Extended Forecast Discussion NWS Weather Prediction Center College Park MD 154 AM EST Wed Feb 19 2025 Valid 12Z Sat Feb 22 2025 - 12Z Wed Feb 26 2025 ...Wet Pacific Northwest pattern this weekend/early next week... ...Overview and Guidance/Predictability Assessment... Recent guidance has offered a reasonably similar larger scale flow evolution over the next week, albeit laden with numerous smaller scale embedded system differences that often do not have good cycle to cycle continuity. Moderate progression of these individual shortwaves aloft in split streams over the lower 48 this week is still expected to lead an evolution toward a larger scale mean upper pattern highlighted by a western ridge and eastern trough positions by the start of next week. This transition will bring the best potential for meaningful precipitation to the Pacific Northwest from the weekend into early next week, along with a pronounced warming trend from west to east over the lower 48. Accordingly, the WPC medium range product suite was mainly derived from a composite blend of the generally compatible 18 UTC GEFS mean and 12 UTC ECMWF/Canadian ensemble means through medium-range time scales. While predictability for flow embedded weather features is below normal, the broader overall solution offers reasonably good continuity and messaging in line with the 01 UTC National Blend of Models and favorable 00 UTC guidance trends. ...Weather/Hazards Highlights... An impressive Arctic airmass has settled over the central and eastern U.S., but will steadily warm through the weekend into next week. Above normal temperatures will develop over the West and eventually the central U.S. where by early next week most locations west of the Mississippi River will warm to above normal with decent coverage of plus 10-25 degree anomalies. Best potential for highest anomalies will be over and near the northern Plains. Temperatures over the East should reach near normal to slightly warmer into early next week. The signal remains strong that from Saturday onward the pattern will become favorable for longer fetch moisture feed to fuel rounds of moderate to heavy lower elevation rain and high elevation/mountain snow into the Pacific Northwest, with enhanced snows to work inland over the northern Intermountain West/Rockies. The best potential for highest precipitation totals exists over the favored terrain and coastal areas of western Washington/Oregon and into northwest California. The Day 4/5 WPC Excessive Rainfall Outlook (ERO) both show a similar focused Marginal Risk area. Farther east, it generally remains the case that strongly organized storm systems generally do not look likely over the central to eastern U.S. despite multiple uncertain impulses riding into the eroding Arctic airmass and with flow transition. One pattern feature to note is how ejecting western U.S. energy may support periodic moderate rainfall over the Gulf and possibly inland into the Gulf Coast states in association with slow moving and wavy frontal zones. Most precipitation should be rain, but though a little wintry weather could be possible in the northern fringe of the moisture shield if it extends far enough north. Confidence is still low regarding how the waviness may evolve over the Gulf during the weekend, and what the surface pattern may look like up off the East Coast into early next week. The majority of guidance still suggests most precipitation should stay offshore the Mid-Atlantic/New England coast. However, digging of northern stream shortwave energy this weekend into early next week will spread light precipitation (mostly snow) from the Great Lakes region through New England where any uncertain wrapback coastal low linkage could enhance activity early-mid next week. 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