898
FXUS21 KWNC 161824
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 16 2023
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS PREDICTED TO PERSIST FROM WEEK-1
THROUGHOUT WEEK-2 ACROSS THE SOUTH-CENTRAL CONTIGUOUS U.S. (CONUS), SUPPORTING
CONTINUED INCREASED CHANCES FOR EXCESSIVE HEAT ACROSS PARTS OF THE REGION
THROUGHOUT MUCH OF THE PERIOD. THERE IS A POTENTIAL FOR SOME AREAS TO
EXPERIENCE NEAR RECORD TEMPERATURES IN THE TRIPLE DIGITS ACROSS THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY. ODDS ARE HIGHEST ACROSS PORTIONS OF TEXAS
EARLY IN THE PERIOD. ANTICIPATED THUNDERSTORMS ASSOCIATED WITH THE NORTHERN
TIER OF THE MID-LEVEL HIGH CENTERED OVER THE SOUTH-CENTRAL CONUS INCREASE THE
ODDS FOR HEAVY PRECIPITATION OVER THE NORTHERN AND CENTRAL PLAINS. SNOWMELT
SEASON CONTINUES FOR PORTIONS OF THE WEST AND ALONG THE JAMES RIVER AFTER
EXCEPTIONAL WINTER ACCUMULATIONS, CONTINUING THE FLOODING POTENTIAL THERE. SOME
AREAS COULD SEE FLOODING POTENTIAL BEGIN TO DECLINE AS THE SNOWPACK BECOMES
DEPLETED.
HAZARDS
MODERATE RISK OF EXCESSIVE HEAT ACROSS PARTS OF SOUTHERN AND WESTERN TEXAS,
SAT-SUN, JUN 24-25.
SLIGHT RISK OF EXCESSIVE HEAT ACROSS PARTS OF THE SOUTH-CENTRAL CONUS AND LOWER
MISSISSIPPI
VALLEY, SAT-FRI, JUN 24-30.
SLIGHT RISK OF HEAVY PRECIPITATION OVER PARTS OF THE NORTHERN AND CENTRAL
PLAINS, SAT-MON, JUN 24-26.
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.
RAPID ONSET DROUGHT RISK ACROSS NORTHERN AND CENTRAL WISCONSIN.
DETAILED SUMMARY
FOR MONDAY JUNE 19 - FRIDAY JUNE 23:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JUNE 24 - FRIDAY JUNE 30: THE PRIMARY HAZARDS CONCERN IS THE
CONTINUED INCREASED RISK FOR EXCESSIVE HEAT ACROSS THE SOUTH-CENTRAL CONUS AND
LOWER MISSISSIPPI VALLEY DURING WEEK-2. THE GFS, ECMWF, AND CANADIAN ENSEMBLE
MEANS ARE IN GOOD AGREEMENT SHOWING A MID-LEVEL RIDGE CENTERED OVER THE
SOUTHERN HIGH PLAINS WITH THE RIDGE AXIS EXTENDING NORTHWARD INTO THE NORTHERN
PLAINS. MOST GUIDANCE SHOWS THE RIDGE REMAINING APPROXIMATELY IN PLACE
THROUGHOUT THE FORECAST PERIOD WITH ONLY SLIGHT WEAKENING. RE-FORECAST TOOLS
AND INTERNAL HEAT INDEX GUIDANCE SHOW ENHANCED ODDS FOR A MARGINAL EXCESSIVE
HEAT EPISODE UNDER THE MID-LEVEL RIDGE. WITH THIS SYSTEM REMAINING ALMOST
STATIONARY AND WEAKENING ONLY SLIGHTLY, THE EXCESSIVE HEAT POTENTIAL WILL
EXTEND THROUGH THE ENTIRETY OF WEEK-2, ALTHOUGH MOST OF THE TOOLS SHOW SLIGHTLY
REDUCED CHANCES COMPARED TO YESTERDAY OVERALL. A MODERATE HEAT RISK IS POSTED
FOR PARTS OF SOUTHERN AND WESTERN TEXAS EARLY WEEK-2, SAT-SUN JUN 24-25. AT
THAT TIME, CALIBRATED INTERNAL HEAT INDEX TOOLS SHOW UP TO A 70% CHANCE FOR
TEMPERATURES TO EXCEED 105 DEG. F. IN THIS AREA. REFORECASTS OF THE GEFS,
CANADIAN, AND EUROPEAN ENSEMBLES ALSO SHOW AN ENHANCED RISK, WITH UP TO A 50%
CHANCE FOR TEMPERATURES IN THE TOP 85TH PERCENTILE CLIMATOLOGICALLY.
