Preliminary Forecasts
Issued by NWS
Issued by NWS
015 FXUS02 KWNH 190701 PREEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Sat Apr 19 2025 Valid 12Z Tue Apr 22 2025 - 12Z Sat Apr 26 2025 ...Heavy rain threat for the South-Central U.S. next week... ...Guidance/Predictability Assessment... Tonight`s WPC medium range 500mb and surface progs were mainly derived from a composite of best clustered mass field and QPF guidance of the 12 UTC ECMWF/UKMET/Canadian models valid Tuesday into Wednesday. Switched to best compatible 12 UTC ECMWF/NAEFS ensemble means and the 12 UTC ECMWF model for better details for the remainder of next week amid growing forecast spread, but still with seemingly near normal predictability beyond local convective foci. In addition to smaller scale embedded system differences, this solution in particular offers stronger than concensus upper trough amplification and wavy surface system support from the eastern Pacific through the West Coast heading Friday into next weekend. This is strongly supported by machine learning guidance. ...Weather/Hazards Highlights... A protracted series of generally progressive upper features and associated surface based systems are set to work over the lower 48 next week in multiple stream flows to locally focus April weather, but there is a growing signal to amplify the flow from the eastern Pacific into the West heading into and through next weekend. A WPC Excessive Rainfall Marginal Risk area for portions of the Southern Plains for Day 4/Tuesday and Day 5/Wednesday have been introduced given the potential for repeat/training of cells during the day and with overnight activity with emerging moist and unstable return flow into and over several frontal boundaries. Portions of this area are also forecast to have enhanced rainfall this weekend that would lead to wet soil conditions. Heavy rain and runoff threats along with strong convective potential in this region and into the Mississippi Valley will also be monitored for mid-later next week given lingering support and multi-day potential, albeit with greater uncertainty on the details. An expectation for upper trough amplification, wavy surface system genesis and slow translation from the eastern Pacific to the West Coast Friday into next weekend has the potential to offer increased moderate rain chances with unsettled/cooling weather conditions. 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 $$