860
FXUS21 KWNC 071806
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 07 2023
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FORECAST ACROSS THE SOUTH-CENTRAL AND
SOUTHEASTERN CONTIGUOUS U.S. DURING WEEK-2 FAVORING INCREASED CHANCES OF
EXCESSIVE HEAT OVER PARTS OF THE CENTRAL AND SOUTHERN GREAT PLAINS, MIDDLE AND
LOWER MISSISSIPPI VALLEY, AND SOUTHEAST. A WAVE OF SURFACE LOW PRESSURE MAY
BRING ENHANCED PRECIPITATION ALONG THE FRONTAL BOUNDARY SET-UP OVER THE
EAST-CENTRAL CONUS EARLY IN THE PERIOD. ALTHOUGH RAPID ONSET DROUGHT RISK
REMAINS POSTED ACROSS PARTS OF THE MIDWEST AND CORN BELT, INCREASING
PRECIPITATION SIGNALS IN THE GUIDANCE MAY RESULT IN AN ADJUSTMENT OF THIS AREA
IN TOMORROW’S UPDATE. SNOWMELT SEASON CONTINUES FOR PORTIONS OF THE WEST AFTER
EXCEPTIONAL WINTER ACCUMULATIONS, LEADING TO THE CONTINUED POTENTIAL FOR
FLOODING, EXACERBATED BY THE INCREASED CHANCES OF PRECIPITATION AT THE OUTSET
OF THE PERIOD OVER PARTS OF THE REGION.
HAZARDS
MODERATE RISK OF EXCESSIVE HEAT ACROSS PARTS OF THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY, THU-MON, JUN 15-19.
SLIGHT RISK OF EXCESSIVE HEAT ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS,
MIDDLE AND LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND THE SOUTHEAST, THU-WED,
JUNE 15-21.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE GREAT BASIN, NORTHERN
AND CENTRAL ROCKIES, AND SIERRA NEVADA, THU, JUN 15.
POSSIBLE FLOODING FOR PORTIONS OF CALIFORNIA, NEVADA, UTAH, WYOMING, AND IDAHO.
POSSIBLE FLOODING ALONG PORTIONS OF THE JAMES RIVER IN SOUTH DAKOTA.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF THE GREAT LAKES, THE MIDDLE AND
UPPER MISSISSIPPI AND OHIO VALLEYS.
DETAILED SUMMARY
FOR SATURDAY JUNE 10 - WEDNESDAY JUNE 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JUNE 15 - WEDNESDAY JUNE 21: THE GEFS, ECMWF, AND CANADIAN
ENSEMBLES ARE IN GOOD AGREEMENT DEPICTING AREAS OF WEAK TROUGHING NEAR THE WEST
COAST OF THE CONUS AND OVER THE NORTHEAST AT THE OUTSET OF THE PERIOD. THIS
FAVORS AN EXPANSION OF A RIDGE ACROSS MUCH OF THE INTERIOR EASTERN AND CENTRAL
CONUS AND INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES. EXCESSIVE HEAT IS
LIKELY TO BE A CONCERN ACROSS THE SOUTHERN TIER, PARTICULARLY ACROSS TEXAS,
WHERE THE GEFS AND ECMWF REFORECAST TOOLS DEPICT SOME AREAS WITH AT LEAST A 40
PERCENT CHANCE MAXIMUM TEMPERATURES EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE.
TEMPERATURES ABOVE 100 DEG F ARE INDICATED IN THE UNCALIBRATED GUIDANCE WITH
SOME PARTS OF THE STATE POSSIBLY EXCEEDING DAILY RECORDS BASED ON THE NATIONAL
BLEND OF MODELS. WHILE LOWER ACTUAL TEMPERATURES ARE FORECAST ACROSS PARTS OF
THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST, ELEVATED HUMIDITY LEVELS FAVOR