THEREAFTER, ODDS FOR EXCESSIVE HEAT DECLINE, FALLING IN LINE WITH THE LESS
ROBUST INDICATORS BROADLY COVERING THE SOUTH-CENTRAL CONUS AS THE POTENTIAL FOR
TEMPERATURES OVER THE 85TH PERCENTILE CLIMATOLOGICALLY DROPS BELOW 40%. THE
NATIONAL BLEND OF MODELS (NBM) SHOWS A REDUCED POTENTIAL FOR RECORD OR
NEAR-RECORD BREAKING TEMPERATURES COMPARED TO YESTERDAY, WITH NO LOCATION
FORECAST TO TOP 105 DEG. F AT ANY POINT DURING THE WEEK. IN SUMMARY, THE
SOUTH-CENTRAL STATES ARE EXPECTED TO EXPERIENCE ABOVE-NORMAL TEMPERATURES
THROUGHOUT THE PERIOD, BUT GUIDANCE BROADLY SHOWS SLIGHTLY LOWER ODDS FOR
EXCESSIVE HEAT THAN YESTERDAY, WITH SLIGHTLY LOWER EXTREMES IN BOTH TEMPERATURE
AND HEAT INDEX.
A FLAT STRIPE OF ABOVE-NORMAL 500-HPA HEIGHTS IS EXPECTED TO BE CENTERED OVER
SOUTHEASTERN CANADA AS WEEK-2 BEGINS, WITH POSITIVE ANOMALIES STRETCHING
SOUTHWARD INTO THE GREAT LAKES REGION AND THE NORTHEAST. REFORECAST TOOLS SHOW
ENHANCED CHANCES FOR TEMPERATURES TO TOP THE 85TH PERCENTILE CLIMATOLOGICALLY,
AND TEMPERATURES COULD CLIMB INTO THE LOW 90’S ACROSS THE SOUTHERN AND WESTERN
GREAT LAKES REGION. NO EXCESSIVE HEAT THREAT IS POSTED, HOWEVER, AS
TEMPERATURES AND HEAT INDEX VALUES, WHILE ABOVE NORMAL, ARE FORECAST TO REMAIN
BELOW EXTREME THRESHOLDS. THE MID-LEVEL FEATURE WEAKENS AS THE WEEK PROGRESSES,
SLOWLY BRINGING TEMPERATURES DOWN IN THE GREAT LAKES REGION AND NORTHEAST.
GIVEN THE EXCESSIVE HEAT FORECAST ALONG WITH ANTECEDENT DRY CONDITIONS, RAPID
ONSET DROUGHT (ROD) RISK REMAINS ELEVATED ACROSS PORTIONS OF THE LOWER
MISSISSIPPI VALLEY WHERE SOIL MOISTURE VALUES HAVE DROPPED BELOW THE 30TH
CLIMATOLOGICAL PERCENTILE IN SOME AREAS. ADDITIONALLY, ANTICIPATED HOT AND DRY
CONDITIONS MAY ELEVATE WILDFIRE RISK ACROSS PARTS OF TEXAS AND LOUISIANA,
ESPECIALLY WHERE THE NATIONAL INTERAGENCY FIRE CENTER (NIFC) INDICATES MODERATE
TO HIGH RISK OF SIGNIFICANT FIRE POTENTIAL BY THE END OF WEEK-1. ANOTHER ROD
RISK AREA COVERS NORTHERN AND CENTRAL WISCONSIN, WHERE ABNORMAL DRYNESS HAS
RECENTLY EXPANDED, MINOR AMOUNTS OF RAINFALL ARE EXPECTED THROUGHOUT THE NEXT 2
WEEKS, AND ABOVE-NORMAL TEMPERATURES ARE LIKELY.
