092
FXUS02 KWBC 251922
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
322 PM 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
TROUGHING OVER THE EAST WILL GENERALLY HOLD THROUGH MUCH OF THE
MEDIUM RANGE PERIOD WITH BLOCKY RIDGING OVER THE INTERIOR WEST.
ENERGY DOWN THE WEST SIDE OF THE TROUGH WILL INTERACT WITH FRONTAL
BOUNDARIES AT THE SURFACE TO BRING A HEAVY RAIN THREAT ACROSS
PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS INTO THE MIDDLE
AND LOWER MISSISSIPPI VALLEY LATER THIS WEEK. THE PATTERN BECOMES
MORE UNCERTAIN THIS WEEKEND AND EARLY NEXT WEEK BUT SHOWERS AND
THUNDERSTORMS, WITH LOCALLY HEAVY RAINFALL, SHOULD CONTINUE TO
FOCUS ACROSS THE SOUTHERN ROCKIES/SOUTHERN PLAINS/GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE SHOWS GOOD AGREEMENT ON THE OVERALL TROUGH-
RIDGE-TROUGH PATTERN FOR THE FIRST PART OF THE PERIOD. BY THIS
WEEKEND, SOME OF THE GUIDANCE IS INDICATING ENERGY FROM AN UPPER
LOW OFF THE WEST COAST MAY MAKE ITS WAY INLAND, HELPING TO BREAK
DOWN THE WESTERN U.S. RIDGE. THE GFS IS MORE AGGRESSIVE WITH THIS
THAN THE REST OF THE MODELS AND ENSEMBLES. THE ECMWF AND CMC FAVOR
INITIAL ENERGY MOVING INLAND LATER THIS WEEK, BUT KEEP THE MAIN
UPPER LOW ANCHORED OFF THE COAST AND THIS GENERAL SCENARIO SEEMS
SUPPORTED BY THE ENSEMBLE MEANS TOO. THE ENSEMBLE MEANS OF COURSE
ARE MORE WASHED OUT/WEAKER THAN THE DETERMINISTICS WHICH DOES
INDICATE QUITE A BIT OF UNCERTAINTY IN THE LARGER DISTRIBUTION.
THE WPC FORECAST WAS BASED ON AN EQUAL BLEND OF THE DETERMINISTIC
SOLUTIONS DAYS 3-5, INCREASING TO 60 PERCENT ENSEMBLE MEANS WITH
THE CMC AND ECMWF DAYS 6 AND 7. THIS GENERALLY MAINTAINED GOOD
CONTINUITY WITH THE PREVIOUS WPC FORECAST AS WELL.
..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 OF EXCESSIVE RAINFALL CONTINUES FOR PORTIONS OF EASTERN
COLORADO INTO NORTHEASTERN NEW MEXICO ON THURSDAY DUE TO ANTECEDENT
RAINFALL FROM MONSOON MOISTURE INTERACTING WITH A SURFACE FRONT
AND AN 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. 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 WITH A
BROAD MARGINAL RISK IN PLACE ON THE DAY 5 ERO, FOR NOW. PORTIONS
OF THIS AREA MAY NEED TO BE UPGRADED TO A SLIGHT RISK IN FUTURE
UPDATES IF THE QPF SIGNAL CONVERGES.
A SURFACE FRONT LINGERING NEAR THE GULF COAST WILL CONTINUE A
DAILY THREAT FOR SHOWERS AND STORMS ACROSS MUCH OF THE SOUTHERN
TIER, WITH MONSOONAL MOISTURE CONTINUING FOR PARTS OF THE
CENTRAL/SOUTHERN ROCKIES. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE
IN SOME LOCATIONS.
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.
SANTORELLI/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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