696 FXUS21 KWNC 191827 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT June 19 2026 SYNOPSIS: Forecast mid-level high pressure over the southwestern contiguous U.S. (CONUS) is expected to promote above-normal temperatures with possible extreme heat conditions across the California Valley eastward into the lower Four Corners early week-2. Enhanced subtropical high pressure over the southeastern CONUS brings an increased risk of extreme heat from the Florida Peninsula northward into the Southern and Middle Atlantic regions throughout week-2. Mid-level high pressure also builds toward the High Plains, increasing the risk of extreme heat across the central and south-central CONUS. Meanwhile, surface low development in the lee of the Rockies and enhanced moisture transport from the south support an increased risk of heavy precipitation across parts of the Middle and Upper Mississippi Valley and adjacent areas early in the period. HAZARDS Slight risk of extreme heat for parts of California Central Valley, Desert Southwest, and Southern High Plains, Sat-Sun, Jun 27-28. Slight risk of extreme heat for the central and southern Plains and adjacent Lower Mississippi Valley, Sat-Fri, Jun 27-Jul 3. Slight risk of extreme heat for the Florida peninsula and portions of the South Atlantic and lower Mid-Atlantic regions, Sat-Fri, Jun 27-Jul 3. Slight risk of heavy precipitation for parts of the east-central and northern Plains, Upper and Middle Mississippi Valley, lower Ohio Valley, and adjacent Great Lakes region, Sat-Mon, Jun 27-29. DETAILED SUMMARY FOR MONDAY JUNE 22 - FRIDAY JUNE 26: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SATURDAY JUNE 27 - FRIDAY JULY 03: Mid-level height anomaly forecasts from GEFS, European ensemble (ECENS), and Canadian ensemble (CMCE) favor an zonal pattern early in week-2 with weak mid-level ridging near the West Coast and from the subtropics into Florida, with a weak trough centered near southwestern Alaska. The pattern modestly amplifies as the period progresses, and models generally agree that mid-level high pressure will retrograde into the central North Pacific as weak mid-level troughing drops from near Alaska toward the western CONUS. Meanwhile, the subtropical ridging extending into Florida builds northwestward into the central CONUS and eastern Rockies while a weak trough meanders near the Northeast. By the end of week-2, near to above-normal 500-hPa heights will encompass North America and adjacent areas, including areas of mid-level troughing which are more defined by upstream and downstream ridging and not markedly below-normal 500-hPa heights. Analysis of ECMWF and GEFS 500-hPa height anomalies in standardized space continues shows a fairly strong height maxima centered just west of the CONUS early in the period, supportive of extreme heat risk. Probabilistic Extreme Tools (PETs) from the GEFS and to a lesser extent the CMCE indicate at least 20% chances of daytime temperatures exceeding the 85th climatological percentile in the lower elevations of the Southwest and through the California Valleys, supporting a slight risk of marginally-extreme heat early week-2 before the ridge center retrogrades into the North Pacific and weak mid-level troughing drops toward the region from near Alaska. Within the hazard area, raw temperature tools continue to depict increased chances for maximum temperatures exceeding 105 deg F over parts of the California Valley, and 110 deg F over the lower elevations of the Desert Southwest, although the preponderance of tools shows slightly lower odds than yesterday.. The subtropical mid-level ridging that extends into Florida establishes a slight risk of extreme heat across the Florida Peninsula at the outset of week-2. As mid-level high pressure builds northward and northwestward, temperatures are expected to rise quickly in the south-central and central CONUS and also along the Eastern Seaboard, bringing a slight risk of extreme heat to these regions starting early week-2 and lasting through the period. All three PETs generally keep at least 20 percent chances for daytime highs exceeding the 85th climatological percentile throughout week-2 over the Florida Peninsula, but are less robust farther north and northwest. The GEFS and ECENS PETs show at least 20 percent chances for highs in the 85th climatological percentile across parts of the Southern and Middle Atlantic regions through most of week-2, rising above 30 percent on the ECENS PET on June 30. Across the central and south-central CONUS, the PETs are even less remarkable, showing a minority of the region with at least a 20 percent chance for high temperatures exceeding the 85th percentile each day. However, internal heat tools indicate enhanced chances for heat indexes to rise above 105 deg F at times throughout the Southern and Lower Mid-Atlantic regions, and across the central and south-central Plains and adjacent Lower Mississippi Valley, along with increased odds for temperatures and/or heat indexes to exceed the 90th climatological percentile at times. In addition, the mid-level high pressure slowly building into the central CONUS seems more likely to bring extreme heat into the region than the PETs indicate, with high humidity likely increasing the odds for unusually high heat indexes despite only nominally high temperatures. These factors support a slight risk of extreme heat throughout week-2 across the central and south-central CONUS, and along parts of the Middle and Southern Atlantic region, including the entire Florida Peninsula. At this time, the risk does not appear to systemically relent during week-2, the threat is marginal, and oppressive heat may not occur every day. For precipitation, models continue to point to potential surface low development in the lee of Rockies early in week-2, however ensemble solutions remain diffuse in regards to the location of development and the eventual track of any surface low. Despite this, the combination of lower surface pressures and the robust advection of tropical moisture into parts of the central and north-central CONUS enhances the probability of heavy precipitation across the Middle and Upper Mississippi Valley and adjacent sections of the Great Lakes, eastern Great Plains, and Lower Ohio Valley. The ECENS PET depicts a 20 to 40 percent chance for 3-day precipitation amounts to exceed the 85th climatological percentile and one inch total during the first 3 days of week-2 (Jun 27-29) while the GEFS and CMCE PETs show 20 to 30 percent chances for such conditions over at least part of these areas. Raw ensemble solutions have not been consistent in highlighting either which areas in the heavy precipitation hazard are at greatest risk, nor in forecasting the highest amounts, so nothing beyond a slight risk of heavy precipitation is supported. Due to the slight risk for excessive rainfall forecast during week-1 across parts of lower Missouri River and Ohio River basins, any heavy precipitation realized may trigger scattered flooding during week-2, but chances are not high enough to justify a specific area at risk of broadscale flooding.. No hazards are posted over Alaska. but there is the potential for increased thunderstorm activity that could trigger wildfires. FORECASTER: Rich Tinker $$