Gradually lowering pressures over CA with increasing onshore flow is bringing cooler temps into the region during the next few days, so that temps should be slightly below average by Tuesday, with partly cloudy skies. The Southern Sierra should see shower activity Mon-Wed. Gusty winds will accompany the cooling trend as marine air floods inland thru the coastal gaps and passes. On Wednesday High Pressure returns with a warming trend that pushes temps above average again by the end of next week. Fantasyland 8-16 Day outlook shows the roller-coaster ride with temps continues with another warm spell again and then ending on a cool note, with no precip forecast for CENCAL during the 16 Days except for the Sierra.
Sat, May 3rd The strong High Pressure over the West Coast is collapsing as a -26°C cold trough digs southward offshore the PACNW. Pressures over NORCAL continue to drop, while pressures over SOCAL remain near 582dm heights thus providing another warm day to the southland. The PACNW storm brings heavy precip into the WA coastline, with lighter rains reaching into OR and clouds crossing the CA/OR border with a few showers possible. Temps over CENCAL drop by a few degrees as compared to Friday with increased winds 20-30mph late evening, especially along the Westside SJV in response to a surge of marine air reaching thru the Coastal passes and gaps.
Sun, May 4th The -26°C cold core Low Pressure moves onshore into the Olympic region of WA, while a large section of -24°C isotherm lags behind offshore, west of WA. Pressures over NOR/CENCAL drop slightly as the PACNW trough digs further southward. This increases the amt of marine air entering the interior of CA bringing significantly cooler temps inland. Clouds and a few showers reach into NORCAL and the Northern Sierra down to near Lassen or the Feather River basin.
MAX MIN PRECIP
Mon, May 5h The PACNW trough digs southward into NORCAL with 558dm heights reaching across the NORCAL down to near Santa Rosa to the Feather River basin, with the -24°C isotherm reaching southward to near Cape Mendocino to Mt Shasta, vort energy spreads southward thru NORCAL producing shower activity into the Sierra down to near the Kings and Kaweah River basins with snowfall at the higher elevations. Convective Parameters pop up over NORCAL with garden variety Thunderstorms possible over the northern SAC Valley, producing a threat of hail. Overnight the -24°C cold core drops further southward into NORCAL to near Tahoe accompanied with lowering snowlevels and moderate vort energy which keeps showers going over portions of NORCAL and into the Sierra. Winds pick up throughout the SJV.
MAX MIN PRECIP
Tue, May 6th The northern portion of the trough shifts into the Great Basin with the backside north flow pattern advecting cool/dry air southward into NORCAL, while the southern portion of the trough sags southward, crossing the Tehachapi Mts and reaching into the upper Mojave Desert region, with clearing skies and northerly breezes locally, producing cool temps and partly cloudy skies for the lowlands and cloudy skies and light showers continuing into the Sierra with snowlevels dropping to near 9,000ft. PWAT’s associated with this event are very low, therefore precip accumulations in the Sierra will be light, with high POP’s but low QPF’s. Overnight the trough begins to kick eastward into the Great Basin, with the backside of the trough and it’s northerly flow pattern bringing cooler/drier air into CA with clearing.
MAX MIN PRECIP
Wed, May 7th While the bulk of the Low Pressure trough exits into the Rockies, a portion of the trough lags behind, over SOCAL, providing NOR/CENCAL with more northerly breezes. This delays a rapid warming trend by providing an extension of the cool/dry north flow pattern into CA for an additional day. As gradual clearing occurs over the Southern Sierra the shower activity diminishes. Overnight High Pressure noses toward NORCAL. Noteworthy; the 700mb charts show a low level subtropical disturbance developing SW of Acapulco, Mexico which could be an early detection of an EPAC Tropical Cyclone.
MAX MIN PRECIP
Thu, May 8th As High Pressure rebuilds over CA and clear skies, temps respond in kind with inland temps warming back into 80°’s with additional breezes expected during the evening hrs. An onshore ‘overrunning’ westerly moist flow pattern over the PACNW brings additional rainfall into WA/OR and far NW NORCAL near the OR border with upsloping cloudiness for the Sierra, but no precip expected. Overnight additional clouds move into the northern 1/3 of CA on the dirty NNW flow pattern but with no precip.
