020
FXUS02 KWBC 111858
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EDT TUE JUN 11 2024
VALID 12Z FRI JUN 14 2024 - 12Z TUE JUN 18 2024
...HEATWAVE TO SPREAD FROM THE SOUTHWEST TO PARTS OF THE CENTRAL
AND EASTERN U.S. DURING THE PERIOD...
...EXCESSIVE RAINFALL THREAT FOR FLORIDA THROUGH LATE WEEK AND
PERHAPS THE CENTRAL GULF COAST EARLY NEXT WEEK...
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE REMAINS IN GOOD OVERALL AGREEMENT THROUGH MOST OF THE
PERIOD WITH RESPECT TO THE OVERALL PATTERN, FEATURING MEAN RIDGING
OVER THE WEST PROGRESSING EASTWARD THROUGH THE PERIOD OVER THE
CENTRAL AND THEN EASTERN U.S., AND WITH MEAN TROUGHING SETTLING IN
OVER THE WEST IN THE WAKE. GUIDANCE INDICATES A SOUTHERN STREAM
SHORTWAVE OVER THE SOUTHWEST WILL LIFT NORTHEAST ROUNDING THE
BUILDING RIDGE WITH ADDITIONAL EMBEDDED WAVES TRANSLATING THE
NORTHERN TIER AS THE MEAN TROUGHING BEGINS TO TAKE HOLD OVER THE
WEST. UNCERTAINTY INCREASES LATE THIS WEEKEND INTO EARLY NEXT WEEK
AS AN INITIAL WAVE/POTENTIAL CLOSED LOW LIFTS NORTHEASTWARD OVER
THE NORTHERN PLAINS/SOUTH-CENTRAL CANADA, WITH THE 12Z CMC THE
GREATEST OUTLIER IN TERMS OF WEAKER INTENSITY AND TIMING. THE 00Z
ECMWF/CMC AND 00Z ECENS MEAN ARE THEN INITIALLY MORE AGGRESSIVE
THAN THE 06Z GFS/GEFS MEAN WITH ANOTHER EMBEDDED WAVE DIGGING
FURTHER SOUTHWARD OVER THE WEST. THE SUITE OF MACHINE-LEARNING
MODELS FROM THE EC ENCOMPASS THIS ENVELOPE OF SOLUTIONS,
REINFORCING THE UNCERTAINTY, THOUGH AGAIN WITH THE OVERALL PATTERN
GENERALLY WELL AGREED UPON. THE UPDATED WPC FORECAST FEATURED A
COMPOSITE BLEND OF THE DETERMINISTIC GUIDANCE INITIALLY, WITH A
LOWER CONTRIBUTION FROM THE CMC COMPARED TO THE ECMWF/GFS GIVEN
NOTED DIFFERENCES. THE LATTER HALF OF THE PERIOD INCLUDES A
CONTRIBUTION FROM THE ECENS/GEFS MEANS, 50% OF THE BLEND BY DAY 7
(TUESDAY), AS TIMING/EVOLUTION DIFFERENCES IN THE WEST INCREASE.
MEANWHILE, AN UPPER-LEVEL WEAKNESS INITIALLY REMAINS OVER FLORIDA,
SLOWLY RETROGRADING WEST TOWARDS THE END OF THE PERIOD. THIS KEEPS
A STORMY PATTERN IN THE FORECAST FOR FLORIDA AND THEN THE
CENTRAL/POTENTIALLY WESTERN GULF COAST, WITH THE RIDGE
TRANSITIONING OVER THE EAST ALSO HELPING TO FUNNEL TROPICAL
MOISTURE NORTHWARD. FORECAST QPF AMOUNTS REMAIN THE MOST UNCERTAIN,
WITH THE LATEST GFS/GEFS MEAN GUIDANCE ALONG THE CENTRAL GULF
COAST AND THE ECENS MEAN AND PARTICULARLY ECMWF FAVORING MORE OF
THE WESTERN GULF COAST. THE GFS WOULD ALSO FAVOR A POTENTIALLY MORE
SIGNIFICANT RAINFALL EVENT. FOR QPF, OPTED FOR A COMPOSITE
GUIDANCE BLEND WITH SOME CONTINUITY, WHICH STILL TENDS TO FAVOR AT
LEAST LOCALLY HEAVY AMOUNTS OVER THE CENTRAL GULF COAST FOR NOW BUT
INCLUDES SOME MORE MODERATE AMOUNTS INTO THE WESTERN GULF FROM THE
EC GUIDANCE.
