In the short term forecast period the moist Atmospheric River which has been drenching the PACNW and portions of NORCAL with heavy/warm subtropical rainfall should taper off by Wednesday, with a transition to an amplified pattern beginning on Thursday. The recent forecast models have been consistently trending toward this transition of a more amplified western trough/ridge pattern regime that ends the zonal-type AR storm activity over NORCAL and the PACNW as the pattern buckles and amplification occurs. Since transitional patterns usually lead the forecast charts on a merry chase for a day or two, we’ll have to carefully watch the Thu/Fri time frame. Before the big buckling the PACNW will continue to pile up onshore flow precip with enough zonal component to spread snows all the way into the Rockies. The model spread is still somewhat moderate for the leading features embedded within the fast flow aloft, but it is encouraging to see the GFS and EC models nearly in synch with each other on the large scale pattern solutions. It appears highly likely that most of CENCAL and all of SOCAL will end the month of February with record-setting dryness, compounding the deepening seriousness of the CA Drought. Analysis of the Northern Sierra 8-Station Climate History and the San Joaquin 5-Station Climate History will commence next week.
As the trailing end to an Atmospheric River Event finally pushes thru CA, rainfall amts rapidly diminish over CA on Sunday. One more shot of heavy rains reach into portions of NORCAL on Tuesday, and by Thursday the flow pattern will undergo a fundamental change into a more amplified ridge/trough configuration which shuts the storm door into CA for the remainder of Feb and into the beginning of March. The most recent longer range outlook charts remain consistently dry for most of CA during Week #2 with mild temps… which abruptly plunge at the end of the GFS Fantasyland Forecast realm with the suggestion of a possible major frost event occurring on Mar 3rd with minimum temps reaching at or >28° possible. This event has a low confidence level but should be monitored closely. The GFS 384hr 16Day Outlook now extends thru the end of the month of February into March 3rd. The final week of February should end the “February Monthly Summary” for the Northern Sierra Index…above normal, being the first time in 14 months with an above average monthly total. That’s the good news. Now the not so good news …it appears as though the month of February will end with a worsening Drought deficit for the Central Sierra and especially for the Southern Sierra as the recent heavy rains which have drenched portions of NORCAL have been mostly absent over the Southern Sierra region. In addition the record-setting heat recorded in CENCAL yesterday also produced high evapotranspiration rates of up to 0.15 inch. Some Ag Stations in Tulare and Kern Co reached 84° on Friday! CENCAL yesterday also produced high evapotranspiration rates of up to 0.15 inch. Some Ag Stations in Tulare and Kern Co reached 84° on Friday!
PRECIP past 24hrs over NORCAL; 2.76 Honeydew, 1.96 Elk Valle, 1.68 Ruth Lake and Brandy Crk, 1.60 Fort Dick, 1.40 Leggett, 1.30 Somes Bar, 1.28 Slate Crk, 1.24 Hoopa, 1.16 Hirz, 1.12 Snow Mtn, 1.09 McCloud Dam, 0.98 Crescent City, 0.96 Orleans, 0.92 Sawyers Bar, 0.89 Big Hill, 0.88 Bonanza King and Shasta Dam, 0.80 Willits, 0.77 Friend Mtn, 0.76 Miranda, 0.72 Bridgeville, Taylor Ridge and Hillcrest, 0.68 Lakeshore, 0.64 Four Trees, 0.62 La Porte and Covelo, 0.60 Ft Seward and Bucks Lake, 0.58 Oak Knoll RS, 0.56 Orick and Trinity RS, 0.55 Arcata, 0.44 Mt Shasta City and Diddy Wells, 0.42 Manzanita Lake, 0.41 Redding, 0.40 Cottonwood Crk and Venado, 0.36 Hayfork RS and Saint Helena, 0.28 Cow Crk, Blue Cyn and Yorktown, 0.21 Quincy, 0.16 Saddle Camp, Shingletown, Battle Ridge, Humbug, Strawberry Valley, Alleghany, 0.15 Lassen and the Pit River Powerhouse #1, 0.14 Sierraville, 0.21 Ukiah, 0.10 Weed and Markleeville, 0.09 Lincoln, 0.04 Oroville Dam, 0.03 Englebright Dam, 0.02 Alpine Mdws, 0.01 Bald Mt, Santa Rosa, Napa, Concord, Vacaville, Mt Diablo, SAC, Ben Lomond and Watsonville.
