Quantitative Precipitation Forecast
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FOUS30 KWBC 091407
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
906 AM EST TUE JAN 09 2018

...VALID 15Z TUE JAN 09 2018 - 12Z WED JAN 10 2018...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 S LPC 30 SSW LPC 10 SW VBG 10 W SMX 20 NE SMX 40 ENE SMX
40 WSW BFL 30 SSW BFL 20 SE BFL 25 NW MHV 10 NW MHV 10 SSE MHV
20 SE EDW 25 SW DAG 25 SSW DAG 15 WNW NXP 20 SSW NXP 10 W TRM
35 S TRM 15 ENE CZZ 20 S CZZ 25 SSE MMTJ 20 SSW NRS 25 SW NZY.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 NNW PRC 40 SW INW 60 SSW SOW 35 NNE DMA 25 SSE CGZ
30 NNW GBN 40 SSW EED 15 S HND 40 ENE LSV 25 NE IGM 35 NNW PRC.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SSE LPC 25 S LPC 15 S LPC LPC XVW SMX 15 ENE SMX 30 ENE SMX
40 ENE SMX 40 SW BFL 25 WNW SDB 15 NW SDB 10 NE SDB 10 W WJF PMD
25 ESE PMD 30 NNE RIV 25 NW PSP 20 NW PSP 15 WSW PSP 15 SW PSP
25 NE RNM 20 NNE CZZ CZZ 15 SE MMTJ NRS 20 SW CRQ 30 E NUC
15 ENE NUC 15 N NUC.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WSW SBA 10 SSE LPC 10 SE SMX 25 E SMX 40 N SBA 35 W SDB
10 NW SDB SDB 10 WSW WJF 15 SE PMD 20 NE ONT 25 NE RIV 25 NW PSP
20 WNW PSP 20 ESE RIV 10 SE RIV RAL FUL 10 SW LAX 30 S NTD
35 SW NTD.

...SOUTHERN CALIFORNIA...
...MODERATE RISK OF EXCESSIVE RAINFALL IN PARTS OF SOUTHERN
CALIFORNIA...

RADAR AND WATER VAPOR IMAGERY THIS MORNING SHOWS AN UPPER LEVEL
LOW JUST OFF THE SOUTHERN CA COAST WITH SHOWERS STREAMING ONSHORE
AND INLAND.  WATER VAPOR TRENDS SHOW THE PRIMARY CHANNEL OF
MOISTURE STREAMING TOWARDS SOUTHERN CA...INCLUDING THE SAN DIEGO
AREA.  HIGH RES GUIDANCE INDICATES A TRANSITION TODAY WITH RAIN
RATES GRADUALLY DECLINING AS THE STRONGER LIFT MOVES INTO AREAS
FURTHER INLAND...INTO ARIZONA.
THE 12Z HIGH RES RAPID REFRESH SHOWS HALF TO ONE INCH OF RAIN  IN
THE MOUTNAINS EAST OF LOS ANGELES TO 18Z AND THEN TAPERING TO
UNCER A QUARTER INCH AFTERWARD...WITH THE AREAS EAST OF SAN DIEGO
RECEIVED HALF TO ONE INCH 18-00Z.
THIS MATCHES WITH THE GFS FORECAST OF THE HIGHER PRECIPITABLE
WATER VALUES SHIFTING SOUTH THIS MORNING AND THEN INLAND THIS
AFTERNOON.  THERE IS STILL A CHANCE OF EMBEDDED CONVECTIVE RAINS
UNTIL THE UPPER LOW MOVES INLAND.  WHERE DOWNPOURS OCCUR IN
FRESHLY BURNED AREAS...IMPACTS FROM FLASH
FLOODING...MUDSLIDES...AND DEBRIS FLOWS ARE ANTICIPATED PER
COORDINATION WITH LOCAL OFFICES.

...SOUTHWEST DESERT AREAS OF CA/AZ/NV...

WITH THE CLOSED UPPER LOW MOVING ONSHORE AND DECENT MOISTURE
AVAILABILITY AT ABOUT 0.75 INCH PW EXTENDING INTO THE
DESERTS...THERE SHOULD BE SOME DEEP CONVECTION AND ENHANCED
PRECIPITATION RATES THIS EVENING/OVERNIGHT. THE HI-RES
MODELS...INCLUDING THE UNIVERSITY OF ARIZONA WRF...INDICATE HALF
INCH PER HOUR RATES. THE NAM PRODUCES ABOUT 250 J/KG CAPE OVER
CENTRAL ARIZONA BY NIGHTTIME...AND THE MODELS USUALLY
UNDERESTIMATE THE PRESENCE OF WEAK INSTABILITY IN THESE REGIMES.
GIVEN THE FLASHY NATURE OF THE REGION AND RAIN RATES LIKELY TO AT
LEAST APPROACH THE 1-HOUR FLASH FLOOD GUIDANCE VALUES IN A FEW
SPOTS...A MARGINAL RISK OF EXCESSIVE RAINFALL IS SHOWN HERE.

PETERSEN/BURKE

$$





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