Area Forecast Discussion
FXUS66 KSGX [San Diego/WFO CA] 271554 AFDSGX ∨
FXUS66 KSGX 271554 AFDSGX [HEAD]
National Weather Service San Diego California 8:54am PDT Mon Mar 27 2023 ∨
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 854 AM PDT MON MAR 27 2023 [HEAD]
Synopsis. Locally gusty offshore winds will continue across the coastal slopes this morning before weakening through this afternoon. Warmer west of the mountains today with slight cooling in the mountains and deserts. Onshore winds return on Tuesday, with cooling for the coast and valleys and warming for the mountains and deserts. The next storm system will lead to periods of gusty winds Tuesday through Thursday and the potential for widespread, though generally light to moderate precipitation in two rounds: the first occurring late Tuesday night into Wednesday, and the second late Wednesday night through Thursday. For the second round of precipitation, snow levels will fall, with accumulations above 5000 feet expected. Warmer for Friday into next weekend, but with high temperatures for next weekend mostly 5–10° below average. ∨
.SYNOPSIS... LOCALLY GUSTY OFFSHORE WINDS WILL CONTINUE ACROSS THE COASTAL SLOPES THIS MORNING BEFORE WEAKENING THROUGH THIS AFTERNOON. WARMER WEST OF THE MOUNTAINS TODAY WITH SLIGHT COOLING IN THE MOUNTAINS AND DESERTS. ONSHORE WINDS RETURN ON TUESDAY, WITH COOLING FOR THE COAST AND VALLEYS AND WARMING FOR THE MOUNTAINS AND DESERTS. THE NEXT STORM SYSTEM WILL LEAD TO PERIODS OF GUSTY WINDS TUESDAY THROUGH THURSDAY AND THE POTENTIAL FOR WIDESPREAD, THOUGH GENERALLY LIGHT TO MODERATE PRECIPITATION IN TWO ROUNDS: THE FIRST OCCURRING LATE TUESDAY NIGHT INTO WEDNESDAY, AND THE SECOND LATE WEDNESDAY NIGHT THROUGH THURSDAY. FOR THE SECOND ROUND OF PRECIPITATION, SNOW LEVELS WILL FALL, WITH ACCUMULATIONS ABOVE 5000 FEET EXPECTED. WARMER FOR FRIDAY INTO NEXT WEEKEND, BUT WITH HIGH TEMPERATURES FOR NEXT WEEKEND MOSTLY 5 TO 10 DEGREES BELOW AVERAGE. [DISC]
Discussion. For extreme southwestern California including Orange… San Diego… western Riverside and southwestern San Bernardino Counties. ∨
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... [DISC]
Transient, weak ridging is building over the southwest this morning. The 12Z [5am PDT] miramar sounding showed weak offshore flow from the surface through about 800 mb; weak to locally moderate offshore winds are occurring, with the strongest winds near 50 mph reported at Fremont canyon (Orange County) and Marshall Peak (San Bernardino County). Offshore winds will peak through the next few hours before diminishing through this afternoon and evening, and turning back onshore on Tuesday. ∨
TRANSIENT, WEAK RIDGING IS BUILDING OVER THE SOUTHWEST THIS MORNING. THE 12Z MIRAMAR SOUNDING SHOWED WEAK OFFSHORE FLOW FROM THE SURFACE THROUGH ABOUT 800 MB; WEAK TO LOCALLY MODERATE OFFSHORE WINDS ARE OCCURRING, WITH THE STRONGEST WINDS NEAR 50 MPH REPORTED AT FREMONT CANYON (ORANGE COUNTY) AND MARSHALL PEAK (SAN BERNARDINO COUNTY). OFFSHORE WINDS WILL PEAK THROUGH THE NEXT FEW HOURS BEFORE DIMINISHING THROUGH THIS AFTERNOON AND EVENING, AND TURNING BACK ONSHORE ON TUESDAY. [DISC]
Perhaps the most noticeable element of the offshore winds will be the warming temperatures west of the mountains today. Highs will reach the upper-60s to low-70s for the coast and valleys through the inland empire. Temperatures will actually cool a few degrees for the mountains and deserts today though, with highs ranging 10–20° below seasonal normals. For Tuesday, temperatures will cool a few degrees for the coast and valleys, but will warm about 5–10° across the mountains and deserts. ∨