Fri, May 9th Strong 582dm High Pressure rebuilds into CA from the SW, which by nightfall covers CA from near Ukiah to SAC/FAT to Barstow to Vegas with weakening winds aloft. Temps continue to rise over CENCAL and the SJV with a few hot spots possibly reaching 90°again. There are a few clouds which drift into far NORCAL, from the continuing moist westerly flow that is bringing continuous warm air advection overrunning type precip into the PACNW, with high snowlevels. Noteworthy; The 700mb charts continue to show the development and evolution of an EPAC Tropical Cyclone SW of Acapulco, Mexico with deepening pressures. If charts verify, this system should be named by now. The moisture stream from this disturbance is flowing into Central Mexico.
Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;
Sat, May 10th shows 582dm High Pressure covering CA from near Ukiah to YNP southward with light steering winds aloft and near persistence temps at the surface. With a few clouds over the Sierra, most of CA remains fair.
Sun, May 11th shows broad High Pressure over CA, while a weak shortwave trough approaches the WA coastline with more rains. Clouds extend southward into NORCAL from Cape Mendocino northward with clear skies for the remainder of CA. Meanwhile to the south…the Tropical Cyclonecontinues to churn offshore SW of Acapulco, Mexico in a nearly stationary position, with the moisture field moving across Central Mexico.
Mon, May 12h shows the formation of a weak trough configuration offshore west of CA, with a few high clouds moving over the region and with slight cooling inland. The Tropical Cyclone begins to inch it’s way northward toward the Mexico coastline, while intensifying slightly. Heavy rains reach into Mexico from this system.
Tue, May 13th shows the continued development of weak troughing offshore west of CA with a nearly stationary dry front situated over NORCAL with a few clouds. Overnight the trough begins to move onshore over CA with the -20°C isotherm moving onshore from SFO northward, with increasing cool marine winds spreading inland. This brings a significant cooling trend to CA. Meanwhile, the Tropical Cyclone reaches the Mexico coast with high winds and heavy tropical downpours. Overnight the system begins to breakdown over the Mexico coast. It is moving very sluggishly, so while pressures rapidly fill, the heavy tropical coastal rains continue.
Wed, May 14th shows a potent but dry cold trough moving across CA with a -24°C isotherm moving into NORCAL from the west, reaching as far south as SFO. The dry cold front dips southward into SOCAL, with some vort energy reaching into the Southern Sierra possibly producing showers as far south as YNP or Mammoth Mt. Breezy conditions are expected over most of CA.
Thu, May 15th shows the trough axis moving into SOCAL with the cool/dry backside north flow pattern reaching into NOR/CENCAL. Cool and breezy conditions exits over CENCAL as the -24°C cold core moves SE over CENCAL. At this time the charts show lots of vort energy over CA, but no moisture. Expect at least partly cloudy skies over the Sierra with a few showers possible, otherwise diminishing clouds and increasing winds into the lowlands. Overnight the trough kicks eastward into the Great Basin as High Pressure begins to move onshore.
Fri, May 16th shows a weak ridge of High Pressure moves onshore over CA, with diminishing winds aloft and warming temps at the surface. However, overnight another trough of Low Pressure moves SE from the GOA toward the BC, Canada coastline. So the warmup is short lived.
Sat, May 17th shows a -26°C cold core storm center approaching the Olympic region with pressures rapidly falling over the West Coast as a new trough digs southward offshore. A dried up cold front manages to bring clouds as far south as SFO to Tahoe, with showers reaching as far south as Fort Bragg to Alturas. Temps tumble over the interior sections of CA from both marine intrusion as well as dynamic cooling aloft. Overnight the trough axis moves inland producing clouds into the Southern Sierra and showers down to near Tahoe.
Sun, May 18th shows the southern portion of the trough axis moves into the Great Basin with a WNW flow pattern over CA, while the northern portion of the trough lags behind, with the parent -26°C cold core remaining offshore west of WA and Portland, OR. A steep isothermic barriers lies across CENCAL (Cold Front) with no moisture associated with it.
