Extended Forecast Discussion NWS Weather Prediction Center College Park MD 157 AM EST Mon Jan 27 2025 Valid 12Z Thu Jan 30 2025 - 12Z Mon Feb 03 2025 ***Heavy rain and strong thunderstorms expected across the Southern U.S. to close out the work week*** ...General Overview... The forecast period begins Thursday with a cut off upper low ejecting slowly eastward from the Southern Rockies to the western High Plains, and this will sustain a surface low that is expected to track from Texas and eventually to the East Coast by Saturday. This is expected to fuel the development of numerous showers and some strong/severe thunderstorms on Thursday across portions of the Deep South to close out the week. Back across the Pacific Northwest, a cold front and associated moisture feed ahead of it will lead to the return of rain and mountain snow by Friday and continuing into the weekend. By next Monday, an arctic airmass settles southward across the Northern Plains behind a strong cold front, while most of the U.S. has a return to warmer temperatures. ...Guidance/Predictability Assessment... The 18/00Z model guidance suite is in good synoptic scale agreement across the country for the end of the week, and a general deterministic model blend suffices as a starting point in the forecast process. There has been a notable trend for a much faster progression of the low pressure system crossing the southern tier states, and is easily several hundred miles faster than earlier forecasts since the upper low is progged to get dislodged quicker and become absorbed by the westerlies. Even though the guidance is in good agreement on this scenario, future adjustments in timing are very likely given the recent trends. Given the transition to a more zonal flow pattern aloft by Sunday and into Monday, the guidance differs more with timing and magnitude of features in the northern stream flow, and the arrival of the arctic front across the Northern Plains. The forecast blend transitioned to about 50% ensemble means by Monday to account for the increasing model uncertainty. ...Weather/Hazards Highlights... A slow moving occluded low pressure system is forecast to move across the southern Plains Thursday and then across the Deep South and Tennessee River Valley on Friday. In the warm sector of the surface low, warm air advection in combination with strong forcing aloft will create a favorable environment for heavy rainfall from the ArkLaTex region to the Mid South. There will likely be a corridor of 2 to 4 inch rainfall totals across portions of this region, and there could be the potential for training/repeated convection ahead of the slow trailing cold front. Therefore, a Slight Risk is planned for Day 4 from northeast Texas to near the greater Memphis area, and this has been adjusted about 50-100 eastward compared to the previous Day 5 outlook. For the new Day 5 outlook, a Marginal Risk area is planned from extreme northwest California to the Olympic Peninsula of Washington where a potential atmospheric river event could lead to some periods of heavier rainfall on Friday. This is expected to continue into the weekend as well with additional moist onshore flow. A period of dry weather is expected for the Ohio Valley and into the Northeast before precipitation associated with the occluded low reaches the area. Precipitation chances will extend to the north of the occluded system, and there will be a chance for snow/ice on the northern extent of the precipitation shield given lingering cold air in place. Wintry weather is also anticipated on the backside of that same low on Thursday, and heavy snow/ice will be possible in northern New Mexico and southern Colorado and adjacent portions of Kansas and the OK/TX panhandles. Temperatures are expected to be pleasantly mild to close out the week for this time of year across much of the central and eastern U.S., with highs running about 5-15 degrees above average in most cases, and perhaps 20+ degrees above average across parts of the Upper Midwest on Thursday. This also holds true going into the weekend, although New England and the Mid-Atlantic region likely remain closer to seasonal averages. The next round of arctic cold likely arrives across Montana on Sunday and extends into the Dakotas by Monday, with highs potentially 15-25 degree below average in many cases. 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 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