Preliminary Forecasts
Issued by NWS
Issued by NWS
417 FXUS02 KWNH 220643 PREEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 142 AM EST Sat Feb 22 2025 Valid 12Z Tue Feb 25 2025 - 12Z Sat Mar 01 2025 ...Overview... The upper flow pattern should remain rather progressive through much of the medium range period. By Tuesday, a northern stream shortwave will be shifting through the Northeast, with a southern stream wave through the Gulf and Florida. Out West, a shortwave into the Pacific Northwest on Tuesday will progress downstream, with eventual deepening over the East by Thursday or Friday. This allows for an amplifying ridge upstream across the West late week, with a southern stream trough or cutoff low moving inland across Southern California around next Saturday. ...Guidance/Predictability Assessment... Model guidance shows reasonable agreement in the overall pattern evolution described above, though with typical detail differences that could have sensible weather impacts at times. The first few days of the period, models were clustered well enough for a multi- model blend between the GFS, ECMWF, and CMC as a starting point for the WPC progs. By Wednesday and beyond, differences in energy through the mean midwest-East trough become more apparent, and especially as the overall trough deepens later in the week. The 12z CMC was much stronger with this by next Friday, indicating a closed low over the Southeast, and a notable surface low pressure system off the Mid- Atlantic coast. The GFS and ECMWF were more elongated with the trough, with less stream separation. The new 00z CMC run tonight did come in looking more like the GFS and ECMWF. There also remains considerable timing uncertainty with a cutoff low into California Friday or Saturday, though there is general agreement on the presence of this feature. Lots of run to run variability in timing and so leaning towards the ensemble means, which were on the faster side of the envelope, due to a weaker system, seemed like the best option at this point. ...Weather/Hazards Highlights... An Atmospheric River into the Pacific Northwest during the short range period should be inland by the start of the medium range period, with only lighter lingering rains expected. Some enhanced snows will reach the northern Intermountain West/Rockies as the system translates inland on Tuesday, but the Northwest will trend drier midweek and beyond as upper ridging builds in. Gusty winds are also possible across parts of the northwestern to north- central U.S. next week. The most persistent highest winds are likely to be along the northern/central Rockies ridges, while spilling into the Dakotas at times. Downstream, northern stream energy will spread light precipitation from the Great Lakes region through New England into Tuesday. Then moderate cyclogenesis and frontogenesis are likely over the northern Plains/Mississippi Valley Wednesday and work into the East by Thursday and Friday. This could lead to another round of rain and northern tier snow making its way from the north- central to east- central U.S. midweek and across the East by Thursday. By next week, much of the CONUS will be much above normal in terms of temperatures with decent coverage of plus 10-25 degree anomalies. Best potential for highest anomalies will be near the northern Plains. With a building ridge out West, this should hold into next weekend, but the East should moderate back to normal (or slightly below in spots) by late week underneath of troughing. Santorelli 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 $$