Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
591 FXUS02 KWBC 160800 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Thu Oct 16 2025 Valid 12Z Sun Oct 19 2025 - 12Z Thu Oct 23 2025 ...Guidance/Predictability Assessment... Two main upper troughs/lows and associated weather focusing wavy frontal systems remain slated to impact our nation during this medium range forecast period. A lead system will work from the east-central U.S. Sunday to the east/northeast coast by Tuesday. Meanwhile upstream. a second system breaching the West/Northwest coast Sunday should cross the country to the East around next midweek. Guidance solutions have been reasonably well clustered with the larger scale flow evolution early into medium range time scales, bolstering forecast confidence, but have shown steadily increasing forecast spread and uncertainty by Day 5. Both systems are having still unresolved guidance cycle to cycle continuity issues including latest 00 UTC guidance, mainly with respect to timing and phasing. Accordingly, the WPC medium range product suite was mainly derived from a composite blend of best clustered guidance at time of production of the 18 UTC GFS/GEFS mean and 12 UTC ECMWF/ECMWF ensemble means along with the compatible 01 UTC National Blend of Models, all with an eye on WPC continuity. ...Weather/Hazards Highlights... A lead main upper trough and deepened surface low pushing across the Great Lakes region this weekend will draw anomalous moisture and instability northward in advance of a cold front. The slowly progressive nature of the upper-level and surface features will then spread organized rainfall eastward into the East/Northeast Sunday into early next week. Activity will also focus with development of a deepening/consolidating coastal low pressure system. A WPC Day 4/Sunday Excessive Rainfall Outlook Marginal Risk area was shifted northward to extend from the central Appalachians to the eastern Great Lakes/Ohio Valley. Out West, a main/complex upper trough and surface low/frontal system will approach and push across the Pacific Northwest and northern Rockies over the weekend to produce a period of moderately heavy coastal and valley rains along with higher mountain snow. The WPC Day Winter Weather Outlook shows mountain snow potential inland to the Northern Rockies into Monday. Downstream system translation and some lead return flow looks to support moderate rainfall emergence in an expanding pattern over the north-central to east central U.S. into next Wednesday/Thursday to monitor. Schichtel 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 $$