Extended Forecast Discussion NWS Weather Prediction Center College Park MD 349 PM EST Fri Jan 20 2023 Valid 12Z Mon Jan 23 2023 - 12Z Fri Jan 27 2023 ...Heavy snow threat for the interior Northeast with an exiting storm Monday... ...Second storm to spread a heavy rain/severe weather threat to the South early next week, working up the Eastern Seaboard midweek along with a heavy snow threat from the central Rockies/Plains through the interior Northeast... ...Synoptic Overview... The weather pattern will remain stormy 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 interior snow. Meanwhile, the next closed/deep system will dig robustly over the Southwest into Monday then eject across the south-central U.S. early in next week, with a subsequent 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 will then herald a return to colder conditions from the West to across much of the central and eastern U.S. as amplified upper troughing works develops downstream. ...Guidance/Predictability Assessment... Latest guidance solutions remain better clustered than normal with the overall synoptic scale depiction across the continental U.S. through the middle of next week. Accordingly prefer a composite blend of the GFS/ECMWF/UKMET/CMC for max details consistent with a pattern with high predictability. Added into the mix some GEFS/ECMWF ensemble input for longer time frames to account for increasing, but generally manageable, forecast spread. WPC product continuity is good. ...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 plowable snows from the Adirondacks 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 deepened low pressure system arrives. This storm is forecast to work out from a highly unsettled Southwest/Rockies Monday. Expect a burst of rain and terrain enhanced snow under ample closed upper low/trough support. The system further develops over the southern Plains/Gulf Coast region into Tuesday before tracking northeast across the Ohio Valley and then the Great Lakes through next mid week, reaching the Northeast U.S. by Thursday. The best heavy rainfall potential exists from the South/Southeast and Appalachians to up the Eastern Seaboard, while an axis of wintry weather spreads from the Central Plains northeastward to the interior Northeast. The guidance signal has intensified for excessive rain. Accordingly, an experimental WPC Day 5 Excessive Rainfall Outlook (ERO) "Slight" risk area has now been issued from the Lower Mississippi Valley to the central Gulf Coast states for Tuesday into Wednesday in a region of best Gulf moisture inflow and instability. SPC also identifies this area for a threat for severe weather. 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/Schichtel Hazards: - Heavy precipitation and heavy snow across portions of New England, Mon, Jan 23. - Heavy precipitation and heavy snow across portions of the central High Plains through New England, Mon-Thu, Jan 23-26. - Heavy rain across much of the South into the interior portions of the East Coast, Tue-Wed, Jan 24-25. - Severe weather across portions of the Southeast and the lower Mississippi Valley, Tue, Jan 24. - Much below normal temperatures across portions of the Southwest to the central Rockies, Mon-Wed, Jan 23-Jan 25. 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