221 FXUS02 KWBC 230723 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 323 AM EDT Wed Sep 23 2026 Valid 12Z Sat Sep 26 2026 - 12Z Wed Sep 30 2026 ...Impactful coastal storm meanders near the northern Mid- Atlantic/Northeast through the weekend... ...Overview... An upper low will stall atop the Mid-Atlantic and Northeast into the weekend and early next week, supporting a meandering coastal surface low. This pattern will lead to strong/gusty onshore winds for multiple days, leading to coastal flooding, rip currents and high surf, and potential beach erosion. An upper ridge persisting in the south- central U.S. will promote warm temperatures while a shallow trough moves through the north-central U.S. over the weekend. Upstream, a deeper trough will reach the West Coast Sunday and move through the western and central U.S. early to midweek, spreading ample moisture and precipitation chances ahead of it. ...Guidance/Predictability Assessment... Recent model guidance continues to show a reasonably good handle on the large scale pattern, but with uncertainty in the details that could impact sensible weather. First, the placement of the Atlantic low remains questionable from day to day, impacting wind speed/direction and how much rain falls onshore vs. offshore. The recent 00Z guidance is slightly more agreeable, as the ECMWF shifted east, not so tucked in near Long Island on Sunday than its previous run. The 00Z ECMWF and CMC are pretty close together with the track now, while the AIGFS and GFS are a bit farther north, and the EC-AIFS a bit west. Another interesting trend has been a weaker low than previous forecasts, as most models and ensemble members no longer ever show a central pressure in the 980s. In any case, the low should be weakening by Monday-Tuesday and generally looks to pull away from the Northeast on Tuesday. Meanwhile, an upper ridge will stretch northward across the Mississippi Valley and Great Lakes Saturday. A shortwave looks to pass from the north-central Plains to the Ohio Valley Sunday and could break apart the ridge, with an upper high center contributing to the initially blocky pattern in the Great Lakes/southeast Canada. Ridging should rebuild in the south-central Plains Sunday- Monday. This all shows fairly good model agreement, though varying positions of weak fronts and precipitation potential cause uncertainties in the temperatures. Farther west, a longwave trough is forecast to reach the West Coast Sunday and move through the West early next week and the central U.S. Tuesday-Wednesday. Recent guidance is mostly agreeable that the trough should stay phased as it moves east, so model spread is not too large for its timing tracking east. The pattern could stay progressive as yet another trough could reach the Northwest late period. The ECMWF seems somewhat fast with this trough, moving through the northern Rockies midweek while other models and ensembles are back near the Pacific Northwest. Another feature to note is Hurricane Polo, which will be monitored for its potential moisture connection into the Southwest and beyond next week. After backing off a day ago and keeping Polo farther west, some members do now show Polo approaching Baja California again. See NHC for the official track. The WPC forecast used a blend of deterministic, AI, and ensemble mean guidance through the forecast period, with gradually increasing proportions of the ensemble means to over half by Day 7 to lessen individual model differences. ...Weather/Hazards Highlights... The meandering surface low in the western Atlantic will lead to broad onshore flow across the Mid-Atlantic and Northeast for multiple days. This persistent pattern could lead to coastal flooding and beach erosion concerns, especially when combined with high astronomical tides. Exact placement of the surface low from day to day and thus any heavy rain is more uncertain. The latest forecast continues to offer support that coastal New England may see heavy rainfall into the weekend. However, stay tuned for forecast updates, as small shifts in the low track would lead to significant forecast shifts in rainfall amounts. See WPC's Key Messages for this coastal low for further information. Rain chances are forecast across the Upper/Middle Mississippi Valley into the central Plains on Saturday, with light to moderate amounts. The northern Plains and the Middle/Lower Mississippi Valley could see some rain into Sunday. Meanwhile, Pacific moisture should make a return ahead of the large-scale trough in the West, bringing some rain to the Four Corners states northward Sunday. Precipitation is forecast to become more widespread Monday, stretching into much of the Plains to Upper Midwest, and tracking east to reach the Mississippi Valley on Tuesday. Rain could be heavy in some areas but the details will have to be refined in future forecasts. Some snow is possible in the higher peaks of the Intermountain West/Rockies with the precipitation, as the trough aloft helps to cool temperatures. Warmer than average temperatures will persist in the south-central U.S. into the weekend and early next week under the upper ridge, and highs in the 90s are forecast through the southern Plains and Lower Mississippi Valley. A round of slightly above average temperatures may push through the north-central U.S. as well. On the other hand, cooler than average temperatures (especially for highs) are forecast for the Northwest under troughing aloft, gradually spreading eastward into the Interior West early next week and helping to moderate temperatures in the Plains 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, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at: 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 $$