Winter temperatures have been colder than normal so far in the Conejo and San Fernando valleys and surroundings. On December 11, most valley stations were in the mid-70s. The following 27 days were quite chilly, with the average maximum temperature around 58F from Dec. 12 to January 7 at Pierce College in Woodland Hills. December was characterized by plenty of days with measurable rainfall, as storm systems swept through Southern California from the northwest and north. There were 13 to 14 days with rain during December, about double the normal number. Around December 21, clear skies and light winds enabled early morning temperatures to drop into the mid-20s at the valley bottom cold spots, to 29F at Pierce and 32F at Van Nuys AP. Minimums this low are close to “normal” for coldest temperatures for winter.
On January 8 we were treated to a nice warmup, with max temps into the mid-70s. The mild weather was wiped out early on the 10th, though, as very cold air at mid and upper levels moved over Southern California. Temps at 700mb dropped to near -15C as far south as the Tehachapi Mountains, in northern Los Angeles County. This mid-level air had origins from way up north near the Yukon. At the surface, a low moved eastward through the Mojave Desert and into Arizona, and the flow over Southern California was west to northwest. The low-level flow off of the Pacific Ocean was chilly, and was moist enough to generate showers in some areas. Snow caused the closure of Interstate 5 over the Grapevine for much of the day. Dew points behind the front dropped into the mid-20s to around 30 in the area (Conejo and San Fernando Valley area and vicinity). The word “Arctic” has been used by some of the media to characterize the cold air invasion, and it might apply to the air aloft, but I would not use that term for this event. True Arctic air events, for coastal Southern California, are typically characterized by an extremely cold and dry and deep low-level airmass over the Great Basin area. High pressure associated with the deep and dense airmass helps to shove cold air through the Newhall and Cajon and Banning passes and into coastal sections. For this event, the true bitterly cold Arctic air remains east of the Northern Rockies and in western Canada. The low-level air over coastal Southern California on Jan 10th and 11th is maritime polar, or stretching it a bit — modified Arctic air. Back in February 1989 and December 1990 the area was treated to true Arctic air, with daytime highs in the 40s despite full sunshine (in the case of the December 22-23, 1990 event) and widespread minimums in the low-mid 20s in the western half of the San Fernando Valley.
So, how is the current cold snap shaping up temperature wise? January 11, 2013 is bright and sunny for the most part. There are a few stratocumulus and cirrus around, but these did not keep max temps down. Chatsworth managed to reach only 52F, not quite as low as the record low max temp of 50F for the date in 1971. Westlake Village/EW0033 reached only 52F, and Pierce College hit 54F.
Minimums on the morning of the Jan 11 were similar to those about 3 weeks earlier, around December 21 — low 20s at the coldest frost pockets, and 30s at the stations subject to the northwest breeze. My place here in Westlake Village had about 26.5F, and my minimum thermometer in a frost pocket in an adjacent “canyon” showed 22F. Another canyon about a mile to the east, near Westlake High School, had a minimum of 23F. Westlake Village/EW0033/Press had a chilly minimum of 24.7F around sunrise. Here is a handy list of minimum and maximum temperatures for the area for January 11, 2013:
min/max temps, January 11, Conejo Valley area stations, including unofficial valley-bottom frost pockets
Westlake Village/Northgate/Reid 26/54 (near Westlake and Hillcrest)
frost pocket just west of Northgate 22/mm (1/4 mile west of Westlake and Hillcrest)
frost pocket near Westlake High School 23/52 (Schoolhouse Canyon)
Westlake Village/EW0033/Press 25/52 (Davis weather station readout: 24.7/51.7)
Westlake Village/North Ranch/WU 30/51
Calabasas DW3850 28/58
Agoura Hills/Lobo Canyon/WU 25/51
Agoura Hills/Lost Hills/WU 29/55
Malibu Canyon/RAWS 27/58
Thousand Oaks/Lang Ranch/WU 33/50
Newbury Park DW1941 29/53
Newbury Park/WU 26/63 (Borchard and Michael, max temp too high!)
