Extended Forecast Discussion NWS Weather Prediction Center College Park MD 327 PM EST Mon Jan 24 2022 Valid 12Z Thu Jan 27 2022 - 12Z Mon Jan 31 2022 ...Winter Coastal Storm Threat from the Mid-Atlantic to especially New England Friday/Weekend... ...Overview... Guidance still shows a mean upper level pattern that features troughing over the East, varying degrees of ridging over the West, and a developing northeastern Pacific trough that may approach the West Coast early next week. Within this agreeable regime there are lingering uncertainties regarding specifics of an eastern U.S. amplified trough that has become more likely support a significant and rapidly deepening western Atlantic coastal storm Friday into the weekend with effects from the Mid-Atlantic to New England in particular, as well as for a lead Pacific shortwave approaching the West Coast by Sat. There are also lingering differences with details of a later period northeastern Pacific trough, affecting how much moisture reaches the Northwest. However, these differences are now less profound than earlier. ...Guidance Evaluation/Predictability Assessment... Even though the large scale pattern evolution has been rather consistent in recent guidance, embedded areas of uncertainty involve aspects that are smaller in scale and have lead to lower predictability. However, forecast spread has decreased with the latest couple model and ensemble runs whose systems are now better clustered, bolstering forecast confidence. The WPC medium range product suite was mainly derived from a composite blend of the GFS/ECMWF/Canadian Day 3-5 (Thu-Sat) along with supportive ensembles and the National Blend of Models before transitioning to just the GEFS/ECMWF ensemble means and NBM into Day 6/7 (Sun/Mon). I did apply some manual adjustments to offset composite smoothing. These were primarily to ensure sufficient coastal storm depth consistent with overall support, trending deeper than WPC continuity given improved forecast clustering, ensemble member probabilities, and a deeper/closer track to the coast guidance trends. ...Weather Highlights/Threats... Key Messages for January 28-30 (Friday-Weekend) Winter Storm: Confidence is increasing that a significant winter storm will create considerable impacts Friday through the weekend from the Mid-Atlantic through the Northeast. While uncertainty continues with the track and intensity of this system, it is becoming more likely that it will bring significant snow, sleet, and freezing rain to the region, including the I-95 metropolitan areas. Hazardous travel conditions are possible due to the combination of snow, sleet, freezing rain, and wind. Close to the immediate Atlantic coastline, strong winds combined with high astronomical tides may lead to coastal flooding. Please continue to monitor for future updates as this system develops. Elsewhere, some locations near the West Coast may see an increase in precipitation with an approaching shortwave/possible compact upper low late week into the weekend. This energy should eventually support some precipitation over the southern Plains/western half of the Gulf Coast early next week. Flow ahead of a northeastern Pacific upper trough should bring rain and mountain snow into the Northwest into early next week. A wavy frontal system should also bring mostly light snow to the Great Lakes and Appalachians late this week. One or more trailing weak waves may also produce scattered light snow over areas from the extreme northern tier into the Great Lakes. Mainly the East will experience periods with much below normal temperatures (10-20F below normal). Much of the West should continue to see moderately above normal temperatures (5-10F+ anomalies) while the northern and central Plains will likely see multiple warm days with temperatures 10-20F above normal, especially starting the weekend. Rausch/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 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Sun-Mon, Jan 30-Jan 31. - Heavy precipitation across portions of the Northeast, Sat, Jan 29. - Heavy rain across portions of the Pacific Northwest, Sun-Mon, Jan 30-Jan 31. - Heavy snow across portions of the Central Appalachians, Fri, Jan 28. - Heavy snow across portions of the Mid-Atlantic and the Northeast, Sat, Jan 29. - High winds across portions of the Northeast, Sat, Jan 29. - Much below normal temperatures across portions of the Mid-Atlantic, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Northeast, the Southern Appalachians, the Southeast, the Great Lakes, and the Ohio Valley, Sat-Sun, Jan 29-Jan 30. - Much below normal temperatures across portions of the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley, Fri-Sat, Jan 28-Jan 29. - High significant wave heights for coastal portions of the Mid-Atlantic and the Northeast, Sat, Jan 29. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu-Fri, Jan 27-Jan 28. - High winds across portions of the Alaska Panhandle and mainland Alaska, Thu-Fri, Jan 27-Jan 28. 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