Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1136 AM EDT Tue May 28 2019 Valid 12Z Fri May 31 2019 - 12Z Tue Jun 04 2019 ...Overview and Guidance Evaluation/Preferences... Through the course of this coming week the subtropical ridge over the Gulf of Mexico will slowly retrograde toward the West; which will ease up a bit over the Southeast U.S. A closed low will slowly sink southward through California with minimal eastward progression due to the westward ridge expansion. This will promote a slow moving cold front through the Pacific Northwest and Great Basin regions. As northern stream energy periodically encounters a persistent upper low in the vicinity of Hudson Bay, the energy will amplify in the broad cyclonic flow with shortwaves digging into the north-central and northeastern U.S. The deterministic models had a decent handle on the pattern progression for the first couple of days of the extended forecast then quickly increased their spread, especially across the East. The ensemble means were an improvement over the deterministic solutions for days 5 and beyond. Therefore, the initial starting point for this issuance was 00Z ECWMF, 00Z GFS and the 06 FV3 with some inclusion of the 00Z NAEFS, GEFS and ECENS. Weighting of the means increased while the deterministic decreased June 2nd onward. These continues to be a signal within the models depicting the northern stream ridge axis shifting eastward to the Northern Plains/Midwest, which would allow stronger height falls across the Pacific Northwest. Meanwhile, the subtropical ridge should gradually retrograde to the western Gulf of Mexico, keeping a warm and moist air mass feeding northward into the south central states. Leading shortwave energy crossing the northern Rockies Sun should bring a low pressure system into south central Canada by early next week with the associated frontal system moving across the Northern Plains and Midwest. ...Weather Highlights and Hazards... Areas of showers and thunderstorms with locally heavy rainfall are possible across portion of the Southern and Central Plains Fri-Sat north of a weakening surface front along the Rio Grande Valley. Showers and thunderstorms may become more widespread across these areas Sun-Tue, with continued heavy rain potential, as another cold front arrives from the north, providing additional focus/enhancement of convection. Farther west, periodic showers are expected from the Great Basin to the central/northern Rockies as a couple weak southern stream shortwaves traverse the region. This activity should be a bit more widespread Fri-Sat before becoming more sparse Sun-Tue as the most significant shortwave energy moves east and heights gradually rise across the region. Temperatures across much of the Southeast are expected to continue being above average for early June. Daily maximums are forecast to be 5 to 10 deg F above average across this region into early next week. Farther west, the Pacific Northwest will initially be quite warm, with highs expected to be 10 to 15 deg above average with the upper ridge in the vicinity. These temperatures should moderate slightly by early next week, but above average temperatures are expected to continue as northern stream shortwave energy fails to lower heights substantially across the region. Campbell 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