Area Forecast Discussion
Issued by NWS San Diego, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KSGX 261650
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
850 AM PST MON JAN 26 2015

.SYNOPSIS...
A LOW PRESSURE SYSTEM FROM THE SOUTHWEST WILL BRING SOME LIGHT
SHOWERS AND SPRINKLES THIS MORNING...WITH INCREASE SHOWERS LATE IN
THE AFTERNOON AND EVENING OVER SOUTHERN CALIFORNIA. BEST RAINFALL
AMOUNTS WILL LIKELY OCCUR IN THE MOUNTAINS...DESERTS AND VALLEYS. A
FEW TO SEVERAL INCHES OF SNOW POSSIBLE IN THE MOUNTAINS ABOVE 7500
FOOT ELEVATION WITH THIS SYSTEM. SHOWERS DISSIPATING QUICKLY
TUESDAY...WITH SLIGHTLY WARMER WEATHER AND BETTER SUNSHINE FOR
WEDNESDAY. ANOTHER WEAK LOW PRESSURE SYSTEM FROM THE SOUTHWEST WILL
BRING A CHANCE OF SHOWERS THURSDAY INTO THE WEEKEND.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

SOME WEAK OFFSHORE FLOW IS STILL OCCURRING THIS MORNING...WITH SOME
LOCAL GUSTS IN THE 30-40 MPH RANGE. OFFSHORE PRESSURE GRADIENTS ARE
CURRENTLY DOWN TO 8.2 MB FROM SAN DIEGO TO TONOPAH...WHEREAS THEY
WERE 12.2 MB 24 HOURS AGO. EXPECT WEAK OFFSHORE WINDS TO CONTINUE
TODAY AS THE OFFSHORE PRESSURE GRADIENT WEAKENS FURTHER...WITH SOME
WARMER THAN NORMAL TEMPERATURES POSSIBLE AT THE COAST DESPITE THE
INCREASED CLOUD COVER.

CURRENT WATER VAPOR IMAGERY SHOWS A DEFORMATION ZONE STRETCHING FROM
OFF THE COAST OF CENTRAL CALIFORNIA INTO SOUTHERN CALIFORNIA AND
ARIZONA...WITH A CUT-OFF UPPER LEVEL LOW TO THE SOUTHWEST OF SAN
DIEGO AND AN UPPER RIDGE TO THE NORTHEAST. IT IS EVIDENT THAT THE
LOW IS SPINNING UP MOISTURE INTO THE AREA FROM THE SOUTHEAST THIS
MORNING...BUT MOST OF IT IS IN THE MID AND HIGH LEVELS OF THE
ATMOSPHERE. ACCORDING TO THE 12Z MIRAMAR SOUNDING...MOST OF THE
MOISTURE IS ABOVE 550 MB...AND SO THE ONLY PLACES THAT HAVE REPORTED
MEASURABLE RAINFALL HAVE BEEN MAINLY IN THE HIGHER ELEVATIONS OF THE
MOUNTAINS DUE TO THE RAIN NOT HAVING AS MUCH TIME TO EVAPORATE IN
THE DRY LOW LAYERS BEFORE REACHING THE SURFACE. THE LOW IS STILL ON
TRACK TO MOVE NORTH AND WEAKEN TODAY AND THEN DEVELOP INTO AN OPEN
WAVE AS IT MOVES INTO SOUTHERN CALIFORNIA TONIGHT...BEFORE MOVING
OUT OF THE AREA ON TUESDAY. AS MORE MOISTURE STREAMS IN FROM THE
SOUTHEAST...EVENTUALLY THE LOWER LAYERS WILL SATURATE AS
WELL...RESULTING IN BETTER RAINFALL ACCUMULATIONS PARTICULARLY FOR
THE LOW ELEVATIONS. RADAR IMAGERY SHOWS MOSTLY LIGHT RETURNS
ASSOCIATED WITH THE AFOREMENTIONED DEFORMATION ZONE OVER THE
NORTHERN PORTIONS OF THE FORECAST AREA...WITH SOME LIGHT
SHOWERS/SPRINKLES MOVING UP FROM SOUTH OF THE BORDER. RAINFALL
AMOUNTS FOR THE MOUNTAINS ARE EXPECTED TO RANGE FROM ONE HALF TO ONE
INCH WITH LOCALLY GREATER AMOUNTS WITH ONE THIRD INCH OR LESS IN THE
DESERTS AND INLAND VALLEYS WITH LESSER AMOUNTS TOWARD THE COAST. THE
13Z HRRR COMPOSITE REFLECTIVITY INITIALIZED WELL...AND ACTUALLY
SHOWS THE FORECAST AREA REMAINING MOSTLY DRY THROUGH EARLY AFTERNOON
BEFORE THE MAIN AREA OF PRECIPITATION MOVES INTO THE AREA FROM THE
SOUTH THIS EVENING. IT IS ALSO INTERESTING TO NOTE THAT THE CANSAC
WRF...LOCAL WRF AND NAM4 HAVE ALL NOTICEABLY BACKED OFF ON THE
RAINFALL AMOUNTS WITH THIS SYSTEM COMPARED TO WHAT THEY SHOWED
YESTERDAY. THUS...THE CURRENT POPS AND QPF MAY BE OVERDONE. THE WARM
NATURE OF THE STORM WILL KEEP SNOW LEVELS HIGH...FALLING TO
7500-8000 FEET THIS EVENING...WITH A FEW TO SEVERAL INCHES OF SNOW
POSSIBLE ABOVE THOSE ELEVATIONS. A WINTER WEATHER ADVISORY HAS BEEN
ISSUED FOR THE SAN BERNARDINO AND RIVERSIDE COUNTY MOUNTAINS ABOVE
7500 FOOT ELEVATION. FINALLY...LOOKING AT THE BUFKIT FORECAST
SOUNDINGS FROM LOCAL WRF AND NAM4...DO NOT SEE MUCH IN THE WAY OF
INSTABILITY. HOWEVER...WITH A VORT MAX MOVING THROUGH THIS EVENING
IN COINCIDENCE WITH SOME COLD AIR ALOFT ASSOCIATED WITH THE LOW...A
LIGHTNING STRIKE OR TWO AND SOME HEAVIER DOWNPOURS CANNOT BE RULED
OUT...PARTICULARLY FOR THE COASTAL WATERS AND COAST.

