MESOSCALE PRECIPITATION DISCUSSION 0052
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
349 PM EST WED FEB 15 2017

AREAS AFFECTED...FAR SWRN OR INTO NRN CA

CONCERNING...HEAVY RAINFALL

VALID 152048Z - 160848Z

SUMMARY...A SURGE OF HEAVY RAIN WITH RATES POSSIBLY ECLIPSING 1
IN/HR ALONG COASTAL LOCATIONS FROM SWRN OR TO NRN CA IS EXPECTED
TO AFFECT THE REGION AFTER 00Z. 2-4 INCHES OF RAIN WITH LOCALLY
HIGHER VALUES WILL BE POSSIBLE IN THESE LOCATIONS THROUGH 08Z.

DISCUSSION...A COMBINATION OF GOES WEST WATER VAPOR AND VISIBLE
IMAGERY THROUGH 20Z HELPED PLACE A FEW VORTICITY MAXIMA EMBEDDED
WITHIN A LARGER SCALE MID-LEVEL TROUGH APPROACHING THE WEST COAST.
IR IMAGERY DEPICTED A BAROCLINIC LEAF SIGNATURE AHEAD OF THE SRN
MOST VORT MAX WITHIN THE BASE OF THE TROUGH WHICH IS INDICATIVE
POSSIBLE WEAK WAVE DEVELOPING ALONG A COLD FRONT EXTENDING SWWD
AHEAD OF THE APPROACHING UPPER TROUGH AXIS. A ROBUST AXIS OF
MOISTURE...REPRESENTED BY PRECIPITABLE WATER VALUES IN EXCESS OF
1.5 INCHES WAS LOCATED BENEATH THE SATELLITE SIGNATURE...CAPTURED
REASONABLY WELL BY RECENT RUNS OF THE RAP. AS THE BASE OF THE
TROUGH SHARPENS OVER THE NEXT 6 HRS...LOW LEVEL FLOW WILL
STRENGTHEN FROM CURRY COUNTY OREGON TO NRN MENDOCINO COUNTY
CALIFORNIA INTO THE 70-80 KT RANGE...ADJUSTING UPWARD FROM RAP
FORECASTS WHICH HAVE BEEN 5-10 KT TOO WEAK ALONG THE NRN CA COAST
AS OF 20Z COMPARED TO VAD WIND PLOTS. SATELLITE DERIVED AMSU AND
SSMIS RAIN RATES HAVE BEEN BETWEEN 0.25 AND 0.5 IN/HR ON A
LOCALIZED BASIS WITHIN THE MOISTURE AXIS OFF OF THE WEST COAST
THROUGH 19Z.

850MB FLOW FROM THE S TO SSW WILL COMBINE WITH PRECIPITABLE WATER
VALUES MAXING OUT IN THE 1.3 TO 1.4 INCH RANGE ALONG THE NRN CA
COAST BETWEEN 03-08Z LEADING TO HIGHLY ANOMALOUS MOISTURE FLUX
VALUES. WHILE THIS AXIS IS FORECAST TO STEADILY DESCEND TOWARD THE
SOUTH THROUGH THE NRN CA COAST TONIGHT...SOME GREATER UPPER TROUGH
AMPLIFICATION MAY TEMPORARILY DELAY SWD MOVEMENT OF THE MOISTURE
AXIS COMPARED TO A CONSENSUS OF RECENT HI-RES MODELS. WHEN
COMBINED WITH STRONG UPPER LEVEL DIFFLUENCE AND APPROACHING LEFT
EXIT REGION JET DYNAMICS...RAINFALL RATES ARE EXPECTED TO RANGE
BETWEEN 0.5 AND 1.0 IN/HR AT TIMES WITHIN THE MPD THREAT
AREA...WITH THE POSSIBILITY OF RATES EXCEEDING 1.0 IN/HR ON A
LOCALIZED BASIS FROM CURRY TO NRN MENDOCINO COUNTIES WHERE SSW
FACING TERRAIN INTERCEPTS THE ROBUST MOISTURE FLUX.

OTTO

ATTN...WFO...EKA...MFR...STO...

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

LAT...LON   43022431 42892397 42442387 42142366 42002346
            41832321 41582288 41462254 41462225 41342211
            41052221 40902254 40672296 40302333 39762348
            39662416 40162458 42102478 42892458