751
FXUS21 KWNC 281908
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 28 2024
SYNOPSIS: MID-LEVEL HIGH PRESSURE FAVORED OVER SOUTHEASTERN AND WESTERN CONUS
IS EXPECTED TO INCREASE CHANCES FOR EXCESSIVE HEAT CONDITIONS DURING WEEK-2.
MUCH OF THE ANOMALOUS WARM SUMMERTIME TEMPERATURES AND DRIER THAN NORMAL
CONDITIONS ARE ANTICIPATED TO SUSTAIN THE RISK FOR RAPID ONSET DROUGHT (ROD)
OVER PARTS OF THE PLAINS, CORN BELT AND LOWER HALF OF THE EASTERN SEABOARD
DURING WEEK-2. POSSIBLE MID-LEVEL LOW PRESSURE AND CONTINUED RAINFALL OVER THE
NORTH-CENTRAL CONUS EARLY IN WEEK-2 SUPPORTS POSSIBLE FLOODING ACROSS MANY
PARTS OF THE MIDWEST. AN ACTIVE NORTH AMERICAN MONSOON CIRCULATION AND POSSIBLE
MOISTURE SURGES INTO THE DESERT SOUTHWEST FAVOR AN INCREASED RISK OF LOCALLY
HEAVY PRECIPITATION AND POSSIBLE FLOODING OVER THE LOWER FOUR CORNERS.
HAZARDS
MODERATE RISK FOR EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHEAST, TENNESSEE
VALLEY, AND THE MID-ATLANTIC, SAT-SUN, JUL 6-7.
SLIGHT RISK OF EXCESSIVE HEAT FROM THE SOUTHERN PLAINS EASTWARD TO THE LOWER
EASTERN SEABOARD, SAT-FRI, JUL 6-12.
MODERATE RISK OF EXCESSIVE HEAT FOR THE CENTRAL CALIFORNIA VALLEY AND INTO THE
DESERT SOUTHWEST, SAT-SUN, JUL 6-7.
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF CALIFORNIA, PACIFIC NORTHWEST,
AND THE INTERIOR WEST, SAT-WED, JUL 6-10.
SLIGHT RISK OF PERIODS OF HEAVY PRECIPITATION FOR PARTS OF THE DESERT SOUTHWEST
AND SOUTHERN ROCKIES, SAT-FRI, JUL 6-12.
POSSIBLE FLOODING FOR PORTIONS OF SOUTHERN ARIZONA AND NEW MEXICO.
POSSIBLE FLOODING FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS AND UPPER AND
MIDDLE MISSISSIPPI VALLEY.
RAPID ONSET DROUGHT RISK FOR PARTS OF GREAT PLAINS, MISSISSIPPI VALLEY,
TENNESSEE AND OHIO VALLEYS, APPALACHIANS, SOUTHEAST AND MID-ATLANTIC.
DETAILED SUMMARY
FOR MONDAY JULY 01 - FRIDAY JULY 05:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JULY 06 - FRIDAY JULY 12: THE HAZARDS PERSPECTIVE REMAINS MOSTLY
ON TRACK SINCE YESTERDAY. THE GEFS AND ECMWF ENSEMBLES PREDOMINANTLY FEATURE
ABOVE-NORMAL 500-HPA HEIGHTS IN THE MEAN WEEK-2 FIELDS, BUT CONTINUE TO FAVOR
NEAR TO BELOW NORMAL HEIGHTS EARLY IN THE PERIOD, LIKELY TIED TO SHORTWAVE
ENERGY PROPAGATING ALONG THE LONGWAVE TROUGH AXIS SITUATED OVER CENTRAL CANADA.
THE ECMWF CONTINUES TO BE MORE PRONOUNCED WITH THIS DEVELOPMENT THAN THE GEFS,
FAVORING MORE NORTHWESTERLY FLOW OVER NORTH-CENTRAL CONUS WITH A CLEAR BREAK IN
THE SUBTROPICAL RIDGE PATTERN EXTENDING INTO NORTHERN MEXICO. THE RESULTANT
COOLER AIR HEADING INTO NEXT WEEKEND LOOKS TO QUELL ANY ANOMALOUSLY WARM
DAYTIME TEMPERATURES THROUGHOUT MUCH OF THE PLAINS AND MISSISSIPPI VALLEY,
HOWEVER THE MID-LEVEL TROUGHING PREDICTED LOOKS TO BE FLANKED BY A PAIR OF
STRONG RIDGES CENTERED OVER THE EASTERN AND WESTERN CONUS WHERE THE EXCESSIVE
HEAT RISK IS MOST LIKELY TO PREVAIL DURING THE PERIOD.
BASED ON THE LATEST RAW AND CALIBRATED TEMPERATURE TOOLS OVER THE EASTERN
CONUS, A MODERATE RISK OF EXCESSIVE HEAT REMAINS ISSUED ACROSS PARTS OF THE
SOUTHEAST, TENNESSEE VALLEY AND THE LOWER EASTERN SEABOARD FOR JUL 6-7.
PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT 30-40% CHANCES OF MAXIMUM DAYTIME
TEMPERATURES EXCEEDING THE 85TH PERCENTILE AND 95 DEGREES F, WHERE ELEVATED
DEWPOINT TEMPERATURES FORECAST (> 70 DEG F) ARE LIKELY TO DRIVE HIGH HEAT INDEX
VALUES WITHIN THE HIGHLIGHTED REGION. GIVEN THE PERSISTENCE OF MID-LEVEL
RIDGING FAVORED THROUGHOUT THE PERIOD, A BROADER SLIGHT RISK AREA OF EXCESSIVE
HEAT IS ISSUED FROM THE SOUTHERN PLAINS TO THE EASTERN SEABOARD FOR THE
ENTIRETY OF WEEK-2. WHILE THE GEFS PET FAVORS A WARMER SOLUTION OVER THE
CENTRAL CONUS (LIKELY DUE TO WEAKER TROUGHING FAVORED), THE SLIGHT RISK
COVERAGE IS LIMITED TO THE SOUTHERN TIER OF THE U.S. GIVEN THE POTENTIAL FOR
COLD AIR ADVECTION OVER THE MIDWEST EARLY IN WEEK-2.
THE PERSISTENT WARMER AND DRIER THAN NORMAL CONDITIONS OVER AT LEAST THE PAST
MONTH HAVE LED TO A RISK FOR RAPID ONSET DROUGHT FOR PARTS OF THE OHIO VALLEY
(EASTERN CORN BELT), MID-ATLANTIC, SOUTHEAST, SOUTHERN PLAINS, AND SOUTHERN
CENTRAL PLAINS. THE RECENT HEAT WAVES ACROSS THE EASTERN U.S. HAVE EXACERBATED
THE ONGOING DRYNESS ACROSS THESE AREAS, AND HAVE LED TO MODERATE DROUGHT (D1)
FOR MANY AREAS IN THE EAST. MUCH OF THE AREAS HIGHLIGHTED FOR RISK OF RAPID
ONSET DROUGHT HAVE SEEN LARGE PRECIPITATION DEFICITS OVER THE PAST TWO WEEKS TO
A MONTH AND HAVE SEEN LARGE REDUCTIONS IN AVAILABLE SOIL MOISTURE. THERE IS
ADDITIONAL RISK FOR HIGH EVAPOTRANSPIRATION RATES WITH ABOVE-NORMAL
TEMPERATURES FORECAST ACROSS MUCH OF THE EASTERN CONUS. ALTHOUGH PERIODIC,
LOCALIZED HEAVY PRECIPITATION CANNOT BE RULED OUT DUE TO FRONTAL AND/OR DAYTIME
THUNDERSTORM ACTIVITY. DRY SOILS, STRESSED VEGETATION, AND REDUCED WATER
AVAILABILITY DUE TO LOW PONDS AND STREAMS MAY LEAD TO INCREASED IMPACTS TO
AGRICULTURE AND LIVESTOCK, WITH SEVERAL LOCATIONS ALREADY EXPERIENCING IMPACTS.
UPSTREAM, THERE IS BETTER MODEL AGREEMENT IN REGARDS TO MORE AMPLIFIED RIDGING
EXTENDING FROM THE EASTERN PACIFIC INTO THE INTERIOR WEST. MUCH OF THE
ACCOMPANYING EXCESSIVE HEAT POTENTIAL LOOKS TO ALREADY BE ESTABLISHED LATE IN
WEEK-1, WITH DOUBLE DIGIT TEMPERATURES DEPARTURES FORECAST THROUGHOUT THE
CENTRAL CALIFORNIA VALLEY (BASED ON WPC DAYS 6 AND 7 TEMPERATURE ANOMALIES),
AND THE NWS HEATRISK TOOL INDICATING RED AND MAGENTA LEVELS IN THE REGION.
LEADING INTO WEEK-2, BOTH THE GEFS AND ECWMF PETS SHOW ELEVATED CHANCES
(30-50%) FOR MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE AND 100 DEG F
DURING THE FIRST FEW DAYS OF THE PERIOD. GIVEN THE GROWING SUPPORT FOR
EXCESSIVE HEAT CONDITIONS IN THESE TOOLS, A CORRESPONDING MODERATE RISK IS
INTRODUCED FOR THE CENTRAL CALIFORNIA VALLEY AND THE DESERT SOUTHWEST FOR JUL
6-7. FROM DAY 10 AND BEYOND, THE STRONGEST SIGNALS FOR HEAT WEAKEN IN THE PETS
OVER THE SOUTHWESTERN CONUS, BUT POINT TO A NORTHWARD AND EASTWARD EXPANSION OF
HEAT POTENTIAL. AS A RESULT, THE SLIGHT RISK OF EXCESSIVE HEAT IS EXPANDED TO
INCLUDE MORE OF THE PACIFIC NORTHWEST, GREAT BASIN, AND NORTHERN INTERMOUNTAIN
IN THE UPDATED OUTLOOK FOR JUL 6-10. THE PETS ALSO SHOW HEAT POSSIBLY
RETURNING THE CENTRAL AND NORTHERN HIGH PLAINS TIED TO REBUILDING MID-LEVEL
HEIGHTS LATE IN WEEK-2, THOUGH NO HAZARDS ARE POSTED DUE TO UNCERTAINTY AT THIS
LEAD.
