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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