Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1144 AM EDT Fri Jun 15 2018 Valid 12Z Mon Jun 18 2018 - 12Z Fri Jun 22 2018 ...Heavy rains possible for portions of the northwestern Gulf Coast and portions of the central/northern Rockies and adjacent plains... ...Hot/humid for portions of the Midwest to the Mid-Atlantic and Southeast early next week... ...Pattern overview and guidance assessment/preferences... An upper level low over the Great Basin on Monday should slowly begin to weaken as ridging in the East gives way to cyclonic flow through the Great Lakes. This brings a surface cold front slowly southward out of the Great Lakes on Monday, eventually lingering across the Mid-Atlantic and back to the Plains through the rest of the week. To the south, a weakness aloft and a tropical wave at the surface is expected to produce heavy rainfall along the northwest Gulf Coast region next week. For days 3-5, the GFS/ECMWF and their ensemble means were in very good agreement so a majority deterministic GFS/ECMWF blend served as a good starting point. By days 6-7, the most notable difference was the 06z GFS was faster to erode the western low and eject the energy eastward into the plains. The ECMWF along with the EC and GEFS ensemble means would support holding back the low across the Great Basin even into Day 7. The GFS the past few days has been flip-flopping both solutions, so for days 6-7 the WPC blend leaned heavily towards the ECMWF/GEFS ensemble means and the deterministic ECMWF all of which have showed better overall run-to-run continuity. ...Weather highlights/hazards... Locally heavy (and regionally modest) rain is probable for the northwestern Gulf Coast as the broad trough/area of disturbed weather moves onshore early in the period. Multi-inch rainfall totals appear possible, focused over portions of southeastern Texas and southwestern Louisiana. To the west and northwest, the upper low and moisture from (by then) the remnants of Bud will combine to produce several days of wet weather for the central/northern Rockies and the adjacent High Plains. Moisture may also pool eastward along the quasi-stationary frontal boundary as it lingers across the central Plains for much of the period. Totals of 1-2+" may be common for the 5-day QPF total. Temperatures in the east will be well above average (+10 to +20F) to start the medium range (Monday) from the Midwest to the Northeast/Mid-Atlantic with readings well into the 80s/north and 90s/south, and approaching 100 in some locations. Many daily record maxes will likely be tied/broken along the I-95 corridor. With dew points ranging from the upper 60s to mid 70s, heat indices will be over 100F and close to 110F for some areas. The Pacific Northwest will also see well above average temperatures (especially inland) as they will be located to the northwest of the upper low and coincident with ridging moving out of the northeast Pacific. Temperatures will rise into the 70s/80s west of the Cascades and 90s in the interior of Washington/Oregon. Meanwhile, across the Intermountain West and much of the Plains states, temperatures are forecast to be below normal under the influence of the stubborn upper low and copious amounts of moisture streaming into the region. Santorelli/Fracasso WPC medium range forecasts of 500 mb heights, surface systems, weather grids, quantitative precipitation, and winter weather outlook probabilities can be found at: http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4