Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1157 AM EDT Thu Mar 28 2019 Valid 12Z Sun Mar 31 2019 - 12Z Thu Apr 04 2019 ...Overview... Strong upper ridging over Alaska will drift northwestward into northeastern Russia next week will favor a westward shift in troughing over the CONUS--initially over the Great Lakes and Northeast Sun-Mon then back to the Plains/Upper Midwest next Wed/Thu. Troughing in the northeastern Pacific will continue to send systems into the West underneath the Alaskan upper high, focused around Mon-Tue. ...Guidance Assessment/Preferences... The models/ensembles generally agreed on the longwave pattern with differences on timing/strength of the embedded systems. Areas of concern were 1) over the Gulf Mon/Tue where low pressure is still forecast to develop along a slowly moving cold front, but ensembles show a large amount of separating in timing/location of said low (ECMWF and its ensembles generally slower than the GFS/UKMET and GEFS. Ensemble signal has been inconsistent so an intermediate solution was preferred for now. By Tue/Wed, the 00Z ECMWF/GFS come into better agreement with especially the ECMWF ensemble mean, so that cluster of solutions was preferred which was slower than the 06Z GFS/FV3-GFS, keeping it closer to the Outer Banks but just offshore. In the West, another system will push through the Great Basin Tuesday then onto the Plains Wednesday. 00Z GFS seemed to raise heights too quickly behind this system given the teleconnections (and most ensembles) that favor at least some troughing to remain just east of the Rockies. Ensemble means showed this nicely and was the majority of the preference. With a slowly westward moving trough axis, this would favor any surface low development to lift northeastward through the Great Lakes around next Thursday with a cool shot of Canadian air behind it. ...Weather Highlights/Hazards Cooler temperatures will spread eastward from the Plains to the East Coast behind the exiting system on Sunday while rainfall expands along the central/eastern Gulf Coast into northern Florida and the Southeast Mon/Tue. Rainfall could be locally heavy depending on how and where the surface low (or lows) develop(s). In the West, frontal system will bring rain/snow to Oregon eastward with a modest precipitable water axis back to Hawai'i. PW anomalies of +2 to +3 will support some locally heavy precipitation but progressive movement will limit the duration. As a northern stream front and Pacific energy interact east of the Rockies, another area of at least modest precipitation will expand across the Upper Midwest and western Great Lakes. This may exacerbate ongoing flooding as rain is expected for most areas southeast of a ~Rapid City, SD to International Falls, MN line (per the current forecast) with some snow to the northwest. 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