646
FXUS21 KWNC 091839
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 09 2023
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FORECAST ACROSS THE SOUTH-CENTRAL AND
SOUTHEASTERN CONTIGUOUS U.S. DURING WEEK-2, ALTHOUGH MODELS HAVE BEEN TRENDING
LESS AMPLIFIED WITH THE FEATURE COMPARED TO PREVIOUS DAYS, AND ALSO DEPICTING A
STRONGER AREA OF MID-LEVEL LOW PRESSURE ACROSS THE NORTHEAST. INCREASED CHANCES
OF EXCESSIVE HEAT REMAIN FAVORED OVER PARTS OF THE CENTRAL AND SOUTHERN GREAT
PLAINS, AND THE MIDDLE AND LOWER MISSISSIPPI VALLEY, WITH RAPID ONSET DROUGHT A
CONCERN ACROSS THE LOWER MISSISSIPPI VALLEY. SOME AREAS OF ENHANCED RAINFALL
ARE POSSIBLE ACROSS PORTIONS OF THE MIDWEST AND EXTENDING INTO PARTS OF THE
EAST RELATED TO SURFACE LOW PRESSURE MOVING EASTWARD ACROSS THE REGION EARLY IN
THE PERIOD. SNOWMELT SEASON CONTINUES FOR PORTIONS OF THE WEST AFTER
EXCEPTIONAL WINTER ACCUMULATIONS, LEADING TO THE CONTINUED POTENTIAL FOR
FLOODING.
HAZARDS
MODERATE RISK OF EXCESSIVE HEAT ACROSS PORTIONS OF THE SOUTHERN PLAINS AND
LOWER MISSISSIPPI VALLEY, SAT-MON, JUN 17-19.
SLIGHT RISK OF EXCESSIVE HEAT ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS, AND MIDDLE AND LOWER MISSISSIPPI AND TENNESSEE VALLEYS, SAT-FRI, JUN
17-23.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL PLAINS,
MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND SOUTHEAST, SAT-MON, JUN
17-19.
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 LOWER MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR MONDAY JUNE 12 - FRIDAY JUNE 16:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JUNE 17 - FRIDAY JUNE 23: A WEAK MID-LEVEL RIDGE REMAINS FORECAST
ACROSS THE SOUTH-CENTRAL AND SOUTHEASTERN CONUS DURING WEEK-2. HOWEVER, THE
GEFS, ECMWF, AND CANADIAN ENSEMBLES HAVE ALL BEEN TRENDING WEAKER WITH THIS
FEATURE COMPARED TO PREVIOUS DAYS. OF NOTE IS ALSO THE STRONGER TROUGH OVER THE
NORTHEAST RELATED TO AN ONGOING NEGATIVE PHASE OF THE NORTH ATLANTIC
OSCILLATION THAT IS FORECAST TO CONTINUE INTO LATE JUNE. AS A RESULT, THE
PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE LOWER THROUGHOUT MUCH OF
CENTRAL AND EASTERN CONUS COMPARED TO YESTERDAY, WITH INCREASING CHANCES FOR
BELOW-NORMAL TEMPERATURES EXPANDING ACROSS THE NORTHEAST, OHIO VALLEY, AND
NORTHERN MID-ATLANTIC. WHILE EXCESSIVE HEAT REMAINS POSSIBLE ACROSS PORTIONS OF
THE CENTRAL PLAINS AND MIDDLE MISSISSIPPI VALLEY, THE GREATEST HEAT POTENTIAL
IS BECOMING MORE FOCUSED FURTHER SOUTH. THE HOTTEST TEMPERATURES ARE PREDICTED
ACROSS TEXAS AND THE LOWER MISSISSIPPI VALLEY WHERE THE NATIONAL BLEND OF
MODELS INDICATES THE POSSIBILITY OF DAILY RECORD HIGH TEMPERATURES (UPPER 90S