PERHAPS THE MOST NOTICEABLE ELEMENT OF THE OFFSHORE WINDS WILL BE THE WARMING TEMPERATURES WEST OF THE MOUNTAINS TODAY. HIGHS WILL REACH THE UPPER-60S TO LOW-70S FOR THE COAST AND VALLEYS THROUGH THE INLAND EMPIRE. TEMPERATURES WILL ACTUALLY COOL A FEW DEGREES FOR THE MOUNTAINS AND DESERTS TODAY THOUGH, WITH HIGHS RANGING 10 TO 20 DEGREES BELOW SEASONAL NORMALS. FOR TUESDAY, TEMPERATURES WILL COOL A FEW DEGREES FOR THE COAST AND VALLEYS, BUT WILL WARM ABOUT 5 TO 10 DEGREES ACROSS THE MOUNTAINS AND DESERTS. [DISC]
Previous discussion (issued 4:17am PDT Monday Mar 27 2023). ∨
PREVIOUS DISCUSSION (ISSUED 417 AM PDT MON MAR 27 2023)... [DISC]
Short term (today through Wednesday)… offshore flow will peak this morning, then weaken through the afternoon. There will be periods of gusty east to northeast winds along and below the coast slopes of the mountains this morning, diminishing through the afternoon. The strongest HREF gusts at the 75th percentile are around 50 mph below the cajon pass at 8am and otherwise to around 45 mph. At the 90th percentile, the stronger gusts below the cajon pass are to around 50 mph between 4am and 9am. ∨
.SHORT TERM (TODAY THROUGH WEDNESDAY)... OFFSHORE FLOW WILL PEAK THIS MORNING, THEN WEAKEN THROUGH THE AFTERNOON. THERE WILL BE PERIODS OF GUSTY EAST TO NORTHEAST WINDS ALONG AND BELOW THE COAST SLOPES OF THE MOUNTAINS THIS MORNING, DIMINISHING THROUGH THE AFTERNOON. THE STRONGEST HREF GUSTS AT THE 75TH PERCENTILE ARE AROUND 50 MPH BELOW THE CAJON PASS AT 8 AM AND OTHERWISE TO AROUND 45 MPH. AT THE 90TH PERCENTILE, THE STRONGER GUSTS BELOW THE CAJON PASS ARE TO AROUND 50 MPH BETWEEN 4 AM AND 9 AM. [DISC]
High temperatures for the coast and valleys today will be 5–10° warmer than Sunday, into the lower to mid 70s in the warmer locations from the western valleys into inland coastal areas. With lower-level cold advection from the Great Basin, the lower deserts will be a few degrees cooler than Sunday. ∨
HIGH TEMPERATURES FOR THE COAST AND VALLEYS TODAY WILL BE 5 TO 10 DEGREES WARMER THAN SUNDAY, INTO THE LOWER TO MID 70S IN THE WARMER LOCATIONS FROM THE WESTERN VALLEYS INTO INLAND COASTAL AREAS. WITH LOWER-LEVEL COLD ADVECTION FROM THE GREAT BASIN, THE LOWER DESERTS WILL BE A FEW DEGREES COOLER THAN SUNDAY. [DISC]
Onshore flow will return and strengthen for Tuesday and Tuesday night ahead of a low pressure system moving southward and intensifying well off the Pacific Northwest coast. Southwest to west winds will strengthen in the mountains and deserts with the stronger gusts to around 55 mph. ∨
ONSHORE FLOW WILL RETURN AND STRENGTHEN FOR TUESDAY AND TUESDAY NIGHT AHEAD OF A LOW PRESSURE SYSTEM MOVING SOUTHWARD AND INTENSIFYING WELL OFF THE PACIFIC NORTHWEST COAST. SOUTHWEST TO WEST WINDS WILL STRENGTHEN IN THE MOUNTAINS AND DESERTS WITH THE STRONGER GUSTS TO AROUND 55 MPH. [DISC]
Stratiform precipitation will spread southward across the area for late Tuesday night into Wednesday. Values of integrated water vapor transport may increase to around 250–300 for a less than 12 hour period centered around early Wednesday morning with snow levels rising to 5500–6500 feet. These IVT [GFS Integrated Water Vapor Transport ] values are about half as much and of much shorter duration than recent atmospheric river events. ∨
