Flash Flood Guidance
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000
AWUS01 KWNH 160553
FFGMPD
NVZ000-CAZ000-161622-

MESOSCALE PRECIPITATION DISCUSSION 0934
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1253 AM EST THU NOV 16 2017

AREAS AFFECTED...PORTIONS OF NORTH-CENTRAL CA

CONCERNING...HEAVY RAINFALL

VALID 160552Z - 161622Z

SUMMARY...A PLUME OF MOISTURE AND ASSOCIATED HEAVY RAIN IS
EXPECTED TO SLOWLY DECREASE IN INTENSITY THROUGH 16Z.  UNTIL THEN,
HOURLY RAIN RATES AT OR ABOVE 0.5" WITH LOCAL AMOUNTS TO 4" ARE
EXPECTED.

DISCUSSION...WATER VAPOR IMAGERY SHOWS A PLUME OF MOISTURE
ORIGINATING SOUTHEAST OF HAWAI`I DIRECTED INTO NORTH-CENTRAL CA
AHEAD OF A SHORTWAVE LOCATED NEAR 41N 134.5W AND TO THE SOUTH OF A
JET STREAK ACROSS WESTERN OR.  SHOWERS WITH HEAVY RAINFALL LURK
WITHIN THE BAND, WITH RECENT HOURLY RAINFALL TOTALS OF 0.5-0.6" IN
THE SIERRA NEVADA AND 0.3-0.4" IN THE COASTAL RANGES.  WET BULB
ZERO HEIGHTS NEAR 9,000 FEET PER THE OAKLAND CA SOUNDING ALONG
WITH NEARLY UNIDIRECTIONAL FLOW WITH HEIGHT ARE AIDING
PRECIPITATION EFFICIENCY/TOTALS.  PRECIPITABLE WATER VALUES OF
0.7-1.4" LIE WITHIN THE PLUME ACROSS CA, WITH 1.25-1.5" VALUES
OFFSHORE.  MUCAPE VALUES OF 100+ J/KG EXISTS UPSTREAM PER SPC
MESOANALYSES.  INFLOW AT 850/700 HPA IS 40-50 KTS INTO THE AREA.

BOUNDARY LAYER MOISTURE CONVERGENCE IS EXPECTED TO PERSIST INTO
THE MORNING HOURS, THOUGH 850/700 HPA INFLOW IS EXPECTED TO SLOWLY
WANE WITH TIME AS THE PARENT CYCLONE WEAKENS WHILE MOVING INTO
BRITISH COLUMBIA WHICH SHOULD RESULT IN SLOWLY LOWERING HOURLY
RAIN TOTALS.  THE FREEZING LEVEL IN THE AREA SHOULD SLIGHTLY
DECREASE BETWEEN NOW AND THE HORIZON OF THIS MPD.  HRRR AND ARW
GUIDANCE SUGGESTS THAT THE AREA OF 0.5" AN HOUR RATES SHOULD
MINIMIZE BY AROUND 16Z.  UNTIL THEN, MESOSCALE GUIDANCE SHOWS
LOCAL RAINFALL AMOUNTS NEAR 4" WHICH COULD LEAD TO DEBRIS
FLOWS/ROCK SLIDES NEAR BURN SCARS AND WITHIN RUGGED TERRAIN.

ROTH

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...EKA...HNX...MTR...REV...STO...

ATTN...RFC...CNRFC...

LAT...LON   40392035 40201994 39151969 38431926 37661966
            36812201 37402267 38642357 39982229



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