MESOSCALE PRECIPITATION DISCUSSION 0009
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
205 PM EST FRI FEB 06 2015
 
AREAS AFFECTED...NRN CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 061901Z - 070101Z
 
SUMMARY...FLASH FLOODING WILL REMAIN POSSIBLE THROUGH 00Z ACROSS
PORTIONS OF NRN CALIFORNIA...WITH HOURLY RATES BETWEEN 0.5 AND 1.0
INCHES/HOUR AND 3 HOURLY RATES NEAR 2 INCHES. OROGRAPHIC
ENHANCEMENT WILL BE A SIGNIFICANT FACTOR IN HIGHER RAINFALL TOTALS.

DISCUSSION...WATER VAPOR IMAGERY AT 19Z SHOWED A MID-LEVEL
SHORTWAVE EDGING CLOSER TO THE OREGON/CALIFORNIA COASTS WITH AN
ASSOCIATED BAROCLINIC LEAF SIGNATURE MOVING INLAND FROM NRN
CALIFORNIA TO WASHINGTON AS WELL. MESONET OBSERVATIONS THIS
MORNING HAVE SHOWN WIDESPREAD HOURLY RATES GENERALLY BETWEEN 0.3
AND 0.5 IN/HR WITHIN A BROAD PRECIPITATION SHIELD EXTENDING
THROUGH MUCH OF NRN CALIFORNIA INTO OREGON. RAINFALL WAS OCCURRING
WITHIN A SOUTHWEST TO NORTHEAST ORIENTED PLUME OF ANOMALOUSLY DEEP
MOISTURE AIMED INTO THE NRN CALIFORNIA COAST WITH GPS PRECIPITABLE
WATER VALUES INDICATING BETWEEN 1.2 TO 1.5 INCHES FROM THE NORTH
BAY REGION TO CAPE MENDOCINO...WHICH ARE ARE 3+ STANDARD
DEVIATIONS ABOVE THE MEAN.

AS THE AFOREMENTIONED SHORTWAVE MOVES INLAND THIS EVENING...SHORT
TERM MODEL GUIDANCE IS UNANIMOUS IN SLIDING THE ANOMALOUS PLUME OF
PACIFIC MOISTURE SWD...REACHING THE SAN FRANCISCO BAY REGION BY
00Z. WHILE MID-LEVEL LAPSE RATES ARE FORECAST TO BE LOW ACROSS THE
REGION...KEEPING INSTABILITY GENERALLY LESS THAN 100 J/KG...AN
INCREASE IN THE 850-700 MB FLOW BY ABOUT 10 KTS INTO THE NORTH BAY
REGION THIS EVENING COULD HELP SUPPORT RAINFALL RATES BETWEEN 0.75
TO 1.0 IN/HR WITH SHORT TERM TRAINING POSSIBLY ALLOWING EXCEEDANCE
OF 1 AND 3 HOUR FLASH FLOOD GUIDANCE. THE MAIN FOCI WILL BE THE
COASTAL RANGES AND INTO THE SIERRA NEVADA RANGE WHERE THE FREEZING
LEVEL WILL NEAR 9000 FT.

OTTO

ATTN...WFO...EKA...MFR...MTR...REV...STO...

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

LAT...LON   41792168 41712125 41172125 40782116 40182082 
            39652045 39122015 38752029 38442067 38122141 
            37792254 38012313 38542376 39232416 39992441 
            40572430 41222347 41472290 41712220