HYDROMETEOROLOGICAL DISCUSSION NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA 930 AM PST WED DEC 22 2010 ...MORE HEAVY PRECIP FOR SRN CA TOWARD SRN AND ERN NEV... ...HEAVY TO EXCESSIVE PRECIP INCLUDES THE DESERTS OF SE CA... ...DRYING CONDITIONS EXPECTED IN THE THU AND FRI TIME PERIODS... .24 HOUR PRECIPITATION TOTALS (ENDING DEC 22 AT 400 AM PST)... A LARGE MOISTURE FETCH FROM THE SOUTHERN CA COAST INLAND ACROSS THE SE CA DESERTS ALONG WITH EXTREME SOUTHERN AND EASTERN NEV BROUGHT HEAVY PRECIP TO SIMILAR AREAS AGAIN. THE NEXT COLD FRONT BEGAN TO MOVE ONTO COASTAL SECTIONS FROM PT CONCEPTION NORTHWARD...AND SPREAD PRECIP OVER THE SHASTA DRAINAGE ALONG WITH PORTIONS OF THE NORTHERN SIERRA. BETWEEN THE EASTERN SAN GABRIEL MOUNTAINS AND THE LAGUNA MOUNTAINS TOTALS WERE IN THE RANGE OF 2.00- TO 5.00-INCHES WITH LOCAL TOTALS TO 6.00-INCHES. LOWER ELEVATIONS IN THE SAME AREA SAW AMOUNTS FROM 1.50- TO 3.00-INCHES. THE DESERT LOCATIONS UP INTO EXTREME SOUTHERN AND EASTERN NEVADA SAW AMOUNTS IN THE 0.50- TO 1.50-INCH RANGE. HOWEVER...SOME OF THE HIGHER TERRAIN OF SOUTHERN NEV LIKE THE SPRING MOUNTAINS SAW IN UPWARDS OF 2.25-INCHES. THE SHASTA DRAINAGE SAW SOUTHERLY FLOW DEVELOP AHEAD OF THE COLD FRONT WHICH BROUGHT AMOUNTS OF 1.00- TO 2.00-INCHES (LOCAL 2.50-INCHES). SIMILAR TOTALS WERE RECORDED RIGHT ON CAPE MENDOCINO NEAR HONEYDEW. OTHER NORTH COAST LOCATIONS WERE GENERALLY IN THE RANGE OF 0.75- TO 1.25-INCHES (LOCAL TO 1.75-INCHES OVER THE LOWER RUSSIAN RIVER BASIN). FINALLY FOR THE NORTH PART OF THE STATE...THE FAR NORTHERN SIERRA SAW 0.50- TO 1.25-INCHES WITH 0.10- TO 0.25-INCH FOR THE SACRAMENTO VALLEY. FOR THE CENTRAL PORTION OF CA...GREATEST AMOUNTS WERE OVER THE SANTA CRUZ AND SANTA LUCIA MOUNTAINS. TOTALS WERE BETWEEN 0.75- AND 1.25-INCHES. INLAND LOCATIONS OVER THE SAN JOAQUIN VALLEY WERE NEAR OR LESS THAN 0.25-INCH...WHILE THE SOUTHERN SIERRA SAW 0.25-INCH OR LESS WITH A FEW POCKETS APPROACHING 0.50-INCH. FINALLY...AROUND PT CONCEPTION EAST TOWARD VENTURA COUNTY...THE HIGHER TERRAIN SAW 1.00- TO 2.00-INCHES WHILE THE LOWER ELEVATIONS WERE ON THE ORDER OF 0.50- TO 1.00-INCH. OVER THE PAST 7 DAYS...FROM THE I-80 CORRIDOR SOUTHWARD THE REGION HAS BEEN APPROX 400- TO 600-PERCENT OF NORMAL IN TERMS OF PRECIP TOTALS. THERE ARE MOST LIKELY SOME POCKETS EVEN HIGHER THAN 600-PERCENT OF NORMAL OVER THE SE CA DESERTS UP TOWARDS EXTREME SOUTHERN AND EASTERN NEVADA. .METEOROLOGICAL CONDITIONS... AN AMAZING MOISTURE FEED CONTINUES FROM THE SOUTHERN CA COAST INLAND ACROSS THE COASTAL MOUNTAINS BEFORE SPILLING OVER THE SE CA DESERTS AND EXTREME SOUTHERN AND EASTERN NEV. GPS-MET STATIONS ALONG THE COAST AT POINT LOMA AND LA JOLLA PEAKED OVERNIGHT WITH AN IPW IN THE RANGE OF 1.25- TO 1.50-INCHES. INLAND AT THE ESSEX LOCATION (ALONG I-40 IN THE DESERTS)...THE IPW IS SHOWING A SLIGHT RISE TO NEARLY 1.00-INCH AS THE AXIS OF THE HIGHEST MOISTURE CONTENT AIR MOVES OVERHEAD. 