Extended Forecast Discussion NWS Weather Prediction Center College Park MD 248 AM EST Fri Jan 25 2019 Valid 12Z Mon Jan 28 2019 - 12Z Fri Feb 1 2019 ...Overview... The overall flow pattern across the continental U.S. and Canada will remain highly amplified going into next week with a full latitude ridge situated just off the West Coast and a pronounced upper level trough encompassing much of the central and eastern U.S. A large and cold upper low, which is basically a lobe of the polar vortex, will reinforce the trough through Thursday before a slight deamplification evolves by next Friday. ...Guidance Evaluation/Preferences... The most significant aspect of the forecast is a deep upper low which the operational models and the ensemble means bring down toward Lake Superior by Wednesday, and this has its origin over the Arctic Ocean. Depending on exact upper low depth, 500mb height anomalies may reach at least 3-4 standard deviations below normal along/south of the low's path. This feature may promote further strengthening of the Midwest/Great Lakes system through New England and eastern Canada. Deeper trends in the means for the upper low but some lingering track spread in the guidance favor a combination of ECMWF/GFS along with their respective ensemble means. Around the southern/eastern periphery of the overall trough there continues to be a more suppressed trend for any disturbances across the Gulf of Mexico and into the western Atlantic. Model inconsistency and spread keep confidence below average for specifics that affect intensity of rainfall over the Florida Peninsula. Guidance as a whole is maintaining recent trends toward lower potential for any waves to have a significant effect on the East Coast. The forecast nationwide was based mainly on a blend of the GFS/ECMWF/UKMET earlier in the forecast, and then more ensemble means later in the forecast period. ...Weather Highlights/Hazards... The main storm system of interest during this forecast period will be a clipper type system dropping southeast from central Canada along with an arctic front. This will bring a band of light to moderate snow across the southern Great Lakes and extending across the northern Ohio Valley on Monday, and then reaching the Northeast U.S. and Mid-Atlantic region by late Tuesday. This is still subject to some change due to track variability in the operational guidance. Once the front trailing from the low reaches the Mississippi Valley and points east, some rain may develop in the warm sector and then possibly end as a period of snow with the frontal passage. After this system departs, more lake effect snow is likely downwind of the Great Lakes. Another thing that will be making weather headlines by the middle of the upcoming week will be an impressive round of frigid temperatures as a lobe of the polar vortex sinks southeastward across Canada and then reaches the northern Great Lakes. Temperatures are expected to plummet well below zero across the Upper Midwest, most of the Great Lakes region, and the northern Ohio Valley by Wednesday and Thursday. Anomalies on the order of 25 to 35 degrees below normal are a good possibility for these regions, and it is quite likely that this would warrant wind chill warnings for many of these areas. Although the airmass will modify some by the time it reaches the East Coast, it should still be quite cold for the Mid-Atlantic and Northeast U.S. on Thursday with highs well below freezing. D. Hamrick 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