MESOSCALE PRECIPITATION DISCUSSION 0068
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 AM EDT THU MAR 22 2018

AREAS AFFECTED...CNTRL TO SRN CA COAST INTO THE SIERRA NEVADA MTNS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 220634Z - 221745Z

SUMMARY...RAINFALL RATES OF 0.5 TO 1.0 IN/HR ARE EXPECTED AT TIMES
INTO THE SIERRA NEVADA MOUNTAINS AND ALONG THE COASTAL RANGES OF
CNTRL/SRN CALIFORNIA THROUGH 18Z. 12 HR RAINFALL TOTALS OF 2-4
INCHES ALONG THE COASTAL RANGES AND 3-6 INCHES ALONG THE SIERRA
NEVADA UPSLOPE CAN BE EXPECTED ALONG WITH POSSIBLE FLASH FLOODING
OVER BURN SCAR REGIONS.

DISCUSSION...GOES WEST WATER VAPOR IMAGERY DEPICTED TWO VORTICITY
MAXIMA LOCATED NEAR 32N 132W...LOCATED WITHIN THE BASE OF A
MID-UPPER LEVEL TROUGH AXIS. GOES HIGH DENSITY WINDS AND RAP
ANALYSES HAVE SHOWN A 130-150 KT 250 MB JET CORE TO THE EAST OF
THE UPPER LEVEL TROUGH AXIS WITH RECENT AMSU AND SSMIS MICROWAVE
PASSES SHOWING RAINFALL RATES OF 0.25 TO 1.0 IN/HR WITHIN THE
RIGHT ENTRANCE REGION OF THE JET CORE DOWN NEAR 30N. A SECOND AREA
OF 0.25 TO 0.5 IN/HR RAINFALL RATES FROM A 03Z AMSU PASS MOVED
ASHORE MONTEREY AND SAN LUIS OBISPO COUNTIES WITH OBSERVED RAIN
RATES BETWEEN 0.4 AND 0.5 IN/HR ENDING 05-06Z. BLENDED TPW IMAGERY
AND GPS SITE DATA DEPICTED A BROAD AXIS OF PRECIPITABLE WATER
VALUES IN EXCESS OF 1 INCH OVER THE CNTRL AND SRN CALIFORNIA
COAST...EXTENDING INTO THE SAN JOAQUIN VALLEY...WITH VALUES
PEAKING BETWEEN 1.3 AND 1.4 INCHES JUST NORTH OF POINT ARGUELLO.

AS THE UPPER TROUGH AXIS CONTINUES MOVING EAST OVER THE NEXT 6-12
HOURS...UPPER LEVEL DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF
THE AFOREMENTIONED UPPER JET WILL BEGIN TO APPROACH THE WEST COAST
ALONG WITH INCREASING 850-700 MB FLOW. RECENT RAP FORECASTS HAVE
BEEN CONSISTENT WITH 850-700 MB WIND SPEEDS BETWEEN 35 AND 50 KT
COMBINED WITH PRECIPITABLE WATER VALUES BETWEEN 1.2 AND 1.4
INCHES.

A LONG DURATION OF HIGHLY ANOMALOUS INTEGRATED MOISTURE TRANSPORT
IS EXPECTED INTO CNTRL AND SRN CALIFORNIA...EXPECTED TO PEAK
BETWEEN 09-15Z ACROSS THE CNTRL AND SRN SIERRA NEVADA RANGE WITH
RAINFALL RATES OF 0.5 TO 1.0 IN/HR LIKELY...WITH RATES IN EXCESS
OF 0.5 IN/HR POSSIBLE BEFORE AND AFTER THIS TIME FRAME. PEAK
INTEGRATED MOISTURE TRANSPORT VALUES WILL SLOWLY SLIDE DOWN THE
COASTLINE FROM SOUTH OF MONTEREY BAY TO THE TRANSVERSE RANGES OF
SRN CALIFORNIA THROUGH 18Z ALONG WITH EXPECTED RAINFALL RATES OF
0.5 TO 0.75 IN/HR ALONG WITH PERIODS OF TRAINING ALLOWING FOR
LOCALLY VERY HEAVY RAINFALL THROUGH 18Z. RAINFALL TOTALS OF 2-4
INCHES ALONG THE COASTAL RANGES AND 3-6 INCHES BELOW 8000 FT
ELEVATION IN THE SIERRA NEVADA ARE FORECAST BY THE 00Z HREF MEAN
THROUGH 18Z. GIVEN ANTECEDENT RAINFALL AND AREA BURN SCARS
SCATTERED ACROSS THE REGION...DANGEROUS DEBRIS FLOWS AND
LANDSLIDES WILL BE POSSIBLE.

OTTO

ATTN...WFO...HNX...LOX...MTR...REV...SGX...STO...

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

LAT...LON   40052151 40012118 39702066 39242008 38891990
            38641975 38411959 38001944 37791927 37521896
            37171882 36901867 36551855 36301853 36031867
            35911925 35611956 35201963 35031917 34991903
            34871869 34741832 34581785 34451760 34211747
            33981770 33791813 33751869 34211985 34272046
            34722102 35412157 36112209 37072253 37292242
            37402214 37442182 37602143 37872112 38192097
            38872106 39372135 39702155