Moorpark DW0912 26/56
Simi Valley DW3685 30/52
Camarillo AP 32/57
min/max temps, January 11, western San Fernando Valley and vicinity
Woodland Hills/Pierce College 31/54 (30.5/53.8)
Woodland Hills/Gonzales Dr/WU 30/52
Woodland Hills/CW2288 30/53
Woodland Hills/CW0623 35/57 (near Warner Center)
Winnetka/WU 32/53
Chatsworth/DW0345 35/52
Northridge/CSUN 34/52 (34.0/52.3)
Encino/Hesby Oaks/WU 33/54
Van Nuys AP 34/51
Burbank AP 38/53 (breezy all night)
Studio City/DW6087 35/55
Topanga/DW5544 24/52
min/max temps, January 11, nearby hilltop stations
Cheeseboro/Agoura/RAWS 35/52 elev 1707′
Calabasas/Park Belmonte/WU 37/50 elev 1438′
Malibu/DW5145 37/44 elev 1715′
Malibu DW2363 34/44 elev 2450′
Topanga/RAWS 36/52 elev 1600′
Porter Ranch/DW4339 36/47 elev 1634′
Oat Mountain 28/36 elev 3693′
And, here is the max/min list for Thursday, Jan 11, 2013, from NWS Oxnard, and below it, from NWS San Diego:
:
HIGH TEMPERATURE PAST 12 HOURS AS OF 4PM PST TODAY
LOW TEMPERATURE PAST 18 HOURS AS OF 4PM PST TODAY
PRECIPITATION PAST 24 HOURS. M DENOTES MISSING. T DENOTES TRACE.
** DENOTES 4PM-4PM REPORTING STATION
:
.BR LAX 0111 P DH16/TAIRZS/TAIRZI/PPDRZZ
:
: ID : STATION : HIGH/ LOW / PCPN
:
: …LOS ANGELES COUNTY COAST…
:
AVNC1: AVALON HARBOR : 54 / 44 / 0.00
AIDC1: AVALON INLAND : 55 / 39 / 0.00
CVRC1: **CULVER CITY : M / 43 / 0.00
GTCC1: GETTY CENTER : 52 / 40 / 0.00
HHR : HAWTHORNE : 57 / 45 / 0.00
LAX : LA AIRPORT : 54 / 45 / 0.00
CQT : LA DOWNTOWN/USC : 56 / 44 / 0.00
LGB : LONG BEACH ARPT : 56 / 42 / 0.00
RDOC1: REDONDO BEACH : 56 / 42 / 0.00
SMO : STA MONICA ARPT : 55 / 42 / 0.00
1L2 : STA MONICA PIER : 56 / 46 / 0.00
TOAC1: TORRANCE : 54 / 45 / 0.00
UCLC1: UCLA : 54 / 42 / 0.00
:
: …LOS ANGELES COUNTY VALLEYS…
:
BUR : BURBANK : 53 / 38 / 0.00
CHTC1: CHATSWORTH : 52 / 35 / 0.00
CSUC1: NORTHRIDGE : 52 / 34 / 0.00
PSAC1: PASADENA : 55 / 42 / 0.00
POMC1: POMONA/FAIRPLEX : 54 / 32 / 0.00
JBLC1: SAN GABRIEL : 56 / 44 / 0.00
SAUC1: SAUGUS : 48 / 34 / 0.00
VNY : VAN NUYS : 51 / 34 / 0.00
WPCC1: WOODLAND HILLS : 54 / 31 / 0.00
:
:…LOS ANGELES COUNTY MOUNTAINS AND DESERTS…
:
ATNC1: ACTON : 43 / 25 / 0.00
WJF : LANCASTER : 43 / 29 / 0.00
MWSC1: MOUNT WILSON : 35 / 19 / 0.00
PMD : PALMDALE : 42 / 27 / 0.00
SDB : SANDBERG : 30 / 26 / 0.07
