494 FXUS02 KWBC 121935 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 335 PM EDT Sun Jul 12 2026 Valid 12Z Wed Jul 15 2026 - 12Z Sun Jul 19 2026 ...Dangerous heat continues across the north-central U.S. through next weekend... 19Z Update: The 12Z model guidance suite continues to agree well on most aspects of the forecast going into the middle of the week, with a general deterministic model blend sufficing as a suitable starting point. The GFS and GEFS start becoming more amplified with the upper level trough that will be situated over the Northeast U.S. by the end of the week, which would keep temperatures lower, whereas the non- NCEP guidance portrays a broader trough axis across the region. By the end of the forecast period Sunday, there is good agreement on the upper ridge becoming more established over the Intermountain West, with monsoonal moisture in place south of the upper high that will fuel afternoon/evening convection each day. The ECMWF becomes stronger with a shortwave trough dropping south across the Upper Midwest by next weekend. The ensemble means were increased to about 40% by next Sunday to account for increasing model differences. In terms of the NBM, there were modest downward temperature adjustments for portions of the Great Lakes and into the Northeast given the stronger signal for a trough to be in place, and more deterministic model guidance was added for QPF across the West to show a more convective look to the expected monsoonal showers and storms. There was also a modest increase for portions of the Mid- Atlantic region to coincide with the severe potential noted on SPC's convective outlook for Friday. The previous discussion is appended below for reference. /Hamrick -------------------- ...Overview... An elongated and anomalously strong upper-level ridge will stretch from the Intermountain West through Midwest toward the Mid- Atlantic midweek, with the eastern portion joining up with a subtropical Atlantic ridge and the western portion retrograding a bit into late week and next weekend. Hazardous heat is likely to continue under the ridge, and Major to Extreme HeatRisk will be persistent across the Dakotas to Midwest. Rain and thunderstorms are likely on the southern periphery of the ridge, with elevated chances of heavy rain and flash flooding in western/central Texas in particular. Additionally, monsoonal moisture is forecast to increase and produce showers and storms across the Southwest, Four Corners states, and northward into the northern Rockies/High Plains. Some energies on the northern side of the ridge could also lead to rounds of rain and thunderstorms in the northern tier, including a severe threat over the Mid-Atlantic Friday within a renewed pre-frontal East Coast heat threat. ...Guidance/Predictability Assessment... Model guidance shows good agreement in terms of the 594+ dm upper high centered near the north-central U.S. and meandering through the week, leading to high confidence in multiple days of hazardous heat. Models indicate the ridge should stretch into the Mid- Atlantic midweek and get gradually suppressed by an upper trough moving into the Northeast by the latter half of the week. This eastern part of the ridge may join with the subtropical Atlantic high that shifts west through later week. Meanwhile farther west, the ridge should get renewed across the northern/central Rockies and Plains. Smaller-scale energies to the south of the ridge are relatively more uncertain, but guidance continues to highlight a notable shortwave over the southern High Plains Wednesday-Thursday bringing enhanced QPF. Meanwhile a northeastern Pacific upper low has shown the most notable variations in the guidance over the past day or two. The new 00Z model cycle does show a better consensus, as the 00Z ECMWF has a slower/farther west track than its 12Z run and better matches the remainder of the guidance through Thursday. The track remains uncertain into late week though, and while there is a general signal for a shortwave to move from central Canada into the Great Lakes around Saturday, this timing and track remains rather questionable too. The WPC forecast was based on a multi-model deterministic blend early on, with increasing proportions of the ensemble means to about half the blend by Day 7 amid increasing spread. ...Weather/Hazards Highlights... The strong and expansive upper ridge will continue to create concerns for hazardous heat across the northern Plains to Midwest through midweek and continuing into the weekend, with some day to day variations in the placement. Several days of well above normal and potentially record-breaking maximum and minimum temperatures will lead to Major to Extreme HeatRisk. WPC continues to update Heat Key Messages for this event, which can be found on our homepage. Farther east, warmer than average temperatures are likely for the Great Lakes and Northeast to Mid-Atlantic into Wednesday, but shift gradually southward as an upper trough pushes a cold front slowly south. The upper ridge potentially combining with subtropical ridging down to Florida will maintain warm temperatures and elevated HeatRisk there. Meanwhile, much of the southern tier could see near to slightly below average temperatures as ample moisture leads to clouds and rain/thunderstorms. Increasing southerly flow around the western periphery of the central U.S. ridge will draw significant monsoonal moisture into the Southwest and Intermountain West to Rockies. This moisture will lead to scattered to numerous showers and thunderstorms with the potential to produce heavy rainfall and localized flash flooding. Sensitive places such as burn scars, steep terrain, etc., would be the most vulnerable to any flooding concerns that may develop. Broad Marginal Risks of excessive rainfall remain in place from the Southwest north to Montana for Day 4-5 (Wednesday-Thursday), and monsoonal moisture should continue into next weekend. Farther east, Pacific and Gulf moisture should combine in the vicinity of a shortwave aloft over Texas, leading to further flooding concerns. Slight Risks are in place for western/south-central portions of Texas into Wednesday and Thursday, and the flooding threat could be compounded by the likely rainfall in the short range period causing wetter antecedent conditions. Some showers and storms could stretch into the Southeast. Rounds of rain/thunderstorms are also possible farther north from the Great Lakes to the Mid-Atlantic and Northeast late week as energy moves through the northeastern upper trough. The Storm Prediction Center has delineated a severe threat in the Mid- Atlantic to monitor for Friday. Tate/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, 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 $$