859
FXUS02 KWBC 221846
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
246 PM EDT THU AUG 22 2024
VALID 12Z SUN AUG 25 2024 - 12Z THU AUG 29 2024
..OVERVIEW
THE PERSISTENT BLOCKY PATTERN IS EXPECTED TO TRANSITION INTO EARLY
NEXT WEEKS AS THE EASTERN PACIFIC UPPER TROUGH LIFTS INLAND ACROSS
SOUTHERN CANADA THE PACIFIC NORTHWEST. AS THIS OCCURS, THE
EXPANSIVE UPPER RIDGE OVER THE SOUTH-CENTRAL U.S. WILL SPRAWL INTO
THE EAST-CENTRAL PORTION OF THE COUNTRY. THIS WILL LEAD TO A
RELATIVE LULL IN MONSOONAL FLOW INTO THE SOUTHWEST BEFORE IT
RESUMES TOWARD THE END OF THE EXTENDED PERIOD. THE INCREASINGLY
MORE PROGRESSIVE AND ENERGETIC NORTHERN STREAM UPPER TROUGH ENERGY
WILL DIRECT COOLER AIRMASSES INTO THE WEST AND DOWNSTREAM OVER THE
U.S. NORTHERN TIER STATES MID-LATER NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE TIMING OF THE PATTERN TRANSITION SEEMS TO NOT HAVE RESOLVED
MUCH WITH THE LATEST RUNS OF GUIDANCE. THE ECMWF HAS CONSISTENTLY
BEEN THE SLOWER LESS PROGRESSIVE SOLUTION FOR SEVERAL DAYS AND NOW
THE UKMET IS CLOSELY CLUSTERED. THE CMC HAS BECOME INCREASINGLY
FASTER LIKE THE GFS THE LAST COUPLE OF CYCLES, BOTH SEEM
APPROXIMATELY 12 TO 18 HOURS FASTER WITH THE EVOLUTION THAT THE
ECMWF/UKMET. THE ENSEMBLE MEANS REMAIN FAIRLY CLUSTERED WITH THE
ECMWF/UKMET OR SOMEWHERE BETWEEN THE TWO CLUSTERS THROUGH THE
EXTENDED PERIOD.
THE WPC FORECAST WAS DERIVED FROM A MODEL AND ENSEMBLE BLEND WITH
ENHANCED WEIGHTING APPLIED TO SOLUTIONS ON THE SLIGHTLY LESS
PROGRESSIVE SIDE OF THE FULL ENVELOPE OF GUIDANCE GIVEN RECENT FLOW
NATURE, BUT THE RESULT IS NOT AS SLOWED AS CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
UNSETTLED AND COOLER CONDITIONS WILL FILTER INTO THE NORTHWEST/WEST
OVER THE WEEKEND AND INTO NEXT WEEK AS AN AMPLIFIED TROUGH MOVES
ONSHORE THE WEST COAST. PERIODS OF RAIN AND SPOTTY HIGH ELEVATION
MOUNTAIN SNOWS WILL BE POSSIBLE ACROSS THE NORTHERN INTERMOUNTAIN
WEST/ROCKIES. FOR AREAS DOWNSTREAM, SHOWERS AND THUNDERSTORMS MAY
DEVELOP ACROSS THE NORTH-CENTRAL STATES BY EARLY NEXT WEEK GIVEN
FOCUS FROM POSSIBLE MODERATE CYCLOGENESIS/FRONTOGENESIS, WITH
MODEST FOCUS SHIFTING DOWNSTREAM AS THE WEEK PROGRESSES WITH
SYSTEM/FRONTAL TRANSLATION. RENEWED NORTHERN STREAM UPPER TROUGH
APPROACH AND DIGGING BACK INTO THE NORTHWEST INTO MID-LATER NEXT
WEEK OFFERS POTENTIAL FOR DEVELOPMENT AND DIGGING/INTRUSION OF
UNSETTLED AND COOLED FLOW.
HOT TEMPERATURES UNDER THE UPPER RIDGE WILL PERSIST ACROSS THE
SOUTH- CENTRAL U.S. WHILE EXPANDING TO THE EAST-CENTRAL STATES
DURING THIS PERIOD. DAILY TEMPERATURES WILL ROUTINELY REACH
UPWARDS OF 10 DEGREES ABOVE NORMAL. HEAT RISK GUIDANCE IDENTIFIES
AN ASSOCIATED REGION WITH UPWARDS TO MAJOR LEVEL IMPACTS WITH MAIN
FOCUS SET TO SHIFT SLOWLY FROM THE SOUTH-CENTRAL PLAINS AND MID-
MISSISSIPPI VALLEY SUNDAY SOUTHEASTWARD THROUGH THE SOUTH-
SOUTHEAST INTO NEXT MIDWEEK.
A LINGERING TRAILING FRONT STALLING ACROSS FLORIDA WILL MAINTAIN
PERIODIC RAIN/THUNDERSTORM CHANCES THERE AND INTO SOUTHEAST U.S.
COASTAL AREAS INTO NEXT WEEK. MOIST FLOW AND PATTERN LONGEVITY MAY
LEAD TO POSSIBLE LOCAL RUNOFF ISSUES, ESPECIALLY FOR URBAN AREAS.
CAMPBELL
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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