Extended Forecast Discussion NWS Weather Prediction Center College Park MD 157 PM EST Wed Nov 09 2022 Valid 12Z Sat Nov 12 2022 - 12Z Wed Nov 16 2022 ...Heavy rains from Nicole may continue across parts of the Northeast into Saturday... ...Overview... What is left of Nicole by the start of the medium range period should get picked up by an amplified upper trough moving in from the Midwest. This should help to lift the heavy rainfall from Nicole away from the CONUS by Saturday, aside from perhaps some lingering heavy rain over the Northeast. Otherwise the large scale pattern will feature an amplifying upper ridge over the Northeast Pacific/northwestern North America, promoting broad cyclonic flow and below normal temperatures over much of the lower 48 through at least the middle of next week. Confidence in embedded details is still on the lower side, with particular focus on an upper shortwave/surface system that could spread precipitation of varying types over parts of the central/eastern U.S. in the early-mid week time frame. ...Guidance and Predictability Assessment... The guidance still shows good agreement in principle but locally meaningful detail differences for the eventual absorption of Nicole by the approaching trough/surface front by the start of the medium range period on Saturday. Behind the supporting trough crossing the East, models and ensembles continue to vary for individual features within the overall cyclonic flow covering much of the the lower 48 and southern Canada. At least for the moment though, most of the 00Z/06Z guidance developed some degree of clustering. Currently the primary features of note should be an upper low moving into Oregon/Nevada and shortwave dropping into the northern tier during the weekend. By Monday-Wednesday upstream flow may feed into the northern trough and splitting Pacific energy may drop into the Northwest, sinking southward with time. Meanwhile the majority cluster shows the initial western upper low crossing the southern Rockies around early Monday and then opening up as it accelerates to the east-northeast. GFS runs have been waffling with respect to how much phasing may occur between the northern tier trough and ejecting southern feature, with 00Z/12Z runs more aggressive in that regard (and more inland at the surface) than the 06Z run that compared better to the 00Z ECMWF/CMC as well as the ensemble means (with early day 7 Wednesday surface low pressure near the East Coast). This majority cluster also compared reasonably well for the elongated trough forecast to drop through the West next week. Not surprisingly, new 12Z runs show some significant differences/changes for both the western energy and evolution over the eastern half of the country. This includes the ECMWF shifting to a more phased solution east of the Rockies next week. Based on the 00Z/06Z array of guidance, the updated forecast employed a blend of the 06Z GFS/00Z ECMWF and lesser input of the 00Z CMC/UKMET through about the first half of the period and then incorporated some of the 06Z GEFS/00Z ECMWF means. The refinement of shortwave details has yielded some noticeable continuity changes, including better definition of waviness along the Gulf/East Coast regions late in the period (which still has potential to be stronger and more inland). ...Weather/Hazard Highlights... Heavy rainfall across the Northeast associated with Nicole should be in the process of lifting out during the day Saturday. The trailing upper trough crossing the East along with cool low level cyclonic flow will support some lake effect snow within the typical snow belts over the upper and lower Great Lakes, mainly during the weekend and early next week. The West may see some light precipitation accompanying the upper low expected to track from Oregon southeastward this weekend. Latest consensus is maintaining stronger definition of this feature as it opens and continues east-northeast from the southern Rockies early-mid week, leading to more surface waviness from the Gulf Coast to East Coast. This yields broader coverage of precipitation from the southern half of the Plains through the East. Rain could be locally heavy along the Gulf Coast and it will be possible for some wintry precipitation to exist in the northern fringe of the moisture shield. It will take additional time to resolve important system details that will determine the coverage/intensity/type of precipitation. Below normal temperatures already in place to the west of the Mississippi River as of early Saturday will extend through the East during the weekend. Broad upper troughing in response to the strong ridge offshore the West Coast should keep the cold pattern in place through midweek, and likely beyond per the Climate Prediction Center week 2 forecast. The coldest air should be over parts of Montana and the Dakotas Saturday-Monday with some readings at least 20-30F below normal, including locally subzero morning lows. Some of the cold air will push into the central/southern Plains by Monday-Wednesday, bringing highs down to 15-20F or so below normal. Coldest anomalies over the West should tend to be over the Great Basin with multiple days of highs 10-25F below normal. Above normal temperatures along the immediate East Coast on Saturday should quickly give way to highs 5-15F below normal over much of the East thereafter. Maine and Florida could be exceptions with near to slightly above normal temperatures. Rausch/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