Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FOUS30 KWBC 210217
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
917 PM EST MON NOV 20 2017

...VALID 0217Z TUE NOV 21 2017 - 12Z TUE NOV 21 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
70 WNW CEC 50 SW OTH 30 SSE OTH 20 NW SXT 15 SSW SXT 30 SW MFR
35 N O54 25 N O54 25 W RBL 30 ENE O87 40 NW O87.


...PACIFIC NORTHWEST/NORTHERN CA...

02Z UPDATE:

RECENT RADAR AND SATELLITE OBSERVATIONS NOW INDICATE THAT THE
EXPECTED WEAKENING OF RAINFALL INTENSITY HAS OCCURRED ACROSS THE
AREA. IN GENERAL DO NOT EXPECT INTENSITY TO PICK UP
OVERNIGHT...WITH JUST A GRADUAL NORTHWARD SHIFT TO THE SHOWERY
CONDITIONS. THINK THE FLOODING RISK HAS DECREASED OVER THE AREA
AND WILL THUS REMOVE THE SLIGHT RISK. HOWEVER GIVEN THE ANTECEDENT
RAINFALL AND CONTINUED UPSLOPE ENHANCEMENT RESULTING IN LOCALIZED
1-2" OF ADDITIONAL RAINFALL...WILL MAINTAIN A MARGINAL RISK.

PREVIOUS DISCUSSION

MODERATE TO HEAVY RAINFALL CONTINUES ACROSS PORTIONS OF NORTHWEST
CA AS OF 0Z. RECENT RADAR AND SATELLITE TRENDS SUGGEST THAT THE
RAINFALL AXIS IS PERSISTING A BIT FURTHER SOUTH THAN MOST GUIDANCE
WOULD INDICATE IT SHOULD BE. HAVE SEEN A FEW OBSERVATIONS OF
BETWEEN 0.5"-0.7" IN AN HOUR RECENTLY ALONG THE SOUTHWEST HUMBOLDT
COUNTY COAST IN THE IDEAL UPSLOPE LOCATIONS. FOR THIS REASON WILL
LEAVE THE MARGINAL AND SLIGHT RISK AREAS MAINLY UNCHANGED ALONG
THE NORTHWEST CA INTO SOUTHWEST OR COAST. ISOLATED POCKETS
EXCEEDING 0.5" IN AN HOUR WILL REMAIN POSSIBLE OVER THE NEXT
SEVERAL HOURS...WITH AN ADDITIONAL 1-3" POSSIBLE THROUGH 12Z
TUESDAY. WITH THAT SAID...WE SHOULD SEE THE RAINFALL AXIS SHIFT
NORTH AT AN INCREASING PACE...WITH RATES ALSO GENERALLY ON A
DECLINING TREND THROUGH THE EVENING. FLOODING WILL REMAIN POSSIBLE
IN THE SLIGHT RISK AREA THROUGH 06Z...ESPECIALLY IN BURN SCAR
AREAS. ANTICIPATE ANY FLOODING THREAT TO END BY 06Z AS THE WARM
FRONT LIFTS NORTH AND RAINFALL RATES DECREASE. ITS NOT UNTIL AFTER
12Z THAT RATES PICK BACK UP ACROSS WESTERN WA.

CHENARD
$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.