Quantitative Precipitation Forecast
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FOUS30 KWBC 180024
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
720 PM EST FRI FEB 17 2017

...VALID 01Z SAT FEB 18 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
45 WSW 87Q 10 NNE 87Q 15 WSW PRB 30 ENE SMX 30 WNW SDB
25 NW SDB 10 SSE BFL 15 N PTV 20 NE MCE 25 NNE 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 90 S NUC 135 SSW NSI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 SW SBA 20 NNW SBA 35 NE 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 35 SW NRS 45 SW NRS 75 S NSI.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NNW NSI NTD 20 SSW SDB 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 35 WNW NZY 35 ESE NUC 30 SW NUC.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 S NTD 3A6 10 N BUR 15 S PMD 20 SE PMD 20 N POC 20 NNE POC
20 NNE ONT 25 NNE RIV 20 S RIV 15 N NFG 15 WNW NFG 20 W NFG
25 W NFG 30 S SNA 20 ESE AVX.


2100 UTC UPDATE

EXCESSIVE RAINFALL THREAT WAS ADJUSTED TO TRIM NWRN PORTION OF
MARGINAL/SLIGHT RISK AREAS ACRS THE CA COAST NORTH OF POINT
CONCEPTION..AS STRONGEST UPR DIFLUENCE COINCIDENT WITH MAIN
ANOMALOUS PW PLUME CONTINUES TO SHIFT SLOWLY S AND EAST ACRS SRN
CA.  RECENT HRRR AND 12Z HI RES MODELS SUGGEST ADDITIONAL RAINFALL
AMOUNTS OF 3 TO 5 INCHES INTO PORTIONS OF THE TRANSVERSE
RANGES/SANTA YNEZ MOUNTAINS WITH AMOUNTS OF 1 TO 3 INCHES
SOUTHWARD TOWARD SAN DIEGO.  STORM TOTAL AMOUNTS WILL LIKELY
EXCEED 9 INCHES IN SOME OF THE MORE FAVORED UPSLOPE AREA IN THE
TRANSVERSE RANGE.  THE ADDITIONAL HEAVY RAIN OVERNIGHT WILL LIKELY
RESULT IN ADDITIONAL RUNOFF PROBLEMS ACRS THE OUTLOOK AREA..AND
SUPPORT THE HIGH RISK ISSUANCE.

SULLIVAN


...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/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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