929 FXUS02 KWBC 210812 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 412 AM EDT Tue Jul 21 2026 Valid 12Z Fri Jul 24 2026 - 12Z Tue Jul 28 2026 ...Tropical Storm Bertha impacts Central to Western Gulf Coast... ...Heavy Rainfall/Flooding threat for coastal Southeast U.S.... ...Hazardous heat to build broadly across the West-Central U.S. as ongoing monsoonal rains tend to ease late week into next week... ...Overview... Hot and moist conditions will linger over the South-Central U.S. this week outside of the unsettling influence of Tropical Storm Bertha. Northern stream shortwaves working into an upper trough position over the East and moderating surface fronts will bring focus for rounds of locally heavy rains later this week down over the coastal Southeast U.S. with a slow moving and moisture pooling front. Active stormy conditions will meanwhile work westward over the Gulf Coast and into Texas as fueled by Tropical Storm Bertha track and deep moisture. Monsoonal moisture now streaming over the Southwest and Intermountain West/Rockies and affecting the central U.S. downstream will fuel enhanced showers and thunderstorms. High heat/upper ridging focus over the south-central U.S. will shift northward over the Plains and into the Southwest/Intermoutain West/Rockies. Monsoonal flow eases later period with transition. ...Guidance/Predictability Assessment... Latest guidance continues to show good agreement and forecast confidence on the developing large scale pattern to feature a large warming upper ridge that builds over the Intermountain West/Southwest/Rockies/Plains as sandwiched between amplified upper troughs upstream just off the West Coast and downstream over the East. There are uncertainties with individual systems working through the flow and associated sensible local weather impacts. Differences seem partially mitigated by a favored guidance blend as consistent with individual predictability. The most significant forecast issue concerns the track and impact focus from northern Gulf Tropical Storm Bertha. Bertha is forecast by the National Hurricane Center (NHC) to track westward near the central Gulf Coast then Texas and slowly weaken late week to monitor. Please see the latest advisories from the NHC and your local weather office for updated information. Guidance seems deficient with heavy rainfall potential onshore given deep pooled tropical moisture and track vicinity, so this was manually adjusted at WPC. ...Weather/Hazards Highlights... Flow around a main upper ridge will continue to draw significant monsoonal moisture into the Southwest and Intermountain West/Rockies this week, but may ease this weekend/early next week. Moisture will fuel scattered to numerous showers and thunderstorms with potential to produce heavy rainfall and localized flash flooding. Sensitive places such as burn scars, steep terrain, etc., would be the most vulnerable to possible flooding concerns. Marginal Risks of excessive rainfall span the Southwest and Intermountain West/Rockies and jumps to the mid-Mississippi Valley Friday into Saturday, with a small embedded Slight Risk areas for the mid-Mississippi Valley Friday where convection may focus/train. Upper ridge/closed high influence over the south-central U.S. offers at least Major HeatRisks this week as temperatures up to 5-10F above already hot averages combine with high humidity. Expect spotty record highs and more widespread record overnight lows to limit relief. Heat indices rise rise upwards to 105-110+F in some spots. Heat focus will expand up through the Plains and into the Southwest/Intermountain West/Rockies this weekend/early next week. Elsewhere, repeat heavy rains/convection are forecast to focus over the eastern Carolinas/Southeast later week/weekend given support aloft and slowed frontal push. WPC Excessive Rainfall Marginal Risks Friday and Saturday also has an embedded eastern Carolinas Slight Risk area on Friday. Meanwhile to the South, Tropical Storm Bertha is forecast to track westward near the central and western Gulf coasts to Texas into later this week. Deep tropical moisture associated with this system may fuel a localized threat for heavy rain/runoff issues. A Marginal Risk area is in place for the central to western Gulf Coast Friday into Saturday to monitor. Upstream, persistent upper troughing and embedded moisture feed offers multi-day mid-summer light-moderate rain chances this period working onshore into the Pacific Northwest. 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, 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 $$