Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 170827
QPFERD

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

...VALID 12Z 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 45 NE MOD 50 NNE MCE 40 NNE MAE 35 ENE FAT 25 NE BFL
25 E BFL 25 WNW MHV 15 N SDB SDB 10 NE SDB 10 NE WJF 10 NNE PMD
30 NNE ONT 25 NNE RAL 20 NNE RIV 20 E RIV 20 SW PSP 25 ESE RNM
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 25 ESE PMD 20 NNE ONT 20 NE RAL
15 E RIV 25 WSW PSP 30 SSW PSP 15 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 20 N POC 15 NNE ONT 15 NE ONT RIV 25 NE 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 15 NNE BUR
20 NNE EMT 10 NNE POC ONT RAL 10 SW RIV 15 NNW NFG 20 W NFG
25 ESE AVX 15 SSW AVX 15 WSW AVX.


...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 ANOMOLOUS SET-UP WILL FUEL WIDESPREAD HEAVY
PCPN FOR CENTRAL AND ESPECIALLY SRN CA DAY1 AND HAVE COORDINATED
WITH LOX/SGX 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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