Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
347 FXUS02 KWBC 030656 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 256 AM EDT Thu Jul 3 2025 Valid 12Z Sun Jul 06 2025 - 12Z Thu Jul 10 2025 ...Coastal Southeast heavy rain threat as NHC eyes system.... ...North-central U.S. to Midwest/Northeast heavy rain threats, with trailing activity spread back to the south-central states... ...Hazardous heat and humidity to spread from the Midwest this holiday weekend to the Mid-Atlantic/Northeast early next week as sweltering heat lingers for the South and builds over the West... ...Pattern Overview... The National Hurricane Center shows some potential for Southeast U.S. coastal low development this weekend into early next week to offer enhanced/wind driven rains with any development and track. Pacific shortwaves will work into lingering West Coast mean upper troughs into next week. A building upper ridge downstream will spread a threat of hazardous heat and humidity from the Midwest this holiday weekend to the Mid-Atlantic/Northeast early next week as a hot summer airmass lingers over The South and also builds next week up over the West. There may also be some renewed monsoonal flow into the Southwest. A series of strong to severe convection and heavy rain fueling impulses will progress atop the ridge from the Midwest/Great Lakes to the Northeast, with trailing activity also firing back over the north-central and south-central U.S. ...Guidance/Predictability Assessment The WPC medium range product suite was mainly derived from a blend of compatible GEFS/ECMWF/Canadian ensemble mean guidance along with WPC continuity and the National Blend of Models, but nudged that forecast toward NHC Southeast U.S. low potential. Forecast confidence is high in the overall pattern of widespread heat. Moderate confidence is in the precise timing and intensity of convective outbreaks and the longevity of the most extreme heat in specific locales. The developement and track of the potential tropical system offshore the Southeast U.S. coast will be critical to monitor. ...Weather/Hazards Highlights... WPC Excessive Rainfall Outlook (ERO) Marginal Risk areas have been added for Day 4/Sunday and Day 5/Monday for the coastal Southeast given the increased moisture and rainfall potential associated with possible system development that the NHC is monitoring. A slow main frontal push across from the Great Lakes/Ohio Valley states and the Northeast may focus periods with enhanced pooled moisture and instability to fuel some strong to severe storms and locally heavy rain/runoff threats with training potential in spots Sunuday into Monday as upper trough/impulse energies work on the northern periphery of the main central U.S. upper ridge. Trailing activity extends back next week with impulses over the south- central U.S. and into the Southwest with some renewed monsoonal flow. Elongated WPC ERO Marginal Risk areas are depicted for Day 4/Sunday and Day 5/Monday. Convection/MCS activity will also fire back to the north-central states next week as subsequent upper- level waves interact with moisture/instability pooling fronts/upper diffluence. A Day 5/Monday marginal risk area was introduced there. Meanwhile, a broadening upper ridge will spread a hazardous heat and humidity threat from the Midwest this holiday weekend to the Mid-Atlantic/Northeast into next week as a very hot summer airmass lingers broadly over the South and also builds up across the West. Schichtel 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 $$