000
FXUS66 KSGX 121633
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
930 AM PDT SUN JUL 12 2020

.SYNOPSIS...
TODAY WILL BE ANOTHER HOT DAY WITH RECORD HIGH TEMPERATURES LIKELY 
IN A FEW AREAS. MOISTURE ALOFT WILL BRING OCCASIONAL HIGH CLOUDS 
THIS AFTERNOON ALONG WITH A SLIGHT CHANCE FOR SHOWERS, MAINLY OVER 
THE MOUNTAINS. COOLING WILL SPREAD INLAND ON MONDAY AND TUESDAY AS 
THE HIGH ALOFT WEAKENS, ONSHORE FLOW INCREASES AND THE MARINE LAYER 
DEEPENS. SEASONAL SUMMER WEATHER WILL PREVAIL NEXT WEEK AS A WEAK 
TROUGH SETS UP ALONG THE WEST COAST. 

&&

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

TEMPERATURES SO FAR THIS MORNING ARE ON PACE TO REACH THE SAME 
LEVELS AS YESTERDAY, PERHAPS EVEN HIGHER IN THE DESERTS WHERE 
THERMAL WAS ALREADY 101 AT 9 AM (6 DEGREES HIGHER THAN 24 HOURS 
PREVIOUS). THE MAIN REASON FOR THE RAPID DESERT WARMUP IS THAT THE 
AIRMASS IS MUCH DRIER THAN YESTERDAY, WITH DRY NORTHWEST WINDS 
LOWERING DEWPOINTS INTO THE 30S AND 40S. DEWPOINTS WILL INCREASE 
ONCE THE WINDS SHIFT SOUTHEAST IN USUAL DIURNAL FASHION, BUT THIS 
WARM START WILL BRING AN EXTREMELY HOT DAY TO THE LOWER DESERTS, 
PERHAPS AS HIGH AS 120 IN SOME SPOTS.  

HERE ARE SOME RECORD HIGHS THAT ARE WITHIN REACH TODAY:

NEWPORT BEACH (82)
SAN DIEGO (85)
BIG BEAR (91)
ANAHEIM (98)
RAMONA (99)
ALPINE (101)
RIVERSIDE (107)
BORREGO (116)
PALM SPRINGS (120)
THERMAL (120)

DEBRIS CLOUDS FROM OVERNIGHT CONVECTION OVER SONORA ARE NOT AS 
WIDESPREAD AS YESTERDAY AND THE THREAT FOR SHALLOW HIGH-BASED 
CONVECTION IS LOW. 

*FROM PREVIOUS DISCUSSION*

ANOTHER WEAK IMPULSE DRIFTING NW AROUND THE HIGH WILL BRING ANOTHER 
SHOT OF MOISTURE ALOFT AND A SMALL CHANCE OF SHOWERS. THE 00Z HREF 
ENSEMBLES SHOW LOW RETURN ECHOES DEVELOPING OVER THE MTS ONCE AGAIN, 
AND TIME/HEIGHT CROSS SECTIONS OF THE ATMOSPHERE SHOWS THE MOISTURE 
WILL BE ABOVE 600 MBS WITH A DRY LAYER CONTINUING BELOW TO THE SFC. 
ONCE AGAIN, IT APPEARS THE MAIN IMPACT OF THESE WOULD BE GUSTY SFC 
WINDS FROM POTENTIAL MICROBURST ACTIVITY AS THE ELEVATED CONVECTION 
INITIATES EVAPORATIVE DOWNDRAFTS. 

FORECAST TRENDS HOWEVER ARE CLEAR. THE HIGH WILL WEAKEN AND SHIFT 
SOUTH THROUGH MONDAY. THIS ACCELERATES ONSHORE FLOW, WINDING UP A 
COASTAL EDDY, WHICH IN TURN, WILL DEEPEN THE MARINE LAYER ALONG THE 
COAST AND SPREAD COOLING INLAND. NOTICEABLE COOLING WILL BE FELT ON 
MONDAY OVER AND WEST OF THE MTS, AND SOMEWHAT INTO THE HIGH DESERTS, 
REACHING INTO THE LOWER DESERTS BY TUESDAY. 

FOR NEXT WEEK, STRONG UPPER-LEVEL RIDGES ARE IN PLACE OVER THE 
EASTPAC AND THE SOUTHERN PLAINS STATES, LEAVING A WEAK TROUGH 
POSITION PREVAILING ALONG THE WEST COAST. THIS MAINTAINS ONSHORE 
FLOW AND A SHALLOW MARINE LAYER OVER SOCAL. THE PATTERN RETROGRADES 
LATE IN THE WEEK INTO NEXT WEEKEND, RESULTING IN WARMING BUT STILL 
MOSTLY DRY WITH SW FLOW ALOFT. 

&&

.AVIATION... 
121535Z...COAST...MOSTLY CLEAR FOR THE MORNING WITH SCT-BKN CLOUDS 
15-25K FT MSL APPROACHING FROM THE SOUTH WILL STICK AROUND THIS 
AFTERNOON INTO THIS EVENING. A COASTAL EDDY WILL SLOWLY SPIN UP 
BRINING IN LOW CLOUDS MORE WIDESPREAD IN COVERAGE TONIGHT. 
CONFIDENCE ON COVERAGE IS HIGH, BUT TIMING A LITTLE LESS SO. LOOKING 
LIKE LOW CLOUDS COULD MAKE IT TO VCTY KSAN 07-09Z, AND CLOSER TO 10-
12Z NEAR KSNA. BASES A FEW HUNDRED FEET HIGHER THAN THIS MORNING 
WITH CLEARING BY 15-17Z MONDAY MORNING.  

VALLEYS/MOUNTAINS/DESERTS...FEW-SCT CLOUDS AOA 15000 FT MSL AND 
UNRESTRICTED VIS THROUGH TONIGHT. A FEW CU/ISO TCU WITH BASES NEAR 
8000 FT MSL MAY DEVELOP OVER THE MOUNTAIN RIDGES THIS AFTERNOON, 
DISSIPATING IN THE EVENING.

&&

.MARINE...
SLIGHT CHANCE OF PATCHY FOG OVER THE COASTAL WATERS TONIGHT MORNING, 
WITH VISIBILITY NEAR 1 MILE. NW WINDS WILL STRENGTHEN THIS AFTERNOON 
AND EVENING OVER THE OUTER WATERS, BUT GUSTS ARE EXPECTED TO REMAIN 
BELOW 20 KTS. OTHERWISE, NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED 
THROUGH FRIDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...EXCESSIVE HEAT WARNING UNTIL 8 PM PDT MONDAY FOR APPLE AND 
     LUCERNE VALLEYS-COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS-
     SAN GORGONIO PASS NEAR BANNING.

     HEAT ADVISORY UNTIL 8 PM PDT THIS EVENING FOR ORANGE COUNTY 
     INLAND AREAS-RIVERSIDE COUNTY MOUNTAINS-SAN BERNARDINO 
     COUNTY MOUNTAINS-SAN BERNARDINO AND RIVERSIDE COUNTY 
     VALLEYS-THE INLAND EMPIRE-SAN DIEGO COUNTY MOUNTAINS-SAN 
     DIEGO COUNTY VALLEYS-SANTA ANA MOUNTAINS AND FOOTHILLS.

PZ...NONE.

&&

$$

PUBLIC...MOEDE
PREVIOUS DISCUSSION...10
AVIATION/MARINE...APR

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