466
FXUS02 KWBC 280659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT MON JUL 28 2025
...HEAVY RAIN AND FLASH FLOODING POTENTIAL IN THE EASTERN SEABOARD
AND CENTRAL PLAINS LATER THIS WEEK...
..OVERVIEW
A REASONABLY STRONG COLD FRONT FOR LATE JULY-EARLY AUGUST IS
FORECAST TO PUSH SOUTHWARD ACROSS THE EAST AT THE LEADING EDGE OF
AN UPPER TROUGH LATER THIS WEEK INTO THE WEEKEND. MOISTURE AND
INSTABILITY ALONG AND AHEAD OF THE FRONT WILL PROMOTE HEAVY TO
EXCESSIVE RAINFALL IN THUNDERSTORMS. THE FRONT AND UPPER TROUGH
SHOULD ALSO DISPLACE UPPER RIDGING CAUSING A HEAT WAVE IN THE SHORT
TERM, LIMITING THE HEAT TO THE SOUTHEAST THURSDAY AND GRADUALLY
LESSENING AND SCOPE AND MAGNITUDE EVEN THERE BY THE WEEKEND. THE
FRONT WILL STRETCH WESTWARD INTO THE SOUTH-CENTRAL U.S. AND BEND
NORTHWARD ACROSS MUCH OF THE PLAINS. COMPLEXES OF SHOWERS AND
STORMS ARE LIKELY IN THE INTERIOR NORTHWEST TO THE CENTRAL U.S. FOR
MULTIPLE DAYS WITH SHORTWAVES MOVING THROUGH FLATTENING UPPER
FLOW. MONSOONAL MOISTURE COULD CONTINUE TO CAUSE SHOWERS AND STORMS
IN THE SOUTHWEST THROUGH LATE WEEK WITH LESSENING RAIN CHANCES BY
THE WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT FOR THE EARLY MEDIUM
RANGE PERIOD LATE WEEK. UPPER HIGHS EMBEDDED WITHIN A SOUTHERN U.S.
RIDGE WILL BE IN PLACE, GENERALLY RETROGRADING FROM THE SOUTHERN
PLAINS TO SOUTHWEST AND FROM THE WESTERN ATLANTIC ACROSS FLORIDA
INTO THE GULF. THE RIDGE AXIS EXTENDS INTO THE HIGH PLAINS WHILE AN
UPPER TROUGH EXTENDS FROM EASTERN CANADA INTO THE EASTERN U.S. ON
THURSDAY-FRIDAY. THE WPC FORECAST USED A BLEND OF THE 12Z ECMWF,
18Z GFS, AND 12Z CMC FOR THE EARLY PERIOD AS THOSE MODELS SHOWED
GOOD CONSENSUS. SMALLER SCALE FEATURES COULD STILL CAUSE
DIFFERENCES IN FRONTAL PLACEMENT AND QPF THOUGH.
BY THE WEEKEND, MODEL DIFFERENCES START TO INCREASE AS THE PATTERN
BECOMES MORE QUASI-ZONAL AND UNCERTAIN SHORTWAVES DOMINATE MORE.
ONE LARGER SCALE MODEL DIFFERENCE WAS THE PATTERN IN THE NORTHWEST
ESPECIALLY BY EARLY NEXT WEEK. THIS WILL BE INFLUENCED BY A LARGE
NORTHEAST PACIFIC UPPER LOW WITH SOMEWHAT UNCERTAIN PLACEMENT.
12/18Z GFS RUNS REMAINED SOUTHWEST WITH THE UPPER LOW COMPARED TO
THE ECMWF/CMC, LEADING TO LESS TROUGHING ACROSS THE WEST IN THE GFS
RUNS. MEANWHILE THE AI/ML MODELS HAVE BECOME MORE AGREEABLE WITH
WESTERN TROUGHING. SO TENDED TO FAVOR THE EC/CMC SOLUTIONS OVER THE
GFS. IN THE NEW 00Z MODEL GUIDANCE, THE GFS AND GEFS MEAN ARE
COMING IN FAVORABLY, WITH THE UPPER LOW FARTHER EAST AND MORE
TROUGHING IN THE WEST. HOWEVER, THE NEW 00Z ECMWF SHOWS ITS TROUGH
AXIS WELL OFFSHORE CALIFORNIA IN THE PACIFIC. SO THERE IS STILL
SOME MODEL SPREAD WITH THE PATTERN BY EARLY NEXT WEEK. THE WPC
MODEL BLEND DECREASED AND EVENTUALLY DROPPED THE 18Z GFS IN FAVOR
OF THE ENSEMBLE MEANS, WITH THE ENSEMBLE MEANS REACHING HALF THE
BLEND BY DAY 6 AND MORE DAY 7 AMID THE INCREASING SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
THE COLD FRONT PUSHING THROUGH THE EAST WILL PROVIDE A FOCUS FOR
AMPLE MOISTURE AND INSTABILITY TO POOL WHILE THERE SHOULD BE
INCREASING DYNAMICAL SUPPORT IN THE FORM OF THE RIGHT ENTRANCE
REGION OF THE UPPER JET. HIGH RAIN RATES IN WIDESPREAD
