Area Forecast Discussion
Issued by NWS San Diego, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 010432 CCA
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
930 PM PDT THU JUL 31 2014

.SYNOPSIS...
MOISTURE FROM THE SOUTHEAST WILL INCREASE THROUGH THE WEEKEND AND
COMBINE WITH LOW PRESSURE ALOFT TO BRING SHOWERS AND THUNDERSTORMS
AT TIMES TO THE MOUNTAINS AND DESERTS. SOME THUNDERSTORMS COULD EVEN
OCCUR NEAR THE COAST...ESPECIALLY SATURDAY THROUGH SUNDAY.
TEMPERATURES WILL BE A LITTLE LOWER THE NEXT FEW DAYS...THOUGH
HUMIDITIES WILL BE HIGHER. THE LOW PRESSURE SYSTEM WILL MOVE
NORTHEAST OUT OF THE AREA EARLY NEXT WEEK AND RESULT IN DRIER
WEATHER. AREAS OF LOW CLOUDS AND FOG WILL OCCUR NEAR THE COAST MOST
NIGHTS AND MORNINGS THROUGH THE MIDDLE OF NEXT WEEK.

&&

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

ISOLATED THUNDERSTORMS OCCURRED NEAR BIG BEAR AND OVER THE HIGH
DESERTS OF SAN BERNARDINO COUNTY LATE THIS AFTERNOON INTO EARLY
EVENING...AND A STRAY SHOWER HIT THE SANTA ROSA MOUNTAINS OF
RIVERSIDE COUNTY. GPS MET SENSORS SHOWED SOME PRECIPITABLE WATER
INCREASES IN THE DESERTS...UP TO ABOUT 1.5 INCHES AT BORREGO EARLY
THIS EVENING. SKIES HAD BECOME MOSTLY CLEAR THIS EVENING EXCEPT FOR
THE STRATUS DEVELOPING ALONG THE IMMEDIATE COAST. WITH A MARINE
LAYER AROUND 1200 FEET DEEP AND MODERATE ONSHORE FLOW...ABOUT 7 MB
MSLP GRADIENT FROM SAN DIEGO TO IMPERIAL...THE STRATUS SHOULD COVER
QUITE A FEW COASTAL AND SOME COASTAL VALLEY LOCATIONS BY LATE
TONIGHT.

A HIGH PRESSURE RIDGE COVERED MOST OF THE WESTERN US WITH EASTERLY
FLOW ALOFT DEVELOPING ALONG THE CALIFORNIA-BAJA AND WESTERN
ARIZONA-SONORA BORDERS. AN UPPER LOW IS OVER SOUTHERN BAJA...AND THE
MODELS SHOW THAT MOVING NORTHWEST TOWARDS SOUTHERN CALIFORNIA THE
NEXT FEW DAYS. MOISTURE WILL INCREASE RATHER SUBSTANTIALLY WITH NAM
NOW SHOWING LOCALLY GREATER THAN 2 INCHES OF PRECIPITABLE WATER
SATURDAY NIGHT AND SUNDAY NOT ONLY IN THE LOWER DESERT BUT ALSO AT
THE COAST. LI VALUES DECREASE TO ZERO OR EVEN A LITTLE BELOW NEAR
THE COAST SATURDAY/SUNDAY. WITH THE HIGH PW VALUES...INSTABILITY AND
DYNAMICS WITH THE LOW...THERE IS THE POSSIBILITY OF THUNDERSTORMS
ALONG THE COAST SATURDAY/SUNDAY. WITH A CLOSED LOW LIKE
THIS...ESPECIALLY OF TROPICAL ORIGINS...MODEL CONFIDENCE ON
DETAILS...INCLUDING TIMING...IS LOW. THE ELSINORE CONVERGENCE ZONE
IN THE INLAND EMPIRE WOULD ALSO HAVE A THREAT OF THUNDERSTORMS OVER
THE WEEKEND. OF COURSE...OVER THE MOUNTAINS AND
DESERTS...INSTABILITY WILL BE GREATEST AND HENCE THE THUNDERSTORM
THREAT WILL BE HIGHEST. WITH POSSIBLE DYNAMICS OF THE LOW AND THE
RISK OF OUTFLOW BOUNDARIES MOVING OVER THE AREA...THUNDERSTORMS
COULD OCCUR OUTSIDE THE NORMAL AFTERNOONS/EARLY EVENINGS. REGARDING
ANY FLASH FLOOD RISK...THERE CERTAINLY IS SOME...THOUGH WINDS ALOFT
WITH THE LOW PRESSURE SYSTEM COULD BE HIGH ENOUGH...30+ KNOTS
SATURDAY IN SAN BERNARDINO COUNTY AT 500 MB...TO KEEP THUNDERSTORMS
MOVING. THERE IS SOME SEVERE WEATHER THREAT DUE TO SHEAR IN THE
LOW-TO-MID LEVELS ASSOCIATED WITH THE LOW PLUS AREAS OF TERRAIN
DRIVEN CONVERGENCE...SO THAT COULD CONTRIBUTE TO HAIL AND STRONG
GUSTY SURFACE WINDS...AND 00Z NAM IS ALREADY SHOWING HELICITY VALUES
OVER 200 M2/S2 IN THE 0-3 KM AGL LAYER OVER SAN BERNARDINO COUNTY
FOR SATURDAY NIGHT/SUNDAY. FUTURE SHIFTS WILL NEED TO CLOSELY WATCH
BOTH THE SEVERE WEATHER AND FLASH FLOOD THREATS FOR THE WEEKEND.

