865
FOUS30 KWBC 201936
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EST THU FEB 20 2025
DAY 1
VALID 16Z THU FEB 20 2025 - 12Z FRI FEB 21 2025
THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.
COOK/WEGMAN
DAY 2
VALID 12Z FRI FEB 21 2025 - 12Z SAT FEB 22 2025
THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.
KLEEBAUER/WEGMAN
DAY 3
VALID 12Z SAT FEB 22 2025 - 12Z SUN FEB 23 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF
WESTERN WASHINGTON STATE AND COASTAL OREGON...
20Z UPDATE: NO CHANGES TO THE PREVIOUS FORECAST AS 12Z GUIDANCE
MAINTAINED CONTINUITY IN BOTH THE LOCATION AND MAGNITUDE OF THE
INCOMING ATMOSPHERIC RIVER EVENT. IVT ANOMALIES AROUND THE ORDER
OF +4 TO +5 DEVIATIONS WILL GENERATE A SIGNIFICANT DEEP MOISTURE
REGIME THAT WILL ALLOW FOR STEADY MODERATE TO LOCALLY HEAVY
RAINFALL RATES OVER THE COURSE OF THE SATURDAY AFTERNOON AND
EVENING TIME FRAMES, LINGERING INTO SUNDAY MORNING. QPF IS
CURRENTLY ESTIMATED BETWEEN 2-4" ACROSS THE MOUNTAINS WITH
WIDESPREAD 1-2.5" WITHIN THE LOWER ELEVATIONS, MAINLY THE COASTAL
PLAIN OF WA/OR. THIS IS GENERALLY WITHIN THE LOWER BOUNDS OF AR
OUTPUT FOR A 24 HR PERIOD, SO THE THREAT FOR FLASH FLOODING REMAINS
AT THE LOWER END OF THE MRGL RISK THRESHOLD.
KLEEBAUER
..PREVIOUS DISCUSSION..
A PAIR OF FRONTAL DISTURBANCES ARE EXPECTED TO MOVE INTO THE COAST
OF THE PACIFIC NORTHWEST ON SATURDAY. THESE DISTURBANCES WILL HAVE
PEAK INTEGRATED VAPOR TRANSPORT (IVT) VALUES AROUND 700 KG/MS AS
THEY MOVE ASHORE WITHIN A 130+ KT UPPER LEVEL JET. WITH THAT LEVEL
OF MOISTURE ADVECTION OFF THE PACIFIC, AREAS OF HEAVY RAIN ARE
EXPECTED, ESPECIALLY INTO THE COASTAL RANGES OF OREGON AND
WASHINGTON AS WELL AS INTO THE CASCADES. RAIN RATES MAY REACH UP
TO A HALF INCH PER HOUR AT TIMES. SNOW LEVELS WITH THESE SYSTEMS
WILL BE HIGH ENOUGH (BETWEEN 7,000 AND 8,500 FT MSL) THAT MUCH OF
THE PRECIPITATION FALLING WEST OF THE CASCADES WILL BE IN THE FORM
OF RAIN. COLDER AIR WILL REMAIN IN PLACE FURTHER INLAND,
ESPECIALLY INTO THE HIGHER ELEVATIONS OF IDAHO AND MONTANA SO THE
FLOODING THREAT THERE WILL BE NEAR ZERO. WEST FACING SLOPES WILL
RECEIVE THE GREATEST RAINFALL AMOUNTS SATURDAY AND ESPECIALLY
SATURDAY NIGHT, AND IT'S ALONG THESE SLOPES AND THEIR ADJACENT
VALLEYS WHERE ANY ISOLATED FLASH FLOODING MAY OCCUR. SINCE MOST OF
THE MARGINAL RISK AREA IS ALREADY VERY FLOOD RESISTANT, THIS IS A
LOWER-END MARGINAL RISK.
WEGMAN
DAY 1 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/94EPOINTS.TXT
DAY 2 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/98EPOINTS.TXT
DAY 3 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/99EPOINTS.TXT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page