627
FXUS02 KWBC 060711
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
311 AM EDT SAT JUL 6 2024
VALID 12Z TUE JUL 09 2024 - 12Z SAT JUL 13 2024
...BERYL WILL SPREAD HEAVY RAINFALL ACROSS THE SOUTH-CENTRAL U.S.
AS IT TRANSITIONS TO POST-TROPICAL...
..DANGEROUS HEAT WAVE IN THE WEST PERSISTS INTO NEXT WEEK
..OVERVIEW
THE MOST PROMINENT LARGE SCALE FEATURES DURING THE PERIOD WILL BE
A PERSISTENT UPPER RIDGE OVER THE WEST SUPPORTING A DANGEROUS AND
LIKELY RECORD-SETTING HEAT WAVE ACROSS MUCH OF THE REGION INTO NEXT
WEEK, AND A POSITIVELY TILTED PLAINS/MISSISSIPPI VALLEY/GREAT
LAKES MEAN TROUGH WHOSE SOUTHERN PERIPHERY WILL INTERACT WITH BERYL
AS IT TRANSITIONS TO POST-TROPICAL. HEAVY RAIN IS LIKELY TO SPREAD
FROM PARTS OF TEXAS INTO THE LOWER MISSISSIPPI VALLEY AND POSSIBLY
NORTHEASTWARD INTO MIDWEEK AS BERYL'S LOW PRESSURE AND MOISTURE
INTERACTS WITH A FRONTAL BOUNDARY. MEANWHILE, SEASONABLY HOT AND
HUMID CONDITIONS ALONG WITH SCATTERED THUNDERSTORMS AT TIMES SHOULD
PERSIST ACROSS THE SOUTHEAST TO EAST COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO INDICATE THAT BERYL WILL TRACK FASTER
AND FARTHER NORTHEASTWARD COMPARED TO MODEL RUNS FROM A DAY OR TWO
AGO. CONFIDENCE IN THIS TREND IS RISING, THOUGH THERE IS STILL SOME
SPREAD IN THE TIMING. THE 12Z ECMWF WAS FASTER THAN CONSENSUS
WHILE THE 12Z CMC WAS SLOWER. GFS RUNS WERE CLOSE TO THE NHC 03Z
TRACK FOR BERYL BUT ITS QPF PATTERN WAS NOT IDEAL. THE 12Z UKMET
WAS AN OKAY PROXY FOR QPF BUT A BIT NORTHWEST OF THE PREFERRED
TRACK. THE NEWER 00Z ECMWF AND CMC FORTUNATELY CONVERGED TOWARD
EACH OTHER WITH THE TIMING/TRACK OF BERYL'S LOW AND QPF. BERYL'S
TRACK BEING FASTER ALLOWS FOR IT TO GET PICKED UP BY THE NORTHERN
STREAM TROUGHING AND RECURVE AS IT MERGES WITH A SURFACE FRONT.
THIS NORTHERN STREAM TROUGH SHOWS REASONABLY GOOD AGREEMENT IN
MODELS AS ITS POSITIVELY TILTED AXIS STRETCHES ACROSS THE GREAT
LAKES INTO THE PLAINS/MISSISSIPPI VALLEY INTO MIDWEEK AND BEYOND,
GRADUALLY WEAKENING LATE WEEK WITH FAIRLY TYPICAL SPREAD. THIS
SPREAD DOES AFFECT THE POSITIONING OF AN EAST COAST SURFACE FRONT.
MEANWHILE, MODELS CONTINUE TO SHOW GOOD AGREEMENT ON AN UPPER HIGH
DRIFTING FROM THE DESERT SOUTHWEST INTO THE FOUR CORNERS AS THE
WEEK PROGRESSES, CAUSING THE PROLONGED HEAT WAVE. THE MOST
UNCERTAIN ASPECT OF THE FORECAST CONTINUES TO BE THE FLOW PATTERN
FARTHER NORTH ACROSS THE NORTHEAST PACIFIC INTO WESTERN CANADA MID-
LATE WEEK WITH NO DOMINANT CLUSTERING FOR THE TIME BEING. THIS
FEATURE MAY HELP TO PUSH A FRONTAL SYSTEM INTO THE FAR NORTHWESTERN
U.S. BY LATE NEXT WEEK. A BLENDED/INTERMEDIATE SOLUTION LOOKS LIKE
A GOOD STARTING POINT HERE.
