Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Fri Jan 20 2023 Valid 12Z Mon Jan 23 2023 - 12Z Fri Jan 27 2023 ...Two well organized lows will bring rain and inland snow from the central Plains to the Northeast states... ...Synoptic Overview... The weather pattern is expected to be active but progressive across much of the nation going into next week with two well defined low pressure systems of interest. The first will be affecting the Northeast U.S. going through Monday and then exiting into southeast Canada by Tuesday, with coastal rain and inland snow. Meanwhile, the next low will be gathering strength across the south-central U.S. early in the week and then track in a general northeasterly direction across the Ohio Valley and then the Great Lakes by Wednesday and into Thursday. A building West Coast/western Canada upper ridge as a +PNA pattern tries to develop will herald a return to colder conditions across much of the central and eastern U.S. as a broad upper trough develops downstream of this ridge. ...Guidance/Predictability Assessment... The 00Z guidance has improved its overall synoptic scale depiction across the continental U.S. through the middle of the week, although the UKMET was slower and farther south than the model consensus with the developing low across the south-central U.S. midweek. This lead to more weighting towards a CMC/ECMWF/GFS consensus for fronts and pressures, and an increase of the ensemble means up to about 50% by Friday to account for increasing mesoscale uncertainties. The axis of heaviest QPF with the midweek storm system has now shifted to the northwest compared to the previous forecast cycle across the Deep South and Tennessee River Valley with a farther inland track of the surface low. ...Weather/Hazard Highlights... The first storm system of note will be an intensifying surface low near eastern New England on Monday morning that will quickly lift northward across the southeastern provinces of Canada by Tuesday. This is expected to produce a swath of moderate snow from Vermont to Maine, and a wind-driven rain closer to the coast with gusts over 40 mph at times. High pressure will briefly settle in across the eastern U.S. before the next organized low pressure system arrives. This is forecast to develop over the Gulf Coast region around Tuesday and then track northeast across the Ohio Valley and then the Great Lakes through mid week, and then reaching the Northeast U.S. by Thursday. The best heavy rainfall potential exists over the Southeast and southern Appalachians, and a band of wintry weather from the Central Plains northeastward into interior New England. Across the West, rain and mountain snow of mostly light to moderate amounts should extend south-southeast across the Rockies and nearby areas with upper trough/low support and lower level upslope flow. Temperatures are expected to generally be on the order of 5 to 15 degrees below average from the Intermountain West to the western High Plains for early in the week, and slightly above average across most of the eastern U.S. By the end of the week, most areas across the nation should be between average and 10 degrees below average as broad upper trough and cyclonic flow aloft keep any anomalous warmth away. Hamrick 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, experimental excessive rainfall outlook, 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/#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