Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Thu Mar 2 2023 Valid 12Z Sun Mar 5 2023 - 12Z Thu Mar 9 2023 ...Synoptic Overview... The weather pattern for the Sunday to Wednesday time period will be featured with a persistent upper trough and cold conditions over the western U.S., and a broad upper ridge over the south-central U.S. with April-like temperatures continuing. The upper trough should slowly emerge over the Plains and Great Lakes region by the end of the forecast period next Thursday, along with an impressive surface high over Canada that spreads southward across the north-central states. By Thursday, a low pressure system may develop across the Gulf Coast and Deep South region and bring an increase in rain and thunderstorms. ...Guidance/Predictability Assessment... The model guidance and the ensemble means are initially in above average synoptic scale agreement across the nation for the Sunday and Monday time period with the most notable mesoscale differences across southern Canada, so a multi-deterministic model blend suffices as a starting point during this time. Things become much more unclear going into the middle of next week regarding the eventual evolution of the upper trough across the West. The 12Z and 18Z GEFS means are at odds with both the better clustered CMC and EC means across the West Coast region, and this is where forecast confidence is currently lowest. Better agreement exists across the Eastern U.S. for this time. Taking these factors into account, the latter half of the forecast was hedged in the direction of the ECMWF/ECENS and some of the CMC. ...Weather/Hazard Highlights... A deep upper trough will remain anchored in place over the West Coast this weekend and persist into the first half of next week. This trough along with embedded shortwaves will increase the potential for coastal rain and heavy inland snow from the Pacific Northwest into central California. Some of the highest accumulations are expected to be across the northern California mountains and into the Sierra, adding to the already very impressive snow pack over the region. Moderate snow is likely across portions of the Northern and Central Rockies. Going into the middle of the week, rain is likely to develop from the ArkLaTex region to the Deep South and Tennessee as a potential low pressure system gathers strength, which may also include some thunderstorms. This does not look to be particularly heavy at this juncture. Farther north, some areas of light snow are possible across the northern Great Lakes on Monday and then across the central Plains on Tuesday/Wednesday. Ridging across the Gulf of Mexico will keep much of the south-central states and the Southeast feeling more like late April, with many locations having temperatures 10-20 degrees above early March averages along with increasing humidity levels from Texas to the Southeast states. The warmth is also expected to reach the Midwest and the Ohio Valley by Monday with highs well into the 60s and low 70s. The West will continue to feel like the middle of January through the weekend with the Intermountain West and Rocky Mountains consistently having highs on the order of 10 to 20 degrees below normal, which will equate to highs in the 20s and 30s for most areas north of the Utah/Arizona border. The cold weather will likely spread eastward across the central and northern Plains by Wednesday and Thursday. Hamrick 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, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices are at: 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