838
FXUS02 KWBC 250716
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
316 AM EDT MON AUG 25 2025
VALID 12Z THU AUG 28 2025 - 12Z MON SEP 01 2025
...HEAVY RAINFALL IN STORE FOR PARTS OF THE SOUTHERN/CENTRAL HIGH
PLAINS AND THE MIDDLE/LOWER MISSISSIPPI VALLEYS...
..OVERVIEW
THE UPPER-LEVEL PATTERN WILL REMAIN RELATIVELY STAGNANT ACROSS THE
LOWER 48 LATE THIS WEEK, WITH TROUGHING IN THE EAST PACIFIC AND
EAST COAST AS WELL AS A BLOCKING HIGH OVER THE WEST/CENTRAL U.S..
SHORTWAVE ENERGY ROTATING WITHIN AND AROUND THE PERIPHERY OF THE
UPPER RIDGE WILL LIKELY GENERATE THUNDERSTORM ACTIVITY OVER PARTS
OF THE CENTRAL AND SOUTHERN U.S. LATE THIS WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE EVOLUTION OF TROUGHING IN THE EAST PAC. AND SHORTWAVE ACTIVITY
OVER AND WITHIN THE WEST/CENTRAL U.S. RIDGE ARE THE MOST UNCERTAIN
ASPECTS OF THE GUIDANCE FOR LATE THIS WEEK THROUGH NEXT WEEKEND.
A GENERAL MODEL BLEND CONSISTING OF THE EC/GFS/UKMET/CMC WAS USED
ON DAY 3 WITH HIGHER WEIGHTING TOWARD THE GFS AND EURO. EURO AND
CANADIAN ENSEMBLE MEANS ARE INTRODUCED TO THE BLEND ON DAY 4 TO
ACCOUNT FOR GROWING VARIANCE IN THE DETERMINISTIC GUIDANCE RELATED
TO TROUGHING IN THE EAST PAC.. A EURO/CANADIAN-CENTRIC BLEND IS
USED THROUGH THE REST OF THE PERIOD DUE, IN PART, TO NOTABLE
CLUSTERING OF THEIR DETERMINISTIC AND ENSEMBLE MEAN SOLUTIONS IN
THE WEST. MACHINE LEARNING MODELS LIKE THE AIFS, AURORA AND PANGU
AGREE WITH THE EURO AND CANADIAN SOLUTIONS IN THE E. PAC. AS WELL.
THE GFS, GRAPHCAST AND FOURCAST MODELS IDENTIFY A DEEPER AND MORE PHASED
TROUGH PATTERN OVER THE E. PAC ON DAY 5. THE GEFS MEAN HAS
SIGNIFICANTLY MORE SPREAD THAN THE ECE AND CMCE BEYOND DAY 5.
..WEATHER/HAZARDS HIGHLIGHTS
TROUGHING IN THE EASTERN PACIFIC AS WELL AS SHORTWAVE ENERGY
EMBEDDED WITHIN AN UPPER RIDGE OVER THE WEST SHOULD PROMOTE MONSOON
STORMS OVER MUCH OF THE INTERIOR WEST LATER THIS WEEK.
A SLIGHT RISK (AT LEAST 15% CHANCE) OF EXCESSIVE RAINFALL IS IN
EFFECT FOR PORTIONS OF EASTERN COLORADO INTO NORTHEASTERN NEW
MEXICO ON THURSDAY DUE TO ANTECEDENT RAINFALL FROM MONSOON MOISTURE
INTERACTING WITH A SURFACE FRONT AND AREA OF LOW PRESSURE OVER THE
HIGH PLAINS. MONSOON MOISTURE WILL LIKELY INTERACT WITH THE
DOWNSTREAM PORTION OF THE AFOREMENTIONED FRONT AND PRODUCE HEAVY
RAINFALL OVER THE CENTRAL PLAINS ON WEDNESDAY BEFORE SPREADING INTO
THE LOWER MISSISSIPPI VALLEY ON THURSDAY. THEREFORE, ANOTHER
SLIGHT RISK OF EXCESSIVE RAINFALL IS IN EFFECT FOR PORTIONS OF THE
CENTRAL/SOUTHERN PLAINS INTO THE MIDDLE/LOWER MISSISSIPPI VALLEY.
BY FRIDAY, THE SIGNAL FOR HEAVY RAINFALL BECOMES MUCH MORE DIFFUSE,
DUE, IN PART, TO WEAKENING UPPER-LEVEL SUPPORT. ISOLATED INSTANCES
OF FLASH FLOODING MAY STILL OCCUR FROM STORMS THAT DEVELOP ALONG
THE STATIONARY FRONT DRAPED FROM THE HIGH PLAINS, LOWER MISSISSIPPI
VALLEY AND SOUTHEAST.
SURFACE HIGH PRESSURE FROM CANADA WILL DESCEND ON MUCH OF THE
EASTERN U.S. THIS WEEK. THIS HIGH PRESSURE 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.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page