Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Wed Feb 26 2025 Valid 12Z Sat Mar 01 2025 - 12Z Wed Mar 05 2025 ...Overview... The upcoming medium range period continues to feature a rather progressive overall upper flow pattern. Troughing over the East will be established this weekend, but should shift eastward early next week and replaced by upper ridging. Meanwhile, a cutoff upper low over southern California on Saturday will drift east and get absorbed into the larger scale flow next week over the southern Plains. Behind this, another deep trough or upper low will move into the West Coast Sunday into Monday, with general indications of a more amplified pattern over the West to Central U.S. next week and increasing precipitation for much of the south-central states. ...Guidance/Predictability Assessment... Recent guidance cycles continue to show good agreement on the overall pattern progression and dominant features of the medium range period, but with uncertainty in the details. The two main sources of uncertainty lie with the pair of upper lows through the Western U.S. this weekend and again next week. The first, over southern California by Saturday, has shown improved consistency in the timing, but there is still variability in the track. The last few GFS runs remains notably displaced north of the UKMET, CMC, and ECMWF. Also uncertainty on how far northeast the low lifts across the Central U.S. and how quickly its absorbed into larger scale flow. For the second trough early next week, the guidance agrees on its existence but there's considerable uncertainty still in the timing and evolution. Compared to 24-hours ago, the GFS has sped up and is closer to consensus but is still on the slower side. The ECMWF and CMC right now are most agreeable with the ensemble means. The WPC blend for tonight used a multi-model blend for this weekend, eventually transitioning next week to a 60/40 split ensemble means/deterministic (ECMWF and CMC). For the overlapping Day 3-6 period, this maintains good continuity with the previous WPC forecast. ...Weather/Hazards Highlights... A clipper system should bring a round of precipitation to the Great Lakes and Northeast into Saturday, with moderate snowfall possibly enhanced by the lake waters across the upper Great Lakes, with mixed precipitation just to the south. A period of strong and gusty winds may linger into Saturday near the Great Lakes on the back- side of the system as cold air rushes in behind it. The southern stream upper low moving into southern California Saturday and inland may lead to light showers over California, the Southwest, and into the south- central U.S., with increasing rain chances in the southern Plains by next Sunday as moisture increases. There appears to be a better signal for the precipitation to spread farther east/northeast across the southern Plains and eastward early next week. The northern stream trough moving through the eastern Pacific and into the West next weekend will also bring precipitation chances back for the West Coast, spreading across the Great Basin/Rockies early next week. As this trough moves into the Central U.S. around Tuesday-Wednesday next week, it should tap moisture from the Gulf to fuel more widespread rains across the east-central U.S.. There is the potential for moderate to at least locally heavy rainfall and with ambient moist soil conditions in some areas, this will be something to watch. Much above normal temperatures will be well established by across the West and into the northern/central Plains. The greatest anomalies will be across the northern Plains with daytime highs 20 to locally 30 degrees above normal, with 60s for highs as far north as Nebraska/South Dakota. The above normal temperatures will spread south and east, with the West trending cooler by early next week. Across the East, temperatures will vary between normal and above normal into Saturday, but be mostly below normal Sunday and Monday in post-frontal high pressure before again moderating. Santorelli 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