Special Notation; With regards to the CPC forecast for an warm phase ENSO event occurring later this summer and into fall/winter, the SST’s and wind fields are becoming increasingly favorable Tropical Cyclone development near the southern Mexico coastline. The GFS has been suggesting a Tropical Cyclone developing during Week #2 for the past 5 days and the latest charts continue that theme. An increase in Tropical Cyclone frequency could be expected with the development of the EL NINO, which could lead to the possibilities for remnants left-over’s of a decayed storm to reach into CA during the summer months or with higher incidence possibly occurring during the usual months of August/September/October. If could also infer rain on raisins during harvest. As mentioned earlier, time is very early into the development and evolution of the ENSO Event, so we must be patient and cautious at this time.
EPAC Tropical Cyclone NAMES for the 2014 Season;
NEW CA RECORDS …HEAT!
Station New Record Old Record__
Medford, OR 92° 86° set in 1981 Beats the prior record by +6°
Crescent City 78° 69° set in 1993
San Rafael 91° 90° set in 1996
Oakland 89° 85° set in 1990
Richmond 89° 85° set in 2011
Monterey 88° 87° set in 1996
Salinas 90° Ties 90° set in 1997 and 1947
King City 97° 94° set in 1996
South Lake Tahoe 74° 73° set in 2004
Modesto 95° 93° set in 1996
Merced 96° 90° set in 2004
Madera 95° 92° set in 2004
Hanford 95° 92° set in 2004
Fresno 62° Ties 62° set in 2006 High Min
Los Angeles 64° 63° set in 2011 High Min
Burbank 61° 60° set in 2013 High Min
Woodland Hills 61° 60° set in 2012 High Min
UCLA 68° 63° set in 1960 High Min
El Cajon 97° 87° set in 2011
Campo 92° 90° set in 1966
San Diego 65° 63° set in 2004 High Min
Alpine 60° 57° set in 2000 High Min
Day 1 – 5 QPF:
At 12Z (9am) Saturday thru the period day Wednesday night (Thursday @5am);
7 Day QPF Chart; shows 2 precip focal points for CA, both over the Sierra. With up to 0.5 inch falling into the Lassen/Feather River region, and up to 0.4 inch reaching into the Southern Sierra. The NW coastal region is painted with up to 1 inch for Del Norte Co with amts rapidly diminishing to the south, with the Redding/Shasta region showing up to 0.25 inch. The SAC region, the Delta, the Central Coast and SJV and all of SOCAL remain dry.
16-Day QPF estimates (from the 0Z GFS model) for;
Days 1-7; shows up to 0.5 inch falling into the Lassen/Feather River region, and up to 0.4 inch reaching into the Southern Sierra. The NW coastal region is painted with up to 1 inch for Del Norte Co with amts rapidly diminishing to the south, with the Redding/Shasta region showing up to 0.25 inch. The SAC region, the Delta, the Central Coast and SJV and all of SOCAL remain dry.
Days 8-16; shows CEN/SOCAL remain dry, while NORCAL has up to 0.75 inch near the OR border with rapidly diminishing amts to the south ending with about 0.1 inch for SAC and 0.2 inch for Blue Cyn and traces for YNP and Mammoth.
GFS 384hr, 16Day QPF Chart shows the wettest parts of CA are in the NE quadrant with up to 1.25 inch near Alturas to near Shasta City with diminishing amts further south. The Northern Sierra are painted with up to 1 inch, while the Southern Sierra only receives up to 0.5 inch and the SJV with up to 0.25 inch.
Weekly Evapotranspiration rates for the local 7 Counties shows up to 1.65 inch near Merced, up to 1.85 inch in western Fresno and Kings Co and up to 2.21 inch near Ridgecrest during the next 7 Days. The Sierra Crest evaporation loss ranges from 1.07 inch in the upper Tuolumne River basin up to 2.21 inch near Isabella.
Water Vapor 4KM Image of the West Coast Friday, May 2nd, 2014, shows High Pressure shifting slowly eastward into the Great Basin with some high cloudiness streaming across portions of CA in the warm sector of a weakening/dry cold frontal passage. The dryline is moving into NORCAL. A deep storm system is circulating west of the PACNW.
Visible Satellite Image of the CA Friday, May 2nd, 2014, shows a few high clouds over portions of NOR/CENCAL associated with a weakening/dry cold frontal passage. Most of the State is abundantly clear.
If you have any questions please call or text at any time of day or night.
Comments and suggestions always welcome.
Atmospherics Group International
Dan Gudgel Steve Johnson