Extended Forecast Discussion NWS Weather Prediction Center College Park MD 149 PM EST Tue Feb 22 2022 Valid 12Z Fri Feb 25 2022 - 12Z Tue Mar 01 2022 ...Heavy snow and ice threat spreads across the northern Mid-Atlantic and Northeast into Friday... ...Overview... A potent shortwave interacting with northern stream energy over the Ohio Valley/Great Lakes to start the medium range period Friday will provide forcing for a heavy snow and ice threat in the northern Mid-Atlantic and Northeast. A fairly progressive upper level pattern and overall drier conditions are expected by the weekend into early next week. Generally colder than average temperatures are forecast for much of the country, especially late this week. ...Guidance Evaluation/Predictability Assessment... Model guidance continues to show reasonably good agreement to start the medium range period Friday with the aforementioned shortwave and the associated surface low pressure/frontal system, and with the position of a second shortwave over the Northern Rockies Friday. However, the latter shortwave shows run to run and model differences as it progresses east into the weekend. The 00Z/06Z suite of guidance generally showed less stream separation with the wave compared to the previous cycle (especially yesterday's 12Z ECMWF) and WPC forecast, as recent guidance (including the new 12Z guidance) shows it shearing with most energy phasing with the northern stream troughing entering the Great Lakes led by an upper low in Canada. This also would lead to a quicker moving precipitation swath over the southeastern quadrant of the U.S. over the weekend if this more phased solution with a quicker southern shortwave plays out. The WPC forecast utilized a multi-model composite blend early in the medium range period, with the blending process smoothing individual differences, and trending toward a weaker shortwave solution than the previous forecast given the model consensus. Farther west, agreement is good for a ridge axis to enter the West Coast late Friday into Saturday and progress eastward into the Rockies and Plains early next week. However, ample model differences upstream of the ridge remain within mean troughing entering the West early next week, with variability in strength and track of multiple shortwaves. This leads to low confidence in the evolution of another southern stream feature possibly in the southwestern quadrant of the country by Monday and Tuesday. The CMC and ECMWF runs remain stronger with this feature than GFS runs, and preferred a solution slightly on the more amplified side of the full envelope of solutions, most in line with the ECMWF ensemble mean. ...Weather Highlights/Threats... A potent ejecting southern stream shortwave will interact with northern stream energies over the Great Lakes/Ohio Valley Friday, as moisture streams over a leading front to fuel enhanced precipitation across the high pressure/cold air dammed northern Mid-Atlantic and Northeast. Frontal wave approach and coastal low reformation will favor a pronounced swath of significant snow and ice on the northern/western side of the precipitation shield, with lift enhanced in the right entrance region of a strong upper jet. After that event, the upcoming weather pattern should favor drier conditions for many. An exception may be across the south-central to southeastern U.S. where precipitation could increase once again over the weekend, mainly in the form of rain but with a nonzero chance of wintry weather on the northern side. Rainfall amounts are not expected to be as heavy as the past couple of events, but will continue to monitor, as there could be issues if rain falls over areas that saw heavy rainfall in the ongoing/short range events. In addition, modest precipitation is expected for the Pacific Northwest starting this weekend with the likely slow approach of northeast Pacific systems. Precipitation totals are forecast to increase there by next Monday-Tuesday. Cold high pressure will settle across much of the country in the wake of the initial system. Record-setting cold is possible in pockets of the West and Plains on Friday, while prefrontal warmth under amplified upper ridging in the Southeast could set daily warm records on Friday before moderating over the weekend. Below average temperatures will linger across the Intermountain West/Rockies and Southern Plains Saturday. Another period of below normal temperatures traverses the north-central to northeastern U.S. early next week while the rest of the lower 48 moderates near to slightly above normal. Tate/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, winter weather outlook probabilities and heat indices 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml