Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
243 FXUS02 KWBC 120740 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 340 AM EDT Sun Oct 12 2025 Valid 12Z Wed Oct 15 2025 - 12Z Sun Oct 19 2025 ...Guidance/Predictability Assessment... The models remain in good agreement and multi-model blend seems to offer a solid forecast starting point for Wednesday into Friday, albeit with a slighly less progressive trend with latest 00 UTC guidance that seems reasonable given the overall amplified flow pattern over the nation. Favor a more multi-model ensemble mean solution along with best compatible ECMWF model detail into next weekend amid growing forecast spread but reasonable machine learning guidance support. The flow is complicated by incoming northern stream shortwaves later week into next weekend which could modulate the shape/axis of the trough or split it into multiple shortwaves as is also the trend of latest 00 UTC guidance over the West. Overall, the 01 UTC NBM was the basis for sensible weather grids but with some modification to account for the slightly slower preference. In the central/eastern states, a slower western trough would delay the ridge axis from moving eastward, but this could be complicated by northern stream shortwaves through eastern Canada. Confidence in the forecast started above average with a trend to near/below average by the end of this forcast period. ...Weather/Hazards Highlights... A lead short range coastal storm will be working well out to sea across the western Atlantic by midweek but still support continued unsettled/windy conditions over New England through late week as impulses digging behind the system bring some lingering showers. An incoming upper low/amplified trough slated to bring rain/snow to California early week will lift increasingly inland across the West/Rockies mid-late week. A Day 4/Wednesday WPC Excessive Rainfall Outlook Marginal Risk area remains over New Mexico and southern Colorado where leading moisture levels may fuel some lingering local downpours with runoff issues. Upper system and wavy frontal progresion will also drive organized rain/snow over the north-central Intermountain West/Rockies Wednesday/Wednesday night. Much of the West will see at least some rain or snow, with snow levels lowering as colder air moves in. Temperatures will be well below normal into Wednesday (by 10-20 deg) with some slight moderation for the rest of the week, but still cooler than normal. Later period, there is also some upstream guidance signal supporting approach of another amplified Northeast Pacific storm system toward the Pacific Northwest/Northwest next weekend that may offer quite unsettled flow and enhanced rainfall to monitor. Downstream for the central states, southwesterly upper flow will increase the chances of rain for mid-late week over the Northern Plains into the Upper Midwest closer to the jet stream with wavy surface system translation/genesis. Mild and more moisture-laden air to the south over the central Plains and Mid-Mississippi Valley will support a growing pattern with showers and thunderstorms ahead of the western/Rockies system into Thursday/Friday. Activity may florish as focus shifts slowly with more uncertainty into the east-central states into next weekend in an emerging return flow pattern to monitor for enhanced rainfall/runoff issue potential. 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 $$