:
: …VENTURA COUNTY…
:
CMA : CAMARILLO : 57 / 32 / 0.00
FILC1: FILLMORE : 56 / 29 / 0.00
LOKC1: LOCKWOOD VLY YARD : 36 / 12 / 0.03
OJAC1: OJAI : 54 / 28 / 0.00
LOXC1: OXNARD – NWS : 56 / 33 / 0.00
SMVC1: SIMI VALLEY : 55 / 31 / 0.00
VTUC1: VENTURA : 57 / 37 / 0.00
:
: …SANTA BARBARA COUNTY…
:
CYMC1: NEW CUYAMA : 42 / 25 / 0.00
LPC : LOMPOC : 55 / 28 / 0.00
SBA : SBA ARPT/GOLETA : 58 / 32 / 0.00
SBSC1: SBA CITY FD : 58 / 39 / 0.00
SMX : SANTA MARIA : 53 / 30 / 0.00
IZA : SANTA YNEZ : 52 / 30 / 0.00
:
: …SAN LUIS OBISPO COUNTY…
:
HSCC1: **HEARST CASTLE : 49 / 33 / 0.00
1MB : MORRO BAY : 53 / 38 / 0.00
PRB : PASO ROBLES : 51 / 27 / 0.00
PISC1: PISMO BEACH : 54 / 38 / 0.00
1SL : PORT SAN LUIS : 53 / 40 / 0.00
SBP : SLO AIRPORT : 55 / 30 / 0.00
SBPC1: SLO – CAL POLY : 54 / 33 / 0.00
.END
Regional Max/Min Temp and Precipitation Table
000
ASUS66 KSGX 120036
RTPSGX
:SOUTHWESTERN CALIFORNIA TEMPERATURE AND PRECIPITATION SUMMARY
:NATIONAL WEATHER SERVICE SAN DIEGO CA
:430 PM PST FRI JAN 11 2013
:
:***** PRELIMINARY *****
:
:18 HOUR HIGH AND LOW TEMPERATURES AS OF 4 PM TODAY.
:PRECIPITATION FOR THE PAST 24 HOURS. M DENOTES MISSING.
: T DENOTES TRACE OF PRECIPITATION
:
.BR SGX 0111 P DH16/TAIRZS/TAIRZI/PPDRZZ/SDIRZZ
:
: ID : STATION ELEV : HIGH / LOW / PCPN / SNODEP
: FEET INCHES
:
: …COASTAL AREAS…
:
YBLC1: YORBA LINDA 350 : 57 / 33 / 0.00 /
FUL : FULLERTON AIRPORT 96 : 59 / 40 / 0.00 /
ANAC1: ANAHEIM 335 : M / M / M /
STAC1: SANTA ANA 135 : 56 / 38 / 0.00 /
SDHTB: HUNTINGTON BEACH 5 : 57 / 40 / 0.00 /
SNA : JOHN WAYNE AIRPORT 55 : 56 / 38 / 0.00 /
3L3 : NEWPORT BEACH 10 : 54 / 42 / 0.00 /
LAGC1: LAGUNA BEACH 35 : 54 / 44 / 0.00 /
SDDPC: DANA POINT 305 : 52 / 33 / 0.00 /
SDFRH: LAKE FOREST 970 : 57 / 35 / 0.00 /
L34 : OCEANSIDE HARBOR 10 : 52 / 34 / 0.00 /
OKB : OCEANSIDE AIRPORT 28 : 55 / 29 / 0.00 /
VSTC1: VISTA 330 : 52 / 30 / 0.00 /
CRQ : CARLSBAD AIRPORT 328 : 53 / 38 / 0.00 /
SDETS: ENCINITAS 270 : 53 / 37 / 0.01 /
SOL : SOLANA BEACH 75 : M / M / M /
DMRC1: DEL MAR 100 : 57 / 38 / 0.00 /
NKX : MIRAMAR 477 : 54 / 32 / 0.00 /
MYF : MONTGOMERY FIELD 420 : 53 / 41 / T /
SWDC1: SEA WORLD SAN DIEGO 10 : 53 / 41 / 0.00 /
SAN : SAN DIEGO 15 : 54 / 44 / 0.00 /
L13 : CABRILLO NATL MNMT 364 : 56 / 42 / 0.00 /