22/12Z KNKX RAOB MEASURED A PW OF 1.14-INCHES (APPROX 250-PERCENT OF NORMAL) WITH A SATURATED PROFILE. ONSHORE FLOW HAS ALSO RAMPED UP OVER THE PAST 12 HOURS...ESPECIALLY IN THE LOW- TO MID-LEVELS. 850-MB WINDS ARE UP TO 45-KT...SIMILAR TO JUST A TAD BIT HIGHER IN THE ATMOSPHERE AT 700-MB. THIS STRONG PUSH FROM THE SW IS RESULTING IN IDEAL OROGRAPHIC CONDITIONS. AS STATED...PLENTY OF MOISTURE IS MAKING ITS WAY INLAND OVER THE DESERT LOCATIONS AND ACROSS MUCH OF THE GREAT BASIN...EVEN TOWARD THE CENTRAL ROCKIES. LOOKING AT NUMEROUS RAOBS ACROSS THIS AREA...ITS FAIR TO SAY THAT PW VALUES ARE EASILY TWICE NORMAL VALUES FOR THIS TIME OF YEAR. 88-D INDICATES WIDESPREAD PRECIP AFFECTING THESE AREAS WITH SEVERAL MOUNTAIN STATIONS BETWEEN PT CONCEPTION AND THE US/MEXICO BORDER REPORTING OVER 1.00-INCH SINCE 22/12Z. WHAT IS EVEN MORE IMPRESSIVE IS THE 1.01-INCHES BEING RECORDED AT APPLE VALLEY...WHICH IS OVER THE CREST OF THE SAN BERNARDINO MOUNTAINS NEAR THE CITY OF VICTORVILLE ALONG I-15. EVEN BARSTOW-DAGGETT HAS RECEIVED 0.42-INCH IN THE PAST 3 HOUR WITH STEADY PRECIP CONTINUING TO AFFECT THE AREA. FARTHER INLAND...LOWER ELEVATION LOCATIONS AT DESERT ROCK AND LAS VEGAS HAVE SEEN 0.56- AND 0.54-INCH RESPECTIVELY SINCE 22/12Z...WHICH INDICATES MOST LIKELY THAT INTENSE PRECIP RATES ARE BEING OBSERVED OVER THE SPRING MOUNTAINS AND OTHER HIGHER ELEVATIONS ACROSS EXTREME SOUTHERN AND EASTERN NEV. THESE CONDITIONS LOOK TO PERSIST FOR THE NEXT 3 TO 9 HOURS UNTIL THE MOISTURE FEED IS FINALLY SHUNTED TOWARD THE SOUTH AND EAST OF THE REGION AS THE S/WV TROF MOVES ACROSS THE AREA. LATEST WV IMAGERY SHOWS THE CORE OF THE S/WV TROF NOW SPINNING TO THE WSW OF PT CONCEPTION NEAR 32N/123W. ANOTHER CONCERN AS THE SYSTEM APPROACHES THE COASTAL SECTIONS OF SOUTHERN CA WILL BE THE THREAT OF CONVECTIVE ACTIVITY...WHICH WILL ONLY ADD TO MESS WITH HIGHER PRECIP RATES UNDER STRONGER CELLS. CURRENTLY...LOWEST STABILITY IS OFFSHORE. HOWEVER...THE 22/06Z GFS IS INDICATING THAT BY 22/18Z THE LEADING EDGE OF THIS COOLER AIR ALOFT AND LESS STABLE AIRMASS WILL REACH COASTAL SECTIONS FROM PT CONCEPTION TO NORTHERN BAJA. LIFTED INDICES WILL BE IN THE 0- TO MINUS 1-DEG C RANGE...WHILE SFC-BASED CAPES REACH JUST OVER 100-J/KG. DURING THE AFTERNOON HOURS IS WHEN THE CONVECTIVE THREAT WILL BE AT ITS PEAK. LIFTED INDICES DROP CLOSE TO MINUS 2-DEG C WITH SFC-BASED CAPE VALUES REACHING A PEAK OF 300-J/KG. THIS AREA IS FAIRLY WIDESPREAD FROM A SAN LUIS OBISPO TO LAS VEGAS LINE...INCLUDING ALL POINTS SOUTH TO THE US/MEXICO BORDER. WILL NEED TO KEEP AN EYE ON ANY STRONG CELLS THAT TRACK OVER ALREADY SATURATED BASINS FOR INTENSE PRECIP RATES AND ADDED RUNOFF. AS THE CORE OF THE SYSTEM EXITS THE REGION TONIGHT...THE BEST INSTABILITY SHIFTS ACROSS ARIZONA. AT THIS TIME IS WHEN PRECIP WILL SEE A NOTICEABLE DECREASE IN COVERAGE AND INTENSITY. THERE WILL STILL BE SOME UPSLOPE SHOWERS FROM THE