THINGS GET QUIETER STARTING MONDAY AS THE UPPER LOW MOVES NORTHEAST
OUT OF THE AREA...AND WE GET INTO DRIER WEST FLOW ALOFT. WEAK WAVES
MOVING BY TO THE NORTH NEXT WEEK SHOULD HELP DRY OUT THE ATMOSPHERE.
THUS...BY MONDAY NIGHT...THE THUNDERSTORM THREAT SHOULD BE NIL.
AREAS OF NIGHT/MORNING STRATUS SHOULD GRADUALLY EXPAND...ESPECIALLY
WITH A BROAD UPPER LOW OVER THE INTERIOR WESTERN US POSSIBLY
DEVELOPING AROUND MIDWEEK. TEMPS WILL MOSTLY BE SEASONAL DESPITE THE
ONSHORE FLOW AS LOCAL SEA SURFACE TEMPS REMAIN ABOVE NORMAL.

&&

.AVIATION...
010330Z...COASTS/VALLEYS...STRATUS WITH BASES 900-1200 FT MSL AND
TOPS 1500 FT MSL WILL PUSH INLAND 8-15 SM BETWEEN 03/0600-1530Z
TONIGHT...AFFECTING KSNA...KCRQ...KSAN. VISIBILITY MAY BE LOCALLY
REDUCED TO 1 MILE OR LESS WHERE THE CLOUDS INTERSECT THE TERRAIN ON
THE LOWER COASTAL MESAS. CONFIDENCE OF TIMING AND COVERAGE OF
STRATUS IS LOW TO MODERATE. THE LOW CLOUDS WILL ERODE TO THE BEACHES
BY 01/1530Z. MID AND HIGH LEVEL CLOUDS AT OR ABOVE 10000 FT MSL WILL
PASS OVER THE AREA THROUGH THE AFTERNOON FRIDAY. ANOTHER STRATUS
DECK...SLIGHTLY DEEPER...WILL MOVE FROM THE COAST INLAND FRIDAY
NIGHT AFT 02/0400Z.

MOUNTAINS/DESERTS...SCT CUMULUS DEVELOPMENT WITH BASES AROUND
9000 FT ABOVE MEAN SEA LEVEL AFT 01/1800Z...WITH TOPS RISING UP TO
35000 FT MSL FOR THUNDERSTORMS THAT DEVELOP OVER THE MOUNTAINOUS
TERRAIN. OTHERWISE...INCREASING HIGH CLOUDS AT OR ABOVE 10000 FT MSL.

&&

.MARINE...
900 PM PDT...NO HAZARDOUS MARINE WEATHER EXPECTED THROUGH TUESDAY.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...MAXWELL
AVIATION/MARINE...JT






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