987
FXUS02 KWBC 261912
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
312 PM EDT TUE AUG 26 2025
VALID 12Z FRI AUG 29 2025 - 12Z TUE SEP 02 2025
..OVERVIEW
MEAN TROUGHING OVER THE EAST IS EXPECTED TO PERSIST THROUGH THE
MEDIUM RANGE PERIOD WITH BLOCKY RIDGING OVER THE INTERIOR WEST.
UPPER LEVEL ENERGY ROUNDING THE TOP OF THE RIDGE AND MOVING DOWN
THE WESTERN SIDE OF THE TROUGH WILL INTERACT WITH SURFACE FRONTAL
BOUNDARIES TO CREATE HEAVY RAIN THREATS ACROSS THE PLAINS LATE THIS
WEEK. HEAVY RAIN POTENTIAL WILL ALSO EXIST ACROSS THE SOUTHERN U.S.
AS A SLOW-MOVING FRONTAL BOUNDARY SINKS INTO THE NORTHERN GULF OVER
THE WEEKEND INTO EARLY NEXT WEEK. NEXT WEEK, MONSOONAL MOISTURE MAY
RETURN TO THE FOUR CORNERS REGION, AND ANOTHER FRONTAL SYSTEM MAY
BRING ISOLATED HEAVY RAIN THREATS FROM THE NORTHERN ROCKIES TO THE
UPPER MIDWEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AGREEMENT IS PRETTY GOOD ON THE OVERALL SYNOPTIC PATTERN AND
EVOLUTION THROUGH THE MEDIUM RANGE PERIOD. THERE IS SOME
UNCERTAINTY LATER IN THE PERIOD AS AN UPPER LOW APPROACHES THE
WEST COAST THEN RETROGRADES SLIGHTLY AFTER BEING BLOCKED BY RIDGING
IN THE INTERIOR WEST. WITH A LACK OF STRONG FLOW, THERE IS
UNCERTAINTY IN HOW THIS WEAK FEATURE WILL EVOLVE AND INTERACT WITH
UPSTREAM ENERGY APPROACHING FROM THE PACIFIC. THE GENERAL CONSENSUS
SEEMS TO FALL CLOSER TO THE 00Z ECMWF SOLUTION WHILE THE 00/06Z
GFS RUNS SEEM TO BE OUTLIERS. FOR NOW, WPCS SOLUTION FOR
MONDAY/TUESDAY LEANS CLOSER TO THE ECMWF, BUT THE FORECAST COULD
CHANGE. THERE HAS BEEN A LACK OF CONSISTENCY IN THE MODELS, WHICH
IS A SIGN OF HIGHER UNCERTAINTY.
WPC'S AFTERNOON FORECAST BLEND CONSISTED OF A NEAR EVEN BLEND OF
THE 00Z ECMWF/CMC/UKMET AND 06Z GFS FOR THE FIRST COUPLE DAYS OF
THE PERIOD. FOR LATE THIS WEEKEND AND EARLY NEXT WEEK, ENSEMBLE
MEANS FROM THE ECENS/GEFS/CMCE WERE ADDED TO THE BLEND TO SMOOTH
OUT MODEL DIFFERENCES AND THE GFS WAS PHASED OUT SINCE IT WAS AN
OUTLIER.
..WEATHER/HAZARDS HIGHLIGHTS
A STATIONARY FRONT OVER THE HIGH PLAINS AND A SLOW MOVING COLD
FRONT ACROSS THE GULF COAST STATES WILL BE THE FOCUS FOR SHOWERS
AND THUNDERSTORMS LATE THIS WEEK. SLOW STORM MOTION AND ANOMALOUS
MOISTURE WILL WORK TOGETHER TO SUPPORT HEAVY RAIN THREATS ACROSS
THESE REGIONS. THERE IS A BROAD MARGINAL RISK OF EXCESSIVE
RAINFALL FROM THE GREAT PLAINS DOWN AND ACROSS THE GULF COAST
STATES AND SOUTHEAST ON FRIDAY AND SATURDAY. ON SATURDAY, THERE IS
ALSO AN EMBEDDED SLIGHT RISK OF EXCESSIVE RAINFALL FOR PARTS OF
THE TEXAS/OKLAHOMA PANHANDLES AND EASTERN NEW MEXICO WHERE MULTIPLE
ROUNDS OF STORMS COULD RESULT IN SCATTERED INSTANCES OF FLASH
FLOODING.
ELSEWHERE, THE DOWNSTREAM SECTION OF THE FRONT WILL PROMOTE
ADDITIONAL THUNDERSTORM ACTIVITY ACROSS THE GULF COAST THIS
WEEKEND. A CONVERGENCE AXIS BENEATH A WEAK DISTURBANCE ALOFT COULD
REFOCUS MONSOON MOISTURE OVER MUCH OF NEW MEXICO AND THE FOUR
CORNERS REGION LATER THIS WEEKEND AND INTO NEXT WEEK. SHOWERS AND
STORMS MAY ALSO RETURN TO THE NORTHERN TIER NEXT WEEK AS A COLD
FRONT SINKS SOUTH ACROSS THE NORTHERN ROCKIES, PLAINS, AND UPPER
MIDWEST. THERE MAY BE POTENTIAL FOR ISOLATED HEAVY RAIN THREATS
WITH THIS FRONT, THOUGH IT IS VERY UNCERTAIN AT THIS TIME FRAME.
SURFACE HIGH PRESSURE FROM CANADA WILL DESCEND OVER MUCH OF THE
EASTERN U.S. THIS WEEK. THIS WILL BRING A COOL AND DRY CONTINENTAL
AIRMASS TO THE MIDWEST AND EAST COAST. CLOUDY AND STORMY
CONDITIONS OVER THE PLAINS WILL LIKELY CONTRIBUTE TO WELL BELOW
AVERAGE TEMPERATURES BEGINNING THURSDAY.
DOLAN/KEBEDE
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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