Extended Forecast Discussion NWS Weather Prediction Center College Park MD 245 PM EDT Fri Oct 25 2024 Valid 12Z Mon Oct 28 2024 - 12Z Fri Nov 01 2024 ...Moderate to heavy snow threat increasing for the northern to central Rockies and nearby High Plains Tuesday-Wednesday... ...Moderate to heavy rain threat increasing from the Plains to the Midwest during the latter half of 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... Latest GFS/ECMWF/UKMET/Canadian model guidance seems well clustered through early to middle of next week and enjoys good ensemble and National Blend of Model (NBM) support, bolstering forecast confidence. A composite solution seems to well mitigate lingering system timing differences next week, albeit with favored slow transition from the models to a blend of the NBM and compatible GEFS/ECMWF ensemble means. This holds good WPC product continuity. Timing issues become more noticeable toward the end of next week regarding the next upper trough moving through the Northwest but agreement remains rather good regarding a low pressure wave forecast to track across the Great Lakes toward New England Thursday into Friday. ...Weather/Hazards Highlights... 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 along/behind the front. 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 across the Canadian prairies 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 forecast to anchor across the eastern and southern U.S. Snow will appear to linger over the northern to central Rockies and into the northern High Plains behind a low pressure wave where accumulating snowfall appears likely, especially for the higher elevations of Wyoming Tuesday into Wednesday. Some of the 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 moderate to heavy rain event from the central/southern Plains through the mid-Mississippi Valley and into the Midwest with embedded thunderstorms by midweek next week especially if a low pressure wave is able to consolidate along the front. The front is then forecast to stall across the southern Plains where moderate to heavy rainfall could linger into late next week. In the meantime, precipitation associated with the next Pacific system is forecast to move into the Pacific Northwest through the latter half of 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. Kong/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