SHOWERS WILL DISSIPATE QUICKLY TUESDAY MORNING AS THE TROUGH MOVES
NORTH OF THE AREA. WITH THE CONTINUED CLOUD COVER AND LOWER 850 MB
TEMPERATURES...THERE SHOULD BE SOME COOLING FOR TUESDAY. SLIGHTLY
WARMER WITH BETTER SUNSHINE ON WEDNESDAY WITH SOME WEAK HIGH
PRESSURE ALOFT MOVING OVER THE REGION. THEN MODELS CONTINUE TO SHOW
ANOTHER TROUGH MOVING INLAND OVER SOUTHERN CALIFORNIA THURSDAY AND
FRIDAY...MOVING SOUTHEAST ACROSS SOUTHEAST CALIFORNIA/ARIZONA/BAJA
MEXICO SATURDAY...AND THEN SOUTH INTO LOWER BAJA MEXICO ON SUNDAY.
MODELS DIFFER AS TO THE AMOUNT OF MOISTURE AND PRECIPITATION...WITH
THE 12Z GFS MOSTLY DRY...AND THE 00Z ECMWF SOMEWHAT WET. WITH LOW
CONFIDENCE DUE TO THESE DIFFERENCES...THE SLIGHT CHANCE TO CHANCE
OF SHOWERS CURRENTLY IN THE FORECAST FOR THAT TIME SEEM REASONABLE.

&&

.AVIATION...
261630Z...BKN-OVC080-120 LOWERING TO 050-080 THIS AFTERNOON AND
EVENING WITH INCREASING CHANCES FOR LIGHT SHOWERS. RAIN SHOWERS WILL
BE MOST WIDESPREAD OVER THE MOUNTAINS AND DESERTS FROM 22-06Z...WITH
LCL OVC040-060 IN HEAVIER SHOWERS. SHOWERS MOVING FROM SOUTH TO
NORTH OVERNIGHT AND ENDING EARLY TUESDAY.

&&

.MARINE...
830 AM...THERE IS A SLIGHT CHANCE FOR A THUNDERSTORM OVER THE
COASTAL WATERS LATE THIS AFTERNOON AND EVENING.

TUESDAY THROUGH FRIDAY...NO HAZARDOUS MARINE WEATHER IS EXPECTED
THROUGH FRIDAY.

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT PST
     TONIGHT ABOVE 7500 FEET FOR THE SAN BERNARDINO COUNTY
     MOUNTAINS.

PZ...NONE.

&&

$$

PUBLIC...HARRISON
AVIATION/MARINE...MOEDE




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.