..WEATHER/HAZARDS HIGHLIGHTS
A PROTRACTED PERIOD FAVORABLE FOR HEAVY RAINS SHOULD CONTINUE
THROUGH LATER WEEK FOR THE FLORIDA PENINSULA AS WELL ABOVE NORMAL
TROPICAL/CARIBBEAN MOISTURE POOLS ALONG AND SOUTH OF A WAVY STALLED
FRONT WITH AID FROM UPPER LEVEL IMPULSES/ENERGY BACK THROUGH AN
UNSETTLED GULF OF MEXICO. THERE REMAINS HIGH CONFIDENCE IN HEAVY
RAINFALL IN FLORIDA WITH LOCALLY HEAVY RAINFALL RATES, BUT LOWER
CONFIDENCE ON PLACEMENT OF ANY EXTREME CONVECTIVE AMOUNTS ON ANY
PARTICULAR DAY. STORM TOTAL RAINFALL (INCLUDING WHAT FALLS BEFORE
THE MEDIUM RANGE PERIOD EVEN STARTS) OF 7-10 INCHES, WITH LOCALLY
HIGHER AMOUNTS TO 15 INCHES, IS FORECAST. WPC EXCESSIVE RAINFALL
OUTLOOK SLIGHT RISK AREA IS IN PLACE FOR THE CENTRAL TO SOUTHERN
FLORIDA PENINSULA INTO DAY 4/FRIDAY GIVEN THE PRECEDING DAYS RAINS,
AS UNCERTAINTY WITH THE POTENTIAL TOTALS FROM CONVECTION REMAINS.
HEAVY RAIN MAY LAST INTO SATURDAY ACROSS FLORIDA WHERE A DAY 5
MARGINAL RISK HAS BEEN INTRODUCED FOR LINGERING ACTIVITY. HOWEVER,
AS THE WEEKEND PROGRESSES AND INTO EARLY NEXT WEEK, THERE IS A
GROWING GUIDANCE SIGNAL THAT MOISTURE INFLUX AND POSSIBLE HEAVY
RAINFALL MAY REFOCUS AND INCREASE INTO THE CENTRAL GULF COAST AND
VICINITY, WHICH WILL NEED TO BE MONITORED FOR RUNOFF ISSUES GIVEN
THE FAVORABLE DEEPLY MOIST PATTERN. MUCH UNCERTAINTY REMAINS,
PARTICULARLY WITH THE POTENTIAL AMOUNT OF RAINFALL AND WITH
WESTWARD EXTENT INTO THE WESTERN GULF.
MEANWHILE, LEADING AND DYNAMIC NORTHERN STREAM UPPER TROUGH ENERGY
APPROACH AND PASSAGE IS EXPECTED TO FIRE CONVECTION ALONG/AHEAD OF
A WAVY/POOLING SURFACE FRONT OVER THE NORTHEAST INTO FRIDAY WHERE
A MARGINAL RISK AREA REMAINS IN PLACE AS THE PARALLEL UPPER FLOW
AND CONVECTIVE AXIS MAY LEAD TO REPEAT CELLS AND RUNOFF ISSUES.
ELSEWHERE, AN INCREASING CONVECTIVE PRECIPITATION THREAT WILL
EMERGE ACROSS THE CENTRAL AND NORTHERN PLAINS/UPPER MIDWEST LATE
WEEK INTO THE WEEKEND AS WELL DEFINED SOUTHERN STREAM TROUGHING
EJECTS NORTHEASTWARD TOWARD THE REGION FROM THE SOUTHWEST TO FOCUS
LIFT/INSTABILITY. A WPC ERO MARGINAL RISK AREA REMAINS IN PLACE FOR
DAY4/FRIDAY FROM THE SOUTHERN HIGH PLAINS TO THE CENTRAL PLAINS,
EXCEPT FOR THE SANDHILLS OF NEBRASKA THAT ARE NOT AS SENSITIVE TO
HEAVY RAIN. A DAY5/SATURDAY MARGINAL RISK AREA HAS BEEN MAINTAINED
FROM THE CENTRAL PLAINS TO THE UPPER MIDWEST GIVEN SYSTEM
PROGRESSION AND CONTINUED UNSTABLE FLOW.
AS FOR ANOMALOUS TEMPERATURES, AN AMPLIFIED UPPER RIDGE SLATED TO
STEADILY/BROADLY SHIFT FROM THE SOUTHWEST THROUGH THE SOUTH-
CENTRAL U.S. TO THE EAST WILL PRODUCE MUCH WARMER THAN AVERAGE
TEMPERATURES AND THE THREAT FOR SOME RECORD HEAT INTO NEXT WEEK.
TEMPERATURES WILL INITIALLY ALREADY BE RATHER HOT OVER PORTIONS OF
THE SOUTH INTO MID-ATLANTIC FRIDAY BEFORE THE EVEN BROADER REGION
OF HEAT EXPANDS INTO THE MIDWEST/OHIO VALLEY AS THE UPPER-LEVEL
RIDGING BUILDS IN. HIGHS ARE FORECAST WELL INTO THE 90S,
POTENTIALLY LOW 100S, AND WITH LOWS IN THE 70S PROVIDING LITTLE
RELIEF FROM THE HEAT OVERNIGHT. THE CLIMATE PREDICTION CENTER
CONTINUES A HEAT THREAT INTO WEEK 2.
PUTNAM/SCHICHTEL
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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