792
FXUS02 KWBC 141834
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EDT THU AUG 14 2025
VALID 12Z SUN AUG 17 2025 - 12Z THU AUG 21 2025
..OVERVIEW
A TROUGH/RIDGE/TROUGH PATTERN SUNDAY WILL RETROGRADE WESTWARD
THROUGH THE WEEK, ALLOWING STRONG UPPER RIDGING TO ONCE AGAIN PUSH
BACK INTO THE FOUR CORNERS REGION. THE JET STREAM WILL MAINTAIN A
FAIRLY ACTIVE WEATHER PATTERN ACROSS THE NORTH-CENTRAL STATES
THROUGH THE START OF THE WEEK BEFORE IT SHIFTS A BIT FARTHER
SOUTHEAST. THE VERY WARM TEMPERATURES ACROSS THE CORN BELT TO THE
MIDWEST WILL SLIP BACK SEVERAL DEGREES THROUGH THE PERIOD, BUT
REMAIN NEAR TO JUST ABOVE NORMAL FOR MID- AUGUST. MUCH OF THE WEST
WILL SEE WARMING TEMPERATURES THROUGH THE WEEK. RAINFALL WILL FOCUS
OVER THE NORTHERN TIER (UPPER MIDWEST/GREAT LAKES) THEN INTO THE
MIDWEST AND NORTHEAST/MID- ATLANTIC TUE-THU, ACROSS FLORIDA, AND
OVER THE SOUTHWEST/SOUTHERN ROCKIES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MAINTAINED CONTINUITY BY UTILIZING A MULTI-MODEL APPROACH SINCE THE
CONSENSUS APPROACH WORKED WELL FOR A STARTING POINT TO THE
FRONTS/PRESSURES AND SENSIBLE WEATHER. GUIDANCE CONTINUE TO DEPICT
SHORTWAVE ENERGY EJECTING FROM THE WESTERN TROUGH ACROSS CANADA AND
THE NORTHERN STATES. IN TURN THIS AIDS IN FLATTENING THE FLOW EAST
OF 100W AND HELP MAINTAIN A MORE PROGRESSIVE TROUGH OVER EASTERN
CANADA WHILE REDUCING THE DEGREE OF TROUGHING INTO THE MIDWEST. TC
ERIN IS STILL PROJECTING RECURVATURE IN THE VICINITY OF 70W WHICH
ADDS TO THE UNCERTAINTY OF THE FORECAST. AS PREVIOUSLY MENTIONED,
THIS MAY HOLD UP THE FRONT OVER THE ATLANTIC BUT PERHAPS ACCELERATE
IT TO ITS WEST SIDE BY MIDWEEK NEXT WEEK ONCE IT STARTS GAINING
LATITUDE. PLEASE SEE THE NHC WEBSITE FOR THE MOST UP-TO- DATE
INFORMATION AS ERRORS IN POSITION 5+ DAYS CAN BE SIGNIFICANT.
..WEATHER/HAZARDS HIGHLIGHTS
THREE MAIN REGIONS WILL CONTINUE TO HAVE POTENTIAL FOR HEAVY
RAINFALL WHERE ISOLATED AREAS OF FLASH FLOODING MAY DEVELOP.
LEADING UP TO THE EXTENDED PERIOD, PW VALUES STREAMING INTO THE
PACIFIC NORTHWEST WILL BE NEAR/EXCEEDING THE MAXIMUM PERCENTILE.
THIS STEADY STREAM OF ABUNDANT MOISTURE WILL MERGE WITH EASTERN
PACIFIC/GULF MOISTURE ADVECTING FROM THE SOUTH INTO THE PLAINS
WHICH WILL INTERACT WITH A SLOW/STALLED FRONT OVER THE NORTHERN
TIER STATES. THE ENVIRONMENT WILL BE PRIMED FOR A MULTI-DAY EVENT
FROM THE SHORT-TERM AND CONTINUING INTO THE FIRST HALF OF THE
EXTENDED PERIOD. SOILS WILL BE SENSITIVE TO THAT MUCH MOISTURE AND
WILL HAVE AN ELEVATED THREAT FOR FLOODING. A SLIGHT RISK WAS RAISED
FOR DAY 4 AND IT MAY BE NEEDED FOR DAY 5 WITH FUTURE UPDATES;
HOWEVER HELD OFF FOR NOW DUE TO MODEL SPREAD ON WHERE THE HEAVIEST
QPF WILL FOCUS.
A CONTINUED SURGE OF MOISTURE INTO THE SOUTHWEST COMBINED WITH
DIURNAL HEATING MAY TRIGGER STORMS CAPABLE OF PRODUCING HEAVIER
RAINFALL THAT MAY FALL OVER MORE SENSITIVE AREAS (STEEP TERRAIN,
IN/AROUND BURN SCARS, ETC.). A MARGINAL RISK WAS MAINTAINED FOR
DAYS 4-5. FOR THE SOUTHEAST, PERSISTENTLY HIGH MOISTURE LEVELS
WHEN COMBINED WITH AFTERNOON HEATING, WILL TRIGGER SHOWERS AND
STORMS DEVELOPMENT BOTH DAYS AS THE REMNANT MOISTURE OF AN OLD
FRONT CONTINUE TO SAG SOUTHWARD. A MARGINAL RISK WAS MAINTAINED
FOR DAYS 4-5.
A VAST PORTION OF THE CENTRAL AND EASTERN U.S. WILL REMAIN ABOVE
NORMAL FOR DAILY MAXIMUM TEMPERATURES THIS UPCOMING WEEK, WITH
MANY AREAS CLIMBING INTO THE 90S (HEAT INDICES AROUND 100F) SUNDAY.
THIS WILL DRIVE HEATRISK VALUES INTO THE THE MODERATE (LEVEL 2) TO
MAJOR (LEVEL 3 OUT OF 4) CATEGORY FROM THE CORN BELT THROUGH THE
MIDWEST (SUN/MON). HIGH TEMPERATURES/DEWPOINTS ACROSS THE LOWER
MISSISSIPPI VALLEY AND FLORIDA WILL KEEP CONDITIONS MUGGY AND
UNPLEASANT INTO NEXT WEEK. ACROSS THE WEST, COOLER THAN NORMAL
TEMPERATURES WILL MODERATE AS THE TROUGHING EASES BACK WESTWARD.
ABOVE NORMAL TEMPERATURES WILL LIKELY RETURN TO THE FOUR CORNERS
REGION BY TUESDAY AS THE UPPER RIDGE MOVES INTO THE AREA FROM THE
EAST. THIS MAY BRING MORE WIDESPREAD MODERATE HEATRISK VALUES TO
THE REGION WITH TEMPERATURES BACK TO AROUND 110F IN THE LOWER
DESERTS.
CAMPBELL/FRACASSO
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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