155
FXUS02 KWBC 161859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT SUN JUN 16 2024
VALID 12Z WED JUN 19 2024 - 12Z SUN JUN 23 2024
..RECORD-BREAKING HEAT FROM THE MIDWEST TO THE EAST COAST
...HEAVY RAINFALL THREAT ALONG THE WESTERN GULF COAST AND PARTS OF
THE NORTHERN TIER INTO CENTRAL PLAINS...
..OVERVIEW
LATEST MODELS/ENSEMBLES SHOW A STRONG UPPER RIDGE ALONG THE EAST
COAST ACHIEVING ITS GREATEST STRENGTH AND NORTHWARD POSITION AROUND
WEDNESDAY. FROM LATER IN THE WEEK THROUGH THE WEEKEND EXPECT THIS
RIDGE TO DRIFT SOUTHWARD, ELONGATE WESTWARD, AND WEAKEN A LITTLE--
ULTIMATELY LEAVING A BROAD AXIS OF RIDGING ACROSS THE SOUTHERN TIER
BY NEXT SUNDAY. THIS RIDGE WILL SUPPORT A BROAD AREA OF HOT AND
DRY WEATHER DURING THIS UPCOMING WEEK, WITH THE GREATEST ANOMALIES
AND POTENTIAL FOR DAILY (AND POSSIBLY MONTHLY) RECORDS EXTENDING
FROM THE OHIO VALLEY/LOWER GREAT LAKES INTO THE NORTHERN MID-
ATLANTIC AND NORTHEAST. BETWEEN THIS RIDGE AND MEAN TROUGHING ALONG
OR JUST INLAND FROM THE WEST COAST, THE AREA FROM THE NORTHERN
HALF OF THE PLAINS INTO UPPER MIDWEST MAY SEE MULTIPLE EPISODES OF
HEAVY RAINFALL FROM A COMBINATION OF A PERSISTENT WAVY MEAN FRONT,
ANOMALOUS MOISTURE, AND UPPER LEVEL IMPULSES. THIS ACTIVITY SHOULD
ALSO EXTEND INTO THE NORTHEAST LATE WEEK INTO THE WEEKEND. TO THE
SOUTH OF THE UPPER RIDGE, UPPER LEVEL ENERGY AND ABUNDANT DEEP
MOISTURE NORTH OF AN AREA OF LOW PRESSURE (SEE NHC FOR UPDATES)
WILL BRING THE POTENTIAL FOR A PERIOD OF HEAVY RAIN ALONG AND NEAR
THE WESTERN GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
INTERESTING TREND IN THE UPDATED 00/06Z GUIDANCE OVERNIGHT
COMPARED TO YESTERDAY'S 12/18Z RUNS REGARDING THE EASTERN UPPER-
RIDGE. NEARLY ALL OF THE GUIDANCE, WITH SOME EXCEPTION OF THE 00Z
CMC, HAS TRENDED EASTWARD WITH THE UPPER-RIDGE, WITH THE GENERAL
CENTER ANCHORING A BIT MORE INTO THE WESTERN ATLANTIC LATE THIS
WEEK/EARLY WEEKEND AS OPPOSED TO A MORE INLAND POSITION ALONG THE
EAST COAST. IN TANDEM, THIS ALLOWS FOR A WAVE, WITH POTENTIAL
TROPICAL CHARACTERISTICS (SEE NHC FOR DETAILS), TO LIFT
NORTHWESTWARD ALONG THE WESTERN SIDE OF THE RIDGE. A COMPARISON OF
THE RUN-TO-RUN CONTINUITY OF THIS OVERALL PATTERN SHOWS THAT BOTH
THE GFS AND ECMWF HAVE WAVERED A BIT, HEIGHTENING THE UNCERTAINTY.
IN ADDITION, THE 00Z INITIALIZED SUITE OF EC MACHINE-LEARNING (ML)
MODELS HAS BEEN MORE CONSISTENT IN KEEPING THE INLAND POSITION OF
THE UPPER-RIDGE, AGAIN COMPLICATING THE FORECAST. AS FAR AS
TEMPERATURE IMPACTS, THE 12Z ECMWF HAS REMAINED A BIT STRONGER AND
MAINTAINED A GREATER NORTHERN EXTENT WITH THE RIDGE AS WELL, WHICH
LEADS TO THE POTENTIAL FOR A HIGHER CEILING FOR THE HEAT IN THE
MIDWEST/MID-ATLANTIC LATE THIS WEEK AND INTO THE WEEKEND, WHILE THE
GFS WOULD SUGGEST A QUICKER FLATTENING OF THE NORTHERN PART OF THE
RIDGE. IT SHOULD BE NOTED THAT THE UPDATED 12Z GUIDANCE THIS
MORNING DID LOOK TO TREND A BIT WEAKER WITH THE RIDGE QUICKER LATE
WEEK AND INTO THE WEEKEND.
TO THE WEST, THE GUIDANCE IS RELATIVELY WELL CLUSTERED AROUND A
SOLUTION DEPICTING A TROUGH OVER THE WEST, WITH EVENTUAL
NORTHEASTWARD EJECTION OF SHORTWAVE ENERGY TOWARDS THE NORTHERN
PLAINS OVER THE WEEKEND, THOUGH WITH LINGERING UNCERTAINTY ON EXACT
TRACK/STRENGTH/TIMING. SOME COMBINATION OF WESTWARD EXPANSION OF
THE UPPER-LEVEL RIDGE AND/OR DEVELOPMENT OF UPPER-LEVEL RIDGING
LOOKS TO REPLACE THE TROUGH THROUGH THE SOUTHERN TIER OF THE WEST.
ANOTHER UPPER-LEVEL LOW SHOULD DROP SOUTHEASTWARD FROM THE
NORTHEASTERN PACIFIC TOWARDS THE PACIFIC NORTHWEST BY THE END OF
THE WEEKEND. FOR THE UPDATED WPC FORECAST, USED A COMPOSITE BLEND
OF THE DETERMINISTIC MODELS EARLY IN THE PERIOD GIVEN GOOD
AGREEMENT. BEGAN TO INCORPORATE A GROWING PERCENTAGE OF THE
GEFS/ECENS/CMC ENSEMBLE MEANS MID- TO LATE PERIOD WHICH HELPED
ACCOUNT FOR THE NOTED UNCERTAINTY WITH UPPER-RIDGE PLACEMENT, AS
THE MEANS TENDED TO A BIT MORE SIMILAR TO THE EC ML GUIDANCE.
QPF-WISE, THERE IS QUITE A BIT OF UNCERTAINTY WITH RESPECT TO THE
HEAVY RAINFALL POTENTIAL OVER COASTAL AND CENTRAL/SOUTH TEXAS
ASSOCIATED WITH AN AREA OF LOW PRESSURE APPROACHING THE REGION. THE
GFS AND CMC ARE MORE AGGRESSIVE WITH RAINFALL TOTALS, WITH THE CMC
HAVING THE MOST NORTHERLY TRACK THAT WOULD IMPACT MORE OF NORTH
TEXAS AND THE GFS COVERING PORTIONS OF CENTRAL IN ADDITION TO SOUTH
TEXAS. ON THE OTHER HAND, THE ECMWF/UKMET SUGGEST A MORE SOUTHERLY
TRACK WITH STILL HEAVY BUT LOWER AMOUNTS TRACKING INTO SOUTH
TEXAS. THE CORRESPONDING ENSEMBLE PROBABILITIES FOLLOW A SIMILAR
PATTERN. OPTED TO INCLUDE SOME CONTINUITY ALONG WITH THE NBM
PARTIALLY MODIFIED BY THE GFS/ECMWF TO ACCOUNT FOR A POTENTIALLY
BROADER FOOTPRINT WITH LOCALIZED HEAVIER AMOUNTS, BUT WITH SOME
RESTRAINT ON LEANING TOWARDS THE HIGHER END FOR NOW. FURTHER EAST,
ANOTHER AREA OF INTEREST WILL BE WITH THE TROUGH APPROACHING THE
SOUTHEAST, WITH BOTH THE GFS/ECMWF AND CORRESPONDING ENSEMBLE MEANS
SHOWING AN INCREASE IN AMOUNTS/COVERAGE, LEADING TO AN UPWARD
INCREASE IN QPF COMPARED TO THE PRIOR FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
DURING THE DAYS 4-5 EXCESSIVE RAINFALL OUTLOOK PERIOD COVERING
WEDNESDAY THROUGH THURSDAY NIGHT, LATEST GUIDANCE CONTINUES TO SHOW
AN AREA OF DEEP TROPICAL MOISTURE AND UPPER-ENERGY/SURFACE LOW
(SEE NHC FOR ADDITIONAL DETAILS) SHIFTING NORTHWESTWARD ACROSS THE
WESTERN GULF OF MEXICO INTO THE SOUTHERN HIGH PLAINS. OPERATIONAL
GFS/ECMWF RUNS SHOW PRECIPITABLE WATER ANOMALIES POSSIBLY REACHING
PLUS 4 STANDARD DEVIATIONS OR GREATER. HOWEVER, AS NOTED, THERE
STILL REMAIN SOME SIGNIFICANT DIFFERENCES IN THE
MAGNITUDE/PLACEMENT OF HEAVIEST RAINFALL. HAVE MAINTAINED A SLIGHT
RISK FORM THE TEXAS GULF COAST INLAND INTO CENTRAL AND SOUTH TEXAS
COVERING THE GENERAL OVERLAPPING FOOTPRINT OF BOTH DETERMINISTIC
QPF AND ENSEMBLE EXCEEDANCE PROBABILITIES. NOTE THAT THE SOUTHERN
PART OF THE TEXAS COAST HAS DRIER ANTECEDENT CONDITIONS BUT RAIN
RATES MAY STILL BE HIGH ENOUGH TO CAUSE SOME RUNOFF ISSUES.
PORTIONS OF CENTRAL TEXAS AND SOUTHWARD ALONG THE GULF COAST
CURRENTLY APPEAR MOST LIKELY TO SEE AN OUTLOOK UPGRADE, THOUGH THE
LINGERING UNCERTAINTY AND NOTED ANTECEDENT CONDITIONS PRECLUDE ANY
CHANGES FOR NOW. AS THE MOISTURE/UPPER-ENERGY CONTINUE WESTWARD,
THE UPDATED DAY 5 ERO CONTINUES A SLIGHT RISK AREA OVER PARTS OF
SOUTHWESTERN AND CENTRAL TEXAS ALONG/NORTH OF THE RIO GRANDE RIVER.
THERE IS STILL CONSIDERABLE UNCERTAINTY OVER RAINFALL SPECIFICS IN
THIS TIME FRAME AS WELL.
ELSEWHERE DURING THE DAYS 4-5 ERO TIME FRAME, A PERSISTENT WAVY
FRONTAL BOUNDARY INTERACTING WITH ANOMALOUS MOISTURE AND SHORTWAVE
IMPULSES EJECTING FROM THE WEST COAST MEAN TROUGH WILL MAINTAIN A
THREAT FOR EPISODES OF HEAVY CONVECTION FROM PARTS OF THE
NORTHERN/CENTRAL PLAINS INTO UPPER MIDWEST. THUS FAR THE GUIDANCE
SIGNAL IS DIFFUSE ENOUGH (WITH SOMEWHAT LOWER AMOUNTS/MORE SCATTER
THAN IN THE SHORTER TERM) FOR THIS ACTIVITY TO MAINTAIN ONLY A
MARGINAL RISK EACH DAY. POTENTIAL REMAINS FOR AN UPGRADE IN RISK
AREA CLOSER TO THE EVENT. FINALLY, THERE IS A MARGINAL RISK AREA
ALONG AND INLAND FROM THE GEORGIA/NORTHERN FLORIDA COAST IN
ASSOCIATION WITH POSSIBLE ARRIVAL OF A WEAK WAVE/SURFACE TROUGH AND
ENHANCED MOISTURE, WITH CONFIDENCE GROWING IN AREAL
COVERAGE/AMOUNTS OF AT LEAST MODERATE TO LOCALLY HEAVY RAINFALL.
GRADUAL FLATTENING OF THE UPPER PATTERN BY LATE WEEK INTO THE
WEEKEND, WITH A PERSISTENT WAVY FRONT NEAR THE SOUTHERN PERIPHERY
OF THE WESTERLIES, WILL SUPPORT CONTINUED NORTHERN PLAINS/UPPER
MIDWEST CONVECTION AND A GREATER EASTWARD EXTENT INTO THE GREAT
LAKES/NORTHEAST. CONFIDENCE IN SPECIFICS IS LOWER DUE TO THE LOW
PREDICTABILITY OF IMPORTANT SHORTWAVE DETAILS. SOME OF THE MOISTURE
REACHING THE SOUTHERN HIGH PLAINS BY THURSDAY COULD ULTIMATELY
FACTOR INTO DIURNAL CONVECTION OVER THE ROCKIES THEREAFTER WHILE
MOISTURE EMBEDDED WITHIN EASTERLY FLOW MAY ENHANCE RAINFALL AT
TIMES NEAR THE GULF COAST INTO THE WEEKEND. A WELL-DEFINED FRONTAL
SYSTEM COULD BRING A LITTLE SCATTERED LIGHT RAIN TO THE PACIFIC
NORTHWEST BY NEXT WEEKEND.
THE STRONG UPPER RIDGE BUILDING OVER THE EAST NEXT WEEK WILL TEND
TO PRODUCE THE GREATEST TEMPERATURE ANOMALIES FROM THE MIDWEST AND
OHIO VALLEY/LOWER GREAT LAKES INTO THE NORTHERN MID-ATLANTIC AND
NORTHEAST, WITH MULTIPLE DAYS OF READINGS 10-20F ABOVE NORMAL. THIS
WOULD TRANSLATE TO HIGHS WELL INTO THE 90S, ALONG WITH LOWS IN THE
UPPER 60S TO UPPER 70S PROVIDING LITTLE OVERNIGHT HEAT RELIEF.
DAILY RECORDS WILL BE POSSIBLE WITHIN THE ABOVE AREAS, WITH SOME
ISOLATED MONTHLY RECORDS POSSIBLE AS WELL. WITH SOME TYPICAL DETAIL
DIFFERENCES, THE AXIS OF GREATEST TEMPERATURE ANOMALIES IN THE
CURRENT FORECAST SHOWS SOME SIMILARITY TO THE 1994 HEAT WAVE THAT
WAS OBSERVED AROUND THE SAME TIME IN JUNE. SOME FLATTENING OF THE
NORTHERN PART OF THE RIDGE BY THE END OF THE WEEK MAY MAKE THE HEAT
A LITTLE LESS EXTREME OVER NEW ENGLAND, WHILE THE CENTRAL PLAINS
MAY TREND A LITTLE HOTTER (BUT WITH SINGLE-DIGIT POSITIVE
ANOMALIES). PARTS OF THE MID-ATLANTIC COULD ALSO TREND A LITTLE
HOTTER LATE WEEK INTO THE WEEKEND WITH A TRANSITION TO MORE
WESTERLY FLOW. IN CONTRAST TO THE EASTERN HEAT, SEPARATE AREAS OF
CLOUDS/RAINFALL OVER THE PLAINS WILL SUPPORT HIGHS 5-15F BELOW
NORMAL ON WEDNESDAY AND CONTINUING OVER THE SOUTHERN HIGH PLAINS
AND VICINITY THROUGH LATE WEEK. RISING HEIGHTS ALOFT OVER THE WEST
WILL SUPPORT A WARMER TREND, WITH INCREASING COVERAGE OF HIGHS
10-15F ABOVE NORMAL FRIDAY-SUNDAY.
PUTNAM/RAUSCH
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page