Extended Forecast Discussion NWS Weather Prediction Center College Park MD 310 PM EDT Thu Oct 06 2022 Valid 12Z Sun Oct 09 2022 - 12Z Thu Oct 13 2022 ...Overview... Next week looks to start out with an amplified pattern, with upper troughing over the east-central U.S. and a Canadian surface high creating a cool and dry airmass. Meanwhile an eastern Pacific upper high will extend general ridging into the West, save for a shortwave in the Northwest and another in northern Mexico/southwestern U.S. that should cause continued showers there. The overall pattern becomes more uncertain after energy digs into the western U.S. Tuesday, with model guidance waffling on the evolution of this energy into midweek and beyond. But the current forecast shows troughing progressing into the north-central U.S. with a reasonably strong cold front ahead of it as well as rain chances, while a southern stream upper low may spin into the Great Basin. ...Guidance Evaluation/Predictability Assessment... Model guidance has been and continues to be persistent in showing troughing with its axis across the eastern U.S. early next week. The 00Z UKMET was perhaps a bit of an outlier with the timing of a shortwave within this trough. Models also show good consensus with the general ridge pattern centered in the eastern Pacific and extending into the West Coast, along with better agreement for a shortwave in the Northwest Sun and weak energy over northern Mexico opening into a trough. Thus the early part of the medium range period fronts/pressures forecast was based on a blend of the 00/06Z GFS and 00Z ECMWF and CMC along with a bit of continuity. By Tuesday-Thursday, models have shown considerable changes over the past couple of days with the eventual evolution of potent energy coming into the West. This energy stems from Siberia into the Bering Sea during the short range period, so considering this tends to be an uncertain area for models, more forecast changes may continue over the next few days. After yesterday's guidance indicated a strong upper low was likely to form in the West as most energy dove southward, for the most part the 00Z/06Z model cycle and newer 12Z model cycle shows more of the energy remaining in the northern stream and tracking a trough eastward. The CMC runs have stuck with a closed low type solution, however. Some ECMWF/GFS runs do show a weaker southern stream closed low forming by Wed or Thu, with perhaps some energy tracking south but the aforementioned Northwest shortwave also looks to play a role in forming the low. Thus the WPC forecast trended weaker with the upper low in the West, with a combination of the deterministic models and ensemble means in the forecast blend, and continuing to include some continuity in the forecast blend as well for potential that models could change back. For QPF, this also led to a drier solution than continuity across the Intermountain West per model trends, but wetter and more broad than the 13Z NBM was, as a middle ground. ...Weather/Hazards Highlights... The combination of persistent monsoonal moisture and an upper low evolving into a trough over northwest Mexico will continue to fuel diurnal showers and thunderstorms over parts of the Desert Southwest/southern Rockies through early next week, with the greatest rainfall totals expected for central and southern New Mexico based on latest model guidance. Moisture could stream into the Southern Plains and produce some showers and thunderstorms there as well. Then a strong cold front associated with the western to central U.S. trough will produce rain and potentially some high elevation snow for the northern Rockies around Tuesday-Wednesday, and then moisture and thus rain chances spread into the central U.S. to Midwest/Great Lakes. Elsewhere, light to locally moderate rainfall should spread northward over the Florida Peninsula as easterly low level flow strengthens behind a front. Much of the northwestern U.S. should see above normal temperatures at least through Monday with highs 10 to locally 20F above normal. Recent forecasts show the Pacific Northwest may stay warmer than normal through the week as well if troughing evolves by staying to its east, but areas across the Great Basin/Rockies are likely to cool down, followed by the central U.S. behind a cold front. Highs look to be around 5-10F below normal for those areas, with lows closer to normal. But these forecasts could change as the pattern hopefully becomes clearer with time. The East is likely to start next week with cooler than normal weather and moderate to near normal as the week progresses. Tate 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