STRATIFORM PRECIPITATION WILL SPREAD SOUTHWARD ACROSS THE AREA FOR LATE TUESDAY NIGHT INTO WEDNESDAY. VALUES OF INTEGRATED WATER VAPOR TRANSPORT MAY INCREASE TO AROUND 250 TO 300 FOR A LESS THAN 12 HOUR PERIOD CENTERED AROUND EARLY WEDNESDAY MORNING WITH SNOW LEVELS RISING TO 5500 TO 6500 FEET. THESE IVT VALUES ARE ABOUT HALF AS MUCH AND OF MUCH SHORTER DURATION THAN RECENT ATMOSPHERIC RIVER EVENTS. [DISC]
Long term (Wednesday night through Sunday)… the snow level will lower to 3500–4000 feet on Wednesday night and fluctuate around 4500 feet on Thursday. The precipitation will be more showery for Wednesday night and Thursday with a slight chance of thunderstorms for late Wednesday night into Thursday morning. ∨
.LONG TERM (WEDNESDAY NIGHT THROUGH SUNDAY)... THE SNOW LEVEL WILL LOWER TO 3500 TO 4000 FEET ON WEDNESDAY NIGHT AND FLUCTUATE AROUND 4500 FEET ON THURSDAY. THE PRECIPITATION WILL BE MORE SHOWERY FOR WEDNESDAY NIGHT AND THURSDAY WITH A SLIGHT CHANCE OF THUNDERSTORMS FOR LATE WEDNESDAY NIGHT INTO THURSDAY MORNING. [DISC]
Through Thursday for Orange and southwestern San Bernardino Counties, rainfall is expected to range from around one-half inch near the coast to 1–1.5 inches in the mountains with locally greater amounts. For San Diego and western Riverside Counties, rainfall is expected to range from around one-half inch near the coast to one-half to one inch in the mountains. Rainfall of one-quarter inch or less for the high deserts and one-tenth inch or less for the lower deserts. Snowfall is expected to range from 3–6 inches from 5000–6500 feet with snowfall of 6–10 inches from 6500–7500 feet and with local amounts of 10–14 inches on the higher peaks. ∨
THROUGH THURSDAY FOR ORANGE AND SOUTHWESTERN SAN BERNARDINO COUNTIES, RAINFALL IS EXPECTED TO RANGE FROM AROUND ONE-HALF INCH NEAR THE COAST TO 1 TO 1.5 INCHES IN THE MOUNTAINS WITH LOCALLY GREATER AMOUNTS. FOR SAN DIEGO AND WESTERN RIVERSIDE COUNTIES, RAINFALL IS EXPECTED TO RANGE FROM AROUND ONE-HALF INCH NEAR THE COAST TO ONE-HALF TO ONE INCH IN THE MOUNTAINS. RAINFALL OF ONE- QUARTER INCH OR LESS FOR THE HIGH DESERTS AND ONE-TENTH INCH OR LESS FOR THE LOWER DESERTS. SNOWFALL IS EXPECTED TO RANGE FROM 3 TO 6 INCHES FROM 5000 TO 6500 FEET WITH SNOWFALL OF 6 TO 10 INCHES FROM 6500 TO 7500 FEET AND WITH LOCAL AMOUNTS OF 10 TO 14 INCHES ON THE HIGHER PEAKS. [DISC]
High temperatures will be much cooler for Wednesday and Thursday. Thursday is expected to be the coolest day with high temperatures for the mountains as much as 20–25° below average. ∨
HIGH TEMPERATURES WILL BE MUCH COOLER FOR WEDNESDAY AND THURSDAY. THURSDAY IS EXPECTED TO BE THE COOLEST DAY WITH HIGH TEMPERATURES FOR THE MOUNTAINS AS MUCH AS 20 TO 25 DEGREES BELOW AVERAGE. [DISC]
Drying and warming for Friday into the weekend, but with weekend high temperatures still mostly 5–10° below average. Chances for precipitation could return by early next week. ∨
DRYING AND WARMING FOR FRIDAY INTO THE WEEKEND, BUT WITH WEEKEND HIGH TEMPERATURES STILL MOSTLY 5 TO 10 DEGREES BELOW AVERAGE. CHANCES FOR PRECIPITATION COULD RETURN BY EARLY NEXT WEEK. [DISC]
Aviation. 271530Z [8:15pm PDT]… mostly clear skies with unrestricted visibility will prevail through this evening. ∨
.AVIATION... 271530Z...MOSTLY CLEAR SKIES WITH UNRESTRICTED VIS WILL PREVAIL THROUGH THIS EVENING. [AVIA]
Gusty northeast winds will continue this morning, impacting sna/Ontario/SBD [San Bernardino CA] into this afternoon. Strongest gusts will remain over ridgelines, below passes and through wind-prone canyons where gusts of 40–50 kts [46–58 mph] are expected. Moderate to strong up/downdrafts and low-level wind shear expected over/west of the mountains. ∨
