393
FXUS02 KWBC 230718
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
318 AM EDT SUN AUG 23 2026
VALID 12Z WED AUG 26 2026 - 12Z SUN AUG 30 2026
...HAZARDOUS HEAT TO CONTINUE FROM THE LOWER MISSISSIPPI VALLEY
ACROSS THE SOUTHERN PLAINS TO THE DESERT SOUTHWEST...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE MAINTAINS AN AMPLIFIED AND WELL CLUSTERED LARGER SCALE
UPPER PATTERN HIGHLIGHTED BY A STRONG SOUTHWEST U.S. HIGH ANCHORED
AND MEAN TROUGHS NEAR THE PACIFIC NORTHWEST AND THE EAST-CENTRAL
U.S. THROUGH THIS PERIOD. THIS PATTERN WILL NOT CHANGE VERY MUCH
THIS WEEK, AND AS SUCH WILL CONTINUE TO SUPPORT A PROTRACTED
HEATWAVE WITH HAZARDOUS HEAT THREATS FROM THE SOUTH-CENTRAL TO
SOUTHWEST U.S.. ALONG THE RIDGE'S PERIPHERY MONSOONAL MOISTURE WILL
PROMOTE SCATTERED CONVECTION ACROSS THE EASTERN INTERMOUNTAIN WEST
AND ROCKIES, WITH CONVECTION ALSO WORKING INTO THE CENTRAL U.S..
SHORTWAVES WILL MAINTAIN UPPER TROUGHING OVER THE EAST-CENTRAL U.S.
TO FAVOR WAVY AND TEMPERATURE MODERATING FRONTAL SURGES. EXPECT
ORGANIZED RAIN/THUNDERSTORMS AS WAVY FRONTS PUSH INTO AND STALL
OVER THE EAST/SOUTHEAST AND POOL DEEP MOISTURE AND INSTABILITY.
A BROAD GUIDANCE BLEND SEEMS TO PROVIDE A SOLID FORECAST BASIS
WITH GOOD PRODUCT AND MESSAGING CONTINUITY GIVEN FAVORABLE
CLUSTERING TRENDS FURTHER FOLLOWED WITH LATEST 00 UTC GUIDANCE.
..WEATHER/HAZARDS HIGHLIGHTS
UNDER THE INFLUENCE OF THE MAIN UPPER HIGH/RIDGE, DAILY MAXIMUM
TEMPERATURES ACROSS THE SOUTHERN PLAINS WILL CONTINUE TO RISE INTO
THE 90S AND 100S WITH OPPRESSIVE HEAT INDICES. RECORD-BREAKING
WARM OVERNIGHT TEMPERATURES ACROSS THE SOUTHERN TIER WILL FURTHER
LIMIT RECOVERY FROM THE HEAT, ESPECIALLY GIVEN HEATWAVE LONGEVITY
WHICH MAY CONTINUE TO HEAT RELATED ILLNESSES. WIDESPREAD MAJOR TO
EXTREME HEATRISK WILL PERSIST IN THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY. FOR THE DESERT SOUTHWEST DAY MAXIMUMS MAY
EASILY SOAR TO/ABOVE THE 110S WHICH COULD ALSO CAUSE HEAT CONCERNS
THIS WEEK. PRE-FRONTAL AREAS OF THE SOUTHEAST MAY BE A FEW DEGREES
ABOVE NORMAL, ALBEIT WITH MOIST DEWPOINTS AND HIGH HEAT INDICES.
PLEASE SEE WPC'S KEY MESSAGES FOR MORE EXTREME HEAT DETAILS.
MEANWHILE, LINGERING MONSOONAL MOISTURE WILL STREAM NORTHWARD ON
THE PERIPHERY OF THE UPPER RIDGE TO HELP TRIGGER SCATTERED,
DIURNALLY DRIVEN CONVECTION TO THE EASTERN INTERMOUNTAIN WEST AND
ROCKIES. INDIVIDUAL CELLS MAY LEAD TO ISOLATED INSTANCES OF FLASH
FLOODING FOR SENSITIVE LOCATIONS SUCH AS BURN SCARS, FAVORED
TERRAIN LIKE SLOT CANYONS AND URBAN AREAS. WPC MAINTAINS A MARGINAL
RISK FOR EXCESSIVE RAINFALL DAY 4/WEDNESDAY AND DAY 5/THURSDAY.
SHORTWAVES ROUNDING THE TOP OF THE RIDGE WILL TRIGGER SHOWERS AND
THUNDERSTORMS ACROSS PARTS OF THE CENTRAL U.S.. SOME STORMS WILL
BE STRONG TO SEVERE, HOWEVER THE EXACT LOCATION/TIMING REMAINS
UNCERTAIN. FRONTAL PROXIMITY AND POOLING MOISTURE/INSTABILITY FOCUS
OVER THE CENTRAL PLAINS PROMPTED A WPC MARGINAL RISK FOR EXCESSIVE
RAINFALL. EXPECT ORGANIZED RAIN/THUNDERSTORM CHANCES FOR THE
MIDWEST/GREAT LAKES MIDWEEK. LEAD WAVY FRONTAL PUSHES WILL ALSO
FOCUS WIDESPREAD ACTIVITY OVER A HOT/MOIST/UNSTABLE EAST/SOUTHEAST
THROUGH NEXT WEEKEND. WPC MARGINAL RISK AREAS WEDNESDAY/THURSDAY
COVER PARTS OF THE SOUTHEAST AND EXPAND FAR UP THE EASTERN
SEABOARD THURSDAY AND SEEM LIKELY TO PERSIST INTO NEXT WEEKEND.
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
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