Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 291733
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
933 AM PST THU JAN 29 2015

.SYNOPSIS...
A SLOW-MOVING DISTURBANCE WILL GENERATE RAIN AND HIGH ELEVATION
SNOW AT TIMES LATER TODAY THROUGH SATURDAY...WITH THE MOST
WIDESPREAD PRECIPITATION OCCURRING FRIDAY AFTERNOON THROUGH FRIDAY
NIGHT. WARMER AND DRY NEXT WEEK WITH HIGH PRESSURE ALOFT AND WEAK
TO LOCALLY MODERATE OFFSHORE FLOW.

&&

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

AT 9 AM PST...WATER VAPOR SATELLITE IMAGERY DISPLAYED AN UPPER-LEVEL
LOW AROUND 350 MILES SW OF SAN DIEGO. THE 29/1200 UTC KNKX SOUNDING
DISPLAYED MOSTLY SOUTHWESTERLY FLOW ALONG THE COLUMN...AND WEAK EAST
TO SOUTHEASTERLY FLOW BELOW 14000 FT. VISIBLE SATELLITE DISPLAYED
WIDESPREAD MID AND HIGH LEVEL CLOUDS STREAMING OVER THE AREA. HIGHS
TODAY WILL BE AROUND 5 DEGREES F ABOVE NORMAL...WITH OVERCAST SKIES.

THE AFOREMENTIONED UPPER-LEVEL LOW WILL CONTINUE NORTHEAST THROUGH
FRIDAY AFTERNOON...STALL OVER THE REGION LATE FRIDAY THROUGH EARLY
SATURDAY AND TRACK SOUTH OUT OF THE AREA BY SATURDAY NIGHT. WEAK
UPPER-LEVEL INSTABILITY AND FORECAST PRECIPITABLE WATER VALUES JUST
UNDER AN INCH WILL YIELD SCATTERED LIGHT TO MODERATE SHOWERS LATER
TODAY THROUGH SATURDAY. LOCALLY HEAVY SHOWERS WILL BE
POSSIBLE...MAINLY OVER THE MOUNTAINS. THE 29/0000 UTC ECMWF AND
29/1200 UTC GFS ARE IN BETTER AGREEMENT WITH TIMING OF THE PRECIP.
HOWEVER...THE GFS CONTINUES TO FORECAST AROUND DOUBLE THE STORM
TOTAL AMOUNTS COMPARED TO THE ECMWF/GEM/NAM. THE MORE LIKELY RESULT
WILL BE VALUES BETWEEN THE SOLUTIONS. GREATEST COVERAGE OF PRECIP
WILL BE FRIDAY AFTERNOON INTO FRIDAY EVENING AS WE HAVE WRAP-AROUND
MOISTURE AND NORTH TO NORTHEASTERLY FLOW AROUND THE LOW. OROGRAPHICS
WILL HELP INCREASE PRECIPITATION AMOUNTS ALONG NORTHEASTERLY DESERT
MOUNTAIN SLOPES. SNOW LEVELS WILL BE AROUND 7500 FT THIS
EVENING...AND LOWER TO AROUND 6500 FT BY FRIDAY NIGHT. HIGH
TEMPERATURES WILL LOWER TO NEAR TO OR SLIGHTLY BELOW NORMAL FRI AND
SAT. LOCALLY WINDY OFFSHORE WINDS WILL DEVELOP SATURDAY NIGHT
THROUGH AND BELOW MOUNTAIN PASSES AND CANYONS.

...FORECAST PRECIPITATION AMOUNTS TODAY-SAT...
COAST...0.05 TO 0.10 IN...LOCAL 0.20 IN
DESERTS...0.10 TO 0.25 IN...LOCAL 0.45 IN
VALLEYS...0.10 TO 0.30 IN...LOCAL 0.50 IN
MOUNTAINS...0.30 TO 0.80 IN...LOCAL 1.00 IN

...FORECAST SNOW AMOUNTS TODAY-SAT...
6500-7000 FT...T TO 3 IN
7000-8000 FT...3 TO 5 IN
ABOVE 8000 FT...UP TO 6 IN

UPPER-LEVEL HIGH PRESSURE WILL SLOWLY BUILD OVER THE REGION SUNDAY
THROUGH MID NEXT WEEK. THIS...COMBINED WITH WEAK OFFSHORE
FLOW...WILL RAISE HIGH TEMPERATURES TO 5 TO 10 DEGREES F ABOVE
NORMAL SUNDAY AND MONDAY. WEAKENING OFFSHORE FLOW AND A RETURN OF
THE SEABREEZE ALONG THE COAST WILL LOWER COASTAL HIGHS TO NEAR
NORMAL TUESDAY...WITH SLIGHTLY WARMER HIGHS DEVELOPING ON
WEDNESDAY.

&&

.AVIATION...
291610Z...COAST/VALLEYS...VFR WITH UNRESTRICTED VIS THROUGH 00Z.
WIDESPREAD CIGS AOA FL100...LOWERING AFTER 18Z WITH LAYERS TO 6000
FT AFT 00Z. A MARINE STRATUS LAYER BETWEEN 1500 AND 2500 FT MSL
WILL DEVELOP 03Z THROUGH 09Z THIS EVENING AND SPREAD INLAND
THROUGH FRI MORNING. AREAS OF 3-5SM VIS WITH SCATTERED LIGHT RAIN
SHOWERS ARE LIKELY BY 12Z FRI...BECOMING MORE NUMEROUS THROUGH 18Z
FRI.

MTNS...VFR WITH CIGS AOA FL100 AND UNRESTRICTED VIS THROUGH 00Z.
CIGS LOWERING AND OBSCURING THE MTS AFT 03Z THROUGH 09Z FRI WITH
SCATTERED LIGHT RAIN SHOWERS DEVELOPING AFT 09Z. FRI...MTS
OCCASIONALLY OBSCURED IN SHOWERS WITH FREEZING CONDITIONS AND SNOW
LIKELY ABOVE 6800 FT.

DESERTS...VFR WITH CIGS AOA FL100 AND UNRESTRICTED VIS THROUGH 06Z
FRI...CIGS GRADUALLY LOWERING TO NEAR 5000 FT 18Z FRI THROUGH 00Z
SAT WITH LOCAL VIS 5-6SM IN SCATTERED RAIN SHOWERS.

&&

.MARINE...
810 AM....NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH MONDAY.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...JJT
AVIATION/MARINE...JAD






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