287
FXUS02 KWBC 031857
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT THU JUL 3 2025
VALID 12Z SUN JUL 06 2025 - 12Z THU JUL 10 2025
..COASTAL SOUTHEAST HEAVY RAIN THREAT AS NHC EYES SYSTEM.
...NORTH-CENTRAL U.S. TO MIDWEST/NORTHEAST HEAVY RAIN THREATS,
WITH TRAILING ACTIVITY SPREAD BACK TO THE SOUTH-CENTRAL STATES...
...HAZARDOUS HEAT AND HUMIDITY TO SPREAD FROM THE MIDWEST THIS
HOLIDAY WEEKEND TO THE MID-ATLANTIC/NORTHEAST EARLY NEXT WEEK AS
SWELTERING HEAT LINGERS FOR THE SOUTH AND BUILDS OVER THE WEST...
19Z UPDATE: NOT MUCH HAS CHANGED IN THE OVERALL FORECAST PHILOSOPHY
FOR THE MEDIUM RANGE PERIOD, ALTHOUGH THERE HAS BEEN A MODEST
INCREASE IN OVERALL RAINFALL TOTALS FROM THE MIDWEST TO THE OHIO
VALLEY COMPARED TO THE PREVIOUS FORECAST. THE 12Z MODEL GUIDANCE IS
IN REASONABLY GOOD AGREEMENT FOR THE BEGINNING OF THE PERIOD
SUNDAY, AND THE CMC HAS TRENDED CLOSER TO THE MODEL CONSENSUS WITH
JET STREAM FLOW NEAR THE U.S./CANADA BORDER. THE GFS HAS TRENDED
WEAKER WITH ITS PREVIOUS STRONGER SHORTWAVE CROSSING THE GREAT
LAKES MID-WEEK, AND MORE IN LINE WITH THE OTHER GUIDANCE. THE AREA
WITH THE GREATEST MODEL SPREAD BY THE END OF THE FORECAST PERIOD
THURSDAY IS ACROSS CENTRAL AND WESTERN CANADA, AND AGREES MOST ON
THE BUILDING UPPER RIDGE/HIGH ACROSS THE DESERT SOUTHWEST WITH
INCREASING HEAT EXPECTED. FOR THE SYSTEM THAT IS BEING MONITORED BY
NHC FOR POTENTIAL TROPICAL DEVELOPMENT, THE GUIDANCE GENERALLY HAS
A WEAK LOW WITH A TRAILING TROUGH AXIS ON SUNDAY AND THEN WEAKENS
GOING INTO EARLY NEXT WEEK AS THE FEATURE BECOMES MORE SHEARED OUT.
THE ENSEMBLE MEANS WERE GRADUALLY INCREASED TO ABOUT HALF BY
THURSDAY AMID INCREASING MESOSCALE UNCERTAINTIES. THE PREVIOUS
FORECAST DISCUSSION IS APPENDED BELOW. /HAMRICK
-----------------------
..PATTERN OVERVIEW
THE NATIONAL HURRICANE CENTER SHOWS SOME POTENTIAL FOR SOUTHEAST
U.S. COASTAL LOW DEVELOPMENT THIS WEEKEND INTO EARLY NEXT WEEK TO
OFFER ENHANCED/WIND DRIVEN RAINS WITH ANY DEVELOPMENT AND TRACK.
PACIFIC SHORTWAVES WILL WORK INTO LINGERING WEST COAST MEAN UPPER
TROUGHS INTO NEXT WEEK. A BUILDING UPPER RIDGE DOWNSTREAM WILL
SPREAD A THREAT OF HAZARDOUS HEAT AND HUMIDITY FROM THE MIDWEST
THIS HOLIDAY WEEKEND TO THE MID-ATLANTIC/NORTHEAST EARLY NEXT WEEK
AS A HOT SUMMER AIRMASS LINGERS OVER THE SOUTH AND ALSO BUILDS
NEXT WEEK UP OVER THE WEST. THERE MAY ALSO BE SOME RENEWED
MONSOONAL FLOW INTO THE SOUTHWEST. A SERIES OF STRONG TO SEVERE
CONVECTION AND HEAVY RAIN FUELING IMPULSES WILL PROGRESS ATOP THE
RIDGE FROM THE MIDWEST/GREAT LAKES TO THE NORTHEAST, WITH TRAILING
ACTIVITY ALSO FIRING BACK OVER THE NORTH-CENTRAL AND SOUTH-CENTRAL
U.S.
