Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
587 FXUS02 KWBC 191816 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 216 PM EDT Sun Jul 19 2026 Valid 12Z Wed Jul 22 2026 - 12Z Sun Jul 26 2026 ...Hazardous Heat focus over the South this week may expand to the Northern Plains and the Desert Southwest into next weekend... ...Monsoonal rains for the Southwest/Intermountain West/Rockies... ...East/Southeast U.S. Heavy Rains to work over the Gulf Coast with possible tropical low development being monitored by the NHC... ...Overview... Quite hot and muggy conditions will focus over the South for the coming week as northern tier shortwaves and moderating surface fronts bring rounds of locally heavy rains and a strong to severe thunderstorm focus mid/later week down over the Mid-Atlantic. Lead activity over the South/Southeast will be fueled by Gulf/tropical moisture and the NHC is investigating system genesis. Elsewhere, ample monsoonal moisture will continue to stream from the Southwest and Intermountain West/Rockies to the Plains to fuel enhanced showers and thunderstorms as a closed upper high shifts to the southern Plains before re-expanding heat up through the Plains and into the Southwest as monsoonal flow may ease into next weekend. Meanwhile, current Tropical Storm Elida is forecast by NHC to dissipate over the next few days while lifting northward off the West Coast ~130W with lead moisture feeding up the West Coast. ...Guidance/Predictability Assessment... Overall good agreement for the large-scale pattern across CONUS with a ridge over the west-central U.S. and troughing along the East. There is some differences among the deterministic models concerning the smaller-scale features, especially towards late week. Additionally, the GFS and CMC depicts a shortwave energy moving through the Northern Rockies early in the period but the ECMWF kept the ridging structure through the period. These difference can affect sensible weather and frontal placements. Therefore, much of the forecast weighed in the ensemble means from the start of the period and gradually outweighed the deterministic towards the latter portion of the period. Across the Gulf Coast, many models show large spread and differences concerning the development of the tropical system. The AIGFS and EC-AIFS, helped capture the shape and track of the system that aligned with NHC. ...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 next weekend. 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. Broad Marginal Risks of excessive rainfall span from the Southwest and Intermountain West/Rockies to the central Plains Wednesday and Thursday and an embedded Slight Risk area was introduced for the northern Intermountain West/Rockies for Wednesday given anomalous moisture. Upper ridge/closed high influence shift to south-central U.S. will lead to at least Major HeatRisks over much of the South this week as temperatures upwards 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, with focus expanding up through the Plains and into the desert Southwest by next weekend. Elsewhere, heavy rains with strong to severe thunderstorms per SPC are forecast to focus into the East Coast and especially the Mid- Atlantic/Southeast mid/later week given support aloft and wavy frontal push. Elongated WPC Excessive Rainfall Marginal Risk areas over much of the East Coast Wednesday and Thursday also feature embedded Slight Risk areas over the coastal Mid-Atlantic/Carolinas. Meanwhile to the South, a moist and unstable environment over the northeastern Gulf remains monitored for a tropical depression by NHC. Troughing and tropical moisture in place may lead to heavy rain. A Marginal Risk is in place from the coastal Southeast/northern Florida along the Gulf Coast into Texas, with a Slight Risk added across west-central Gulf Coast for flash flooding threats possible for Wednesday and Thursday. Oudit/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 $$