231
FXUS66 KSGX 130345
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
845 PM PDT MON AUG 12 2013
.SYNOPSIS...
UPPER LEVEL TROUGH OF LOW PRESSURE WILL LINGER ALONG THE WEST COAST
THROUGH WEDNESDAY...WITH DRY SOUTHWESTERLY FLOW ALOFT PREVAILING
ACROSS SOUTHERN CALIFORNIA. COASTAL AREAS WILL CONTINUE TO SEE
NIGHT AND MORNING LOW CLOUDS AND FOG...WITH TEMPERATURES REMAINING
BELOW NORMAL. HOWEVER...HIGH PRESSURE WILL TRY TO REBUILD FOR THE
LATTER PART OF THE WORK WEEK...WITH SOME MINOR WARMING FOR THE
INLAND AREAS AND A SHALLOWER MARINE LAYER DEVELOPING. SOME
SUBTROPICAL MOISTURE MAY ALSO SPREAD INTO THE SOUTHLAND ON THURSDAY
AND FRIDAY...WITH A FEW CUMULUS BUILD UPS POSSIBLE OVER THE
MOUNTAINS. THE TROUGH THOUGH WILL THEN MOVE INLAND ACROSS THE WEST
FOR THE WEEKEND...WITH DRY AND SLIGHTLY COOLER CONDITIONS PREVAILING
ONCE AGAIN.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
WATER VAPOR IMAGERY CONTINUES TO SHOW A BROAD TROUGH OF LOW PRESSURE
OVER THE EASTERN PACIFIC THIS EVENING...WITH SEVERAL DISTURBANCES
ROTATING THROUGH THIS TROUGH. AT THIS TIME...TWO ARE MOVING INLAND
ACROSS THE WEST COAST...ONE WITH A NICE NEGATIVE TILT MOVING ACROSS
VANCOUVER ISLAND AND THE OTHER SLIGHTLY NEGATIVE NOW LIFTING ACROSS
NORTHERN CALIFORNIA AND EASTERN OREGON. THESE TWO DISTURBANCES ARE
TRIGGERING PLENTY OF THUNDERSTORMS FOR THE PACIFIC NORTHWEST.
HOWEVER...SOUTHERN CALIFORNIA REMAINS UNDER THE DRY SOUTHWESTERLY
FLOW ALOFT...WITH ANY MOISTURE SHUNTED WELL TO OUR NORTH...EAST...OR
SOUTH. IN FACT...THE 00Z KNKX SOUNDING SHOWS PRECIPITABLE WATER
VALUES DOWN TO 0.53 INCHES...WITH THE ONLY MOISTURE IN THE LAYER AT
THE SURFACE...IE...THE MARINE LAYER UP TO 1800 FEET DEEP.
THIS OVERALL PATTERN WILL NOT CHANGE MUCH OVER THE NEXT SEVERAL
DAYS...AS ANOTHER VERY IMPRESSIVE UPPER LEVEL LOW DROPPING DOWN THE
BACK SIDE OF THE BROAD TROUGH MOVES INTO POSITION OVER THE
NORTHEASTERN PACIFIC. THAT BEING SAID...THE MODELS ARE STILL
HINTING THAT HIGH PRESSURE WILL BRIEFLY TRY TO BUILD BACK ACROSS
SOUTHERN CALIFORNIA AS THIS TERTIARY LOW LIFTS TO THE NORTH AND
BEFORE THIS TROUGH MOVES INLAND THIS WEEKEND. THEREFORE...EXPECT
SOME MINOR WARMING...MAINLY FOR THE INLAND AREAS...OVER THE NEXT FEW
DAYS. THERE ARE EVEN SOME HINTS OF SOME SUBTROPICAL MOISTURE
SPREADING INTO THE REGION ON THURSDAY AND FRIDAY...BUT AS QUICKLY AS
THE FLOW TURNS SOUTHERLY TO INTRODUCE THIS MOISTURE...IT CHANGES
BACK TO SOUTHWESTERLY. THEREFORE...AM SOMEWHAT SKEPTICAL AS TO
WHETHER OR NOT THE MOUNTAINS AND DESERTS OF SOUTHERN CALIFORNIA WILL
SEE THE RETURN OF THE THUNDERSTORMS. AT THIS TIME...THINK A FEW
HIGH CLOUDS WILL BE LIKELY...ALONG WITH SOME TOWERING CUMULUS
POSSIBLE BY THE LATE AFTERNOON HOURS. MEANWHILE...COASTAL AREAS
WILL CONTINUE TO SEE NIGHT AND MORNING LOW CLOUDS AND FOG...WITH
SOME ONLY PARTIAL CLEARING POSSIBLE ALONG THE BEACHES DURING THE
AFTERNOON.
&&
.AVIATION...
130300Z...COAST/VALLEYS...WIDESPREAD LOW CLOUDS OVER THE COASTAL
WATERS MOVING ASHORE AT THIS HOUR WITH BASES AROUND 1300 FT MSL AND
TOPS NEAR 2000 FT MSL. KSAN AND KCRQ ARE ALREADY BEING
IMPACTED...AND KSNA WILL LIKELY BE IMPACTED BY 06Z. LOW CLOUDS WILL
SPREAD 15-20 MILES INLAND BY SUNRISE WITH AREAS OF VIS 3-5SM LOCALLY
BLO 1SM WHERE TERRAIN AND CLOUDS INTERSECT. LOW CLOUDS AND FOG COULD
APPROACH THE RUNWAY COMPLEX AT KONT BETWEEN 12Z AND 16Z...BUT IS
UNLIKELY TO IMPACT OPERATIONS. EXPECT CLEARING TO THE COAST BETWEEN
16Z AND 18Z BUT CLOUDS WILL LIKELY LINGER AT THE BEACHES INTO THE
AFTERNOON. LOW CLOUDS SHOULD RETURN TO COASTAL TAF SITES BETWEEN 03Z
AND 06Z WED.
MTNS/DESERTS...CLEAR WITH UNRESTRICTED VIS THROUGH TUE.
&&
.FIRE WEATHER...
VERY DRY CONDITIONS WILL CONTINUE ACROSS THE MOUNTAINS AND DESERTS
THROUGH AT LEAST WEDNESDAY...WITH SOME LOCALLY GUSTY WEST WINDS
POSSIBLE EACH AFTERNOON AND EVENING. DAYTIME HUMIDITY VALUES WILL
FALL BELOW 15 PERCENT DURING THE DAY...WITH POOR TO MODERATE
RECOVERIES AT BEST.
SOME SUBTROPICAL MOISTURE WILL SPREAD INTO SOUTHERN CALIFORNIA ON
THURSDAY AND FRIDAY. AT THIS TIME...IT APPEARS THAT ANY INSTABILITY
WILL BE MARGINAL AT BEST...AND ONLY ANTICIPATE SOME CUMULUS BUILD
UPS OVER THE MOUNTAINS THESE DAYS. IF A THUNDERSTORM DOES
DEVELOP...IT WILL BE CAPABLE OF PRODUCING DRY LIGHTNING AS WELL AS
GUSTY AND ERRATIC WINDS.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC/FIRE...PALMER
AVIATION/MARINE...PG