Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 PM EST Sat Jan 25 2025 Valid 12Z Tue Jan 28 2025 - 12Z Sat Feb 01 2025 ...South-Central U.S. Heavy Rainfall Threat Wednesday-Saturday... ...General Overview... The WPC medium range forecast period begins on Tuesday with a very slow moving closed low over California, and broad cyclonic flow aloft from the Northern Plains to the Northeast states, with a split upper level flow pattern in place for the beginning of the week. The closed low only makes it to eastern New Mexico by Friday, with a ridge axis trying to build north ahead of it across the Midwest and The South, a trough remaining over New England and a separate trough near the Pacific Northwest. It appears likely that surface cyclogenesis will take place over Texas in response to the approaching upper low, and this has become increasing likely to fuel an increase in Gulf return flow to fuel a multi-day heavy rainfall threat focus from Texas to the lower Mississippi Valley Wednesday- through next Saturday. ...Guidance/Predictability Assessment... 00/06/12 UTC guidance runs generally offers better than normal forecast agreement and predictability across the Continental U.S. for the beginning to mid-later next week. Recent guidance has overall trended slower with the upper low slated to slowly eject out from the Southwestern U.S. through the southern Rockies/High Plains, with the ensemble means generally a little faster than the deterministic guidance. The surface low evolution is a bit more uncertain, but there is a trend for this to be a little more to the south compared to past forecasts. The WPC product suite was primarily derived from a GFS/ECMWF/UKMET/Canadian model composite for Tuesday into early Friday to provide best smaller scale detail. Beyond that, opted to switch to a blend of guidance on the slightly slower side of the full envelope of solutions given latest guidance trends and historical nature of closed lows/troughs in a separated southern stream. Guidance used for this was the GFS/Canadian and ECMWF/Canadian ensemble means. ...Weather/Hazards Highlights... It remains the case that the evolution of the southern Plains low pressure system starting mid-week will likely produce increasing showers and thunderstorms from central Texas to the ArkLaTex region, but given model differences with respect to location and magnitude, no risk areas are currently warranted for either the Day 4 or Day 5 excessive rainfall outlooks in the initial stages of rainfall development. However, this could change as specifics become clearer in future outlooks. Looking beyond the Day 5 period, there has been a general upward trend in expected rainfall totals compared to the previous WPC forecast over the ArkLaTex region to the western Gulf Coast, with the potential for 2 to 5+ inches for this region during the Thursday to Saturday time period. Some strong thunderstorms are also possible depending on how the warm sector of this low pressure system evolves. Training of activity seems increasingly likely to offer local runoff issues to monitor given return Gulf inflow should provide ample moisture. There is also some threat for a snow/ice threat on the northern periphery of this expanding precipitation shield given lingering cold air. Elsewhere across the nation, a swath of light to moderate snow is likely from northern Minnesota to northern New England Tuesday into Wednesday as a clipper type low pressure system crosses the region. Later in the week, rain and mountain snow is expected to make a return to the Pacific Northwest as the next shortwave trough and surface cold front moves into the region, and this could reach much of California going into Friday. Much of the East should finally be back up towards normal temperatures early next week, followed by a return to colder readings by Thursday into Friday after a cold front moves through. Anomalously cold temperatures are expected across the southwestern U.S. under the influence of upper troughing/closed low, with snow for the mountains of Arizona and New Mexico. Hamrick/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