Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1203 PM EDT Thu Sep 19 2019 Valid 12Z Sun Sep 22 2019 - 12Z Thu Sep 26 2019 ...Heavy rainfall threats in the Mid-MS Valley/Midwest as well as the Southwest Sun/Mon... ...Overview... Amplified pattern will only slowly transition toward more zonal flow by the end of next week as multiple tropical systems traverse the Atlantic and Pacific waters. Two troughs in the Pacific Northwest and Plains will be significant players for the rainfall early in the medium range period (Sun/Mon) as each will tap tropical moisture due to Mario/Lorena in the East Pacific and leftover moisture from Imelda in the Mid-Mississippi Valley. The pattern will tend to favor broad troughing by next Thursday across the northern tier as an upper low deepens over Hudson Bay. ...Guidance Evaluation/Preferences... Ensemble guidance continues to show a closed low cutting off from the main flow in the Great Basin around Monday and then slowly moving through the Southwest thereafter. There still remains a large degree of east-west spread in the initial sharpening of the trough and resultant location (then movement) as a closed low. With a slight eastward shift in the guidance, followed the consensus near the 00Z GFS/ECMWF and their ensemble means with more emphasis on the ECMWF guidance by late in the period due to its better consistency and preference downstream over the western Atlantic (a bit slower with Jerry nearer to the NHC forecast). ...Weather Highlights/Threats... Moisture from the remains of Imelda combined with a strong trough in the northern stream will fuel a threat of locally heavy rainfall from the mid-Mississippi Valley eastward through the Midwest ahead of an approaching cold front. This may extend into the Great Lakes/Northeast late Monday into early Tuesday but with less areal coverage. In the Southwest, tropical systems Lorena and Mario will lift north-northwestward and their moisture will get drawn north/northeastward ahead of the deepening troughing (eventual closed low) out of the Great Basin early in the period. Southwest flow aloft will intersect the approaching cold front and aide in precipitation production initially over Arizona that may spread into New Mexico as the upper low moves eastward. Temperatures will generally be above average in the east/Southeast and below average in the West. Overnight lows will be above average for most areas CONUS-wide. Some record highs will be possible from the central Gulf Coast through the Southeast Tue/Wed with temperatures into the lower and mid-90s. 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