Graphic for MPD #0107

MESOSCALE PRECIPITATION DISCUSSION 0107
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
358 AM EDT FRI APR 07 2017

AREAS AFFECTED...CNTRL CA COASTAL RANGES INTO THE SIERRA NEVADA
MTNSH

CONCERNING...HEAVY RAINFALL

VALID 070758Z - 071500Z

SUMMARY...AN ATMOSPHERIC RIVER EVENT APPEARS TO HAVE PEAKED WITH A
GRADUAL DOWNWARD TREND EXPECTED THROUGH THIS MORNING. ADDITIONAL
HEAVY RAIN IMPACTS ARE EXPECTED FOR THE CNTRL CA COASTAL RANGES
INTO THE SIERRA NEVADA WITH AN ADDITIONAL 2-3 INCHES OF RAIN
THROUGH 15Z.

DISCUSSION...AS OF 07Z...GOES WATER VAPOR IMAGERY SHOWED THAT THE
NEGATIVELY TILTED TROUGH AXIS TIED TO A MID-UPPER LEVEL LOW
LOCATED WEST OF THE OR COASTLINE HAD MOVED INLAND ACROSS NRN CA.
THIS HAS ALLOWED THE BEST UPPER DIFFLUENCE TO TRANSLATE NWD INTO
OR...AND ALONG THE CA COAST...INFRARED CLOUD TOPS HAVE BEEN
TRENDING WARMER OVERALL SINCE AROUND 02Z.

A STRONG UPPER JET CENTERED NEAR 250 MB REMAINS AIMED
PERPENDICULAR INTO THE NRN CA COAST WITH ESTIMATED WINDS OVER THE
COAST OF 100 KT...10-20 KT WEAKER THAN RECENT RAP/GFS FORECASTS
BASED ON EARLIER COMPARISON WITH GOES HD WIND DATA.
NONETHELESS...06Z GPS DATA PUTS ANOMALOUS PRECIPITABLE WATER
VALUES OF 1.1 TO 1.2 INCHES OR 3 STANDARD DEVIATIONS ABOVE THE
MEAN NEAR THE SANTA CRUZ MOUNTAINS WITH KMUX 850 MB VAD WINDS OF
55 KT PERPENDICULAR OT THE TERRAIN. RESULTANT LOW LEVEL MOISTURE
FLUX CONTINUES TO ALLOW HEAVY RAINFALL RATES NEAR 0.5 IN/HR IN THE
SANTA CRUZ MOUNTAINS.

AS A POWERFUL 975 MB SURFACE LOW LOCATED ABOUT 200 MI WEST OF THE
OR COAST TRACKS NORTH OVER THE NEXT 6-12 HOURS...850 MB WINDS WILL
REMAIN PERPENDICULAR TO THE CNTRL CA COAST BUT WEAKEN TO ABOUT 30
KTS BY 15Z. PRECIPITABLE WATER MAGNITUDE IS ALSO EXPECTED TO
GRADUALLY DIMINISH WHICH WILL CONTINUE A DOWNWARD TREND IN
RAINFALL INTENSITY ALONG THE CNTRL CA COASTAL RANGES. GIVEN THE
BEST OROGRAPHIC ENHANCEMENT WILL FOCUS INTO THE SANTA LUCIA
RANGE...AN ADDITIONAL 2-3 INCHES OF RAINFALL IS EXPECTED BY
15Z...PERHAPS LOCALLY HIGHER.

INLAND ACROSS THE SIERRA NEVADA RANGE...SNOW LEVELS WILL CONTINUE
TO FALL ACROSS NRN LOCATIONS AS THE ATMOSPHERIC RIVER SLOWLY SINKS
SOUTH. SNOW LEVELS FOR LOCATIONS SOUTH OF ABOUT 38N WILL REMAIN
ABOVE 7000 TO 8000 FT WITH GRADUALLY LOWERING MOISTURE FLUX IN THE
850-700 MB LAYER. OCCASIONAL RAINFALL RATES ABOVE 0.5 IN/HR WILL
BE POSSIBLE UNTIL ABOUT 12Z WITH ADDITIONAL RAINFALL OF 2-3 INCHES
IN UPSLOPE FAVORED TERRAIN THROUGH ROUGHLY 15Z. BEYOND
15Z...CONTINUED WEAKENING OF MOISTURE FLUX SHOULD REDUCE THE
REGION TO STEADY LIGHT AND MODERATE RAINFALL RATES OF 0.3 IN/HR OR
LOWER INTO THE AFTERNOON.

OTTO

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

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

LAT...LON   40112156 39952102 39712055 39172025 38591977
            38021924 37481872 36891832 36431837 36341882
            36391949 36191995 35742016 35492100 36172196
            37182247 37562237 37722184 37412112 37612060
            38202078 38902117 39442145 39912171


Last Updated: 358 AM EDT FRI APR 07 2017