MESOSCALE PRECIPITATION DISCUSSION 0023
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
107 PM EST FRI JAN 29 2016
 
AREAS AFFECTED...CNTRL TO NRN SIERRA NEVADA MOUNTAINS 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 291805Z - 300600Z
 
SUMMARY...RAINFALL RATES OF 0.50 - 0.75 IN/HR ARE EXPECTED TO
IMPACT THE CNTRL TO NRN SIERRA NEVADA MOUNTAINS THROUGH 06Z. THERE
IS HIGH CONFIDENCE IN THESE RATES LEADING TO 12 HR TOTALS OF 3-5
INCHES BY 06Z.

DISCUSSION...LOOPING IMAGERY OF BLENDED TOTAL PRECIPITABLE WATER
SHOWS A NEARLY STATIONARY PLUME OF PRECIPITABLE WATER AIMED INTO
THE N-CNTRL CALIFORNIA COAST WITH SURFACE OBSERVATIONS CONFIRMING
A COLD FRONT STEADILY MOVING THROUGH NRN CALIFORNIA. EARLIER
RAINFALL RATES FROM THIS ATMOSPHERIC RIVER WERE 0.60 TO 0.85 IN/HR
NEAR CAPE MENDOCINO THROUGH 14Z. HOWEVER...THE SWD MOVEMENT OF THE
COLD FRONT INTO THE AFTERNOON AND EVENING HOURS WILL SHIFT THE
BEST 850-700 MB MOISTURE TRANSPORT SOUTH OF THE NRN CALIFORNIA
COASTAL RANGES ACROSS SAN FRANCISCO BAY INTO THE SIERRA NEVADA
RANGE. WHILE RECENT MICROWAVE PASSES ONLY SHOW RAIN RATES OFFSHORE
WITHIN THE MOISTURE PLUME UP TO 0.25 IN/HR...AS 40-50 KTS OF LOW
LEVEL FLOW INTERCEPTS THE TERRAIN OF THE SIERRA NEVADA
RANGE...THESE RAIN RATES WILL SIGNIFICANTLY INCREASE. THERE WERE
NO NOTABLE SHORTWAVE IMPULSES WERE NOTED IN WATER VAPOR IMAGERY
OFFSHORE WITHIN THE POWERFUL MID-UPPER LEVEL JET CORE STREAMING
ENEWD ACROSS THE E-CNTRL PACIFIC...SO IT APPEARS THE ONGOING PLUME
WILL NOT BE AUGMENTED IN THE NEAR TERM.

THE LATEST 12Z HI-RES MODELS INDICATE VERY GOOD AGREEMENT WITH THE
ONGOING SITUATION...AND FORECAST HOURLY RATES OF 0.50 TO 0.75
IN/HR...PERHAPS LOCALLY HIGHER...SLOWLY SINKING SOUTH ACROSS THE
SIERRA NEVADA THROUGH 06Z. SNOW LEVELS ARE CURRENTLY NEAR 9000
FT...ABOVE MOST OF THE MOUNTAIN PEAKS THROUGHOUT THIS SECTION OF
THE SIERRA NEVADA RANGE...BUT SNOW LEVELS WILL LOWER BETWEEN 00Z
AND 06Z TO ABOUT 7500 FT...FROM THE NORTH. SOME RUNOFF ISSUES MAY
RESULT...ESPECIALLY ACROSS ANY BURN SCARRED LOCATIONS.

OTTO

ATTN...WFO...REV...STO...

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

LAT...LON   40202147 40192127 40082089 39752033 39212008 
            38871996 38521972 38151979 38062025 38212055 
            38542071 39172123 39682162 40022168