Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1200 PM EDT Mon Oct 21 2019 Valid 12Z Thu Oct 24 2019 - 12Z Mon Oct 28 2019 ...Guidance/Uncertainty Assessment and Weather Highlights/Threats... Guidance agrees that the active flow pattern will reload over the cooling/unsettled West Wed/Thu as digging upper impulse/jet energies support some enhanced Rockies snows. Height falls should then act to carve out an amplified central U.S. upper trough later week. Pattern evolution uncertainty grows quickly thereafter, resulting in low forecast confidence for the southern and eastern U.S. Guidance continues to indicate two possible scenarios by this weekend: (1) A more amplified upper trough draws in deep moisture from the Gulf and results in a low pressure system that spreads heavy rainfall well inland, as represented by ECMWF/UKMET and CMC solutions; or (2) less flow separation between the northern and southern streams will keep a cold front moving steadily across the southern and eastern U.S., as represented by recent GFS runs. Overall, the operation models that indicating scenario 1 show a trend toward a slower eastward progression regarding the subsequent ejection of the amplified upper trough. The UKMET is hinting at a tropical low center lingering off the Texas coast as the upper trough approaches. The GEFS/EC/CMC ensembles are mixed, with ECMWF ensembles showing scenario 1 but with highly variable forward motion of the associated upper-level shortwave. WPC progs modestly lean the forecast to show such potential. This considers upstream upper ridge amplitude and as the next main upper trough does not bring renewed cooling with enhanced precipitation/mountain snows through the Northwest then Rockies until next weekend, so wavelength spacing with the downstream system seems sufficient to allow for at least some southern stream separation. The new WPC prognostic charts now show a less prominent frontal wave moving across the Southeast during the weekend compared with previous progs. Schichtel/Kong Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml