Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Thu Feb 6 2025 Valid 12Z Sun Feb 09 2025 - 12Z Thu Feb 13 2025 ...Heavy rain developing in the southeastern quadrant of the lower 48 Monday-Wednesday... ...Rounds of snow and ice are possible stretching from the central Plains to Mid-Atlantic/Northeast next week... ...Overview... The synoptic pattern setting up next week will consist of a developing positively tilted trough axis in the interior West toward Hudson Bay, with general southwesterly upper flow over the East that allows for shortwaves moving through. One shortwave and surface low will pull away from the Northeast Sunday after spreading some heavy snow to the region. Rain chances will increase from the Ark-La-Tex into the Southeast Monday and beyond, with heavy rain and flooding possible. Meanwhile snow is possible on the northern side of the precipitation shield, generally across the central Plains/Middle Mississippi Valley and Ohio Valley toward the Mid-Atlantic and Northeast, with some places seeing multiple rounds of wintry weather. Sleet and freezing rain are possible as well. Meanwhile, the West will see drier conditions early next week before an atmospheric river returns around midweek. Temperature- wise, below average temperatures in the northern tier are forecast to trend colder and spread across the central U.S. as the week progresses. ...Guidance/Predictability Assessment... Models show generally good agreement on the overall pattern during the period but with differences in the smaller scale details that will have sensible weather implications. Models show a western Atlantic surface low producing snow in the Northeast at the start of the period Sunday that quickly pulls away to the Northeast. In the southern to eastern U.S. next week, the pattern will be dominated by small frontal position differences and low pressure waves along the front. These lead to differences in precipitation type and amounts and timing, but are rather unpredictable this far out. In the western and central U.S., several northern and southern stream energies moving through the trough are more uncertain as the period progresses. After several CMC runs showed a trough axis oriented to the southwest in the eastern Pacific early next week unlike other guidance, the 00Z run finally aligns better with the consensus. But there remains considerable spread with a shortwave dropping southward through the northern side of the trough Monday- Tuesday and its pivot eastward. This results in considerable QPF differences along the West Coast by Tuesday and Wednesday, including the timing of precipitation arrival, and models like the 12Z ECMWF and 18Z GFS focusing heavier QPF amounts in southern California by midweek. Expect further changes to the forecast with this uncertain system. The WPC forecast used a blend of the deterministic ECMWF/GFS/UKMET early in the period, and gradually increased the proportion of ensemble means to just over half by the late period given the increase of spread in individual models. ...Weather/Hazards Highlights... The pattern looks to become increasingly favorable for rain across parts of the southern Plains and Lower Mississippi Valley to Tennessee Valley and Southeast for early to mid-next week. Local to widespread heavy rain could be a threat in these areas. On Monday, moisture and instability may pool centered in Arkansas and training of convection is possible given the west-east oriented fronts. Thus a Marginal Risk seems prudent for the Day 5/Monday ERO. ERO areas will likely be needed in the Southeast Tuesday- Wednesday once those heavy rain areas phase into the ERO timeframe. On the northern side of the precipitation shield, rounds of potentially disruptive wintry precipitation are possible next week. The favored area for winter weather will be generally from the central Plains into the Middle Mississippi Valley, Ohio Valley, central Appalachians, and Mid-Atlantic/Northeast where moisture overrunning southern tier fronts will interact with cold air. Currently the highest probabilities (50-70 percent) for a quarter inch of liquid equivalent snow/sleet are in place across the Mid- Atlantic to southern parts of the Northeast for Tuesday to Wednesday morning, including some of the larger I-95 metropolitan areas. Meanwhile sleet and freezing rain are possible in between the chances for heavy rain to the south and snow to the north. Stay tuned for refinements to the forecast as the placement, amount, and type of precipitation remains uncertain at any individual location. Precipitation is finally forecast to lessen in scope and magnitude in the West early next week, with just some light amounts in the Pacific Northwest and parts of the northern/central Rockies. Models vary on the timing, strength, and positioning of another round of precipitation entering the West next week with a possible atmospheric river. Precipitation chances generally look to increase Tuesday and especially Wednesday for parts of the West Coast, but stay tuned for potential forecast changes for this uncertain system. Colder than average temperatures are forecast for northwestern and north-central parts of the lower 48 through the period. The cold will be especially pronounced across Montana and North Dakota into Minnesota as the workweek begins. By Monday through much of the week, lows are forecast to be in the -10s and -20s, along with some below zero highs. Colder than average temperatures will spread south behind a cold front next week, displacing unseasonable warmth that persists across the southern tier into Sunday. Warmer than average temperatures should be limited to Florida and the adjacent Southeast by midweek. Tate 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