Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 171459
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
958 AM EST FRI FEB 17 2017

...VALID 15Z FRI FEB 17 2017 - 12Z SAT FEB 18 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
90 SW SFO 70 WSW SFO 60 W SFO 35 SSW STS 30 WSW APC 20 NNW SFO
10 NNW SFO SQL 15 SSE LVK 20 E RHV 30 ENE WVI 20 SSW MCE MCE
30 ENE MOD 40 NE MOD 55 NE MOD 55 S TVL 50 WNW MMH 40 WSW MMH
40 NE FAT 40 NE VIS 30 NE PTV 30 E BFL 25 WNW MHV 15 N SDB SDB
10 NE SDB 10 NE WJF 10 ENE WJF 30 NNE ONT 35 S DAG 30 NNW PSP
20 NW PSP 10 WSW PSP 25 NE RNM 20 N CZZ 10 NE CZZ 15 SE CZZ
40 SSE MMTJ 45 S NRS 80 SW NRS 75 S NUC 70 SSW NUC.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
75 WSW VBG 30 SW 87Q 25 SSW MRY 20 WSW MRY MRY 35 SE SNS
45 NNW PRB 10 E PRB 40 ENE SMX 35 NNE SBA 30 N OXR 20 WSW SDB
15 WSW SDB 10 SE SDB 10 SW WJF PMD 15 ESE PMD 20 ESE PMD
25 N ONT 30 NE ONT 30 NNE RIV 35 NNE RIV 35 NE RIV 25 NW PSP
20 SW PSP 20 E RNM CZZ 15 SSW CZZ 20 S MMTJ 45 WSW NRS
55 SSE NUC 45 SSW NUC.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
75 SSW LPC 45 SSW LPC 30 SSW LPC 15 SSW XVW LPC 20 ESE SMX
25 N SBA 25 NNE SBA 25 NNW OXR 20 N CMA 15 SSE SDB 15 NNW 3A6
15 NE 3A6 15 SW PMD 10 SSE PMD 20 SE PMD 20 NNE POC 20 NNE ONT
30 NNE RIV 30 NE RIV 20 ENE RIV 15 E RIV 25 ENE NFG 10 ENE OKB
CRQ 30 WSW CRQ 30 SE NUC 20 SSW NUC 35 SE NSI.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SW NTD 10 WNW OXR 15 N OXR 15 NNE CMA 3A6 10 N BUR 15 S PMD
20 SE PMD 20 N POC 20 NNE POC 20 NNE ONT 20 NE ONT 15 NNE RAL
RAL 15 N NFG 15 WNW NFG 20 W NFG 25 ESE AVX 15 SSW AVX
15 WSW AVX.


1500 UTC UPDATE

ONLY SOME MINOR CHANGES MADE TO THE PREVIOUS EXCESSIVE RAINFALL
POTENTIAL OUTLOOK.  THE RISK AREAS WERE EXTENDED SLIGHTLY FARTHER
EASTWARD IN THE TRANSVERSE RANGE OF SOUTHERN CALIFORNIA.  THE
MARGINAL RISK AREA WAS ALSO PUSHED SLIGHTLY EASTWARD OVER THE
SOUTHERN SIERRA TO REFLECT INITIAL HIGHER SNOW LEVELS HERE.

ORAVEC


...CENTRAL TO SRN CALIFORNIA...

WIDESPREAD VERY HEAVY TO EXCESSIVE RAINFALL AMOUNTS REMAIN ON TAP
FOR THE CENTRAL TO SRN CA. WATER VAPOR AND BLENDED TPW LOOPS SHOW
AN IMPRESSIVE AND LONG FETCH ATMOSPHERIC RIVER EXTENDING BACK TO
HAWAII AND WELL BEYOND OVER THE SUBTROPICAL
W-CENTRAL PACIFIC. PW ANOMALIES OF 2-3+ STANDARD DEVIATIONS ABOVE
THE MEAN WILL IMPACT THE THREAT AREA THROUGH THE DAY 1 PERIOD AS
THE AMPLIFYING UPSTREAM TROF APPROACHES SRN CA. LOWER LATITUDE
PACIFIC FLOW ALOFT IS HIGHLY AMPLIFIED AND DYNAMIC WITH A 190 KT
UPPER JET TO THE NORTH OF HAWAII AND ROBUST DOWNSTREAM FLOW
BUCKLING INCLUDING A POTENT SHORTWAVE/LOW SET TO APPROACH CA IN A
PATTERN WITH SUBSTANTIAL LEAD DIFFLUENT FLOW. PREDICTABILITY IS
HIGH THAT THIS HIGHLY ANOMALOUS SET-UP WILL FUEL WIDESPREAD HEAVY
PCPN FOR CENTRAL AND ESPECIALLY SRN CA DAY1 AND HAVE COORDINATED
WITH LOX/SEX ISSUANCE OF A HIGH RISK EXCESSIVE AREA TO ADDRESS
EXPECTED WIDESPREAD RUNOFF PROBLEMS TO BE LOCALLY ENHANCED BY
OVERALL FLOW INSTABILITY...TERRAIN AND EFFECTS A BURN SCAR RUNOFF
ISSUES. AREAL AVERAGE PRECIP TOTALS OF 3-5" POSSIBLE FROM THE
CENTRAL TO SRN CA RANGES...WITH ISOLATED MAXIMA OF 6-9" AS
SATELLITE DERIVED RAINFALL RATES ADJUSTED FOR TOPOGRAPHY MAY YIELD
1"/HOUR LOCALLY.

SCHICHTEL
$$




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