423
FXUS02 KWNH 100650
PREEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 AM EDT THU JUL 10 2025
VALID 12Z SUN JUL 13 2025 - 12Z THU JUL 17 2025
...HEAVY RAIN WITH FLASH FLOODING POTENTIAL FROM THE SOUTHWEST TO
NORTHEAST, FOR THE UPPER MISSISSIPPI VALLEY/DAKOTAS AND FLORIDA...
..OVERVIEW
UPPER RIDGING WILL BE ANCHORED OVER THE WEST/SOUTHWEST WHILE THE
MAIN JET STREAM PUSHES (ANCHORED BY A NORTH-CENTRAL CANADA UPPER
LOW) MULTIPLE SHORTWAVES AND FRONTS THROUGH THE NORTHERN TIER
STATES. MEANWHILE WEAK SHORTWAVES CAUSE MINOR DISTURBANCES IN THE
LARGE SUBTROPICAL RIDGE ACROSS THE SOUTHERN TIER CAUSING SUMMER
HEAT. THESE SHORTWAVES, SURFACE FRONTS, AND INSTABILITY CREATED BY
HOT AND MOIST AIR WILL CAUSE RAIN AND THUNDERSTORM CHANCES FOR THE
CENTRAL AND EASTERN U.S., WITH A PARTICULAR FOCUS IN THE SOUTHERN
PLAINS OVER THE WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE CONTINUES TO HAVE A GOOD GRASP ON THE
SUBTROPICAL RIDGING AND THE TROUGHING FROM THE NORTH-CENTRAL U.S.
TO THE NORTHEAST. MODEL VARIANCES PERSIST PER DAY FOR INDIVIDUAL
SHORTWAVES THEREFORE THE SPECIFICS FOR SENSIBLE WEATHER PARAMETERS
LIKE FRONTAL PLACEMENT AND QPF REMAIN A BIT UNCERTAIN. AS
PREVIOUSLY NOTED, THE UKMET CONTINUES TO DEPICT A STRONGER SURFACE
LOW OVER THE MIDWEST WHEREAS THE REST OF THE GUIDANCE DOES NOT.
MODELS
SHOW JUST MINOR TIMING DIFFERENCES WITH THE INITIAL TROUGH AS IT
TRACKS INTO THE NORTHEAST WITH EVEN GREATER SPREAD WITH THE
FOLLOWING TROUGH AS IT NEAR THE U.S./CANADIAN BORDER. BY MIDWEEK
ALL SOLUTIONS HAVE THIS TROUGH OVER THE CENTRAL PORTIONS OF THE
CONTINENT.
WPC UTILIZED A MULTI-MODEL APPROACH TO INITIALIZE, USING THE 12Z
ECMWF/CMC AND 12Z/18Z GFS. THROUGH THE MID TO LATE MEDIUM RANGE
PERIOD, REDUCED THE PROPORTION OF DETERMINISTIC MODELS IN FAVOR OF
THE GEFS/EC ENSEMBLE MEANS TO MINIMIZE INDIVIDUAL MODEL SPREAD.
THIS APPROACH MAINTAINED A SENSE OF CONTINUITY FROM THE PREVIOUS
FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
OVER THE WEEKEND A FRONTAL SYSTEM WILL ADVANCE THROUGH THE MIDWEST
AND TRAIL ACROSS THE CENTRAL/SOUTHERN PLAINS WHILE CONVECTION FIRES
UP AHEAD OF IT WHERE MOISTURE AND INSTABILITY POOL. THERE WILL BE A
BROAD AREA WHERE ISOLATED FLASH FLOODING MAY ARISE, PARTICULARLY
CENTERED OVER OKLAHOMA AND SURROUNDING AREAS, WHERE AN MCS IS
LIKELY TO DEVELOP AND TRAIN. A BROAD MARGINAL RISK WAS MAINTAINED
FOR DAY 4 AND STRETCHES FROM NEW MEXICO NORTHEASTWARD TO UPSTATE
NEW YORK. SIMILAR CONDITIONS ARE EXPECTED FOR DAY 5 ONLY SHIFTED A
BIT FURTHER EAST. A SMALL MARGINAL RISK AREA WAS RAISED FOR DAY 5
IN NEW MEXICO TO COVER SENSITIVE BURN SCARS THERE.
ABUNDANT MOISTURE WILL BE FEEDING INTO FLORIDA THANK TO THE BROAD
SUBTROPICAL RIDGE. SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP
WITH THE AMPLE INSTABILITY UNDERNEATH THE RIDGE AND MAY LEAD TO
FLASH PONDING/FLOODING FOR COASTAL AND URBAN LOCATIONS ACROSS THE
PENINSULA. A MARGINAL RISK WAS MAINTAINED FOR DAY 4 AND RAISED FOR
DAY 5. CONVECTION MAY INCREASE IN THE SOUTHEASTERN STATES BY
TUESDAY AS A FRONT MOVES CLOSER.
A SECOND FRONTAL SYSTEM IS ANTICIPATED TO ENTER THE NORTH-CENTRAL
STATES NEAR THE BEGINNING OF THE WEEK AND WILL BE USHER IN THE
NEXT ROUND OF RAIN WITH IT. DETAILS IN PLACEMENT AND AMOUNTS WILL
VARY DEPENDING ON THE EVENTUAL EVOLUTION OF THE TROUGH AND REMAIN
UNCERTAIN AT THIS TIME. GIVEN THE RECENT RAINS ACROSS PARTS OF THE
DAKOTAS AND MINNESOTA, SOILS REQUIRE LESS MOISTURE BEFORE RAIN
BECOMES EXCESSIVE. A MARGINAL RISK AREA IS IN EFFECT FOR THIS PART
OF THE COUNTRY FOR DAY 5.
HOT WEATHER WILL REMAIN FOR MUCH OF THE WESTERN U.S. AS UPPER
RIDGING MOSTLY SETS UP TO THE WEST OF ROUNDS OF TROUGHING. DAILY
MAXIMUMS WILL BE ABOVE NORMAL WITH MANY LOCATIONS CLIMBING INTO
THE
100S AND 110S FOR THE DESERT SOUTHWEST, AND NEARING/EXCEEDING 100F
FARTHER NORTH IN INTERIOR/LOWER ELEVATION AREAS OF THE GREAT
BASIN. TEMPERATURES COULD BE A FEW DEGREES COOLER THAN AVERAGE
ESPECIALLY FOR HIGHS FOR THE SOUTH- CENTRAL U.S. THIS WEEKEND AS
CLOUDS AND RAIN HOLD TEMPERATURES DOWN. THE SOUTHEAST SHOULD BE
NEAR NORMAL TO A FEW DEGREES ABOVE, FOR TYPICAL SUMMER HEAT AND
HUMIDITY. TEMPERATURES WILL GENERALLY BE 5-10 DEGREES ABOVE NORMAL
IN THE GREAT LAKES TO NORTHEAST. INTO NEXT WEEK, DEPENDING ON THE
EVOLUTION OF THE NORTH- CENTRAL U.S. TROUGH, TEMPERATURES MAY COOL
NOTABLY, WITH HIGHS PERHAPS ONLY IN THE 70S THROUGH THE NORTH-
CENTRAL PLAINS FOR TUESDAY/WEDNESDAY.
CAMPBELL/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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