721
FXUS02 KWNH 050639
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 AM EDT WED AUG 5 2026
VALID 12Z SAT AUG 08 2026 - 12Z WED AUG 12 2026
...HEAT WAVE CONTINUES THROUGH THE WEEKEND FOR THE SOUTHWEST, WITH
SOME EXPANSION INTO THE INTERMOUNTAIN WEST, CENTRAL U.S., AND
PARTS OF THE SOUTHEAST NEXT WEEK...
..OVERVIEW
A STRONG UPPER HIGH OVER THE SOUTHWEST WHICH HAS BEEN ANCHORED
THERE FOR A LONG TIME, SHOULD BRING HAZARDOUS HEAT CONCERNS TO THE
REGION THROUGH THE WEEKEND BEFORE IT FINALLY BEGINS TO BREAK DOWN.
RIDGING WILL THEN EXPAND EASTWARD OVER THE CENTRAL U.S. AND THE
SOUTHEAST, BRINGING INCREASING HEAT CONCERNS FOR PARTS OF THOSE
REGIONS NEXT WEEK. MEANWHILE, EXPECT A PROGRESSIVE NORTHERN STREAM
WITH A TROUGH AND SURFACE FRONT MOVING ACROSS THE NORTHERN U.S.
INTO THE EAST WITH MODERATE TO LOCALLY HEAVY RAINFALL TO ACCOMPANY.
TROPICAL MOISTURE INTO THE SOUTHEAST AND GULF COAST WILL CONTINUE
A WET PATTERN THROUGH THE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE OVERALL LARGE
SCALE PATTERN AND EVOLUTION, BUT WITH SOME DISAGREEMENT IN THE
DETAILS AND TIMING OF INDIVIDUAL SYSTEMS. THERE ARE SOME MINOR
TIMING DIFFERENCES WITH ENERGY ROTATING THROUGH THE BASE OF A
TROUGH THROUGH THE GREAT LAKES AND NORTHEAST, AND WITH ENERGY AS IT
ENTERS THE NORTHWEST EARLY NEXT WEEK. NO CLEAR OUTLIERS AND THE
DIFFERENCES ARE WELL WITHIN THE NORMAL RANGES FOR THE TIME PERIOD.
THE TROUGH INTO THE NORTHWEST THOUGH DOES INCREASE UNCERTAINTY WITH
HOW QUICKLY THE SOUTHWEST UPPER HIGH/RIDGE ERODES, AND THERE'S
ALSO QUESTION ON THE EXTENT AND STRENGTH OF A SUBTROPICAL ATLANTIC
RIDGE WHICH MAY EXTEND INTO THE SOUTHEAST AT TIMES NEXT WEEK.
THE WPC FORECAST USED A BLEND OF THE DETERMINISTIC GUIDANCE FOR
THE FIRST HALF OF THE PERIOD, INCREASING WEIGHTING OF THE ENSEMBLE
MEANS TO 40 PERCENT OF THE BLEND FOR DAYS 6 AND 7. THIS MAINTAINS
GOOD AGREEMENT WITH THE PREVIOUS SHIFT AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
GOING INTO NEXT WEEKEND, A SLIGHTLY WEAKER UPPER RIDGE WILL ALLOW
FOR LESSENING HEATRISK ACROSS THE SOUTHWEST COMPARED TO THE SHORT
RANGE PERIOD, THOUGH MODERATE HEATRISK WILL STILL BE WIDESPREAD
WITH ISOLATED MAJOR AND EXTREME VALUES. HEAT SHOULD BUILD GRADUALLY
NORTHWARD ACROSS THE INTERMOUNTAIN WEST AND ROCKIES TO THE HIGH
PLAINS, AND EASTWARD TOWARDS THE CENTRAL PLAINS AND MISSISSIPPI
VALLEY NEXT WEEK AS THE UPPER RIDGE EXPANDS. AREAS OF SMOKE WILL
ALSO REMAIN LIKELY GIVEN ACTIVE FIRES ACROSS THE WESTERN STATES.
HEAT ACROSS THE SOUTHWEST SHOULD FINALLY WANE BY EARLY NEXT WEEK
WITH INCREASING MONSOONAL MOISTURE AND A WEAKENING UPPER RIDGE.
TEMPERATURES ACROSS THE NORTHERN TIER SHOULD BE NEAR NORMAL THE
WHOLE PERIOD. THE EAST MAY BE NEAR OR SLIGHTLY ABOVE NORMAL, WITH
SOME MAJOR HEATRISK CREEPING INTO PARTS OF THE SOUTHEAST COAST NEXT
WEEK. A SLIGHT COOLING TREND IS EXPECTED FOR THE PACIFIC NORTHWEST
IN THE WAKE OF A WEAK/DRY COLD FRONT THIS WEEKEND.
INTERACTION BETWEEN A WEAKENING FRONT IN THE EAST AND A STRONGER
ONE INTO THE NORTHERN PLAINS WILL ALLOW FOR ONGOING SHOWERS AND
STORMS ACROSS THE MIDWEST TO THE EAST THIS WEEKEND. A WET PATTERN
LOOKS TO SET UP BY THE WEEKEND AND INTO EARLY NEXT WEEK, ESPECIALLY
FOR THE SOUTH AND SOUTHEAST, AS TROPICAL MOISTURE ROUNDS THE WEST
SIDE OF THE SUBTROPICAL ATLANTIC RIDGE. MORE WIDESPREAD, MODERATE
TO HEAVY RAINFALL IS ALSO LOOKING INCREASINGLY LIKELY ACROSS
PORTIONS OF THE UPPER MIDWEST/GREAT LAKES/UPPER OHIO VALLEY EARLY
NEXT WEEK WITH ADDITIONAL ENERGY MOVING THROUGH. MONSOONAL MOISTURE
IS LIKELY TO CONTINUE THROUGH THE PERIOD FOR ARIZONA AND NEW
MEXICO, REACHING PORTIONS OF UTAH AND COLORADO AS WELL. THE
REMAINDER OF THE WEST INTO THE NORTHERN PLAINS SHOULD BE MOSTLY DRY
DURING THE PERIOD.
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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