Sun, Feb 16th The trailing end to an Atmospheric River Event which has been drenching NORCAL for the past several days travels thru CENCAL during the early morning hours, with precip reaching Modesto to YNP and possibly down to Merced to YNP and the upper Crest region of the Southern Sierra with some light shower activity. Moderate precip falls north of YNP. Weak High Pressure extends over CA and a deep storm system is located in SW Alaska with the associated trough covering most of the GOA. The stead-state moist WSW flow pattern keeps warm/heavy rainfall into the PACNW, but not reaching into CA any longer. Fair skies over CENCAL. Overnight the wet storm activity returns to near the CA/OR border.
Mon, Feb 17th The flat pressures over CA keep the warm/moist SW flow barreling into the PACNW and reach into the far NW Coastal region of CA with light rains, while the reminder of CA remains fair/mild/dry. Overnight as the GOA trough axis approaches the PACNW and the far NW NORCAL Coastal region the warm rains continue from Cape Mendocino northward. A new Atmospheric River (AR) attachment from Hawaii connects to the moist flow pattern offshore.
Tue, Feb 18th As the trough axis nears the NORCAL coastline the newly attached AR supplied heavy rains gradually spread over NORCAL down to near Marysville/Oroville, while partly cloudy to sunny skies remain over CENCAL. Overnight the RRR High Pressure ridge begins to rebuild over 140W which realigns the flow pattern over NORCAL to the WNW as rains spread further south into NORCAL and begin to diminish and temps begin to lower slightly due to the cooler NW flow pattern.
Wed, Feb 19th The trough axis moves into the Great Basin and deepens with rainshowers over NORCAL diminishing from the NW as High Pressure builds onshore. SOCAL remains fair/dry. The NW flow pattern continues to bring slightly cooler maritime temps to most of CA. Overnight another disturbance flows into the PACNW from the NW, reaching into the far northern counties near the CA/OR border region.
Thu, Feb 20th The RRR High Pressure shifts to 140W as the trough in the Great Basin, provide CA with a drier NW flow pattern with cooler temps and diminishing shower activity in the far north. Overnight the pressure gradient over CA tightens over the PACNW with increased NW winds while CA develops a light northerly flow pattern becoming offshore over SOCAL.
Fri, Feb 21st The RRR High Pressure ridge moves closer to the West Coast with a NW flow pattern over NORCAL and a N flow pattern over CEN/SOCAL, with fair skies. Drier air also reaches into CEN/SOCAL while temps remain near persistence. Overnight the ridge moves closer toward CA.
Sat, Feb 22nd Shows the broad RRR High Pressure ridge moving onshore over the West Coast, with fair skies as the main storm track is diverted into southern Canada, and temps slowly rebound. Overnight as the High Pressure continues to move over the West Coast, a weak frontal boundary pushes thru the PACNW and into far NW CA with a few light showers.
Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;
Sun, Feb 23rd shows the RRR High Pressure ridge anchored over the West Coast, providing abundantly sunny skies over CA. A long-fetched Atmospheric River (AR) develops across the PAC basin, originating from the Maritime Continent NE into the GOA.
Mon, Feb 24th shows the RRR High Pressure ridge remains over the West Coast with the storm track displaced northward into SW Canada, which is attached to the AR that is trailing southward offshore west of the PACNW. Overnight the rains reach closer toward the PACNW as a large trough carves out in the GOA.
Tue, Feb 25th shows the RRR High Pressure ridge dominant over the West Coast as the backside of the ridge brings a moist SW flow pattern into Vancouver, BC and WA. Fair skies prevail over CA.
Wed, Feb 26th shows the High Pressure shifting eastward into the Great Basin, with strong Low Pressure covering the GOA providing a longwave trough pattern that reaches into Vancouver, BC and into the PACNW. Overnight a weak frontal boundary reaches into NORCAL with a chance of showers down to Fort Bragg to Shasta and partly cloudy skies reach down to SFO to Tahoe.
