788 FXUS02 KWBC 210759 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 359 AM EDT Tue Oct 21 2025 Valid 12Z Fri Oct 24 2025 - 12Z Tue Oct 28 2025 ***Heavy rain and strong storms becoming more likely for the southern Plains late this week*** ...General Overview... The large synoptic scale trough that will be in place across the Great Lakes and Northeast through mid-week will be lifting out across eastern Canada by Friday. A southern stream shortwave crossing from the Rockies to the central/southern Plains will support a surface low and warm front with plenty of moisture from Kansas to the ArkLaTex region, with numerous showers and storms. Out West, a pattern change will take place going into the weekend as an upper trough amplifies over the region and leads to colder weather and widespread mountain snow. This same trough is expected to spur surface cyclogenesis over the central/northern Plains by early next week with additional showers and storms expected. ...Guidance/Predictability Assessment... The 00Z model guidance suite is in good overall agreement across the Continental U.S. for the beginning of the period Friday, and this also holds true going into Saturday, with mainly minor mesoscale differences, so a multi-deterministic model blend was used through Saturday night. Overall, there has been a slightly slower trend with the southern stream shortwave that spurs surface cyclogenesis over Texas and Oklahoma late this week, and also a stronger trend in the guidance overall with this low as it reaches the Mid-South this weekend. The shortwave ejecting from the Rockies to the central Plains has also trended a little stronger in the model guidance over the past few cycles by early next week. There is a growing signal overall for a closed upper low over the Midwest by Tuesday, with differences in placement. In terms of QPF, amounts have trended down some across the Pacific Northwest and up for the central Gulf Coast region, although the NBM is likely a little too high with coverage of higher QPF across the ArkLaTex region, so this was reduced a little until the overall model signal becomes more refined in future forecasts. The ensemble means were increased to about half by next Tuesday. ...Weather/Hazards Highlights... The surface low that is forecast to evolve over Kansas and Oklahoma later this week, along with strong warm air advection and increasing instability, will likely fuel the development of widespread showers and thunderstorms, some of which will be strong and slow moving. There will likely be patchy QPF maxima on the order of 2 to 4 inches from eastern Oklahoma to central Louisiana through Saturday, and higher rainfall rates with the storms that develop could lead to some instances of flash flooding. Therefore a Slight Risk area is valid on Friday across portions of central Oklahoma into north-central Texas where the model signal is greatest for instability and QPF. Rain and mountain snow also increases from northern California to western Washington going into Friday and the weekend, and a Marginal Risk of excessive rain will be valid from near Eureka, CA to the coastal ranges and the Cascades of Washington as an atmospheric river advects copious moisture inland. Elsewhere across the nation, lake enhanced showers from Michigan to Upstate New Year will be prevalent as colder air aloft moves across the warmer lake waters late this week, but likely too warm for any snow this time. By the weekend, widespread snow develops across the higher terrain of the Intermountain West and the central/northern Rockies as multiple shortwaves pass through the amplifying upper trough, with over a foot of accumulation possible for the higher ranges. A new surface low is likely to develop by Monday across the central/northern Plains as a potent shortwave ejects eastward from the Rockies, supporting an increase in showers/storms and gusty winds from the Dakotas to Missouri. Warm to hot conditions are expected to continue across the southern Plains through the weekend with highs running about 5 to 15 degrees above average, equating to readings topping out from the middle 80s to middle 90s. It should also be rather mild for this time of year across the Dakotas through Saturday with the upper ridge in place. Much colder weather makes its arrival for the West Coast and into the Intermountain West by the weekend as the upper trough builds in along with widespread cloud cover. Temperatures should be near to slightly below average for most of the East Coast states. Hamrick 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 $$