Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 PM EST Sun Jan 26 2025 Valid 12Z Wed Jan 29 2025 - 12Z Sun Feb 02 2025 ...South-Central U.S. Heavy Rainfall Threat Wednesday-Saturday... ...General Overview... A main weather system this week will be a slow moving closed upper low will linger over the Southwest Wednesday and Thursday, then gradually eject northeast towards the southern/central Plains and Midwest Friday and Saturday. This feature will be accompanied by an occluded low pressure system at the surface that could bring a heavy rainfall threat to the south- central U.S. during the second half of the week. Meanwhile, a broad upper trough will swing across the north- central and northeastern U.S. and ridging will extend north into the Pacific Northwest. By Friday, a trough will approach the West Coast and push a Pacific frontal system east across the West next weekend while an Arctic front sinks south across the north-Central U.S.. ...Guidance/Predictability Assessment... Model guidance has been in reasonable agreement on the overall pattern through the end of the week, and to a lesser degree by next weekend. There is uncertainty surrounding the evolution of the main Southwest U.S. occluded surface low, and recent guidance including the latest 12 UTC cycle has trended more progressive except for the GFS. While the timing could be faster, closed upper lows tend not to be. Overall, there is still good agreement for development of heavy rainfall downstream, especially in the warm sector of the system over the south-central U.S. later this week, with expected strong to severe convections as per SPC. The WPC forecast model blend consists of a blend of best clustered guidance of earlier cycle 06 UTC GFS and 00 UTC ECMWF/UKMET for Wednesday to Friday. Opted to add to the mix input from the GEFS/ECMWF ensemble means for next weekend amid generally slow forecast spread growth. ...Weather/Hazards Highlights... A slow moving occluded low pressure system is forecast to move across the southern Plains Wednesday through Friday with a cold front extending southwest into Mexico and a warm front lifting into the Lower Mississippi Valley. Warm, moist air from the Gulf will be in place across the south-Central U.S., setting the stage for a multi-day heavy rainfall event. The best chance for heavy rainfall will be in the warm sector and in the vicinity of the triple point low where moisture and instability will be maximized, and there could be potential for training/repeat convection ahead of the slow trailing cold front. Heavy rainfall could lead to flash flooding concerns across the southern Plains and Lower Mississippi Valley, especially in the Ark-La-Tex region down to the Gulf on Thursday and the central Gulf Coast states Friday into Saturday. For the Day 4/Wednesday Excessive Rainfall Outlook, there is a bit too much uncertainty in rainfall location to introduce any risk areas at this time, but there still could be limited potential for heavy rainfall in portions of Texas in an emerging pattern to monitor. For the Day 5/Thursday Excessive Rainfall Outlook, a broad Marginal Risk from the southern Plains to the Mid/Lower Mississippi Valley and a Slight Risk for the Ark-La-Tex has been depicted given the strong signal for heavy rainfall. Early in the period, a clipper type low pressure system will bring a swath of wintry weather to the Great Lakes and Northeast, with some localized heavy snow potential. This system will quickly move east, and a couple days of dry weather are expected for the northern tier before precipitation associated with the occluded low reaches the area. Precipitation chances will extend to the north of the occluded system, spreading to encompass much of the eastern third of the nation by Saturday, and there will be a chance for snow/ice on the northern extent of the precipitation shield given lingering cold air dammed in place. Wintry weather is also anticipated on the backside of the low, and heavy snow/ice will be possible in northern New Mexico and southern Colorado and then northeastward out across the central U.S into Thursday and Friday. In the West, precipitation chances will gradually increase across the region late week into the weekend as a Pacific frontal system pushes inland. Widespread rain and mountain snow is expected, and heavy snowfall is forecast for the Cascades and the Sierra inland through the northern Rockies. The guidance signal has increased with the digging of ample upper trough/low energy down the coast. Temperatures will generally be near or above normal for much of the lower 48 late this week into the weekend, but there will be a few opportunities for below normal temperatures. The Southwest will likely be below normal Wednesday and Thursday under the influence of the closed upper low. The Northeast will likely be below normal Wednesday into next weekend in as clipper systems move through and colder air sinks into the region. Finally, there will be a chance for well below normal temperatures in the northern Rockies/High Plains next Sunday as an Arctic front sinks south over the region. Dolan/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