RELATIVE TO YESTERDAY, ALL DETERMINISTIC MODELS AND ENSEMBLE MEANS SHOW A MUCH
LOWER CHANCE FOR A SURFACE LOW PRESSURE SYSTEM TO FORM NEAR THE SOUTHEAST
COAST. THUS THE SLIGHT RISK AREA FOR HEAVY PRECIPITATION HAS BEEN REMOVED.
ENSEMBLE MEANS SHOW PRECIPITATION TOTALS FOR WEEK-2 AROUND AN INCH ABOVE NORMAL
OR LOWER.
MID-LEVEL SHORTWAVE TROUGHS MOVING OVER THE TOP OF THE SOUTH-CENTRAL CONUS
RIDGE ARE EXPECTED TO CONTRIBUTE TOWARD INCREASED MCS (MESOSCALE CONVECTIVE
SYSTEM) ACTIVITY. THE MOST LIKELY REGION INCLUDES THE NORTHERN AND CENTRAL
GREAT PLAINS, WHERE THERE IS A SLIGHT CHANCE (20% OR GREATER) OF 3-DAY
PRECIPITATION AMOUNTS EXCEEDING THE 85TH PERCENTILE, THOUGH THE ODDS FOR TOTALS
EXCEEDING AN INCH HAVE DECLINED SINCE YESTERDAY.
SNOWMELT SEASON CONTINUES ACROSS PORTIONS OF 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.
AS SNOWMELT CONTINUES IN PARTS OF THE SIERRA NEVADA, GREAT BASIN, AND NORTHERN
ROCKIES, FLOODING MAY CONTINUE TO OCCUR ALONG SOME RIVERS AND CREEKS, AND IN
AREAS ADJACENT TO THE HIGHER ELEVATIONS. IMPROVEMENTS IN FLOOD CONDITIONS ARE
POSSIBLE TOWARD THE END OF WEEK-2 ACROSS PARTS OF THE WEST AS THE SNOWPACK
BECOMES DEPLETED FROM SPRING SNOWMELT. POSSIBLE FLOODING ALSO REMAINS ACROSS
LOCALIZED NORTHERN PARTS OF THE JAMES RIVER IN SOUTH DAKOTA. MULTIPLE GAUGES
ARE ANTICIPATED TO SHOW AT LEAST MODERATE IMPROVEMENT BY THE END OF WEEK-2.
WEAK POSITIVE MID-LEVEL HEIGHT DEPARTURES ARE EXPECTED NEAR SOUTHERN ALASKA,
ESPECIALLY SOUTHEASTERN PARTS OF THE STATE. ENSEMBLE MEANS ALSO SHOW A WEAK
MEAN MID-LEVEL TROUGH CENTERED OVER THE BERING SEA. THIS SUPPORTS NEAR TO BELOW
NORMAL TEMPERATURES ACROSS THE SOUTHWESTERN QUARTER OF THE STATE, WARMER THAN
NORMAL WEATHER OVER SOUTHEASTERN ALASKA, AND NEAR TO ABOVE-NORMAL TEMPERATURES
ELSEWHERE. ALSO, THE MID-LEVEL TROUGH WILL SLIGHTLY ENHANCE CHANCES FOR
ABOVE-NORMAL PRECIPITATION STATEWIDE. THE 500--HPA PATTERN IS NOT HIGHLY
AMPLIFIED, HOWEVER, SO EXTREME WEATHER IS NOT ANTICIPATED, PRECLUDING ANY
HAZARDS BEING DESIGNATED FOR THE STATE.
FORECASTER: RICH TINKER
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