Extended Forecast Discussion NWS Weather Prediction Center College Park MD 116 AM EST Fri Feb 01 2019 Valid 12Z Mon Feb 04 2019 - 12Z Fri Feb 08 2019 ...Much above average temperatures for the eastern half of the lower 48 early next week... ...Overview... Active pattern in the west will translate eastward next week as a deep trough digs through the Great Basin Mon/Tue and then lifts northeastward toward the Great Lakes. A secondary Canadian shortwave will bring in a renewed push of cold air for the northern Rockies into the High Plains. The east will see a dramatic rise in temperatures to well above freezing (rather than well below zero) ahead of the Pacific system. Record high temperatures Mon-Wed are even possible where record low temperatures were just observed yesterday/this morning. ...Guidance/Predictability Assessment... The 18Z GFS and 12Z ECMWF clustered fairly well with their ensemble means to start the forecast Mon-Tue as an upper low drops southward near the WA/OR coast and then into northern California. Arctic boundary to the north will push over the Divide with colder air sinking southward and both westward/eastward through some mountain passes. To the east, another surface low will lift from the Midwest into southern Canada and drag its cold front to the Mid-Atlantic/Ohio Valley by Wednesday. At that time, the Pacific system will slide into the Plains and begin to turn northeastward toward the Great Lakes by early Thursday. The GFS/GEFS have been less consistent in timing/track of the mid-week to late week period while the ECMWF and its ensemble mean have trended a bit slower over the past several cycles with the western trough. Opted to rely mostly on that slower guidance with only a small weighting to the slightly quicker 12Z NAEFS. Upstream Pacific flow becomes quite uncertain as the ridge center moves northward into Alaska next Thursday. Back to the east, ensembles seem to take the surface low eastward out the St. Lawrence Valley which will bring an end to the well above average temperatures. ...Weather Highlights/Hazards... Deep system in the west will bring valley rain and higher elevation snow (with lowering snow levels), wind, and cooler temperatures from Oregon/southern Idaho southward and southeastward. To its north will be a slowly advancing arctic front that will bring well below average temperatures to much of Montana where highs will struggle to get to zero (about 20-45 degrees below average) that will bleed into the Dakotas as well. The Sierras will see another round of snow with more than a foot likely. To the east, Great Lakes system will spread snow from the Upper Midwest to the northern Lakes with plain rain for much of the east south of about ~45N (NY-VT/Canada border). Record mild temperatures may precede the front from the Midwest to the Northeast with anomalies of about +10 to +30 (generally above freezing to the north and 50s/60s in the Mid-Atlantic. By next Thursday, Pacific system will lift into the Great Lakes with another snow threat for the Upper Midwest eastward to northern New England. Warm sector rain from the mid-Mississippi Valley eastward may be much more widespread and locally heavy with increased Gulf moisture. The west will trend quieter but temperatures will be near to below average. Fracasso WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation and winter weather outlook probabilities are found 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