646
FXUS02 KWNH 040626
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 AM EDT TUE AUG 4 2026
VALID 12Z FRI AUG 07 2026 - 12Z TUE AUG 11 2026
...HEAT WAVE CONTINUES THROUGH THE WEEKEND FOR THE SOUTHWEST, WITH
SOME EXPANSION INTO THE INTERMOUNTAIN WEST...
..OVERVIEW
A STRONG UPPER-LEVEL RIDGE WILL PERSIST OVER THE SOUTHWESTERN U.S.
AND EXPAND NORTH AND EAST OVER THE WEEKEND TO ALLOW EXCESSIVE HEAT
TO EXPAND ACROSS THE INTERMOUNTAIN WEST INTO THE HIGH PLAINS.
MEANWHILE, EXPECT A PROGRESSIVE NORTHERN STREAM WITH A TROUGH AND
SURFACE FRONT MOVING ACROSS THE NORTHERN U.S. INTO THE EAST WITH A
CONTINUED WET PATTERN. EARLY NEXT WEEK, TROUGHING WILL MOVE INTO
THE NORTHWEST, AND SHOULD FINALLY WEAKEN THE SOUTHWEST RIDGE,
ENDING THE OPPRESSIVE HEAT WAVE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS CONTINUE TO SHOW STRONG AGREEMENT ON THE SYNOPTIC SCALE
PATTERN THROUGH EARLY NEXT WEEK. DIFFERENCES FOCUS WITH ENERGY
THROUGH THE NORTHERN U.S. TROUGH WITH IMPLICATIONS ON QPF COVERAGE
AND FRONTAL PROGRESSION. ALSO SOME QUESTION ON TIMING AND DEPTH OF
THE NORTHWEST TROUGH EARLY NEXT WEEK WHICH MAY ACT TO WEAKEN THE
SOUTHWEST RIDGE. NO MAIN OUTLIERS AND DIFFERENCES ARE WELL WITHIN
THE NORMAL RANGE FOR THIS TIME PERIOD. SOME DIFFERENCES IN THE
INTERACTION (OR NOT) OF THE SOUTHWEST RIDGE WITH THE SUBTROPICAL
ATLANTIC RIDGE IMPACTS QPF COVERAGE AND INTENSITY ACROSS THE GULF
COAST AND SOUTHEAST INTO NEXT WEEK. THE WPC FORECAST USED A BLEND
OF THE DETERMINISTIC GUIDANCE FOR THE FIRST HALF OF THE PERIOD,
INCREASING THE ENSEMBLE MEANS TO 40 PERCENT OF THE WEIGHT DAYS 6
AND 7. THIS MAINTAINS GOOD AGREEMENT WITH THE PREVIOUS WPC
FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
FOR MIDWEEK, 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 LATE THIS WEEK INTO THE WEEKEND, AND EASTWARD TOWARDS THE
MISSISSIPPI VALLEY NEXT WEEK AS THE UPPER RIDGE EXPANDS. 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 AND INTO THE EAST SHOULD BE
GENERALLY NEAR AVERAGE MOST OF THE PERIOD, WITH A SLIGHT COOLING
TREND 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 STRONG ONE
INTO THE NORTHERN PLAINS AND GREAT LAKES LATER THIS WEEK WILL
ALLOW FOR ONGOING SHOWERS AND STORMS ACROSS THE MIDWEST TO THE
EAST. 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.
MONSOONAL MOISTURE IS LIKELY TO CONTINUE INTO NEXT WEEK 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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