Extended Forecast Discussion NWS Weather Prediction Center College Park MD 233 AM EDT Wed Mar 13 2019 Valid 12Z Sat Mar 16 2019 - 12Z Wed Mar 20 2019 ...Overview... Upper ridging over western Canada will slowly nudge eastward next week with its axis down the spine of the Rockies. This favors broad troughing downstream over the central/eastern states and a slowly approaching trough off the West coast as well as a southern stream trough moving across Mexico Monday and through the Gulf next Tue/Wed. ...Guidance Assessment/Preferences... The 18Z GFS/FV3-GFS and 12Z ECMWF offered reasonable clustering near their ensemble means such that a blended solution was utilized for the first few days of the period (Sat-Mon). By next Tue/Wed, differences in the upstream shortwave speed/track expand as they move across the northern tier and/or get left behind under the expanding ridge (or upper high) over Alberta/Saskatchewan. In the Pacific, trend has been toward a deeper/slower trough or upper low that may aim toward southern California (or even Baja California Norte) and opted to weight the ECMWF ensemble mean more than the GEFS mean as it was deeper, but not as deep as the deterministic run. ...Weather Highlights and Hazards... A cold front will settle near the Florida Keys as a wavy stationary front late this weekend, providing a focus for rainfall through the period. The combination of this front and one or more southern stream shortwaves aloft may produce periods of locally moderate or heavy rainfall over the Florida Peninsula. Extreme southern Texas may see some enhanced rainfall with the energetic flow aloft as well. The rest of the East will see a drier period except for some areas of lake enhanced snow as weak fronts rotate through the Lakes. The West should be mostly dry until moisture reaches the West Coast around next Tue and especially Wed, focused from NorCal northward west of I-5. The north-central and southern Plains may see the most persistent cold anomalies with some locations at least 15-20F below normal for highs through the weekend. The warming trend over/near the West Coast states should bring readings 5-10F above normal by Sun-Tue that will shift into Idaho next Wed. The East will generally see cooler than normal temperatures through the period due to northwesterly flow. Fracasso Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php 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