THE WPC FORECAST USED A BLEND OF DETERMINISTIC MODELS FAVORING THE
12Z ECMWF EARLY IN THE PERIOD, TRANSITIONING TOWARD A HALF
MODELS/HALF ENSEMBLE MEANS BLEND BY THE END OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
BY THE START OF THE MEDIUM RANGE PERIOD EARLY TUESDAY, BERYL IS
FORECAST TO BE TRACKING INLAND IN EAST TEXAS AS A TROPICAL STORM,
AND THEN LOOKS TO PHASE WITH A FRONTAL SYSTEM TO ITS NORTH BY
MIDWEEK. THESE FEATURES SHOULD LEAD TO THE POTENTIAL FOR HEAVY RAIN
CAUSING FLASH FLOODING CONCERNS IN EASTERN TEXAS AND THE LOWER
MISSISSIPPI VALLEY TUESDAY AND TUESDAY NIGHT, AND A SLIGHT RISK
REMAINS IN PLACE IN THE DAY 4/TUESDAY ERO. THE PERSISTENT MODEL
TREND OF BERYL BEING FASTER NECESSITATES AN EXPANSION OF THE SLIGHT
FARTHER NORTHEAST COMPARED TO THE PREVIOUS ISSUANCE, AND TRIMMING
OFF ON THE SOUTHERN SIDE IN SOUTH TEXAS. AS BERYL'S LOW GETS STRUNG
ALONG A FRONTAL BOUNDARY INTO WEDNESDAY, THE FOCUS FOR THE
PLACEMENT OF HEAVY RAINFALL IS LESS CLEAR. HOWEVER THE INGREDIENTS
FOR ISOLATED FLASH FLOODING LIKE ABOVE NORMAL MOISTURE ARE IN PLACE
ACROSS THE SOUTH-CENTRAL U.S. AND NORTHEASTWARD INTO THE
OHIO/TENNESSEE VALLEYS AND MUCH OF THE EASTERN SEABOARD, SO A BROAD
MARGINAL RISK IS IN PLACE FOR DAY 5/WEDNESDAY FOR THESE AREAS. A
SLIGHT RISK UPGRADE MAY BE NECESSARY IN FUTURE CYCLES IF THE
PLACEMENT OF HIGHER TOTALS COMES INTO BETTER AGREEMENT. THIS
APPEARS MOST LIKELY IN THE OHIO VALLEY.
MEANWHILE FARTHER NORTH, THE UPPER TROUGH PUSHING ONE OR MORE COLD
FRONTS ACROSS THE NORTHEASTERN U.S. WILL ALSO LEAD TO SOME
THUNDERSTORM CHANCES. SOME FOCUS OF THE CONVECTIVE RAIN AHEAD OF
THE FRONT(S) AND SUFFICIENT INSTABILITY FOR HEAVY RAIN RATES IN THE
NORTHERN MID-ATLANTIC TO NORTHEAST HAVE PROMPTED A MARGINAL RISK
IN THE ERO FOR DAY 4/TUESDAY. STALLING FRONTS AND PERSISTENT MOIST
CONDITIONS WILL PROMOTE SCATTERED STORMS CONTINUING INTO LATER WEEK
ACROSS THE SOUTHEAST/CAROLINAS AND INTO THE MID-ATLANTIC. FARTHER
WEST, SOME MOISTURE MAY FEED INTO THE FOUR CORNERS STATES IN A
MONSOONAL PATTERN. MARGINAL RISKS ARE IN PLACE FOR TUESDAY AND
WEDNESDAY MAINLY FOR NEW MEXICO--ESPECIALLY CONSIDERING
SENSITIVITIES DUE TO BURN SCARS AND AREAS THAT HAVE SEEN AMPLE
RAINFALL RECENTLY.
THE WEST WILL CONTINUE TO SEE A MAJOR TO EXTREME AND LONG-LIVED
HEAT WAVE INTO NEXT WEEK. HIGHS EXCEEDING 110F SHOULD BE WIDESPREAD
IN THE DESERT SOUTHWEST, WITH TYPICALLY HOTTER LOCATIONS EXCEEDING
120F. FARTHER NORTH, HIGHS INTO THE 100S ARE FORECAST INTO OREGON
AND WASHINGTON AND EAST INTO THE INTERMOUNTAIN WEST, AS
TEMPERATURES SOAR 10-20F ABOVE NORMAL WITH LOCALLY HIGHER
ANOMALIES. NUMEROUS DAILY RECORDS ARE LIKELY TO BE BROKEN DURING
THIS HEAT WAVE, WITH MONTHLY/ALL-TIME RECORDS NOT OUT OF THE
QUESTION. THE PROLONGED NATURE OF THE HEAT WAVE AND RECORD WARM
OVERNIGHT TEMPERATURES WILL INCREASE HEAT STRESS. THE PACIFIC
NORTHWEST LOOKS TO MODERATE CLOSER TO NORMAL LATER WEEK WITH
POSSIBLE TROUGHING ALOFT, BUT INTERIOR AREAS AND EXPANDING INTO THE
NORTH-CENTRAL U.S. WILL BE ABOVE NORMAL. MEANWHILE, WARMER THAN
AVERAGE TEMPERATURES IN THE NORTHEAST TUESDAY SHOULD MODERATE BY
MIDWEEK. THE SOUTHEAST CAN EXPECT NEAR NORMAL HEAT FOR THIS TIME OF
YEAR-- WHICH IS STILL HOT AND HUMID. THE SOUTH-CENTRAL U.S. SHOULD
SEE SOME MINOR HEAT RELIEF THROUGH THURSDAY OR SO WITH BELOW
AVERAGE TEMPERATURES GIVEN THE CLOUDS AND RAIN CHANCES.
TATE
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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