Extended Forecast Discussion NWS Weather Prediction Center College Park MD 937 AM EST Sun Feb 24 2019 Valid 12Z Wed Feb 27 2019 - 12Z Sun Mar 03 2019 ...Pattern Overview... A strong mid-level positive anomaly starting in AK will drift northeast into the Canadian Archipelago, forcing changes downstream, such as a consolidating mid-level vortex in southeast Canada which, sooner or later, should settle into the Labrador Sea early next week. Overall, this maintains a zonal-ish flow through the medium range period. While zonal flow can lead to milder than climatological conditions across the Lower 48, below average mid-level heights near and west of a cold low dropped southeast into southeast Canada continue over the northern Plains, promising continued colder than average temperatures for the remainder of February into early March. Any mildness should be generally constrained across the southern tier of the country. ...Model Preferences... The guidance showed very good agreement overall. For the pressures, winds, and 500 hPa heights, used a blend of the 00z UKMET, 00z Canadian, 00z GFS, and 00z ECMWF which incorporates slowly increasing percentages of the 00z bias-corrected NAEFS mean and 00z ECMWF ensemble mean with time. The remainder of the weather grids, including QPF, used a more even blend of the deterministic and ensemble mean guidance. ...Weather Highlights/Hazards... Over the West, expect areas of enhanced precipitation (rain and higher elevation snow) to extend from California through the Great Basin and into the north-central/central Rockies. There will be two main systems of note, one arriving around the start of the period and bringing rain/snow during Wed-Thu and the next most likely spreading moisture across the region during the weekend. The second system's moisture axis should be somewhat southward of the first. Highest totals during the period should be over the Sierra Nevada range. Around midweek modest shortwave energy/surface waviness may bring an area of mostly light snow across the northeastern quadrant of the Lower 48. Another small area of rain/snow may cross parts of the Ohio Valley/Mid-Atlantic later in the week. Then guidance is starting to show more similar ideas for potentially strong surface development with low pressure reaching the Great Lakes around Saturday morning and continuing northeastward thereafter. Highest snow potential would extend across parts of the Midwest into the northwestern Great Lakes with meaningful snowfall also possible over New England. Expect rain farther south and some pockets of locally moderate-heavy activity may be possible. Slightly better potential for highest totals will be over the Gulf Coast states but relative maxima may be possible over other parts of the East as well. Continue to expect very cold temperatures centered over and near the northern half of the Plains. Wed-Fri readings will be extreme enough at 10-30F below normal but a stronger surge of cold air Fri into the weekend could bring some areas to 30-40F below normal while less extreme cold anomalies spread farther south and east. Meanwhile Pacific flow will keep min temperatures in particular above normal over the southern 2/3 of the West. The southern tier states should see above normal temperatures on average but with a cooling trend next weekend. Roth/Reinhart/Rausch WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation and winter weather outlook probabilities are found 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/wwd/pwpf_d47/pwpf_medr.php?day=4