Extended Forecast Discussion NWS Weather Prediction Center College Park MD 219 AM EST Tue Feb 07 2023 Valid 12Z Fri Feb 10 2023 - 12Z Tue Feb 14 2023 ...Guidance/Predictability Assessment... Models and ensembles offer a reasonably similar larger scale pattern evolution through med-range time scales, but have been having some difficulties with even the main embedded systems. Overall, the WPC medium range product suite was earlier prepared from a composite blend of then best clustered guidance from the 12 UTC ECMWF/Canadian/UKMET and ECMWF/NAEFS ensemble means Friday/Saturday before replacing the Canadian/UKMET with a more healthy dose of these ensembles Sunday and early next week amid growing forecast spread. As such, forecast spread remains an issue with the progression of an emerging southern stream upper trough tracking from The South to up the East Coast along with a complex surface system reflection. Latest 00 UTC guidance has overall trended slower with progression and that seems generally seems reasonable given southern stream separation. Well upstream, compared to the ECMWF/Canadian/UKMET and ECMWF ensembles that drop along/just off the West Coast, recent GFS/GEFS runs offer more on an inland slider into the West then Southwest closed low with the digging of upper trough energies, but the 00 UTC versions have trended partially westward. Meanwhile, the 12 UTC UKMET and Canadian were mild outliers into next week with more progressive northern stream than the GFS/ECMWF and the bulk of ensembles, but their newer 00 UTC runs have trended more in line. ...Weather/Hazard Highlights... Lead upper shortwave trough ejection through the Northeast will bring a complex surface low/frontal system through the region into the Canadian Maritimes Friday. This will occur as a potent upper trough works down across The South, amplifying downstream of an amplified upper ridge over the West. Guidance has trended slower with this latter feature allowing for 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. Rain rates could be high given the potential for instability to be in place so the WPC experimental Day 4 Excessive Rainfall Outlook (ERO) has collaborated the issuance of a "marginal" risk area from the FL Panhandle/Southern GA to the eastern Carolinas 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. Expect trailing lake-effect snows into the weekend given lingering cold/windy flow. 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. 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