Extended Forecast Discussion NWS Weather Prediction Center College Park MD 352 AM EDT Thu Oct 13 2022 Valid 12Z Sun Oct 16 2022 - 12Z Thu Oct 20 2022 ...Pattern Overview... An amplified upper-level pattern, with a ridge in the West and a trough in the East will support Autumn-like temperatures across the CONUS. A potent upper low will weaken as it moves into the Southwest from the Baja Peninsula early next week. This weakened upper low may produce heavy rainfall over parts of the Southwest and Texas Gulf Coast through Monday. Deep troughing in the East will produce rain showers and cool temperatures through Tuesday. Some light lake effect snow is possible over the Great lakes. Well below average temperatures are likely over much of the East on the backside of the deep trough. ...Model and Predictability Assessment... Guidance was in reasonable agreement regarding the evolution of the synoptic scale pattern across the lower 48 during the medium range period. A general model blend of predominantly deterministic guidance consisting of the 12z EC/UK/CMC and 18z GFS were used through day 5 before incorporating a majority ensemble mean blend consisting of the 12z ECE/CMC and 18z GEFS. QPF trends suggest a more progressive solution with respect to the heaviest axis of rainfall in the Southern Plains/Southwest early next week. The last several runs of the GFS and EC seesawed 24 hour qpf maxima along the central Texas coast next Monday. The GFS is a bit faster than the EC with the axis of rainfall along the Northeast coast early next week. Some uncertainty exists with respect to the weakening upper low over the Southwest. This will influence rain hazards in the Southern Plains/Texas next week. ...Sensible Weather and Potential Hazards... Heavy rainfall is likely to develop along a surface boundary over the Southwest and Southern Plains Sunday and then focus over central/coastal Texas on Monday. A potent cut-off low, embedded within an amplified upper ridge, will weaken as it moves into the Southwest, but the extent to which it weakens will determine the amount of rainfall that parts of eastern Arizona, New Mexico and southern/central/coastal Texas get on Sunday and Monday. For now, a slight risk of excessive rainfall is in effect over portions of eastern-central Arizona into the big bend of Texas on Sunday. Parts of southeastern New Mexico are embedded within the slight area, but dry soils and a lack of antecedent precipitation may make flash flooding more of a marginal risk. By Monday the flash flood threat shifts into coastal Texas where an upgrade to a slight risk can't be ruled out if models trend a bit higher with qpf to overcome dry soils in the coming days. Meanwhile, shortwaves rotating around a mean upper-level trough will develop a potent surface wave that will generate moderate to heavy rainfall over the Great Lakes and Northeast on Monday and Tuesday. Well below average temperatures and light lake effect snow are possible on the backside of this system as it pushes into eastern Canada. High pressure builds over the Midwest and Southeast in the wake of a cold front, which will all for the flow of cool northerly air to settle over the region. Things quiet down a bit by midweek. The West will experience above average temperatures due to the presence of an amplified ridge next week. Parts of the Northwest will be particularly warmer than normal with highs between 10-20 degrees above average. Kebede 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