NBM consistent with the latest 03z advisory points from NHC. Out West, models and ensemble members continue to be all over the place for exactly how initial eastern Pacific shortwave energy may split to produce one or more Pacific upper lows/shortwaves (which may or may not reach the West Coast), with the rest of the energy rounding a larger scale mean ridge and dropping into southern Canada and the lower 48. There may also be a southern stream that carries shortwave energy across the eastern Pacific and far southern tier U.S.. Confidence is very low in the details out west beyond as early as day 4. Given these uncertainties, the WPC forecast trended very quickly towards the ensemble means the second half of the period to help mitigate the differences. ...Weather/Hazard Highlights... The significant snowstorm likely to accompany the deepening surface low into the Upper Midwest will largely be coming to an end by early Friday. The exception to this could be some lingering modest accumulations across northern Minnesota and the Upper Peninsula of Michigan on Friday into early Saturday. The greatest threat now for the medium range period will be Nicole as it tracks quickly up the East Coast through Saturday. Coastal and maritime impacts that include coastal flooding, tropical storm force winds, heavy rainfall, rough surf, and beach erosion are possible associated with Nicole near/over Florida and the Southeast. Moisture from this system should move up much of the East Coast into the weekend though with more uncertainty in the amounts and coverage. An approaching cold front will likely help to provide some focused enhancement of rainfall as well. Given trends in the guidance, the day 4 experimental ERO made a significant change from what was yesterdays day 5, with a large slight risk now into much of the Mid-Atlantic and Northeast. Note that this area, especially the eastern/western fringes, remains highly uncertain still and these areas may have to shift or be upgraded in future forecasts depending on rainfall amounts and the track of the tropical system. Expect much of the West/Rockies into the Northern Plains to see below normal temperatures through the first part of next week. The coldest air will likely be across the northern High Plains and Plains Friday-Sunday with highs in that area up to 20-30F below normal. Some locations in the Great Basin may see similar anomalies mainly on Friday. In contrast, well above normal temperatures will be in place along the East Coast Friday although a strong cold front crossing through this region late this week will usher in a much colder airmass this weekend. High temperatures from the Midwest to parts of the interior Mid-Atlantic could be as much as 10 to 20 degrees below normal. The cooler temperatures will also reach the East Coast this weekend, and Sunday-Tuesday look to be near or below normal for almost the entire CONUS. 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 WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml