425
FXUS02 KWBC 141858
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EDT FRI JUN 14 2024
VALID 12Z MON JUN 17 2024 - 12Z FRI JUN 21 2024
..EARLY SEASON HEAT WAVE FROM THE MIDWEST TO THE EAST COAST
...HEAVY RAINFALL THREAT ALONG THE CENTRAL-WESTERN GULF COAST AND
PARTS OF THE NORTHERN TIER...
19Z UPDATE: THE 12Z MODEL GUIDANCE SUITE IS IN VERY GOOD SYNOPTIC
SCALE AGREEMENT WITH A DEEPENING TROUGH OVER THE NORTHERN ROCKIES,
AND A BUILDING RIDGE OVER THE EASTERN HALF OF THE COUNTRY. THERE
ARE SOME MODEST DIFFERENCES WITH THE SHORTWAVE CROSSING SOUTHERN
CANADA BY MIDWEEK, AND THE ECMWF IS GENERALLY STRONGER WITH THE
EXPANSIVE UPPER HIGH OVER THE NORTHEAST STATES. MORE DIFFERENCES
BECOME APPARENT OVER THE WEST COAST REGION BY NEXT FRIDAY, BUT
STILL NOTHING UNUSUAL FOR A DAY 7 FORECAST. THE WPC FRONTS AND
PRESSURES WERE DERIVED FROM A MULTI-DETERMINISTIC MODEL BLEND FOR
THE FIRST HALF OF THE WEEK, FOLLOWED BY GRADUALLY INCREASING
PERCENTAGES OF THE ENSEMBLE MEANS TO ACCOUNT FOR 40% BY FRIDAY.
THE PREVIOUS FORECAST DISCUSSION IS APPENDED BELOW. /HAMRICK
-------------------
..OVERVIEW
A STRONG UPPER RIDGE FORECAST TO BUILD OVER PARTS OF THE EAST
WILL LIKELY SUPPORT A BROAD AREA OF HOT AND DRY WEATHER NEXT WEEK,
WITH THE GREATEST ANOMALIES AND POTENTIAL FOR DAILY RECORDS
EXTENDING FROM THE OHIO VALLEY/LOWER GREAT LAKES INTO THE NORTHERN
MID-ATLANTIC/NORTHEAST. MEANWHILE STRONG DYNAMICS EJECTING FROM THE
NORTHWEST AND ASSOCIATED SURFACE DEVELOPMENT/FRONTS EARLY IN THE
WEEK SHOULD PRODUCE ONE OR MORE AREAS OF SIGNIFICANT PRECIPITATION
BETWEEN THE NORTHERN ROCKIES AND MIDWEST. THE LINGERING WESTERN
U.S. MEAN TROUGH ALOFT MAY RETROGRADE TO THE WEST COAST BY LATE IN
THE WEEK. BENEATH THE UPPER RIDGE THAT SHOULD EXTEND BACK TO THE
SOUTHERN PLAINS/ROCKIES BY THE LATTER HALF OF THE WEEK, THE
COMBINATION OF UPPER LEVEL IMPULSES AND ABUNDANT DEEP MOISTURE WILL
BRING A POTENTIAL FOR AREAS OF HEAVY RAIN ALONG AND NEAR THE
WESTERN HALF OF THE GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
EARLY IN THE PERIOD, THE PRIMARY GUIDANCE DIFFERENCE OF NOTE IS
THAT LATEST GFS RUNS ARE A BIT ON THE SLOW SIDE VERSUS MOST OTHER
SOLUTIONS WITH THE STRONG UPPER SYSTEM CROSSING THE NORTHWEST
DURING MONDAY-TUESDAY. THIS RESULTS IN THE MODEL PULLING ITS HEAVY
QPF AXIS FARTHER WEST THAN CONSENSUS IN THE VICINITY OF THE
NORTHERN ROCKIES.
MEANWHILE GUIDANCE AGREES THAT THE CENTER OF THE STRENGTHENING
EASTERN U.S. UPPER RIDGE SHOULD TRACE A PATH FROM NEAR THE WESTERN
CAROLINAS EARLY MONDAY INTO THE NORTHERN MID-ATLANTIC/SOUTHERN NEW
ENGLAND BY EARLY WEDNESDAY. THEN CONSENSUS SHOWS EXPANSION OF UPPER
RIDGING BACK INTO THE SOUTHERN HALF OF THE PLAINS/SOUTHERN ROCKIES
BUT WITH INCREASING SPREAD FOR WHERE THE STRONGEST PART OF THE
RIDGE WILL BE (RANGING BETWEEN THE OHIO VALLEY AND WESTERN ATLANTIC
BY FRIDAY). MOST OF THE 12Z ECMWF-INITIALIZED MACHINE LEARNING (ML)
MODELS SHOW THE UPPER HIGH OVER OR A LITTLE SOUTH OF THE 12Z ECMWF
MEAN LOCATION OVER THE EAST AS OF EARLY NEXT FRIDAY WHILE THE NEW
00Z GFS/CMC HAVE IT OVER THE WESTERN ATLANTIC. THE MEAN TROUGH OVER
THE WEST SHOULD WEAKEN AND RETROGRADE A BIT MID-LATE WEEK AS THE
UPPER RIDGE EXPANDS, WITH LOW PREDICTABILITY FOR SHORTWAVE DETAILS
AFTER THE VIGOROUS EARLY WEEK SYSTEM EJECTS. BY NEXT FRIDAY THE ML
MODELS SUPPORT A SOLUTION CLOSEST TO THE GEFS/ECENS MEANS, SHOWING
A LITTLE BETTER DEFINITION FOR THE WEST COAST TROUGH THAN SOME OF
THE 12Z/18Z DYNAMICAL MODEL RUNS. PREDICTABILITY IS TYPICALLY
FAIRLY LOW FOR THE UPPER IMPULSES RETROGRADING UNDERNEATH THE
RIDGE, AND WHILE THERE IS A FAIRLY GOOD CONSENSUS FOR THE AREA OF
ENHANCED DEEP MOISTURE RETROGRADING ACROSS THE WESTERN HALF OF THE
GULF OF MEXICO/GULF COAST, QPF SOLUTIONS ARE MUCH MORE DIVERSE.
THE UPDATED FORECAST BLEND BASED ON 12Z/18Z GUIDANCE STARTED WITH
AN OPERATIONAL MODEL COMPOSITE FOR THE FIRST HALF OF THE PERIOD
FOLLOWED BY GRADUALLY INCREASING 18Z GEFS/12Z ECENS MEAN WEIGHT SO
THAT THE MEANS WERE 60 PERCENT OF THE BLEND BY THE END OF THE
FORECAST NEXT FRIDAY.
..WEATHER/HAZARDS HIGHLIGHTS
STRONG DYNAMICS EJECTING FROM THE NORTHWEST WILL PROMOTE PLAINS
SURFACE DEVELOPMENT (ULTIMATELY TRACKING INTO CANADA) DURING THE
FIRST PART OF THE WEEK. FROM MONDAY INTO EARLY TUESDAY, A LEADING
NORTHERN TIER FRONT WILL LIKELY STALL AHEAD OF THE EVOLVING SURFACE
WAVE, WITH GUIDANCE SHOWING A FAIRLY STEADY AREA OF ANOMALOUS
MOISTURE OVER THE UPPER MIDWEST. THE SLIGHT RISK AREA REMAINS VALID
WITH A SMALL EXTENSION TO THE WEST. MEANWHILE THERE IS A MARGINAL
RISK ACROSS MUCH OF MONTANA WHERE THE UPPER SYSTEM MAY PRODUCE SOME
AREAS OF HEAVY RAINFALL, AND LATE SEASON SNOW EXPECTED FOR THE
HIGHEST ELEVATIONS OF THE NORTHERN ROCKIES. BY THE DAY 5 TIME
FRAME TUESDAY/TUESDAY NIGHT, EXPECT CENTRAL U.S. CONVECTION TO
START EXPANDING SOUTHWARD ALONG THE COLD FRONT ANCHORED BY THE
SURFACE WAVE TRACKING INTO CANADA. THE 12Z GUIDANCE IS NOW IN
BETTER AGREEMENT ON THE MAIN QPF AXIS, AND A SLIGHT RISK AREA HAS
BEEN ADDED FROM NORTHEAST NEBRASKA TO THE GREATER DULUTH METRO
AREA.
GUIDANCE GENERALLY AGREES THAT AN AREA OF DEEP TROPICAL MOISTURE
SHOULD SHIFT WESTWARD ACROSS THE WESTERN HALF OF THE GULF OF
MEXICO, BRINGING A POTENTIAL FOR SOME HEAVY RAINFALL. GIVEN A
BETTER MODEL SIGNAL FOR 2+ INCH RAINFALL TOTALS OVER SOUTHERN
LOUISIANA MONDAY INTO MONDAY NIGHT, A SLIGHT RISK AREA IS PLANNED
FOR THE UPDATED DAY 4 ERO.
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. THIS HEAT
WAVE WILL LIKELY EXTEND BEYOND FRIDAY. WHILE SOME PATTERN DETAILS
DIFFER OF COURSE, 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. IN CONTRAST TO THE
EASTERN HEAT, THE DEEP UPPER TROUGH CROSSING THE NORTHWEST EARLY
NEXT WEEK WILL BRING A COUPLE DAYS OF HIGHS 10-20F BELOW NORMAL TO
PARTS OF THE WEST AND NORTHERN HIGH PLAINS. AFTER THIS SYSTEM
DEPARTS, EXPECT THE WEST TO TREND WARMER, REACHING ABOVE NORMAL BY
LATE WEEK. MOIST EASTERLY FLOW SHOULD BRING A COOLER TREND TO THE
SOUTHERN HIGH PLAINS BY LATE WEEK.
RAUSCH/HAMRICK
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
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