Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Sat Oct 26 2024 Valid 12Z Tue Oct 29 2024 - 12Z Sat Nov 02 2024 ...Heavy snow and wind threat for the north-central Rockies and nearby High Plains Tuesday-Wednesday... ...Heavy rain threat for the Plains/Midwest mid-later next week... ...General Overview... An amplified upper-level trough set to dig into the West this weekend will spread highly unsettled weather across much of the western U.S. early next week to include high-elevation snow, gusty winds and colder temperatures. This trough will then push eastward against a warm and expanding upper ridging over the central to eastern U.S., resulting in a wavy sharp front across the mid- section of the country where a moderately heavy rain event appears to emerge from the Plains through the Mississippi Valley and Midwest for the latter half of next week. ...Guidance/Predictability Assessment... Forecast spread seems lower than normal Tue/Wed and a guidance blend seems to offer a solid forecast base. Model differences grow Thu into Fri with 12/18 UTC GFS runs outliers with slower bringing of Pacific system energy inland into the West. ECMWF/GEFS/Canadian ensembles support a solution closer to best clustered guidance of the more preferred 12 UTC ECMWF/Canadian. However, subsequent Pacific system energy into next weekend may dig more robustly into the West than the ECMWF/Canadian given upstream upper ridge amplitude. This solution is championed by the machine learning 18 UTC AIFS and GEFS mean that were mainly utilized at this long time frame. Latest 00 UTC model runs have overall trended favorably. ...Weather/Hazards Highlights... Guidance has been consistent that a cold front associated with a digging upper level trough from the Pacific will be steadily moving through the western U.S. early next week. Periods of rain, high elevation snow, windy and colder conditions are expected to overspread much of the region with frontal passage. Locally high winds could impact portions of the southern Rockies and southern High Plains as the colder airmass digs into the region. This may also lead to the onset of frost/freeze for some of these areas for the first time this season. Modest cyclogenesis will advance a front across the northern Plains and upper Midwest through early next week. This front is forecast to sharpen with time as it continues to push against an expansive high pressure system across the eastern and southern U.S. Snow will linger over the northern to central Rockies and into the northern High Plains behind a low pressure wave, especially for the higher elevations of Wyoming Tuesday into Wednesday given upper divergence and lower level upslope flow. Accumulating snow could spill into the nearby High Plains and Black Hills as well. Ahead of the sharpening front, a long fetch of return flow from the Gulf of Mexico appears to initiate and support a threat of heavy rain from the central/southern Plains through the Mississippi Valley and into the Midwest with embedded thunderstorms emerging midweek, with lingering focus holding back over the southern Plains where moderate to heavy rainfall could linger into late next week. The WPC Day5/Wed Excessive Rainfall Outlook introduced a Marginal Risk area given potential for training and favorable upper trough and right entrance region jey dynamics. In the meantime, precipitation associated with the next Pacific system and long fetch moisture is forecast to re-focus moderate precipitation into the Pacific Northwest through latter next week, with high- elevation snow reaching into the northern Rockies. The digging trough in the West will usher in and sustain colder than normal temperatures for pretty much the entire western U.S. through late next week. In contrast, high temperatures reaching into the upper 80s to lower 90s will challenge some daily records across the southern Plains to the mid-South early next week. The expanding upper ridge together with a long fetch of strong and gusty southerly winds at the surface will send the warmth well to the north and east, reaching into the Great Lakes and eventually New England through the middle and late next week. High temperatures reaching well up into the 70s to near 80 degrees will be enough to set some new daily record high temperatures from the Great Lakes to New England Wednesday and Thursday. Schichtel 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 forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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 https://www.wpc.ncep.noaa.gov/#page=ovw