Thu, Feb 27th shows the RRR High Pressure ridge nosing into the West Coast with an offshore flow pattern developing over SOCAL and partly cloudy skies for NOR/CENCAL.
Fri, Feb 28th shows the High Pressure ridge flattens over the PACNW which allows for another moist flow pattern to bring additional rains into that region which brush thru the far northern counties of CA. Meanwhile fair skies continue over CEN/SOCAL. An interesting notation in the Global GFS model shows a Tropical Cyclone forming in the WPAC, which is highly unusual for February. It is exceedingly rare for a Typhoon to form during February, although it has happened before…in climate history the month of February has the least favorable chances for Tropical Cyclone development. This feature has a low confidence level but it is very curious and exemplifies the warm SST’s in the WPAC. It rapidly intensifies and reaches peak strength overnight, located at 14N 140E.
Sat, Mar 1st shows the RRR High Pressure ridge at 140W with a developing trough diving into the Great Basin creating an increasingly strong NW flow pattern which intensifies overnight as the flow pattern over CA veers to the N-NE…advecting much colder temps into the region.
Sun, Mar 2nd shows High Pressure offshore the West Coast with deep Low Pressure over Las Vegas producing a strong offshore NE flow pattern with Mono Winds possible over the Sierra and Santa Ana’s for SOCAL. High winds are possible along the Westside SJV if this pattern verifies. Overnight a very tight pressure gradient produces High Winds over CEN/SOCAL from the NE.
Mon, Mar 3rd shows the RRR High Pressure ridge extending from offshore CA northward at a steep angle into Alaska with the downwind flank bringing a POLAR flow pattern down thru the Yukon into BC, Canada and then into the PACNW and into CA. As the Vegas -32°C Low Pressure circulation shifts into AZ, the strong NE flow pattern over CEN/SOCAL switches to a cold NORTH flow pattern …advecting much colder/drier air into CA as the upper Jet Stream dives southward at 125kts over CA. BEWARE of the potential for a MAJOR FROST EVENT if this pattern verifies… in the days to follow as the pressure gradient relaxes and winds calm, this pattern produces the potential for very cold overnight temps to possibly reachCRITICAL 28° or lower. The upper flow pattern with Jet Stream Chart attached below ↓. Since this event is on Day 16 of the GFS Fantasyland realm, of course it has a low confidence level, but should be closely monitored in the upcoming subsequent model runs to see if it has credibility.
300mb Chart depicting a Polar airmass dipping into the West Coast on Mon, Mar 3rd.
Station New Record Old Record__
Stockton 72° (Ties) 72° set in 1977
Reno 71° 69° set in 1977
Bakersfield 78° (Ties) 78° set in 1991
Hanford 74° 70° set in 2006
Madera 73° 68° set in 1999
Merced 72° 69° set in 2006
Lancaster 83° 80° set in 1955 This ties the record for 4 consecutive days in Feb for temps at or above 80°
Palmdale 83° 78° set in 1996 and 1955 This ties the record for 4 consecutive days in Feb for temps at or above 80°
Sandberg 77° 67° set in 1991 and 1955
Sandberg 55° 54° set in 1991 Record High Min
Bishop 76° 75° set in 1985
Barstow/Daggett 87° 80° set in 1996
Ramona 86° 85° set in 1977
Elsinore 90° 89° set in 1898 Beats a 116 year old record.
Escondido 88° (Ties) 88° set in 1943 A 71 year old record.
El Cajon 88° 87° set in 1997
Big Bear 64° 63° set in 1985
Palomar 71° (Ties) 71° set in 1957
Palomar 57° 50° set in 1991 Record High Min
Campo 87° 79° set in 1955 Beats a 59 year old record by +10°!