GUSTY NORTHEAST WINDS WILL CONTINUE THIS MORNING, IMPACTING SNA/ONT/SBD INTO THIS AFTERNOON. STRONGEST GUSTS WILL REMAIN OVER RIDGELINES, BELOW PASSES AND THROUGH WIND-PRONE CANYONS WHERE GUSTS OF 40-50 KTS ARE EXPECTED. MODERATE TO STRONG UP/DOWNDRAFTS AND LLWS EXPECTED OVER/WEST OF THE MOUNTAINS. [AVI2]
Marine. No hazardous marine conditions are expected through Tuesday. An incoming storm system will bring rain and gusty winds Wednesday and Thursday. ∨
.MARINE... NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH TUESDAY. AN INCOMING STORM SYSTEM WILL BRING RAIN AND GUSTY WINDS WEDNESDAY AND THURSDAY. [AVIA]
Skywarn… skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. ∨
.SKYWARN... SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS. [DISC]
SGX [San Diego/WFO CA] Watches/Warnings/Advisories
.SGX WATCHES/WARNINGS/ADVISORIES... CA...WIND ADVISORY UNTIL 2 PM PDT THIS AFTERNOON FOR ORANGE COUNTY INLAND AREAS-SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS- THE INLAND EMPIRE-SAN DIEGO COUNTY VALLEYS-SANTA ANA MOUNTAINS AND FOOTHILLS. [WARN]
Public: EA; Aviation/Marine: Adams ∨
PUBLIC...EA AVIATION/MARINE...ADAMS [CRED]
This Afternoon Sunny, with a high near 69°. East wind 5 to 10 mph becoming NW.
Tonight Mostly clear, with a low around 48°. East wind 5 to 10 mph.
Tuesday Sunny, with a high near 68°. Light and variable wind becoming west 5 to 10 mph in the morning. Winds could gust as high as 20 mph.
Tuesday Night Increasing clouds, with a low around 47°. West wind around 5 mph becoming calm in the evening.
Wednesday Rain likely, mainly after 11am. Mostly cloudy, with a high near 56°. South wind 5 to 15 mph becoming NW in the afternoon. Winds could gust as high as 20 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.
Wednesday Night Showers likely, mainly after 11pm. Mostly cloudy, with a low around 44°. Chance of precipitation is 60%.
Thursday Showers and possibly a thunderstorm before 11am, then a chance of showers. High near 55°. Chance of precipitation is 80%.
Thursday Night Partly cloudy, with a low around 44°.
Friday Partly sunny, with a high near 61°.
Friday Night Partly cloudy, with a low around 44°.
Saturday Sunny, with a high near 65°.
Saturday Night Mostly clear, with a low around 46°.
Sunday Partly sunny, with a high near 63°.
Sunny, with a high near 69. East wind 5 to 10 mph becoming northwest.
Mostly clear, with a low around 48. East wind 5 to 10 mph.
Sunny, with a high near 68. Light and variable wind becoming west 5 to 10 mph in the morning. Winds could gust as high as 20 mph.
Increasing clouds, with a low around 47. West wind around 5 mph becoming calm in the evening.
Rain likely, mainly after 11am. Mostly cloudy, with a high near 56. South wind 5 to 15 mph becoming northwest in the afternoon. Winds could gust as high as 20 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.
Showers likely, mainly after 11pm. Mostly cloudy, with a low around 44. Chance of precipitation is 60%.
Showers and possibly a thunderstorm before 11am, then a chance of showers. High near 55. Chance of precipitation is 80%.
Partly cloudy, with a low around 44.
Partly sunny, with a high near 61.
Partly cloudy, with a low around 44.
Sunny, with a high near 65.
Mostly clear, with a low around 46.
Partly sunny, with a high near 63.
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