Extended Forecast Discussion NWS Weather Prediction Center College Park MD 236 PM EDT Mon Jul 12 2021 Valid 12Z Thu Jul 15 2021 - 12Z Mon Jul 19 2021 ...Remaining hot in the northern Great Basin to the High Plains... ...Overview... Upper pattern will remain somewhat anchored during the period with troughing just west of British Columbia and over the Great Lakes/Northwest with building upper ridging into the Four Corners Region. This will promote above normal temperatures for much of the interior West, especially into Montana and the High Plains. A frontal boundary will slowly push eastward out of the Corn Belt into the Northeast and eventually Mid-Atlantic with showers and storms along and ahead of the boundary. Some rainfall may be locally heavy. Over the Southwest, the Monsoon will help touch off some showers and storms around the upper high across portions of AZ/NM/CO. ...Guidance/Predictability Evaluation... Models and ensembles showed better than average predictability in the longwave pattern evolution/orientation but less agreement on the embedded shorter-scale features. The 06Z GFS and 00Z ECMWF offered reasonable clustering with their ensemble means and each other such that a blended solution (with added detail from the UKMET and somewhat the Canadian) sufficed as a starting point. The GFS was a little quicker to bring in some height falls to the Pac NW early next week compared to the ECMWF (along with their ensembles), but this may be a function of how the upper low may send shortwaves around its base and has limited predictability. Over the East, the GFS and Canadian were slower to move the upper trough eastward than the ECMWF, with the ensemble consensus a little on the slower side. ...Weather Highlights/Hazards... As the cold front moves out of the Midwest to the East, showers and storms will be capable of producing scattered light to moderate rainfall with locally heavier amounts where thunderstorms maximize. Moisture will be above normal, though modestly, along with dew points well into the 60s and low 70s. Temperatures will be near to above normal ahead of the front by a few degrees, with only a few to several degree drop in its wake. Areas of highest rainfall chances will slowly shift southward and eastward this weekend into early next week. In the West, rising heights will maintain dry and warming conditions for the Interior through Montana where temperatures will climb from the 90s to low 100s in eastern lower elevation areas by next Sun/Mon (as well as in favored/warmer valley locations in ID and UT). Temperatures in the Southwest will be near to perhaps slightly below normal due to increased cloud cover and higher rainfall chances. Rainfall will be favored over higher elevations of AZ/NM/CO during the afternoon and early evening (perhaps into some valley locations). Fracasso Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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