EASTERN SAN GABRIEL MOUNTAINS SOUTH TOWARD THE LAGUNA MOUNTAINS. LOWER ELEVATIONS WILL BEGIN TO DRY OUT. DESERT LOCATIONS...EXCEPT IN CLOSE PROXIMITY TO THE CORE OF THE SYSTEM (LOWER COLORADO RIVER BASIN) WILL ALSO BEGIN TO SEE PRECIP COME TO AN END. A POSITIVELY TILTED UPR RIDGE WILL BUILD ACROSS THE AREA THU INTO FRI BRINGING COMPLETELY DRY CONDITIONS TO THE REGION...FINALLY! NEXT COLD FRONT SLOWLY APPROACHES THE NORTH COAST AS AN UPR TROF DIGS SOUTH OUT OF THE GULF OF ALASKA LATER ON FRI. FIRST SIGNS OF PRECIP ALONG THE NORTH COAST APPEAR ON THE OVERNIGHT INTO CHRISTMAS DAY WITH THE BULK OF THE PRECIP MOVING ACROSS THE REGION DURING THE DAYTIME AND EVENING HOURS. 22/00Z EC IS ABOUT 6 HOURS SLOWER THAN THE 22/06Z GFS...BUT TRACK THE SYSTEM IN A FAIRLY SIMILAR TRAJECTORY. THIS IS A BIT DEEPER THAN PREVIOUS THINKING WITH PRECIP MAKING ITS WAY SOUTH TO NEAR PT CONCEPTION AND EVENTUALLY THE REST OF SOUTHERN CA. ANOTHER SYSTEM THEN LOOKS TO MOVE INTO THE AREA FOR THE MIDDLE OF NEXT WEEK. DAY 1 QPF (WED 22/12Z TO THU 23/12Z): HEAVIEST PRECIP WILL FALL IN A SWATH FROM THE SOUTHERN CA COAST NNE ACROSS THE SE CA DESERTS BEFORE SPREADING OVER EXTREME SOUTHERN AND EASTERN NEV. GREATEST TOTALS WILL FALL OVER THE EASTERN SAN GABRIEL AND WESTERN SAN BERNARDINO MOUNTAINS...AS WELL AS THE SAN JACINTO AND LAGUNA MOUNTAINS WITH 2.00- TO 4.00-INCHES (LOCAL 5.00-INCHES). THE SANTA YNEZ AND SAN RAFAEL MOUNTAINS WILL SEE SLIGHTLY LESS TOTALS WITH 1.00- TO 2.50-INCHES. FOR LOWER ELEVATION COASTAL STATIONS...EXPECT AMOUNTS FROM 1.00- TO 2.00-INCHES. INLAND OVER THE SE CA DESERTS TOTALS WILL GENERALLY RANGE FROM 0.75- TO 1.50-INCHES WITH SOME LOCAL AMOUNTS EXCEEDING 2.00-INCHES. FOR EXTREME SOUTHERN AND EASTERN NEVADA THE GREATEST AMOUNTS WILL FALL OVER THE SPRING MOUNTAINS AND THE GRANT RANGE WITH 1.50- TO 3.00-INCHES (LOCAL 4.00-INCHES FOR THE SPRING MOUNTAINS). ELSEWHERE...HIGHER TERRAIN LOCATIONS FOR THIS AREA WILL BE IN THE RANGE OF 1.00- TO 2.00-INCHES WITH 0.50- TO 1.00-INCH LOWER ELEVATIONS. FOR THE LENGTH OF THE SIERRA TOTALS WILL RANGE FROM 0.75-INCH NORTH TO 1.50-INCHES SOUTH. THE SHASTA DRAINAGE WILL SEE ANOTHER 0.25- TO 0.50-INCH. ELSEWHERE...EXPECT AMOUNTS NEAR OR LESS THAN 0.25-INCH. DAY 2 QPF (THU 23/12Z TO FRI 24/12Z): DRY. DAY 3 QPF (FRI 24/12Z TO SAT 25/12Z): A FEW LIGHT SHOWERS ALONG THE FAR NORTH COAST WILL RESULT IN AMOUNTS CLOSE TO 0.10-INCH. .HYDROLOGICAL CONDITIONS... SOUTHERN CALIFORNIA RIVERS AND STREAMS ARE EXPERIENCING MAJOR RENEWED RISES THIS MORNING. FORECAST POINTS ON THE SAN DIEGO, SANTA MARGARITA AND MOJAVE RIVERS ARE ABOVE FLOOD STAGES. THE WAVES OF HEAVY RAIN SHOULD FINALLY DECREASE LATER TODAY ALLOWING FOR MOSTLY RECEDING RIVERS ON THURSDAY. IN NORTHERN AND CENTRAL CALIFORNIA MOST RIVERS AND STREAMS REMAIN WELL ABOVE SEASONAL NORMALS BUT AT MANAGEABLE FLOW VOLUMES. MORE INFORMATION ON THE CNRFC WEBSITE AT HTTP://WWW.CNRFC.NOAA.GOV DRK/AM