TO LOW 100S DEG F) EARLY IN WEEK-2. THE SKILL-WEIGHTED GEFS/ECMWF EXCESSIVE
HEAT TOOL ALSO INDICATES AT LEAST A 40 PERCENT CHANCE THAT HEAT INDICES EXCEED
105 DEG F (110 DEG F IN SOME AREAS). THEREFORE, A MODERATE RISK OF EXCESSIVE
HEAT CONTINUES ACROSS PARTS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY
FOR JUN 17-19. A SLIGHT RISK FOR EXCESSIVE HEAT REMAINS POSTED FOR ALL OF
WEEK-2, WITH THE NORTHWARD AND EASTWARD EXTENTS CUT BACK COMPARED TO YESTERDAY
DUE TO RELATIVELY COOLER TEMPERATURES IN TODAY’S GUIDANCE AND INCREASING
POTENTIAL FOR PRECIPITATION ACROSS THE MIDDLE MISSISSIPPI AND TENNESSEE
VALLEYS. WHILE MAXIMUM TEMPERATURES HAVE DROPPED ALONG THE GULF COAST IN
TODAY’S UNCALIBRATED GUIDANCE, RELATIVELY HIGHER DEWPOINTS ARE NOTED IN THE
LAST SEVERAL DETERMINISTIC GFS RUNS WHICH MAY RESULT IN HEAT INDICES CONTINUING
TO EXCEED HAZARDOUS THRESHOLDS.
GIVEN THE EXCESSIVE HEAT FORECAST ALONG WITH ANTECEDENT DRY CONDITIONS, RAPID
ONSET DROUGHT RISK REMAINS ELEVATED ACROSS PORTIONS OF THE LOWER MISSISSIPPI
VALLEY WHERE SOIL MOISTURE VALUES HAVE DROPPED BELOW THE 30TH CLIMATOLOGICAL
PERCENTILE IN SOME AREAS. THE LARGEST SOURCE OF UNCERTAINTY IS THE INCREASING
POTENTIAL FOR TROPICAL MOISTURE TO MOVE ACROSS THE REGION LATER IN WEEK-2 AND
INTO WEEK-3. HOWEVER, INDIVIDUAL MODELS ARE INCONSISTENT, AND REFORECAST TOOL
GUIDANCE FROM THE GEFS AND ECMWF LEANS TOWARD NEAR TO SLIGHTLY BELOW-NORMAL
PRECIPITATION FOR WEEK-2 AS A WHOLE. THIS AREA WILL LIKELY NEED TO RE-EVALUATED
EARLY NEXT WEEK SHOULD MODELS COME INTO BETTER AGREEMENT.
THERE IS A POTENTIAL FOR A MID-LEVEL SHORTWAVE DISTURBANCE TO PROPAGATE FROM
THE NORTH-CENTRAL CONUS INTO THE EAST, BRINGING ENHANCED PRECIPITATION CHANCES
TO PARTS OF THE MIDWEST AND THE EASTERN CONUS EARLY IN THE PERIOD. THE ECMWF
REFORECAST TOOL CONTINUES TO DEPICT SOME AREAS OF THE MIDDLE MISSISSIPPI VALLEY
HAVING AT LEAST A 20 PERCENT CHANCE OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE
85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH. WHILE THE GEFS REFORECAST TOOL DOES
NOT INDICATE THESE ENHANCED PROBABILITIES, THE UNCALIBRATED 0Z GEFS ENSEMBLE
DEPICTS ELEVATED DAILY PRECIPITATION TOTALS SHIFTING FROM THE MIDDLE
MISSISSIPPI VALLEY TO THE SOUTHEASTERN CONUS DURING THE 8-10 DAY TIMEFRAME. DUE
TO THESE INCREASING SIGNALS, A SLIGHT RISK OF HEAVY PRECIPITATION IS
HIGHLIGHTED ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE
VALLEYS, AND THE SOUTHEAST FOR JUN 17-19.
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. 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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