Extended Forecast Discussion NWS Weather Prediction Center College Park MD 414 PM EST Wed Feb 09 2022 Valid 12Z Sat Feb 12 2022 - 12Z Wed Feb 16 2022 ...Weather Pattern Overview... Guidance continues to show a significant upper-level pattern change over the course of the period. The West Coast ridge/eastern trough configuration this weekend should transition toward an amplified western trough and southwesterly mean flow farther east, as a shortwave traversing the North Pacific ultimately drops southeastward downstream from a building Pacific ridge likely to reach near 140W longitude by the middle of next week. Within the upper trough crossing the East, some details seem to be more uncertain than 24 hours ago--affecting specifics of low pressure expected to develop off the East Coast around Sunday-Sunday night, along with the corresponding moisture shield. There are also detail questions for the trough digging into the West during the first half of next week, affecting specifics of associated precipitation and the leading wavy cold front. Precipitation should increase over the central U.S. around midweek as low level flow from the Gulf begins to interact with this front. ...Guidance Evaluation/Predictability Assessment... Compared to earlier runs, some guidance has noticeably diverged for the eastern U.S./western Atlantic evolution around Sunday-Monday. There is still a relative majority that shows offshore development in response to energy within the upper trough remaining open. However the 00Z UKMET/12Z CMC have a closed upper low crossing the Great Lakes region, drawing the surface low closer to the East Coast and spreading much more precipitation across the Northeast. Meanwhile some GFS runs have been sharp enough with energy farther south to emphasize the central-southern Appalachians into Mid-Atlantic for precipitation while keeping the developing low far enough offshore just to brush southern/eastern New England. Recent ECMWF runs have tended to be lighter/more suppressed with its snow. The 00Z UKMET/12Z CMC scenario is a relative minority among ensembles (but within the envelope) thus requiring minimal weight for a single deterministic forecast, but taken as a whole there is somewhat more of a signal for at least some snow over parts of the Mid-Atlantic/Northeast as ensemble means had been hinting. Meanwhile most models and means have come into better than average agreement for the upper trough digging into the West, relative to typical 5-7 day forecasts. There is still some debate over whether an embedded low may exist as it comes ashore (new 12Z ECMWF adding to that cluster) and the 12Z UKMET is a little southwest of models that show a low center at that time, but ultimately by day 7 Wednesday the latest GFS/ECMWF/CMC runs all show an upper low reaching the Southwest/Four Corners region while the GEFS/ECens/CMCens means all imply such a low would exist at a similar location. Between these two features, in the Saturday-Monday time frame models have been diverse and inconsistent with the details of a weak clipper-type wave that may drop southeastward between the Plains and west of the Appalachians before dissipating. These issues correspond to varying depictions of shortwave energy forecast to feed into the mean trough aloft crossing the East. Guidance behavior up to this point as well as the small scale of the feature yield low confidence in any particular solution. The early-period operational model blend of 00Z/06Z guidance placed the least weight on the UKMET given its lower-probability solution over the East. Favorable guidance comparisons led to transitioning the forecast blend toward the 06Z GFS/GEFS mean and 00Z ECMWF/ECMWF mean/CMC by days 6-7 Tuesday-Wednesday. ...Weather Highlights/Threats... Brisk winds and colder air behind the system tracking just north of Maine on Saturday should support an episode of light to moderate lake effect snow across portions of Michigan and upstate New York. Expect low pressure to form along the trailing front near the East Coast by Sunday, but with lower than desired confidence in the strength/track of the system and coverage/intensity of associated precipitation. Recent trends are at least signaling potential for some snow from the central-southern Appalachians into the Mid-Atlantic and southern/eastern New England with rain possible over parts of the Southeast/Florida. However the current possibilities for the Mid-Atlantic/Northeast still range between minimal and significant snowfall. Continue to monitor forecasts of this system closely. Expect the upper trough/wavy front moving into the West early next week to bring an episode of rain and mountain snow, with highest totals likely to extend from the Pacific Northwest into the northern-central Rockies. Precipitation should increase in coverage and intensity over the central/southern Plains and vicinity by next Wednesday or so as the surface front interacts with a strengthening low level flow of Gulf moisture. Some snow may be possible from the central High Plains northeastward. Many parts of the West will see well above normal temperatures extend through the weekend with some areas seeing plus 10-20F anomalies. Best potential for daily records will be over California Saturday-Sunday. The upper trough approaching from the Pacific will begin a cooling trend over the Pacific Northwest/northern California by Monday while the Great Basin and Southwest remain quite warm. Then expect moderately below normal highs to spread across the West/Rockies by Tuesday-Wednesday. Meanwhile the Plains will see a warming trend (up to plus 10-20F or so anomalies) from the weekend into early next week before the western front approaches. Areas near the East Coast will see a warm day Saturday (plus 10F or greater anomalies) before passage of a cold front, with trailing temperatures generally 10-20F below normal progressing from the Mississippi Valley Saturday through the East into early next week. The East will likely rebound to near or above normal by next Wednesday. Rausch Hazards: - Heavy snow possible across portions of southeastern New England, Sun, Feb 13. - Heavy snow possible across portions of the northern Cascades and northern Rockies, Mon, Feb 14. - Heavy rain possible across portions of the southern Plains to the mid-Mississippi Valley, and into the Midwest, Wed, Feb 16. - Much below normal temperatures across the upper Midwest into the upper Great Lakes, Sat, Feb 12. - Much below normal temperatures across the lower Great Lakes and northern New England, Sun-Tue, Feb 13-Feb 15. 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