AGUS76 KRSA 151848
HMDRSA
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
930 AM PDT SUN APR 15 2012
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PLEASE NOTE...THIS WILL REPRESENT THE LAST HYDROMETEOROLOGICAL
DISCUSSION FOR THE 2011-2012 WINTER OPERATIONS SEASON. IF
CONDITIONS WARRANT...A SPECIAL ISSUANCE OF THIS PRODUCT MAY OCCUR
DURING THE DRY SEASON. THE NEXT SCHEDULED ISSUANCE OF THIS
PRODUCT WILL TAKE PLACE ON OCTOBER 15 2012 WHEN THE 2012-2013
WINTER OPERATIONS SEASON BEGINS.
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...LIGHT PRECIP FOR CA/ORE BORDER REGION TONIGHT INTO TOMORROW...
.24 HOUR PRECIPITATION TOTALS (ENDING APR 15 AT 500 AM PDT)...
AN UPR LOW SHIFTED FROM THE LAS VEGAS AREA TOWARD THE EAST
YESTERDAY. SCATTERED SHOWERS IN BROAD CYCLONIC FLOW RESULTED IN
SCATTERED LIGHT PRECIP FOR THE SIERRA...PORTIONS OF THE CENTRAL AND
SOUTHERN CA COASTS. AMOUNTS IN THIS AREA WERE GENERALLY NEAR
0.10-INCH OR LESS WITH A FEW HIGHER TOTALS UNDER HEAVIER CELLS.
THE BEST WIDESPREAD PRECIP WAS RECORDED OVER THE STATE OF NEVADA.
GREATEST AMOUNTS WERE OBSERVED OVER THE NORTH-CENTRAL PORTION OF THE
STATE WITH THE HIGHER TERRAIN RECEIVING 0.25- TO 0.50-INCH. SIMILAR
AMOUNTS WERE RECORDED ACROSS THE RUBY MOUNTAINS AS WELL. LOWER
ELEVATIONS SAW TOTALS IN THE RANGE OF A FEW HUNDREDTHS OF AN INCH TO
ALMOST 0.25-INCH.
.METEOROLOGICAL CONDITIONS...
LATEST WV/IR IMAGERY SHOWS AN UPR TROF OVER THE ROCKY MOUNTAINS WITH
AN UPR RIDGE JUST OFF THE WEST COAST. MUCH OF THE REGION CURRENTLY
SITS UNDER NORTHERLY FLOW ALOFT BETWEEN THESE TWO FEATURES. THERE IS
A FAIRLY DEEP UPR LOW SPINNING OVER THE GULF OF ALASKA THIS MORNING
WITH A S/WV TROF ROTATING THROUGH THE BASE OF THE FEATURE. AT THE
SFC...A WEAK WARM FRONT EXTENDS ALONG 130W BETWEEN 40N AND
45N...WHILE THE COLD FRONT ARCS SW FROM 45N/130W TO 40N/140W.
THROUGH TODAY...THE WARM FRONT WILL TRAVERSE THE CA/ORE BORDER
REGION. WEAK WAA/ISENTROPIC LIFT WILL BRING LIGHT PRECIP TO COASTAL
SECTIONS NORTH OF CAPE MENDOCINO STARTING LATE THIS AFTERNOON.
LOWEST CONDENSATION PRESSURE DEFICITS AND BEST UPGLIDE ARE FOCUSED
ON THE CA/ORE BORDER AND POINTS NORTH.
THE MID-LEVEL S/WV TROF WILL REACH THE COASTAL WATERS WEST OF THE
PACNW TOMORROW LATER MORNING INTO THE AFTERNOON HOURS. THE COLD
FRONT WILL BRING PRECIP TO THE FAR NW CORNER OF CA BEGINNING DURING
THE LATER MORNING HOURS BEFORE SPREADING INLAND ACROSS NORTHERN CA
DURING THE AFTERNOON. THE SOUTHERN EXTENT OF THE PRECIP LOOKS TO
MAKE ITS WAY DOWN TO PT ARENA ALONG THE COAST AND INLAND TOWARD
LASSEN NP. FOR THE EVENING...AS THE S/WV TROF TRACKS OVER THE
PACNW...EXPECT LIGHT PRECIP TO AFFECT NEV NORTH OF I-80. ONLY A FEW
LIGHT SHOWERS WILL REMAIN ACROSS NE NEV OVERNIGHT AS THE S/WV TROF
TRACKS TOWARD THE NORTHERN ROCKIES.
CONSOLIDATED ZONAL FLOW WILL BE THE RULE FOR THE MID-WEEK PERIOD
OVER THE NE PACIFIC BETWEEN 40N AND 50N...AND INLAND ACROSS THE
NORTHERN TIER OF THE COUNTRY. ONE WEAK SYSTEM RIDING ALONG THIS FLOW
TOWARD THE PACNW ON TUE WILL BRING LIGHT PRECIP TO THE UPPER KLAMATH
RIVER BASIN AND POTENTIALLY EXTREME FAR NW CA. OTHERWISE...THE
MAJORITY OF THE REGION REMAINS DRY.
FOR THE EXTENDED PERIOD (DAYS 4 THROUGH 6)...THE MODELS DISAGREE
WITH THE STRENGTH OF A S/WV TROF EXPECTED TO SHIFT ACROSS THE PACNW
ON WEDNESDAY. THE GFS IS WEAKER AND KEEPS PRECIP FOR THE MOST PART
NORTH OF THE REGION. THE EC IS A BIT DEEPER AND SPREADS LIGHT PRECIP
ACROSS THE NORTHERN TIER OF THE REGION NEAR THE CA/ORE BORDER AND
THEN INLAND OVER FAR NORTHERN NEV. THE TREND OF THE MODELS OVER THE
PAST FEW RUNS HAS BEEN SLIGHTLY WEAKER. FOR NOW...TOOK A COMPROMISE
SOLUTION WITH THIS SYSTEM.
THEN ON THU...WAA/ISENTROPIC LIFT TYPE PRECIP WILL SET UP OVER THE
CA/ORE BORDER REGION. A WARM FRONT EXTENDING FROM A SYSTEM FROM A
SFC LOW WEST OF BC WILL CLIP THE AREA DURING THE DAYTIME HOURS ON
THU. FRI WILL BE DRY AS THE BAROCLINIC ZONE REMAINS TO THE NORTH AND
WEST.
.HYDROLOGICAL CONDITIONS...
ALL RIVERS ARE WELL BELOW MONITOR LEVELS AND EXPECTED TO STAY THAT
WAY THROUGH THE FORECAST PERIOD.
MORE INFORMATION ON THE CNRFC WEBSITE AT HTTP://WWW.CNRFC.NOAA.GOV
DRK/BW
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