HAZARDOUS HEAT INDICES OVER THESE AREAS. EXCESSIVE HEAT GUIDANCE INDICATES AT
LEAST A 40 PERCENT CHANCE HEAT INDICES EXCEED 105 DEG F ACROSS PARTS OF THE
LOWER MISSISSIPPI VALLEY AND SOUTHEAST DURING WEEK-2, WITH SOME AREAS POSSIBLY
ABOVE 110 DEG F. GIVEN THESE FAVORABLE SIGNALS IN THE GUIDANCE, A MODERATE RISK
FOR EXCESSIVE HEAT CONTINUES ACROSS MUCH OF CENTRAL AND EASTERN TEXAS,
SOUTHEAST OKLAHOMA, AND EXTENDING EASTWARD INTO PARTS OF THE LOWER MISSISSIPPI
VALLEY AND SOUTHEAST FOR JUN 15-19. A BROADER SLIGHT RISK IS HIGHLIGHTED FOR
ALL OF WEEK-2 EXTENDING NORTH THROUGH THE CENTRAL PLAINS AND MIDDLE MISSISSIPPI
VALLEY WITH THE ECMWF AND GEFS REFORECAST TOOLS GENERALLY DEPICTING AT LEAST A
20 PERCENT CHANCE MAXIMUM TEMPERATURES EXCEED THE 85TH CLIMATOLOGICAL
PERCENTILE AND 90 DEG F, WITH THE POTENTIAL FOR HEAT INDICES TO REACH OR EXCEED
100 DEG F BASED ON EXCESSIVE HEAT GUIDANCE.
THERE IS A POTENTIAL FOR A WEAK WAVE OF SURFACE LOW PRESSURE TO DEVELOP ALONG
THE FRONTAL BOUNDARY SET-UP ACROSS THE EAST-CENTRAL CONUS EARLY IN WEEK-2. THE
CANADIAN REFORECAST TOOL IS MOST ROBUST, INDICATING AT LEAST A 20 PERCENT
CHANCE 3-DAY PRECIPITATION TOTALS EXCEED THE 85TH PERCENTILE AND 1-INCH OVER
SOME AREAS. WHILE THE ECMWF AND GEFS REFORECAST TOOLS BOTH DEPICT WEAKER
PROBABILITIES COMPARED TO THE CANADIAN, THE UNCALIBRATED ENSEMBLE MEANS FROM
THE ECMWF AND GEFS INDICATE SOME ENHANCED PRECIPITATION TOTALS ON DAYS 8 AND 9
(JUN 15-16). WHILE NO RELATED PRECIPITATION HAZARD IS DEPICTED, THIS POTENTIAL
SYSTEM COULD MAINTAIN RELATIVELY COOLER TEMPERATURES ACROSS EASTERN CONUS, AND
DELAY THE EXPANSION OF WARMTH INTO PARTS OF THE MIDWEST UNTIL LATER IN WEEK-2.
RAPID ONSET DROUGHT RISK REMAINS POSTED ACROSS PARTS OF THE MIDWEST, OHIO
VALLEY, GREAT LAKES, AND INTERIOR NORTHEAST WHERE SOIL MOISTURE CONTINUES TO
DECLINE (SOME AREAS NOW FALLING BELOW THE 20TH CLIMATOLOGICAL PERCENTILE).
HOWEVER, THERE ARE INCREASING CHANCES FOR PRECIPITATION DURING THE NEXT WEEK
AND INTO EARLY WEEK-2 OVER SOME OF THESE AREAS, ESPECIALLY FURTHER SOUTH. AS A
RESULT, RAPID ONSET DROUGHT RISK MAY SHIFT MORE TO THE NORTHWEST ACROSS
PORTIONS OF THE UPPER MISSISSIPPI VALLEY, AND THIS MAY BE REFLECTED IN
TOMORROW’S UPDATE IF CURRENT TRENDS CONTINUE. THERE ARE ALSO EMERGING DROUGHT
CONCERNS ACROSS PARTS OF THE DEEP SOUTH GIVEN THE HOT AND DRY CONDITIONS
FORECAST.
SNOWMELT SEASON CONTINUES ACROSS THE WESTERN CONUS AFTER ACCUMULATING A VERY
LARGE AND IN SOME CASES RECORD-BREAKING SNOWPACK, INDUCING RIVER FLOODING
ESPECIALLY ACROSS HIGHER ELEVATIONS FOR SOME AREAS IN THE WEST, WHERE A FEW
SITES STILL REPORT OVER 40 INCHES OF SNOW WATER CONTENT. AS SNOWMELT CONTINUES
IN PARTS OF THE SIERRA NEVADA, GREAT BASIN, AND NORTHERN ROCKIES, FLOODING MAY
CONTINUE TO OCCUR ALONG MANY RIVERS, AND IN AREAS ADJACENT TO THE HIGHER
ELEVATIONS. A SLIGHT RISK OF HEAVY PRECIPITATION CONTINUES TO BE POSTED ACROSS
PARTS OF THE WEST FOR JUN 15 AS WEAK TROUGHING LEADS TO SOME INCREASED FORCING
OVER THE REGION. WHILE THE GEFS AND CANADIAN REFORECAST TOOLS GENERALLY KEEP
PROBABILITIES UNDER 20 PERCENT FOR 3-DAY PRECIPITATION EXCEEDING A HALF-INCH,
THE ECMWF REFORECAST TOOL DEPICTS HIGHER PROBABILITIES EARLY IN THE PERIOD.
BASED ON THE UNCALIBRATED GUIDANCE, THE STRONGEST PRECIPITATION SIGNAL IS ON
DAY-8 (JUN 15), CORRESPONDING WITH THE SLIGHT RISK. ANY ADDITIONAL
PRECIPITATION COULD EXACERBATE ONGOING FLOODING ACROSS THE WEST. POSSIBLE
FLOODING ALSO REMAINS ACROSS NORTHERN PARTS OF THE JAMES RIVER IN SOUTH DAKOTA
AS RIVER LEVELS ARE RECEDING SLOWER DUE TO SATURATED GROUND CONDITIONS AND
RELATIVELY FLAT TOPOGRAPHY.
MID-LEVEL TROUGHING IS FAVORED FOR THE ALEUTIANS AND ALASKA MAINLAND, RESULTING
IN INCREASED CHANCES FOR NEAR TO BELOW NORMAL TEMPERATURES AND SLIGHTLY
ABOVE-NORMAL PRECIPITATION ACROSS MUCH OF THE STATE. NO AREAS OF HAZARDOUS
WEATHER ARE INDICATED ACROSS ALASKA.
FORECASTER: THOMAS COLLOW
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