Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Sat Feb 8 2025 Valid 12Z Tue Feb 11 2025 - 12Z Sat Feb 15 2025 ...Heavy rain and potential flooding concerns developing in the southeastern quadrant of the lower 48 through Wednesday... ...Rounds of snow and ice are possible stretching from the central Plains to Mid-Atlantic/Northeast next week... ...Overview... Models and ensembles show a very active pattern during the Tuesday-Saturday period. Shortwave energy emerging from the West/Plains and associated frontal waves will likely focus an axis of heavy rainfall and flooding concerns over parts of the southeastern quarter of the lower 48 early-mid week with snow farther north from the central Plains into the Northeast Tuesday into Thursday. A wintry mix will be possible between the rain/snow areas. Then during the latter half of the week a Pacific system should bring areas of significant rain and mountain snow to parts of the West. This system may reach far enough east to develop precipitation over the central/eastern U.S. once again by next Saturday. Expect well below normal temperatures to persist over the Northwest and into the northern-central Plains Tuesday-Thursday. The West should see some moderation late week into the weekend as the region sees greater influence from Pacific flow. The central/southern Plains will briefly trend warmer late in the week but expect the cold air still over the northern Plains to push southward again on Saturday. The greatest number of days with above normal temperatures will likely be over the Gulf Coast and far Southeast. ...Guidance/Predictability Assessment... The updated forecast started with a 12Z operational model composite consisting of 40 percent ECMWF and lesser weights of the GFS/CMC/UKMET for about the first half of the period and then transitioned to 40 percent ensemble means (18Z GEFS and 12Z ECens/CMCens) and the rest evenly split among the GFS/ECMWF/CMC by Day 7 Saturday. The best clustering of dynamical and machine learning (ML) guidance continues to be somewhat faster than the GFS/GEFS mean (and especially the 18Z GFS) for shortwave energy initially dropping into the Northwest and then ejecting eastward, leading to low pressure reaching the East by Thursday and continuing on toward the Canadian Maritimes by Friday. However there were a couple 12Z ML models that had hedged a bit slower than the ECMWF/CMC cluster, with some guidance also hinting at potential for a little more northern stream shortwave influence. This supported at least a minimal inclusion of the 12Z GFS which was closer to the other guidance than the 18Z run. The new 00Z ECMWF/UKMET also show some nudges, in particular toward slower progression of the southern part of the trailing cold front. At least through the 12Z/18Z cycle, guidance was showing better clustering for the Pacific system tracking toward the West Coast after midweek, with consensus trending stronger over the past couple days along with the surface low track clustering in the central-northern part of the prior envelope. The new 00Z ECMWF/ICON add a little doubt though, with a southward adjustment. The ECMWF also trended noticeably slower. As this system continues eastward, there is better than average agreement in concept but with typical differences in timing/strength of the upper trough and associated central U.S. surface pressure by next Saturday. ML models suggest some skepticism of the strong 12Z ECMWF and new 00Z GFS for the Plains surface low. Consensus is also decent for a North Pacific system whose leading warm front may approach the Northwest by next Saturday. ...Weather/Hazards Highlights... Rapid progression of a leading wave and the approach of a stronger shortwave from the West will maintain a wavy frontal boundary over the South during Tuesday-Wednesday, essentially parallel to southwesterly flow aloft, and interacting with anomalous moisture. Guidance has been signaling the potential for excessive rainfall with flash flood potential during this time frame in recent days and continues to refine the expected axis of heaviest rainfall in successive runs. The new Day 4 Excessive Rainfall Outlook valid on Tuesday has expanded the Slight Risk area back to the northern part of the Texas/Louisiana border per latest guidance, while holding the eastern extent of the fairly consistent over far southeastern Tennessee and northwestern Georgia. The favored area for heavy rainfall on Day 5 Wednesday comes close to overlapping this region, shifting only a fraction east/northeast, with a Slight Risk again indicated. Rainfall from the previous day would make this region increasingly sensitive to additional rainfall. Eastern U.S. low pressure tracking northeastward on Thursday should drag a cold front through the Southeast, with associated rain trending less intense. The northern side of the precipitation shield may contain rounds of potentially disruptive wintry precipitation next week. The favored band for winter weather should extend from the central Plains through the Middle Mississippi Valley, Ohio Valley, central Appalachians, and Mid-Atlantic/Northeast where moisture overrunning southern tier fronts will interact with cold air. 50+ percent probabilities for a quarter inch of liquid equivalent snow/sleet remain in place from the central Appalachians into parts of the Mid-Atlantic for Tuesday to Wednesday morning (70-90 percent over parts of West Virginia and Virginia), including some of the larger I-95 metropolitan areas--albeit with a very slight southward nudge from prior issuance based on trends from some incoming 00Z models. Meanwhile sleet and freezing rain are possible 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. The next wave, reaching the East on Thursday, should produce a somewhat farther northward band of snow, from the Midwest into the northern Mid-Atlantic and Northeast. After a fairly dry period early in the week, expect a Pacific system to spread potentially significant rain and mountain snow into the West after midweek. For the Day 5 ERO period Wednesday- Wednesday night, models vary between heavy and minimal precipitation reaching California. Starting out with a Marginal Risk area along the northern half to two-thirds of the California coast provides a reasonable intermediate reflection of the guidance envelope at this time, with confidence lower than average. After early Thursday expect moisture to continue through the West, with this system likely emerging into the Plains next Saturday and developing another area of various precipitation types over the central/eastern U.S. Northwestern and north-central parts of the lower 48 will see colder than average temperatures next week. The cold will be especially pronounced across Montana and North Dakota early in the week, with lows 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 across the southern tier during the weekend. Warmer than average temperatures should be limited to Florida and the adjacent Southeast by midweek. Introduction of Pacific flow should promote a moderating trend over the western-central U.S. by next Friday (but remaining quite cold over the northern Plains). Low pressure emerging over the Plains by next Saturday will help to pull down the lingering northern Plains cold air back down into the central Plains. At the same time, parts of the East should begin to trend somewhat warmer. Rausch 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