...GUIDANCE/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A BLEND
OF COMPATIBLE GEFS/ECMWF/CANADIAN ENSEMBLE MEAN GUIDANCE ALONG
WITH WPC CONTINUITY AND THE NATIONAL BLEND OF MODELS, BUT NUDGED
THAT FORECAST TOWARD NHC SOUTHEAST U.S. LOW POTENTIAL. FORECAST
CONFIDENCE IS HIGH IN THE OVERALL PATTERN OF WIDESPREAD HEAT.
MODERATE CONFIDENCE IS IN THE PRECISE TIMING AND INTENSITY OF
CONVECTIVE OUTBREAKS AND THE LONGEVITY OF THE MOST EXTREME HEAT IN
SPECIFIC LOCALES. THE DEVELOPMENT AND TRACK OF THE POTENTIAL
TROPICAL SYSTEM OFFSHORE THE SOUTHEAST U.S. COAST WILL BE CRITICAL
TO MONITOR.
..WEATHER/HAZARDS HIGHLIGHTS
WPC EXCESSIVE RAINFALL OUTLOOK (ERO) MARGINAL RISK AREAS HAVE BEEN
ADDED FOR DAY 4/SUNDAY AND DAY 5/MONDAY FOR THE COASTAL SOUTHEAST
GIVEN THE INCREASED MOISTURE AND RAINFALL POTENTIAL ASSOCIATED WITH
POSSIBLE SYSTEM DEVELOPMENT THAT THE NHC IS MONITORING.
A SLOW MAIN FRONTAL PUSH ACROSS FROM THE GREAT LAKES/OHIO VALLEY
STATES AND THE NORTHEAST MAY FOCUS PERIODS WITH ENHANCED POOLED
MOISTURE AND INSTABILITY TO FUEL SOME STRONG TO SEVERE STORMS AND
LOCALLY HEAVY RAIN/RUNOFF THREATS WITH TRAINING POTENTIAL IN SPOTS
SUNDAY INTO MONDAY AS UPPER TROUGH/IMPULSE ENERGIES WORK ON THE
NORTHERN PERIPHERY OF THE MAIN CENTRAL U.S. UPPER RIDGE. TRAILING
ACTIVITY EXTENDS BACK NEXT WEEK WITH IMPULSES OVER THE SOUTH-
CENTRAL U.S. AND INTO THE SOUTHWEST WITH SOME RENEWED MONSOONAL
FLOW. ELONGATED WPC ERO MARGINAL RISK AREAS ARE DEPICTED FOR DAY
4/SUNDAY AND DAY 5/MONDAY. CONVECTION/MCS ACTIVITY WILL ALSO FIRE
BACK TO THE NORTH-CENTRAL STATES NEXT WEEK AS SUBSEQUENT UPPER-
LEVEL WAVES INTERACT WITH MOISTURE/INSTABILITY POOLING FRONTS/UPPER
DIFFLUENCE. A DAY 5/MONDAY MARGINAL RISK AREA WAS MAINTAINED THERE.
MEANWHILE, A BROADENING UPPER RIDGE WILL SPREAD A HAZARDOUS HEAT
AND HUMIDITY THREAT FROM THE MIDWEST THIS HOLIDAY WEEKEND TO THE
MID-ATLANTIC/NORTHEAST INTO NEXT WEEK AS A VERY HOT SUMMER AIRMASS
LINGERS BROADLY OVER THE SOUTH AND ALSO BUILDS UP ACROSS THE WEST.
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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