Extended Forecast Discussion NWS Weather Prediction Center College Park MD 145 PM EST Wed Feb 21 2024 Valid 12Z Sat Feb 24 2024 - 12Z Wed Feb 28 2024 ...Overview... An upper ridge traversing the country this weekend into early next week will spread much above normal temperatures to the Plains and Midwest and eventually the East by the middle of next week. Meanwhile an eastern Pacific upper low should spread some increasing precipitation chances to the West Coast once again, possibly by the weekend but more confidently by early next week as northern and southern stream troughing phase and track into the West. Cooler temperatures, lower elevation rain and higher elevation snow, and windy conditions are all expected for the West Coast to the Rockies early next week. Increased precipitation is also likely for the Ohio Valley/Great Lakes by Monday-Tuesday with a frontal system or two ahead of this trough. ...Guidance/Predictability Assessment... The latest model guidance today continues to be fairly consistent with previous guidance requiring no major changes needed for the updated progs compared to previous WPC continuity. There were some mainly minor timing differences in the guidance with an initial shortwave out of the Northeast and another behind across the Great Lakes this weekend/Monday but a general model compromise seemed to serve as a good starting point. Otherwise, the greatest uncertainties seem to be late period regarding the details of phasing between a northern stream shortwave into the Northwest and an opening low off the Southern California coast. Guidance agrees the two features should phase resulting in one elongated trough through the West by next Tuesday-Wednesday but there are some timing inconsistencies. The GFS is slowest to move into the Plains, while the CMC is noticeably faster. The ECMWF seems to be right in the middle of the two and the new 12z run is a tad slower than it's previous 00z run, and it's also fairly consistent with the ensemble means. So with that, the late period blend for the WPC progs today transitioned to a 50/50 blend of the ensembles with the GFS/ECMWF. ...Weather/Hazards Highlights... An upper low and its surface reflection look to meander in the eastern Pacific late this week, perhaps reaching close enough to California to provide some shower activity. But by Sunday into Monday model guidance is more agreeable that precipitation should spread into the Pacific Northwest and California with some moisture spreading farther inland into the Intermountain West. Snow and rain should continue to increase in interior parts of the West into Monday-Tuesday. Heavy snow with the highest likelihood for impacts is in the Cascades Sunday-Tuesday, but the snow will likely cause at least minor impacts to much of the higher elevation areas of the Sierra into the Intermountain West and Rockies. Gusty winds are forecast for the Interior West behind a couple of cold fronts on Monday-Tuesday as well. Farther east, light rain and snow are possible Saturday focused in the southern Appalachians. A cold front tracking through the northeastern U.S. could spread some light to moderate precipitation from the Ohio Valley into the northern/central Appalachians and the Northeast on Sunday. Then ahead of the approaching upper trough and cold front, precipitation chances will increase late Monday into Tuesday in the Midwest to the Ohio Valley and Great Lakes. Most precipitation will be in the form of rain given the anomalous warmth, but some snow in the Northeast ahead of the system and some snow on the backside of the low in the north-central U.S. is possible, though with low confidence. Rainfall amounts could be locally heavy in the Ohio Valley. The central U.S. will see quite a mild to warm weekend to early next week underneath an upper ridge. Temperatures of 15-25 degrees above average in the north-central U.S. on Saturday will only increase in coverage and magnitude by early next week. Highs and lows that are 20-35 degrees above normal should expand southward into the Plains and Mississippi Valley early next week. This puts actual temperatures into the 80s and even 90s in Texas Monday-Tuesday while 60s reach as far north as South Dakota and Iowa, with potential for widespread record daytime highs and warm overnight lows. A gradual eastward spread/shift should warm the Southeast in to the 70s next week. The central U.S. should moderate closer to normal by midweek while the highest anomalies shift into the East, after a cool weekend and gradual warm-up. Meanwhile the West is forecast to see near to slightly above normal temperatures late week into the weekend, but cooling to below normal particularly in terms of highs by Monday-Tuesday as upper troughing comes in. Santorelli/Tate 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, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at: 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