THUNDERSTORMS SHOULD LEAD TO A FLASH FLOODING RISK, AND A SLIGHT
RISK REMAINS IN PLACE IN THE DAY 4/THURSDAY ERO FOR THE MID-
ATLANTIC, PARTS OF WHICH ARE STARTING WITH WETTER THAN AVERAGE
ANTECEDENT CONDITIONS THAT COULD AUGMENT THE FLOODING RISK. THE
SLIGHT HAS BEEN EXPANDED NORTH INTO SOUTHERN PARTS OF THE NORTHEAST
PER RECENT MODEL GUIDANCE INDICATING THE FRONT MOVING MORE SLOWLY
SOUTH THAN PREVIOUS FORECASTS. BY FRIDAY THE FRONT IS FORECAST TO
PUSH INTO THE CAROLINAS, AND SHOW A SLIGHT RISK FOR THE NEW DAY
5/FRIDAY ERO THERE INTO THE SOUTHERN APPALACHIANS AND EASTERN
GEORGIA WITH SIMILAR ENVIRONMENTAL FACTORS AS THURSDAY FARTHER
NORTH. THE CAROLINAS MAY SEE ADDITIONAL CONVECTION INTO THE
WEEKEND. THE FRONT STRETCHING WEST ACROSS THE GULF COAST STATES IN
A MOIST AND UNSTABLE ENVIRONMENT COULD PROMOTE SCATTERED DIURNAL
THUNDERSTORMS THERE THROUGH LATE WEEK INTO THE WEEKEND, AND
MARGINAL RISKS ARE IN PLACE IN THE DAY 4/5 EROS DUE TO HIGH RAIN
RATES THAT MAY OVERCOME THE HIGH FLASH FLOOD GUIDANCE AND/OR FALL
ATOP URBAN AREAS.
FARTHER WEST AS THE FRONT BENDS BACK INTO THE PLAINS, ROUNDS OF
RAIN AND THUNDERSTORMS ARE LIKELY WITH POSSIBLY MULTIPLE MCSS. SOME
SHORTWAVE FORCING AND ABOVE NORMAL MOISTURE AND INSTABILITY SHOULD
LEAD TO HIGH RAIN RATES, AND SOME AREAS COULD SEE REPEATING ROUNDS
OF STORMS WITH THE FRONT STALLING. FOR DAY 4/THURSDAY, THE ERO
DEPICTS A SLIGHT RISK OVER THE CENTRAL PLAINS WHERE THERE MAY BE A
PARTICULAR FOCUS FOR RAIN. BROAD MARGINAL RISKS COVER MUCH OF THE
HIGH PLAINS ON BOTH DAYS 4 AND 5 AND BACK INTO THE NORTHERN
ROCKIES/HIGH PLAINS NEAR THE BACK END OF THE FRONT AS MUCH HIGHER
THAN AVERAGE INSTABILITY (PER THE EXTREME FORECAST INDEX) IS IN
PLACE. FARTHER SOUTH, MONSOONAL MOISTURE (WITH PRECIPITABLE WATER
VALUES GENERALLY IN THE 75TH-90TH PERCENTILE) WILL BE PRESENT OVER
THE SOUTHWEST WITH SOME INSTABILITY. MARGINAL RISKS ARE IN PLACE IN
THE DAYS 4 AND 5 EROS FOR PARTS OF THE SOUTHWEST, REACHING INTO
THE CENTRAL ROCKIES/HIGH PLAINS AS AS THE MONSOONAL MOISTURE MEETS
THE FRONTAL SYSTEM TO THE NORTH. MOISTURE LOOKS TO LESSEN IN THE
SOUTHWEST BY THE WEEKEND.
ANOTHER HOT DAY IS FORECAST FOR THE CAROLINAS INTO GEORGIA AND
FLORIDA THURSDAY AHEAD OF THE COLD FRONT AND UNDER WHAT REMAINS OF
THE SHORT RANGE UPPER RIDGE. HEATRISK IS MAINLY IN THE MAJOR (LEVEL
3/4) CATEGORY WITH SOME EMBEDDED EXTREME (LEVEL 4/4) AREAS AS
TEMPERATURES REACH WELL INTO THE 90S WITH HIGHER HEAT INDICES
(NEARING 110F), WHILE MORNING LOWS WELL INTO THE 70S AND NEARING 80
WILL NOT PROVIDE MUCH RELIEF. THE COLD FRONT GRADUALLY PASSING
THROUGH THE SOUTHEAST WILL BRING MODERATING TEMPERATURES, AND
FLORIDA WILL BE THE LAST TO SEE RELIEF FROM THE HEAT THIS WEEKEND.
COOLER THAN AVERAGE TEMPERATURES (ESPECIALLY HIGHS) ARE LIKELY IN
THE NORTHERN/CENTRAL PLAINS ON THE COOL SIDE OF THE FRONT AND WITH
THE CLOUDS AND RAIN CHANCES -- A FEW LOCATIONS MAY EVEN CHALLENGE
RECORD COOL MAXES FOR THE DAY (LOW 70S). MEANWHILE THE SOUTHWEST
CAN EXPECT SEASONABLE HEAT, WITH DESERT AREAS SEEING TEMPERATURES
AROUND 110 DEGREES.
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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