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WPC Medium Range Archive
Medium Range Products Valid On:
10/02/2025
(Day 7 PMDEPD: Valid 09/28/2025 to 10/02/2025
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD 345 PM EDT Thu Sep 25 2025 Valid 12Z Sun Sep 28 2025 - 12Z Thu Oct 02 2025 ...Heavy rain threat continues through Sunday for the Southwest... ...Tropical Disturbance may bring tropical impacts to the Southeast and Mid-Atlantic next week... ...Overview... An upper trough/low will remain stalled over the Southwest through Sunday, blocked by strong ridging downstream. A deep upper low and trough will move towards the West Coast early next week, lifting the upper low out of the Southwest and increasing precipitation chances across the West. The Central U.S. will remain mostly dry through the period under the influence of high pressure ridging, but the Eastern U.S. may be entering a wetter pattern. A cold front will move across the Northeast Sunday into Monday while a stationary front lingers along the Southeast and Mid-Atlantic coasts. There may be a chance for heavy rainfall and flash flooding over portions of the Southeast and Mid-Atlantic Monday through Wednesday, but that will depend on the evolution of a likely tropical low forming near the Bahamas over the next few days. ...Guidance/Predictability Assessment... Model guidance continues to show good agreement on the large scale synoptic pattern through the medium range period, with some differences over the East and West Coasts. The most impactful are of uncertainty will be over the Eastern U.S. where a tropical low may create hazardous weather for the Carolinas and the Mid-Atlantic next week. Most guidance has clustered around two solutions, either bringing the tropical low north into the Carolinas or stalling offshore and being swept out into the Atlantic. The evolution will ultimately be determined by interactions between the tropical low, Hurricane Humberto to the east, a frontal boundary to the north, and an upper trough over the East. WPCs afternoon forecast reflects the solution that brings the low into the Carolinas Monday into Tuesday, which is in line with the National Hurricane Center's (NHC) approach to the system as well. This was a large shift from the overnight forecast, resulting in significantly higher precipitation totals over the Mid-Atlantic and Southeast. Please refer to the NHC for the latest information on this system. There is still a large amount of uncertainty surrounding the evolution and track of this low, and the forecast will likely change over the next few days. For the West, the uncertainty comes from timing and evolution differences of low pressure systems moving onshore from the Pacific. This uncertainty will affect precipitation location and amounts near the Coast, especially Monday into Tuesday when locally heavy precipitation will be possible. WPC's afternoon forecast for Sunday through Tuesday was based on a blend of the 00Z ECMWF/CMC/UKMET and 06Z GFS. Given relatively good agreement, this provided a good middle ground starting point. For Wednesday and Thursday, ensemble means from the 06Z GEFS and 00Z ECENS were added in increasing amounts to smooth out model differences. ...Weather/Hazards Highlights... A frontal boundary lingering along the East Coast will support daily showers and storms, especially for the Mid-Atlantic states, through early next week. Anomalous moisture with a possible tropical connection will maintain at least a localized heavy rainfall threat for the Mid-Atlantic/Carolinas and parts of the Appalachians. There will be a Marginal Risk of excessive rainfall over eastern Virginia, North Carolina, and South Carolina on Sunday, and another Marginal Risk for most of the Mid-Atlantic and Carolinas on Monday. With increasing potential for tropical moisture leading to enhanced precipitation in the Carolinas on Monday, a Slight Risk of excessive rainfall was introduced for portions of the Carolina Coasts. The threat may continue beyond Monday depending on the evolution of the tropical systems off the Southeast coast, and there are pieces of guidance suggesting significantly higher rainfall amounts will be possible. The rainfall forecast will likely change over the next few days. Regardless of how the rainfall forecast turns out, the Southeast Coast will likely experience dangerous surf and rip current conditions early next week, and some areas may experience increased winds. To the west, Pacific moisture ahead of an upper low over southern California will result in rainfall continuing into Sunday, though with lesser intensity than the short range. Anomalous moisture and sufficient instability will continue to support at least a localized flash flood threat Sunday into Monday, particularly for vulnerable burn scars. This region remains highlighted with a Marginal Risk of excessive rainfall for both Sunday and Monday, with a more targeted Slight Risk on Sunday across central New Mexico where QPF amounts are greatest. Precipitation will increase by next week across the Northwest U.S. associated with amplified troughing over the region. Widespread rain is expected across the Pacific Northwest and into the northern Great Basin/Rockies. The heaviest precipitation is expected from western Washington to northern California and the Sierra Nevada. A Marginal Risk of excessive rainfall was added for Monday for northern California. Some snow may fall in the highest elevations of the West as well. Warmer than average temperatures will shift into the Northern Plains and maintain as upper ridging builds over the region next week. Daytime highs could be 10-20 degrees above normal for parts of the Upper Midwest. Below normal temperatures over the Southwest will expand northward along much of the West Coast by next week. Dolan/Santorelli 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 Select Another Day
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