Extended Forecast Discussion NWS Weather Prediction Center College Park MD 209 PM EST Thu Feb 20 2025 Valid 12Z Sun Feb 23 2025 - 12Z Thu Feb 27 2025 ...Wet Pacific Northwest pattern this weekend/early next week... ...Overview and Guidance/Predictability Assessment... The medium range period (Sunday, 2/23) begins with an upper ridge in the West and shortwave energy diving through the Southern Plains. The 00z Euro and 06z GFS were heavily favored at this timestep given the 00z CMC and UKMET's noticeably divergent solutions timing-wise with respect to the shortwave energy in the Plains. On Monday, we have ridging in the West and mean troughing in the East with shortwave energy propagating through the Upper Midwest/Ontario as well as a positively tilted shortwave extending from the Mid-Atlantic to the Gulf Coast/Southern Plains. The Canadian attempts to over amplify a closed low over the Gulf, which is why it and the UKMET represented a minority of the day 4 blend, as well. Shortwave energy slides across the Midwest on Tuesday, while some upper-level energy pushes onshore in the Northwest. A more consensus approach was taken on this day due to some more variance, particularly in the 00z Euro's more progressive solution compared to the rest of the guidance. By Wednesday, another shortwave emerges over the Plains and deepens as it moves into the Midwest. The 12z GFS appears to be the only piece of guidance that weakens the trough throughout the day while all of the other guidance, including the ensemble means and AIFS strengthen it. Just about all of the available guidance agree on amplified mean troughing in the West and mean troughing in the East on day 7. A run-of-the-mill blend consisting of the available ensemble means and 06z GFS were used despite some minor timing details. Not in the blend, but worth noting that the latest AIFS run has a noticeably over amplified closed low (compared to other guidance) over the Mississippi Valley at the start of day 7. ...Weather/Hazards Highlights... It remains the case that above average temperatures will develop over the West then for much of central U.S. where by early next week most locations west of the Mississippi River will warm to much above normal with decent coverage of plus 10-25 degree anomalies. Best potential for highest anomalies will be near the northern Plains. The East should also warm to above normal next week. Guidance continues to offer a strong signal for a pattern favoring a longer fetch moisture feed to fuel moderate to heavy lower elevation rain and high elevation/mountain snow into the Pacific Northwest this weekend into early next week. Enhanced snows will also work inland over the northern Intermountain West/Rockies with downstream system translation. Expect highest precipitation totals exists over the favored terrain and coastal areas of western Washington/Oregon and into northwest California. The Days 4/5 WPC Excessive Rainfall Outlooks valid for Sunday and Monday each show a Marginal Risk threat area given the cumulative effect of the multi-day episode. The Northwest should trend drier midweek as a dynamic Monday- Tuesday system departs and upper ridging builds in. Downstream, shortwave energy ejecting from the southern Rockies out from the weekend and may support periods of moderate rainfall over the Gulf and possibly inland into the Gulf Coast states and Southeast to the north of a wavy frontal zones. Most guidance holds main instability over the Gulf. Most precipitation should be rain, though a little wintry weather could be possible in the northern fringe of the moisture shield early period if it extends far enough north before the airmass moderates. Surface wave/frontal details over the Gulf and the western Atlantic remain quite uncertain for details into next week. However features may evolve, waves should be relatively weak and most precipitation should stay offshore the Mid- Atlantic/New England. Digging of northern stream shortwave energy this weekend into early next week will spread light-side precipitation (mostly snow) from the Great Lakes region through New England. Latest guidance is not too enthusiastic about potential for wrapback coastal low linkage over the Northeast to enhance activity early- mid next week, but it remains worth monitoring in future runs. Moderate cyclogenesis and frontogenesis may develop over the Plains/Mississippi Valley next Wednesday and work over the east- central U.S. by Thursday. The warmer pattern by then should mostly favor an emerging area of moderate wrapping rains with return Gulf moisture flow aside from a little wintry weather on the far north cool side of the low. Kebede/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