Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Wed Oct 12 2022 Valid 12Z Sat Oct 15 2022 - 12Z Wed Oct 19 2022 ...Pattern Overview... A more active fall weather pattern is expected to remain in place through the upcoming weekend and beyond as a couple of cold fronts associated with an Eastern U.S. amplifying upper level trough (and embedded shortwaves) move across the central and eastern states. The first cold front will have exited the East Coast before Saturday with rain exiting eastern New England, and lake effect precipitation behind it. By Sunday and into Monday, a second cold front dropping southward from Canada is expected to reinforce the cool airmass across the eastern half of the nation and will last into early next week. The opposite is expected to be the case across the West Coast region as an upper ridge brings a period of well above normal temperatures from California to the Pacific Northwest as summer tries to hang on a little longer. ...Model and Predictability Assessment... The synoptic scale pattern has very good overall agreement and this also holds true for run-to-run model consistency over the past few runs. The main model differences through Monday reside across Ontario and the northern Great Lakes with the overall orientation of the main upper low, but the broad cyclonic flow pattern is in excellent agreement. The models are also hinting at another potential closed low developing off the California coast by next Wednesday. Given the lower predictability elements within the more confident mean pattern, the updated forecast started with an operational model composite for about the first half of the period and transitioned to a model/mean blend thereafter. In terms of QPF, amounts were raised from the NBM across the Great Lakes to better account for lake effect precip and increased light amounts in other parts of the east-central U.S. to account for the typically low NBM bias for such amounts and intermediate frontal timing. ...Sensible Weather and Potential Hazards... Periods of lake enhanced rain and snow showers are likely across the Great Lakes for the Friday through Saturday time period. Showers could become more widespread Sunday into next week with another frontal system and trailing cold cyclonic low level flow. Timing differences in the guidance for this latter front keep confidence more in check for rainfall amounts/coverage over the eastern U.S. early next week. Meanwhile showers and thunderstorms are forecast to increase in coverage over Arizona and New Mexico by Saturday, and then into Texas from Sunday into early next work week, as the upper low tracking into the region from the Pacific advects copious moisture out to its east. A coordinated Slight Risk for excessive rainfall for Day 5 is now in effect for southern New Mexico and southwestern Texas. There has been a trend for heavier rainfall in the latest model guidance across central and southern Texas going into Monday/Tuesday as deep moisture converges near a frontal boundary. Much of the northwestern U.S. as well as northern California into parts of the Great Basin should have above normal temperatures each day with the upper ridge anchored over or near the region, with some highs reaching 10-20 degrees above normal, making it feel more like early September for many areas. To the contrary, a series of fronts pivoting around the main eastern upper trough/closed low will bring progressively colder temperatures to areas east of the Rockies. The coolest anomalies (up to 10-20F below normal) should extend from the Upper Midwest into Great Lakes and Ohio Valley for several days as the upper trough persists. The southern Plains and vicinity will be warm through Saturday but then this region will trend cooler as rainfall spreads across the region. Hamrick/Rausch 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