974
FXUS02 KWBC 240701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT SAT JUN 24 2023
VALID 12Z TUE JUN 27 2023 - 12Z SAT JUL 01 2023
...PROLONGED HEAT WAVE CONTINUES ACROSS TEXAS AND SOUTHEASTERN NEW
MEXICO AND WILL EXPAND NORTHEAST NEXT WEEK...
...EXCESSIVE RAINFALL THREAT FOR THE NORTHERN ROCKIES/PLAINS AND
NORTHEAST EARLY-MID NEXT WEEK...
..OVERVIEW
A POTENT UPPER RIDGE WILL PERSIST OVER THE SOUTH-CENTRAL U.S. WELL
INTO NEXT WEEK WHILE MEAN UPPER LOW/TROUGHING HOLDS OVER THE EAST
AND MORE TRANSITIONALLY OVER THE WEST. THE RIDGE IS RESPONSIBLE
FOR EXCESSIVE HEAT IN THE SOUTHERN PLAINS, AND HEAT WILL EXPAND
NORTH AND EAST INTO PARTS OF THE LOWER AND MIDDLE MISSISSIPPI
VALLEY AND CENTRAL PLAINS NEXT WEEK. THERE IS NOW SOME GUIDANCE
SIGNAL FOR EASING, BUT NOT UNTIL HEADING INTO NEXT WEEKEND SO WE
HAVE A LONG WAY TO GO. WPC AND CPC CONTINUE TO JOINTLY PRODUCE
"KEY MESSAGES" FOR THIS HEATWAVE. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO FOCUS IMPACT OVER THE NORTHEAST AND THE NORTH-CENTRAL
U.S. THIS PERIOD.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE SOLUTIONS OVERALL REMAIN WELL CLUSTERED NEXT
WEEK, BOLSTERING FORECAST CONFIDENCE. THE WPC MEDIUM RANGE PRODUCT
SUITE WAS PRIMARILY DERIVED FROM A COMPOSITE
GFS/ECMWF/UKMET/CANADIAN MODEL BLEND TUESDAY-THURSDAY TO PROVIDE
MAX DETAIL CONISTENT WITH A PATTERN WITH SEEMINGLY ABOVE NORMAL
PREDICTABILITY. ADDED SOME GEFS/ECMWF ENSEMBLE MEAN GUIDANCE TO
THE COMPOSITE INTO FRIDAY-NEXT SATURDAY AS FORECAST SPREAD
GRADUALLY INCREASES. THIS OVERALL SOLUTION MAINTAINS GOOD WPC
PRODUCT CONTINUITY IN LINE WITH NATIONAL BLEND OF MODELS (NBM)
GUIDANCE. NBM QPF AGAIN SEEMS UNDERDONE IN AREAS SUPPORTED BY
AMPLIFIED WARM SEASON UPPER LOWS/TROUGHS THAT HISTORICALLY BECOME
EFFICIENT ENHANCERS OF LOCAL DOWNPOURS. WPC QPF GUIDANCE TRIES TO
ACCOUNT FOR THIS BIAS.
..WEATHER/HAZARDS HIGHLIGHTS
A PESKY AND VERY WET LEAD LOW/FRONTAL SYSTEM CURRENTLY BRINGING
PRECIPITATION TO THE EASTERN U.S. WILL MOVE OFFSHORE OVER THE
WEEKEND, BUT YET ANOTHER WELL ORGANIZED AND SLOW MOVING SYSTEM
WILL FOLLOW HOT ON ITS HEELS. THE SECOND SYSTEM WILL PUSH ACROSS
THE EASTERN U.S. EARLY NEXT WEEK ACCOMPANIED BY AMPLE MOISTURE
THAT WILL SUPPORT WIDESPREAD PRECIPITATION. MOISTURE WILL FOCUS
AHEAD OF AND ALONG THE COLD FRONT AND WRAP AROUND THE LOW PRESSURE
CENTER IN THE GREAT LAKES REGION. LOCALLY HEAVY RAINFALL WILL BE
POSSIBLE AS WELL WITH POTENTIAL TRAINING/REPEAT ACTIVITY
ASSOCIATED WITH THIS SYSTEM THAT SHOULD AGAIN PROVE SLOW TO MOVE
ON. A WPC EXCESSIVE RAINFALL OUTLOOK (ERO) "MARGINAL RISK" AREA IS
PLANNED OVER THE NORTHEAST IN A SLOW TO EVOLVE FLOW PATTERN AND AS
THE AREA WILL HAVE EXPERIENCED SHORTER TERM ENHANCED RAINFALL TO
MOISTEN SOILS. EMBEDDED "SLIGHT RISK" AREAS REMAIN POSSIBLE IN
FUTURE ERO UPDATES WHEN CONFIDENCE IN THE LOCATION OF HEAVIER
RAINFALL TOTALS INCREASES. FOR NOW, TOO MUCH UNCERTAINTY REMAINS
IN THE FORECAST TO HIGHLIGHT A SPECIFIC AREA. THE SYSTEM WILL SLOW
DOWN AS IS APPROACHES THE EAST COAST, AND PRECIPITATION CHANCES
WILL LINGER ALONG THE EASTERN SEABOARD THROUGH THE END OF THE
PERIOD.
MEANWHILE, THE EJECTION OF UPPER TROUGH ENERGIES OUT FROM THE WEST
WILL BRING SCATTERED SHOWERS AND STORM CHANCES, WITH ACTIVITY
LIKELY TO BE ON THE INCREASE AND SPREAD DOWNSTREAM TO THE NORTHERN
ROCKIES AND NORTHERN PLAINS, AND HEAVY RAINFALL MAY BE A CONCERN.
THERE IS A PLANNED "MARGINAL RISK" OF EXCESSIVE RAINFALL FOR PARTS
OF THIS REGION TUESDAY AND WEDNESDAY TO ADDRESS POTENTIAL
TRAINING/REPEAT CELL RUNOFF CONCERNS. PRECIPITATION WILL SPREAD
INTO THE UPPER MIDWEST AND OHIO AND TENNESSEE VALLEYS MID-TO-LATE
NEXT WEEK AS THE SYSTEM PROGRESSES.
IN TERM OF TEMPERATURES, EXCESSIVE HEAT IS FORECAST TO CONTINUE TO
PLAGUE THE SOUTH-CENTRAL U.S. THROUGH AT LEAST NEXT WEEK WITH A
MID-WEEK EXPANSION NORTH AND EAST INTO THE CENTRAL PLAINS AND
MIDDLE AND LOWER MISSISSIPPI VALLEY. THE HEAT WILL BE OPPRESSIVE
WITH WIDESPREAD HIGH TEMPERATURES EXCEEDING 100 DEGREES AND HEAT
INDICES AS HIGH AS 120 DEGREES. HEAT INDICES MAY EVEN EXCEED 120
DEGREES IN SOME LOCATIONS IN SOUTH TEXAS. SEVERAL TEMPERATURE
RECORDS ARE IN DANGER OF BEING BROKEN DURING THIS SIGNIFICANT HEAT
WAVE. THE DESERT SOUTHWEST WILL ALSO EXPERIENCE TEMPERATURES WELL
OVER 100 DEGREES NEXT WEEK, BUT THAT IS NOT REALLY ANOMALOUS FOR
THIS TIME OF YEAR. ELSEWHERE IN THE COUNTRY, NEAR NORMAL HIGH
TEMPERATURES ARE FORECAST WITH BELOW NORMAL HIGHS LIKELY IN AREAS
OF PRECIPITATION EACH DAY.
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND
KEY MESSAGES ARE AT:
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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