THE SHORTWAVE ENERGY FAVORED OVER THE NORTH-CENTRAL CONUS IS EXPECTED TO
PROMOTE ABOVE-NORMAL PRECIPITATION OVER MANY PARTS OF THE MIDWEST LATE NEXT
WEEK AND INTO NEXT WEEKEND. ALTHOUGH THE RAW AND CALIBRATED PRECIPITATION TOOLS
SHOW THE HEAVIEST PRECIPITATION AMOUNTS TIMING OFF, A FLOODING POSSIBLE HAZARD
REMAINS POSTED FOR MANY PARTS OF THE MIDWEST. ANY CONTINUED RAINFALL HEADING
INTO WEEK-2 MAY WORSEN ONGOING FLOODING ALONG THE MISSOURI AND MISSISSIPPI
RIVERS.
UNDERNEATH THE ANOMALOUS MID-LEVEL RIDGING FAVORED OVER THE SOUTHERN TIER OF
THE CONUS, EASTERLY FLOW FROM THE GULF OF MEXICO CONSISTENT WITH THE NORTH
AMERICAN MONSOON CIRCULATION IS EXPECTED TO PROMOTE INCREASED PRECIPITATION
AMOUNTS OVER NORTHERN MEXICO AND THE SOUTHWESTERN U.S. WITH INTENSE DAYTIME
HEATING TO DEEPEN THE THERMAL LOW OVER THE SONORAN DESERT, AND SOME MODEL
SOLUTIONS CONTINUING TO DEPICT PERIODS OF DEWPOINT TEMPERATURES INCREASES,
THERE REMAINS THE POTENTIAL FOR GULF OF CALIFORNIA MOISTURE SURGES, AND A
SLIGHT RISK OF HEAVY PRECIPITATION REMAINS POSTED OVER THE LOWER FOUR CORNERS
REGION. THIS SLIGHT RISK IS EXTENDED TO INCLUDE ALL OF WEEK-2 BASED ON SUPPORT
FROM THE GEFS AND ECMWF PETS, WHICH INDICATE AT LEAST A 20% CHANCE FOR 3-DAY
AMOUNTS EXCEEDING THE 85TH PERCENTILE. A FLOODING POSSIBLE RISK IS ALSO
DESIGNATED FOR SOUTHERN PARTS OF ARIZONA AND NEW MEXICO WHERE STRONGER
PRECIPITATION SIGNALS ARE DEPICTED IN MULTIPLE MODELS. PRECIPITATION IS
EXPECTED TO BE ISOLATED AND NOT ALL LOCATIONS WILL EXPERIENCE HEAVY RAINFALL.
HOWEVER, FLASH FLOODING IS POSSIBLE BOTH WHERE PRECIPITATION OCCURS AND IN
DOWNSTREAM VALLEYS, PARTICULARLY IN AND AROUND BURN SCARS WHERE DEBRIS FLOWS
CAN BE TRIGGERED BY HEAVY RAINFALL.
ACROSS THE TROPICS, THE MADDEN-JULIAN OSCILLATION (MJO) HAS BEEN LARGELY
DISORGANIZED FOR MUCH OF JUNE. HOWEVER, THERE IS GOOD CONTINUITY IN THE MODEL
GUIDANCE FAVORING A MORE COHERENT MJO SIGNAL EMERGING OVER THE INDIAN OCEAN AND
PROPAGATING EASTWARD INTO THE MARITIME CONTINENT DURING THE NEXT TWO WEEKS.
HISTORICALLY, THIS EVOLVING SIGNAL IS SUPPORTIVE FOR TROPICAL CYCLOGENESIS IN
THE WESTERN HEMISPHERE BASED ON MJO COMPOSITES DURING JUN-AUG, AND THE NATIONAL
HURRICANE CENTER (NHC) IS MONITORING THE POTENTIAL FOR TROPICAL CYCLONE (TC)
DEVELOPMENT ASSOCIATED WITH THREE TROPICAL WAVES IN THE ATLANTIC. OF THE THREE,
INVEST 95L HAS THE HIGHEST ODDS FOR DEVELOPMENT (CURRENTLY 100% AT 1:24 PM EDT
). NO CORRESPONDING HAZARDS ARE POSTED GIVEN LARGE UNCERTAINTY WITH EVENTUAL
STRENGTH AND TRACK OF THE DISTURBANCE, BUT THE TROPICS BEAR MONITORING DURING
THE NEXT SEVERAL DAYS, AS THE SHEARING ENVIRONMENT LOOKS FAVORABLE FOR FURTHER
DEVELOPMENT AS IT APPROACHES THE CARIBBEAN.
FORECASTER: NICK NOVELLA
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