798
FXUS02 KWBC 100709
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
309 AM EDT FRI JUL 10 2026
VALID 12Z MON JUL 13 2026 - 12Z FRI JUL 17 2026
...DANGEROUS HEAT SPREADS FROM THE INTERMOUNTAIN WEST TO THE
NORTHERN PLAINS AND UPPER MIDWEST THROUGH NEXT WEEK...
..OVERVIEW
A BROAD AND ANOMALOUSLY STRONG UPPER-LEVEL RIDGE WILL BE IN PLACE
ACROSS THE INTERMOUNTAIN WEST TO NORTH-CENTRAL U.S. NEXT WEEK,
LEADING TO A SIGNIFICANT AND DANGEROUS HEAT WAVE CONTINUING ACROSS
THOSE REGIONS. RAIN AND THUNDERSTORM CHANCES WILL MAINLY OCCUR
ACROSS SOUTHERN STATES TO THE SOUTH OF THE RIDGE, THOUGH SOME
NORTHERN TIER RAIN/STORMS ROUNDING THE RIDGE ARE POSSIBLE AS WELL.
ADDITIONALLY, MONSOONAL MOISTURE IS FORECAST TO INCREASE AND
PRODUCE SHOWERS AND STORMS ACROSS THE SOUTHWEST AND FOUR CORNERS
STATES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE SHOWS GOOD AGREEMENT IN TERMS OF THE 594+ DM UPPER
HIGH CENTERED NEAR THE NORTH-CENTRAL U.S. AND MEANDERING NEXT WEEK,
LEADING TO HIGH CONFIDENCE IN MULTIPLE DAYS OF HAZARDOUS HEAT. THE
RIDGE MAY STRETCH INTO THE EAST AT TIMES, AFTER A NORTHEAST TROUGH
MOVES AWAY MONDAY AND TO THE SOUTH OF ANOTHER TROUGH MOVING IN BY
THE LATTER HALF OF THE WEEK. SMALLER-SCALE ENERGIES TO THE SOUTH OF
THE RIDGE ARE RELATIVELY MORE UNCERTAIN, AND CAUSE SOME VARIANCE
IN QPF, BUT WITHIN REASON FOR THE MEDIUM RANGE PERIOD.
THE PRIMARY SYNOPTIC SCALE MODEL DIFFERENCES ARE ON THE
NORTHWESTERN SIDE OF THE RIDGE. BY TUESDAY-WEDNESDAY, NORTHEASTERN
PACIFIC ENERGY FORMING AN UPPER LOW/TROUGH SHOWS DIFFERENCES IN
PLACEMENT. WITH THE NEWER 00Z GUIDANCE, THE ECMWF IS NOW PRETTY
MUCH ALONE IN ITS FARTHER WEST POSITION COMPARED TO OTHER DYNAMICAL
AND AI GUIDANCE. WITH THE PREVIOUS 12Z CYCLE, THE CMC WAS SIMILAR
TO THE EC, BUT THE 00Z CMC HAS JUMPED EAST AND NOW ALIGNS WELL WITH
THE GFS, AIFS/AIGFS, AND ENSEMBLE MEANS. THUS PREFERRED A BLEND OF
THE DETERMINISTIC AND ENSEMBLE GUIDANCE OTHER THAN THE ECMWF, AND
WITH NEAR HALF ENSEMBLE MEANS FOR THE MODEL BLEND FOR DAYS 6-7 TO
MITIGATE INDIVIDUAL MODEL DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
A STRONG AND EXPANSIVE RIDGE SPRAWLING FROM THE WESTERN U.S. TO
THE CENTRAL U.S. WILL LEAD TO AN EXTENDED PERIOD OF DANGEROUS HEAT
FOR PARTS OF THE INTERMOUNTAIN WEST, NORTHERN PLAINS, AND UPPER
MIDWEST THROUGH MOST OF NEXT WEEK. SEVERAL DAYS OF WELL ABOVE
NORMAL AND POTENTIALLY RECORD-BREAKING MAXIMUM AND MINIMUM
TEMPERATURES WILL LEAD TO WIDESPREAD MAJOR TO EXTREME HEATRISK. WPC
CONTINUES TO UPDATE HEAT KEY MESSAGES FOR THIS EVENT, WHICH CAN BE
FOUND ON OUR HOMEPAGE. FARTHER EAST, PERIODS OF WARMER THAN
AVERAGE TEMPERATURES ARE LIKELY FOR THE NORTHEAST PARTICULARLY ON
TUESDAY, SHIFTING INTO THE MID-ATLANTIC MIDWEEK AND BEYOND WHILE
THE NORTHEAST COOLS BEHIND A COLD FRONT.
MEANWHILE, MUCH OF THE SOUTHERN TIER COULD SEE NEAR TO SLIGHTLY
BELOW AVERAGE TEMPERATURES AS A FRONT STALLS NEAR THE GULF COAST
AND ACTS AS A FOCUS FOR SHOWERS AND THUNDERSTORMS THROUGH AT LEAST
MIDWEEK. THE VERY MOIST AND UNSTABLE ENVIRONMENT COULD LEAD TO
FLASH FLOODING CONCERNS, AND MARGINAL TO SLIGHT RISKS OF FLASH
FLOODING ARE IN PLACE FOR DAYS 4-5 (MONDAY-TUESDAY). BY THE LATTER
PART OF NEXT WEEK, SUBTROPICAL RIDGING IS FORECAST TO BUILD INTO
FLORIDA, WHERE TEMPERATURES SHOULD STAY WARM AND ELEVATED HEATRISK
IS FORECAST.
INCREASING SOUTHERLY FLOW AROUND THE WESTERN PERIPHERY OF THE
CENTRAL U.S. RIDGE WILL DRAW MONSOONAL MOISTURE INTO THE SOUTHWEST
AND THE CENTRAL GREAT BASIN EARLY NEXT WEEK. THIS MOISTURE WILL
LEAD TO SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WITH THE
POTENTIAL TO PRODUCE HEAVY RAINFALL AND LOCALIZED FLASH FLOODING.
SENSITIVE PLACES SUCH AS BURN SCARS, STEEP TERRAIN, ETC., WOULD BE
THE MOST VULNERABLE TO ANY FLOODING CONCERNS THAT MAY DEVELOP.
MARGINAL RISKS OF EXCESSIVE RAINFALL ARE DELINEATED FOR MONDAY IN
THE SOUTHWEST AND EXPANDING TOWARD THE FOUR CORNERS TUESDAY, AND
THE RAINFALL POTENTIAL IS FORECAST TO CONTINUE EXPANDING
NORTHEASTWARD AS THE WEEK PROGRESSES.
TATE
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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