809
FXUS02 KWBC 021945
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
345 PM EDT SUN AUG 2 2026
VALID 12Z WED AUG 05 2026 - 12Z SUN AUG 09 2026
...HEAT WAVE CONTINUES THROUGH THE WEEK ACROSS THE SOUTHWEST AND
INTERMOUNTAIN WEST, EXPANDING NORTHEASTWARD WITH TIME...
..OVERVIEW
THE UPPER RIDGE CAUSING EXCESSIVE HEAT ATOP THE SOUTHWEST MIDWEEK
WILL GRADUALLY INTENSIFY AND EXPAND NORTH AND EAST LATE WEEK INTO
NEXT WEEKEND, BRINGING HOT TEMPERATURES ACROSS THE INTERMOUNTAIN
WEST TO PLAINS AND POTENTIALLY THE SOUTH. MEANWHILE, A HANDFUL OF
FRONTAL SYSTEMS IN THE CENTRAL AND EASTERN U.S. WILL TRIGGER
SCATTERED SHOWERS AND THUNDERSTORMS THERE, WITH MONSOON CONVECTION
IN THE SOUTHWEST AS WELL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS SHOW GOOD AGREEMENT ON THE LARGE SCALE PATTERN EVOLUTION
THROUGH THE PERIOD, WHICH FEATURES A NORTHERN STREAM TROUGH THROUGH
THE NORTH-CENTRAL U.S. AND A SPRAWLING SOUTHERN TIER RIDGE. THE
MAIN FOCUS OF UNCERTAINTY CONTINUES TO BE WITH THE POSITIONS OF
VARIOUS ENERGIES ALOFT WITHIN THE BROADER TROUGH, ESPECIALLY THE
LATTER PART OF THE WEEK AND INTO THE WEEKEND. POSSIBLY A COUPLE OF
ROUNDS OF WEAK ENERGY MOVING INTO THE NORTHWEST ALSO SHOW SOME
VARIABILITY. RECENT TRENDS HAVE BEEN FOR THE PEAK VALUES OF THE
UPPER RIDGE (594DM AT 500MB) TO STAY SEPARATE IN THE SOUTHWEST AND
FARTHER EAST WITH A SUBTROPICAL ATLANTIC RIDGE WITH SOME WEAK
ENERGY IN BETWEEN THEM. OVERALL, THERE ARE NOT REALLY CONSIDERABLE
OUTLIERS WITH THE PATTERN. THUS THE WPC FORECAST USED A BLEND OF
DETERMINISTIC GUIDANCE FOR THE EARLY PART OF THE PERIOD, BUT USED
GRADUALLY INCREASING PROPORTIONS OF ENSEMBLE MEANS AS THE PERIOD
PROGRESSED TO HELP SMOOTH OUT INCREASING UNCERTAINTY. THIS
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS 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, AS WELL AS EASTWARD IN THE MID-SOUTH 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. AFTER ONE MORE COOL DAY IN THE NORTH-CENTRAL U.S.
WEDNESDAY, TEMPERATURES ACROSS THE NORTHERN TIER AND INTO THE EAST
SHOULD BE GENERALLY NEAR AVERAGE MOST OF THE PERIOD.
A REASONABLY STRONG FRONT WILL PUSH INTO THE MIDWEST AND CENTRAL
PLAINS BY WEDNESDAY AND TRIGGER A CORRIDOR OF POTENTIALLY HEAVY
RAIN AND THUNDERSTORMS ALONG AND AHEAD OF IT. MEANWHILE, WEAK
FRONTAL BOUNDARIES WILL ALLOW FOR SHOWERS AND THUNDERSTORMS TO BE
SCATTERED ACROSS THE EAST, WITH SOME LOCALLY HEAVY TO EXCESSIVE
RAINFALL POSSIBLE THERE AS WELL. THESE INTERACTING FEATURES SHOULD
ALLOW FOR ADDITIONAL ROUNDS OF RAIN AND STORMS ACROSS THE NORTH-
CENTRAL TO EASTERN U.S. THROUGH LATE WEEK AS THE MEAN FRONTAL
BOUNDARY MAY STALL FOR A BIT. ELSEWHERE, MONSOONAL CONVECTION IS
LIKELY FOR ARIZONA AND NEW MEXICO IN PARTICULAR, WITH SCATTERED
CONVECTION OCCASIONALLY REACHING PORTIONS OF UTAH AND COLORADO. THE
REMAINDER OF THE WEST INTO THE NORTHERN PLAINS SHOULD BE MOSTLY
DRY DURING THE PERIOD.
TATE/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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