642
FXUS02 KWBC 010718
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
318 AM EDT SAT AUG 1 2026
VALID 12Z TUE AUG 04 2026 - 12Z SAT AUG 08 2026
...HEAT WAVE LIKELY TO CONTINUE ACROSS THE SOUTHWEST AND
INTERMOUNTAIN WEST INTO NEXT WEEK...
..OVERVIEW
THE UPPER RIDGE DOMINATING THE WEATHER PATTERN ACROSS THE WESTERN
HALF OF THE COUNTRY WILL WEAKEN SLIGHTLY AND GET SUPPRESSED SOUTH
EARLY NEXT WEEK AS A STRONG COLD FRONT IS FORECAST TO BRING MUCH
COOLER AIR THROUGH THE NORTHWEST AND INTO THE NORTHERN PLAINS THE
FIRST HALF OF THE WEEK. MEANWHILE, A SLOWLY DISSIPATING FRONT
MERGING WITH A WAVE LIFTING FROM THE MIDWEST TO THE NORTHEAST WILL
TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS, WHICH WILL GRADUALLY
EDGE TOWARD THE EAST COAST THROUGH MUCH OF THE WEEK. EXCESSIVE HEAT
WILL BE PERSISTENT ACROSS THE SOUTHWESTERN QUADRANT OF THE
COUNTRY, AND SHOULD GRADUALLY SPREAD NORTHEAST INTO THE CENTRAL
ROCKIES/PLAINS AS THE UPPER RIDGE RE-INTENSIFIES, AS WELL AS
FARTHER EAST ACROSS THE SOUTH AS IT COULD JOIN WITH SUBTROPICAL
ATLANTIC RIDGING COMING IN FOR LATER WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THERE IS GENERAL AGREEMENT ON THE OVERALL SYNOPTIC SCALE PATTERN
AND EVOLUTION THROUGH THE PERIOD FEATURING PROGRESSIVE ENERGY
THROUGH THE NORTHERN TIER, AND AN EXPANDING RIDGE BUILDING FROM THE
SOUTHWEST INTO THE SOUTH AND SOUTHEAST. UNCERTAINTIES LIE MAINLY
WITH ENERGY TIMING WITHIN THE BROADER CENTRAL CANADA TO NORTHERN
TIER U.S. TROUGH WHICH LEADS TO DIFFERENCES AT THE SURFACE AS WELL,
AND HAS IMPLICATIONS FOR QPF COVERAGE AND INTENSITY ALONG
ASSOCIATED FRONTAL BOUNDARIES. THERE ARE DIFFERENCES EARLY PERIOD
OVER THE MID-SOUTH AS ENERGY LOOKS TO GET LEFT BEHIND BY A
DEPARTINGNORTHEAST TROUGH AND HOW QUICKLY THAT ENERGY WEAKENS OR
GETS ABSORBED BY THE NEXT SHORTWAVE REACHING THE GREAT LAKES AROUND
THURSDAY. OUT WEST, ADDITIONAL WEAK ENERGY MOVES INTO THE
NORTHWEST, THOUGH THE ECMWF SEEMS TO WANT TO HOLD ON TO A STRONGER
RIDGE THAN CONSENSUS WOULD SUGGEST. EITHER WAY, DIFFERENCES DURING
THE MEDIUM RANGE PERIOD ARE PLENTIFUL, BUT MORE OR LESS ALL WITHIN
THE REALM OF POSSIBILITIES. A GENERAL MODEL COMPROMISE, WITH MORE
ENSEMBLE MEAN WEIGHTING FOR THE LATTER HALF OF THE PERIOD, SEEMED
TO WORK AS A GOOD STARTING POINT FOR THE WPC PROGS AND MAINTAINS
GOOD CONSISTENCY WITH THE PREVIOUS SHIFT.
..WEATHER/HAZARDS HIGHLIGHTS
THOUGH MUCH MORE SUPPRESSED COMPARED TO THE SHORT RANGE,
WIDESPREAD MAJOR TO EXTREME HEATRISK WILL CONTINUE FOR MUCH OF THE
SOUTHWEST THROUGH MUCH OF NEXT WEEK. THEN, HEAT SHOULD BUILD AGAIN
GRADUALLY NORTHWARD ACROSS THE INTERMOUNTAIN WEST AND ROCKIES TO
THE HIGH PLAINS, AS WELL AS EASTWARD IN THE MID-SOUTH AND SOUTHEAST
AS THE UPPER RIDGE EXPANDS. SEE KEY MESSAGES ISSUED BY WPC FOR
THIS EVENT FOR ADDITIONAL INFORMATION REGARDING THIS LONG LASTING
AND DANGEROUS HEAT WAVE. TEMPERATURES ACROSS THE EAST SHOULD BE
GENERALLY NEAR AVERAGE.
SHOWERS AND THUNDERSTORMS LOOK TO LINGER ACROSS THE EAST FOR MUCH
OF NEXT WEEK AS MOISTURE STREAMS NORTHWARD AHEAD OF THE NORTHERN
STREAM SHORTWAVES AND INTERACTS WITH WEAK FRONTAL BOUNDARY DRAPED
ACROSS THE REGION. LOCALLY HEAVY TO EXCESSIVE RAINFALL IS POSSIBLE.
ELSEWHERE ACROSS THE CONTIGUOUS U.S., MOST OF THE MONSOONAL
RAINFALL SHOULD BE CONFINED TO EASTERN ARIZONA AND INTO CENTRAL NEW
MEXICO, WITH SCATTERED CONVECTION REACHING INTO PORTIONS OF UTAH
AND COLORADO. A CORRIDOR OF SHOWERS AND STORMS IS LIKELY AHEAD OF
THE FRONT THAT CROSSES THE DAKOTAS AND INTO MINNESOTA EARLY IN THE
WEEK, AND THIS MAY ALSO BE ACCOMPANIED WITH SOME SEVERE WEATHER.
HEAVY RAIN SEEMS POSSIBLE IN THE CENTRAL PLAINS/MID-MISSISSIPPI
VALLEY INTO TUESDAY- WEDNESDAY WITH THAT FRONT.
SANTORELLI
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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