Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 PM EST Thu Nov 10 2022 Valid 12Z Sun Nov 13 2022 - 12Z Thu Nov 17 2022 ...Overview... An amplified upper trough over the East on Sunday should lift out by Monday with some weak ridging returning early next week over the far Southeast/Bahamas. Meanwhile, a strong and blocky ridge over the Eastern Pacific will favor cyclonic mean flow aloft across most of the lower 48 during the period, with embedded shortwaves/upper lows dropping into the CONUS. This pattern should lead to below normal temperatures over much of the country through next Thursday and likely beyond. 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. Other areas of precipitation will also be possible over parts of the northern tier, Rockies, and late in the period over the southern tier. ...Guidance and Predictability Assessment... There continues to be fairly high confidence/predictability for the large scale pattern, but with lower confidence in the embedded smaller scale features that have lower predictability. Over recent days guidance has varied for how much interaction may occur between a trough/upper low reaching the northern tier by Sunday and the upper low forecast to track from the Great Basin through southern Rockies/High Plains Sunday-Monday. Sporadic GFS/ECMWF runs have been phasing the two, leading to a more inland surface evolution over the East by Tuesday-Wednesday. On the other hand the CMC, remaining GFS/ECMWF runs, and the ensemble means have been keeping the two features separate. That majority scenario yields low pressure along the East Coast by Wednesday (but still the possibility of a weak surface reflection over the Great Lakes in response to the northern stream dynamics). Latest GFS runs have actually switched to the most suppressed side of the envelope for the East coast surface pattern. Preference sided with the majority cluster, essentially a slightly weaker version of the 00Z ECMWF, as solutions diverge after early Tuesday. This maintains good continuity. The next feature of interest is a trough/possible embedded low dropping southward through the West during early-mid week. A fair amount of detail spread develops already by Monday with differences continuing onward with time. The 00Z ECMWF offered the most notable difference from most other guidance, showing less southwestward amplitude versus other models and ensemble means (including the ECens), due to the model pulling off an upper low that stays just off the West Coast for multiple days. By day 7 Thursday this difference leads the 00Z ECMWF to be much drier across the southern tier than most other models and means. The new 12Z ECMWF has trended somewhat closer to consensus. Also by next Thursday the models/means suggest another east-west oriented shortwave may reach down close to the western U.S.-Canadian border. A model-mean blend is reasonable to depict this feature while accounting for detail uncertainty. This cycle's consideration of 00Z/06Z guidance led to starting the updated forecast with a 00Z/06Z model composite (06Z GFS favored over the 00Z run) early in the forecast and then transitioning to a combination of operational models and means (06Z GEFS/00Z ECens and CMCens). 00Z ECMWF question marks over the West after early day 3 led to lower weight of its solution than would sometimes be the case. In addition to the eastern U.S. pattern next week, the preferred solution also provided good continuity with most other aspects of the forecast. ...Weather/Hazard Highlights... An 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 early in the week. The upper low tracking from the Great Basin into the southern Rockies Sunday-early Monday may produce scattered light precipitation. This feature should then open up but its continued progression may promote some surface waviness from the Gulf Coast to East Coast, with an area of precipitation extending from the southern half of the Plains through portions of the East. Rain could be locally heavy along the west-central/central Gulf Coast and it will be possible for some wintry precipitation to fall in the northern fringe of the moisture shield. Confidence remains below average for the specifics of precipitation coverage, intensity, and type. Trailing energy dropping through the West may push one or more areas of mostly light snow southward over the Rockies/High Plains. Toward next Thursday enough of this energy may emerge from the West to support increasing precipitation over the southeast quadrant of the lower 48. Northern tier dynamics may also generate areas of light snow between the Plains and Great Lakes. Broad upper troughing in response to the strong ridge offshore the West Coast should keep a cold pattern in place Sunday-Thursday, and likely beyond per the Climate Prediction Center 8-14 day forecast. The coldest air relative to normal should be over parts of the Great Basin and Plains where multiple days with highs 15-25F below normal are likely. Over the Plains, northern locations will be most consistently cold from the start of the period while central/southern areas will see the coldest anomalies settle in Monday onward. Maine, Florida, and the Pacific Northwest coast have the best chance to be the 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