weather.gov |
Site Map | News | Organization |
DOC | NOAA | NWS | NCEP Centers: | AWC | CPC | EMC | NCO | NHC | OPC | SPC | SWPC | WPC |
|
WPC Medium Range Archive
Medium Range Products Valid On:
09/12/2024
(Day 7 PMDEPD: Valid 09/08/2024 to 09/12/2024)
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD 253 PM EDT Thu Sep 5 2024 Valid 12Z Sun Sep 08 2024 - 12Z Thu Sep 12 2024 ...Overview... An amplified upper-level pattern will be in place this weekend with an upper ridge over the West that shifts east with time, as a mean upper low/trough slowly works through the Northeast. This will usher in a fall-like dry and cool air mass across much of the eastern half of the country. Elsewhere, a lingering and wavy front will keep rain chances across the Gulf Coast to Florida, while tropical moisture moving into the southwestern Gulf could bring heavy rain into South Texas by early next week. ...Guidance/Predictability Assessment... Models have been very consistent with the upper level pattern in the eastern and southern U.S., but they have been struggling with an amplified trough that's forecast to move into the West during the second half of the period. The 00Z ECMWF seems to deviate the most from the consensus and yesterday's ECMWF runs, it splits the trough energy, resulting in a much weaker wave in the West compared to other guidance like the GFS and CMC. Today's 12Z ECMWF run was not available at the time the forecast was made, but it has fallen back into line with the consensus, having a stronger trough move into the West mid/late next week. For the WPC afternoon forecast, a blend of the deterministic GFS/CMC/UKMET/ECMWF was used for the first half of the period, opting to use yesterday's 12Z ECMWF run instead of the 00Z run. Ensemble means were added gradually to make up to 50% of the blend for the second half of the period, which helped to smooth out differences in the West by Days 6 and 7. ...Weather/Hazards Highlights... A lingering front across North Florida and along the Gulf Coast will continue to focus showers and storms, locally heavy, into next week. Heavy rain that is forecast across North Florida and southern Georgia in the short term period will likely saturate soils and could make this region more prone to flooding with any locally heavy rain that may fall on days 4 and 5 (Sunday and Monday). A Marginal Risk area will likely be introduced in the Day 4/Sunday ERO, and an additional Marginal Risk may eventually be needed on day 5/Monday. Tropical moisture moving into the southwestern Gulf may bring an increasing threat for heavy rain to South Texas, which is covered by a Marginal Risk on the Day 5/Monday ERO. Some guidance shows potential for locally significant amounts that will need to be monitored. Otherwise, much of the country should be quiet and dry, although shortwave energy within and around the western U.S. upper ridging may produce isolated to scattered rainfall with mostly light amounts. Rainfall ahead of the next Western U.S. trough should begin to move into the region late Tuesday. Above normal temperatures across the Northwest on Sunday will shift into the Northern Plains early next week and into the Midwest by mid-next week. Daytime highs are forecast to be 10-20 degrees above normal, but this may only equate to a moderate HeatRisk threat. In contrast, a much cooler airmass will be in place across the East this weekend, but may trend back towards normal next week. Below normal temperatures should also develop along the West Coast mid-next week as an upper trough moves onshore. Santorelli/Dolan 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
|