Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
798 FXUS02 KWBC 051848 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 248 PM EDT Sat Jul 5 2025 Valid 12Z Tue Jul 8 2025 - 12Z Sat Jul 12 2025 ...Hazardous heat and humidity over parts of the East; building heat over the West... 19Z Update: The overall forecast has not changed very much from the overnight issuance, with mainly minor adjustments to QPF based on the new NBM and deterministic model guidance. In terms of the models, the 00Z CMC strayed from the consensus and the AIFS across the north- central U.S. by the end of the week with a much stronger trough/closed low dropping south across the Dakotas, so the forecast transitioned to more of the GFS/ECMWF and their ensemble means for Thursday-Saturday. There is still very good agreement with the building upper ridge across the Southwest, so that remains the most confident part of the forecast. Across the East Coast region, a Marginal Risk is planned for portions of southern Virginia and eastern North Carolina for Wednesday with a more concentrated axis of QPF noted in the guidance south of a stationary frontal boundary. The previous forecast discussion is appended below for reference. /Hamrick ---------------- ...Pattern Overview... Quasi-zonal flow over most of the CONUS to start the week will transition toward an upper high starting to take residence near Las Vegas and increased troughing into the Northeast. This will favor a fairly typical summertime pattern but without much, if any, monsoon signal into the Southwest. ...Guidance/Predictability Assessment The large scale pattern remains in good agreement through the extended period. Like its previous runs, the GFS and the GEFS mean were persistent in being the faster solutions from the Northeast Pacific into western North America than the other models therefore had limited inclusion in the forecast. The preferred blend was a comprise of the 12Z ECMWF/Canadian/UKMET/ECMWF ensemble mean and the NBM. ...Weather/Hazards Highlights... Showers and thunderstorms are expected to be focused in proximity to progressive cold fronts, stalled boundaries and round the upper high in the Southern Rockies. The wavy front into the eastern U.S. may be a focus for heavier rain and thunderstorms. This includes areas from the Corn Belt into the Midwest and Ohio Valley, Appalachians, Mid-Atlantic, and Northeast. There are Marginal Risks in place (level 1 of 4) for the Southwest, Central Plains/Midwest to the Upper Mississippi Valley/Upper Great Lakes region and portions of the Northeast for Day 4, and for the Mid-Mississippi Valley/Midwest and portions of the Mid-Atlantic for Day 5 for an axis of heavier rainfall possible south of a frontal boundary. Heights across the Northeast and Mid-Atlantic regions will gradually lower as troughing moves in. With the higher heights shifting southward the heat will increase as well as begin to build to the west as the upper high strengthens over the Southwest. Many locations will have daily maximums climbing well into the 100s at lower elevations which will greatly limit rain except for perhaps far southeastern AZ into NM early in the week. Experimental HeatRisk values may rise to Major or Extreme levels (3 out of 4 or 4 out of 4) from the California deserts into southern Nevada, Utah, and Arizona. Campbell/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 forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$