Idyllwild 46° 43° set in 1977 Record High Min
Phoenix 86° 83° set in 1977
Yuma 89° 87° set in 1947
Day 1 – 5 QPF:
At 12Z (9am) Saturday thru the period Wednesday night (Thursday @4am) shows;
Sat shows heavy precip continuing into the far NW Coastal region with up to 2 inches in the wet spots of the Smith River basin diminishing down to 1 inch for portions of the NW coastal region in the Klamath, Eel and Shasta River basin, and the wet spots of the Feather River basin, with up to 0.75 inch from the Russian River basin northward along the coast up to Shasta Dam then southward into the Sierra down from the Feather River basin to the American River basin, with up to 0.5 inch from the North Bay region northward along the coast to near Redding then southward into the Sierra down to near the upper Stanislaus River basin, with 0.2 inch from Watsonville NE into the Delta then eastward into the Tuolumne River basin, with >0.1 inch from near San Simeon to near Merced/Madera to near Huntington Lake. No precip is expected to fall south of Fresno Co in the SJV
Sun shows a drying trend with light amts of precip into portions of NORCAL with >0.1 inch for the Sierra from near Lassen southward to the Kings River basin, with up to 0.2 inch falling from the Yuba River basin south to the Tuolumne River basin. The remainder of CA stays DRY.
Mon shows up to 1 inch of precip into the wet spots in the higher elevations of Del Norte Co, with rapidly diminishing amts to the south dropping down to >0.1 inch reaching the Eel River basin and into the Trinities northward to Crater Lake, OR. The remainder of CA stays DRY.
Tue shows increased precip into NORCAL, with up to 2 inches falling into the higher terrain of the Smith River basin, diminishing to 1 inch for the Klamath River basin, down to 0.75 inch for the Eel River basin and into portions of the Shasta River basin, with 0.2 inch from near Pt Arena to Clear Lake northward to Redding then eastward to Alturas and Susanville, with >0.1 inch from the North Bay to near Lodi to Lake Tahoe. The remainder of CA stays DRY.
Tue shows much lighter amts of precip over NORCAL with >0.1 inch into the Klamath River basin eastward into the Shasta River basin and throughout the NE quadrant of the State, then southward into the northern Sierra to near Kirkwood. The remainder of CA stays DRY.
5DAY ACCUMULATION CHART:
Saturday’s 7 Day Chart; shows up to 3-4 inches of precip for the far NW Coastal region with rapidly diminishing amts to the south showing up to 2 inches near Fort Bragg northward, up to 1.5 inch from near Ukiah northward and also into the wet spots of the Feather River basin, with up to 0.5 inch from near Santa Rosa northward to near Chico and then southward into the Sierra to near YNP, with up to 0.25 inch from the Bay region to Stockton to near the San Joaquin River basin and >0.1 inch from near Big Sur to Madera/Fresno to Kings Canyon.
16-Day QPF estimates (from the 0Z GFS model) for;
Days 1-7; shows NORCAL receiving up to 3-4 inches of precip for the far NW Coastal region with rapidly diminishing amts to the south showing up to 2 inches near Fort Bragg northward, up to 1.5 inch from near Ukiah northward and also into the wet spots of the Feather River basin, with up to 0.5 inch from near Santa Rosa northward to near Chico and then southward into the Sierra to near YNP, with up to 0.25 inch from the Bay region to Stockton to near the San Joaquin River basin and >0.1 inch from near Big Sur to Madera/Fresno to Kings Canyon.
Days 8-16; shows most of CA remaining DRY, except in the far northern counties with up to 0.5 inch into the NW Coastal region and no precip south of Ukiah to Redding to Blue Cyn.
Saturday’s 0Z 9pm GFS 384hr, 16Day QPF Chart, depicting a wet NORCAL, semi-wet CENCAL, and a dry SOCAL. With up to 2 inches of rainfall along the CA/OR coastline, diminishing to 1 inch from Fort Bragg to Redding, diminishing to 0.5 inches from near Santa Rosa to the Feather River basin and 0.25 inch from the Bay region to Stockton to near the Stanislaus River basin, with >0.1 inch from near Morro Bay to near Fresno to Kings Canyon.
Water Vapor 4KM Image of the West Coast Saturday, February 15th, 2014, shows a massive surge of subtropical moisture passing over CA, with high level moisture streaming across CENCAL producing overcast skies.
Visible Satellite Image of the CA Saturday, February 15th, 2014, shows abundant cloudiness passing over most of CA, but producing rainfall only into the far northern regions.
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Atmospherics Group International
Dan Gudgel Steve Johnson