SDNAC: NATIONAL CITY 25 : M / M / M /
CVAC1: CHULA VISTA 56 : 57 / 38 / 0.00 /
NRS : IMPERIAL BEACH 23 : 54 / 39 / 0.00 /
SDM : BROWN FIELD 525 : 53 / 39 / T /
:
: …INLAND AREAS…
:
ONT : ONTARIO 943 : 53 / 32 / 0.00 /
CNO : CHINO 652 : 54 / 25 / 0.00 /
SDALO: RANCHO CUCAMONGA 1940 : 50 / 32 / 0.00 /
SDSBO: SAN BERNARDINO 1050 : 52 / 34 / 0.00 /
AJO : CORONA 531 : M / M / M /
RAL : RIVERSIDE AIRPORT 818 : 53 / 32 / 0.00 /
UCRC1: RIVERSIDE 986 : 55 / 31 / 0.00 /
RIV : RIVERSIDE MARCH 1542 : 50 / 22 / 0.00 /
BUO : BEAUMONT 2680 : 45 / 30 / M /
EORC1: ELSINORE 1285 : 53 / 28 / 0.00 /
HEMC1: HEMET 1811 : 48 / 29 / 0.00 /
SDTEC: TEMECULA 1020 : 56 / 30 / 0.00 /
SDFBK: FALLBROOK 680 : 54 / 33 / 0.00 /
SDSMP: SAN MARCOS 630 : 53 / 38 / 0.00 /
ESCC1: ESCONDIDO 645 : M / M / M /
PSQC1: SAN PASQUAL VALLEY 255 : 54 / 26 / 0.00 /
RNM : RAMONA AIRPORT 1393 : 50 / 24 / T /
SGX : RANCHO BERNARDO 690 : 53 / 30 / 0.00 /
POWC1: POWAY 648 : 53 / 31 / 0.00 /
ALPC1: ALPINE 1695 : 48 / 30 / 0.02 /
SDLAM: LA MESA 500 : 52 / 38 / 0.00 /
SDSNL: SANTEE 425 : 54 / 31 / 0.00 /
ELJC1: EL CAJON 405 : M / M / M /
SDRSC: RANCHO SAN DIEGO 400 : 53 / 33 / 0.00 /
:
: …MOUNTAIN AREAS…
:
ECSC1: EL CARISO 2730 : 48 / 31 / 0.00 /
SOX : SANTA ANA RADAR 3092 : M / 31 / 0.04 /
WRIC1: WRIGHTWOOD 5980 : 26 / 15 / M /
SDARN: LAKE ARROWHEAD 5180 : 34 / 15 / 0.00 /
BBLC1: BIG BEAR LAKE 6760 : M / M / M /
SDBDN: BALDWIN LAKE 6770 : 23 / 11 / 0.01 /
SDAOK: ANGELUS OAKS 5800 : 29 / 17 / 0.01 /
SDPCV: PINE COVE 6299 : 25 / 15 / 0.00 /
IDYC1: IDYLLWILD 5380 : M / M / M /
NZAC1: ANZA 3939 : 38 / 16 / 0.00 /
PYNC1: PINYON PINES 4060 : 42 / 27 / 0.00 /
PLRC1: PALOMAR MOUNTAIN 5550 : 32 / 20 / 0.00 /
JULC1: JULIAN 4240 : 36 / 24 / 0.00 /
MLNC1: MOUNT LAGUNA 5920 : 25 / 16 / 0.00 /
CZZ : CAMPO COOP 2615 : 47 / 23 / 0.07 /
:
: …DESERT AREAS…
:
HESC1: HESPERIA 3055 : 42 / 30 / 0.02 /
APLC1: APPLE VALLEY 2780 : 43 / 31 / 0.00 /
PSP : PALM SPRINGS 425 : 56 / 38 / 0.00 /
IDOC1: INDIO -21 : 59 / 45 / 0.00 /
TRM : THERMAL -117 : 59 / 32 / 0.00 /
BROC1: BORREGO 805 : M / M / M /
OCTC1: OCOTILLO WELLS 390 : M / M / 0.00 /
TYEC1: JOSHUA TREE N.P. 1975 : M / M / M /
BLH : BLYTHE 397 : 54 / 33 / 0.00 /
IPL : IMPERIAL -56 : 58 / 37 / 0.00 /
.END
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