Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 PM EDT Wed Oct 12 2022 Valid 12Z Sat Oct 15 2022 - 12Z Wed Oct 19 2022 ...Pattern Overview... Expect a more active fall weather pattern to remain in place over many areas through the upcoming weekend and next week as a couple of cold fronts associated with an amplifying Eastern U.S. upper level trough (and embedded shortwaves) move across the central and eastern states. There may also be some degree of low pressure development in the vicinity of New England/southeastern Canada early-mid week. Trailing colder cyclonic flow will support periods of lake effect precipitation that may include snow by next week. Meanwhile the moisture ahead of an upper low tracking into the Southwest will produce an area of moderate to heavy rainfall across parts of Arizona/New Mexico/Texas from the weekend into early next week. In contrast to the increasingly cold pattern over the East, summer will try to hang on a little longer over the Northwest where temperatures should remain well above normal through the period. ...Model and Predictability Assessment... Within the agreeable large scale pattern, the primary differences involved the upper trough/low and surface system reaching the East during the latter half of the period (GFS on the fast side but a bit less extreme in the new 12Z run, while the ECMWF has nudged a bit faster than runs from a day or so ago) along with timing of the Southwest upper low and its eventual weakening (GFS faster than the majority, including the GEFS mean, though even the 00Z ECMWF was a little faster than the GEFS/ECens). GFS/ECMWF runs and their means are similar for the upper low that settles offshore from California late in the period after splitting of initial trough energy. The CMC has been a western extreme with this feature. The northern portion of the original shortwave should bring a system into south-central Canada/northern tier U.S. around midweek with typical spread for specifics. The updated forecast maintained the approach of starting with an operational model composite for about the first half of the period and transitioning to a model/mean blend thereafter. This reflected a lean away from GFS specifics where the model agreed the least with consensus. In terms of QPF, amounts were again 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... The heaviest rainfall during the period will likely extend from Arizona/New Mexico into southern Texas, with the upper low tracking into the region from the Pacific advecting copious moisture out to its east. Interaction of the deep moisture with a couple fronts pushing southward across the southern Plains may serve to enhance amounts. The current issuance of the experimental Day 5 Excessive Rainfall Outlook maintains a Slight Risk area over southern New Mexico and southwestern Texas, with modest expansion of the Texas portion to incorporate latest guidance forecasts and fairly high soil moisture. Note that there is still some spread for the exact axis of heaviest rainfall, due in part to differences in timing of the upper low and when it weakens. Elsewhere, the leading front pushing through the central/eastern U.S. during the weekend may support some locally moderate to heavy rain from the south-central Plains into parts of the Ohio/Tennessee Valleys, with the front possibly beginning to tap some of the moisture emerging from the Southwest. Eastern portions of this region should see some rain in the short term but overall dry ground conditions should mitigate effects from any heavier bands of rain. This area could still merit monitoring, depending on how shorter term models cluster for such bands. Periods of lake enhanced rain and snow showers are likely across the Great Lakes, possibly becoming more widespread Sunday into next week with another frontal system and trailing cold cyclonic low level flow. The proportion of snow relative to rain will likely increase somewhat with time as colder air reaches the East. Continued spread for timing/evolution of potential low pressure over New England/southeastern Canada next week tempers confidence in precipitation details over that area. 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. The best chance for a few scattered daily record highs will be over the Pacific Northwest during the weekend. 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. Coolest anomalies during the weekend should be over the Upper Midwest and Great Lakes with highs up to 10-15F below normal. A more impressive southward/eastward surge of colder air will spread a broad area of temperatures 10-20F or so below normal across the eastern half of the country Monday-Wednesday. The southern Plains and vicinity will be warm through Saturday but then this region will trend cooler as rainfall spreads across the region and drops highs to 10-20F below normal for multiple days. Rausch/Hamrick 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