Extended Forecast Discussion NWS Weather Prediction Center College Park MD 146 PM EST Tue Feb 07 2023 Valid 12Z Fri Feb 10 2023 - 12Z Tue Feb 14 2023 ...Guidance/Predictability Assessment... The latest model guidance provides a general agreement with the large scale pattern through the extended period, however there continues to be struggles with specific details with the embedded systems. Several runs of the GFS of late have been toeing the line of being an outlier, especially with the feature that exits into the Southern Plains and lifts north and east toward the Eastern Seaboard. It has been consistent with developing a closed low/trough that swings trough the South and on the more progressive side of the cluster. It also favors a further northwest placement near the Mid-Atlantic Coast while the rest of the guidance is clustered offshore. A small amount of the 06Z GFS was included in the multi-model initialization but was dropped after day 3. A compromise between the 00Z ECWMF, CMC and UKMET was used for a majority of the extended forecast. The EC ensemble mean and the NAEFS had similar solutions to the preferred trio. The weighting of the means were steadily increased through the middle and latter periods to reduce the amount of spread with the system as it nears the East Coast and track offshore. ...Weather/Hazard Highlights... A complex surface low pressure system will track through the Northeast and the Canadian Maritimes Friday as an upper level trough advances into the southern tier of the U.S.. Meanwhile, the West will continue to having an amplifying ridge in place. With guidance favoring a slower progression there will likely be a lingering heavy rainfall potential along with some risk of runoff issues with repeat/training of cells along a slow moving and Gulf moisture pooling front over the moist soils of the Southeast. High rainfall rates may lead to local areas of flash flooding. WPC has maintained an experimental Day 4 Marginal Risk for excessive rainfall for portions of the Southeast Friday. Meanwhile, cold air draped to the north of the system and cold Canadian air in the wake of system passage will also offer a threat for snow/ice on the northern periphery of the precipitation shield through northern portions of the Northeast and southeast Canada. Lake-enhanced snow and gusty winds will linger into the weekend. The deep upper trough then slated to lift from the Southeast to up the East Coast for the weekend offers moderate coastal low genesis and Atlantic inflow potential to lift enhanced late week rains up the eastern Carolinas/Mid-Atlantic before renewing some mainly interior Northeast weekend snows. Cold fronts passing ahead of the trough in the East should meanwhile lead to a transition from much above normal temperatures through late workweek to near normal conditions for the weekend. While there is a growing guidance signal for the amplification of the overall flow significantly later week across the nation and adjoining oceans, subsequent precipitation re-emergence may otherwise be limited through the weekend. Northern stream shortwave trough passage should support several shots for modest precipitation, mainly for the Pacific Northwest and inland to the northern Rockies. Meanwhile, uncertain eastern Pacific/West Coast upper trough/low amplification in a defining southern stream could lead to modest precipitation southward along the California coast and eventually into the Southwest. But with guidance pointing toward an upper low in the Southwest by around Monday, Gulf moisture streaming ahead of it could renew a rainfall threat in the Southern Plains to Lower MS Valley by Monday-Tuesday. Campbell/Schichtel 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