Rain Sunday? Warming Trend And Then Possible COLD Snap Coming

16 Day Forecast, Thursday, March, 6th, thru Friday, March, 21st, 2014 from Atmospherics Group International

Possible cold air arriving with frost/freezing temps.  This forecast is with a low confidence level but potentially significantly damaging to AG!

Held off issuing Forecast until now, because of model uncertainty, regarding the potential arrival of extreme cold air into CA late in the Fantasyland Forecast realm, which was progged by models last night.  Before we issued the forecast last night we decided to wait to analyze the Operational GFS on Thursday for comparison.  There is a major difference between the two models, however cold air is still depicted as ultimately knocking at the door for CA.  Last night’s 0Z GFS showed a plunge of Polar air into CA around the 18th.   Thursday’s GFS shows a timing delay of 5 Days, with cold air arriving on the 22nd.  Either way this time frame needs close attention and monitoring of subsequent model runs to gain forecast confidence.

 

 A series of warm/wet disturbances continue to move thru the PACNW and NORCAL, occasionally brushing CENCAL with clouds and some shower activity reaching as far south as Fresno Co Thursday morning.  Some of this moisture has originated from a rare Tropical Storm in the WPAC.  Friday High Pressure rebuilds over CA with a warming trend into the weekend producing above average temps.  Another warm/moist storm moves into the PACNW and NORCAL on Saturday night into Sunday, with the decaying trailing end passing thru CENCAL early Monday.  Steep High Pressure rapidly rebuilds offshore the West Coast forcing the storm track northward into Alaska next Tuesday, with warming temps expected.  High Pressure dominates the West Coast thru Sun, Mar 16th with fair wx and above normal temps.  And now the big change… 

Analysis of last night’s 0Z GFS Operational model run for comparison to the current 12Z GFS on Thursday morning, regarding the possible influx of COLD air into CA;

0Z GFS  Wednesday evening; On Sun, Mar 16th the GFS charts show a Polar Storm from the Yukon begins to dig southward as the High Pressure ridge along the West Coast retrogrades westward.  By nightfall a Low Pressure trough forms near Vancouver, BC.  Mon, Mar 17th a -32°C cold core Low Pressure circulation develops over WA, with a frigid/dry north flow pattern developing over the PACNW.  Tue, Mar 18th the -32°C cold/dry storm center is located near the ID/OR/NV triple point with a moisture starved, but dynamically powerful Polar cold front moving thru CENCAL.  A cold north flow pattern develops from the Yukon southward thru BC, Canada into the PACNW and advects COLD air into CA as temps at 500mb over Fresno drop to -30°C!  On Wednesday the Polar isothermic barrier is piercing SE thru NOR/CENCAL and exiting near Ridgecrest to Las Vegas with cold/dry air continuing to drop southward from the Yukon.  Thu, Mar 20th the pattern pushes slightly west with colder air advecting into CA, with the -32°C isotherm running from Alturas south to near Mammoth Mtn with a vortmax crossing CENCAL with a very short water trajectory.  Overnight the trough begins to shift into the Great Basin.  On Fri, Mar 21st a baggy cold trough lags over the West Coast as the bulk of the coldest air shifts into the Rockies.  Current worst case scenario shows SJV morning temps reaching well below 32° and possibly below CRITICAL 28° at the coldest Stations.  The end of the GFS Fantasyland Forecast realm leaves us with very cold air over the West Coast.  Confidence on this event is low…although for the past 7 model runs the GFS has been painting a frigid cold trough reaching into the West Coast in one configuration or another.  The models have been running colder with each new successive run, with the latest 0Z GFS being the coldest thus far.  This is a somewhat similar pattern to December and is borderline ARCTIC, especially in light of the fact the upper charts show the flow pattern into CA originates on the North Slope of Alaska.   The event undoubtedly would be problematic for Ag Interests if it does verify to anything closely resembling the current charts.  Let’s hope this is a big BUST!  This is the last thing Ag needs right now and would add insult to injury.

12Z GFS  Thursday morning; Shows a significant timing delay by 5 Days which places the timing of the cold event at the very end of the 16 Day Forecast range.   The forecast pattern is similar to last night’s model run, with regards to cold air diving south from the Yukon into the PACNW, but with colder temps aloft showing a -34°Ccold core Low Pressure sagging southward into OR on Mar 21st.  Thus the interpretation of the previous 0Z model run was likely a fluke, we hope.  Such significant model timing differences produces a very low forecast confidence level on either scenario, although it is apparent that at some point during the later portion of the 16 Day Forecast, that the GFS is attempting to build the RRR High Pressure ridge up into Alaska along 140W, which then could allow the downwind flank to carry a Polar or ARCTIC airmass southward with an unknown trajectory into the WCONUS.  Therefore it’s best that we keep a close monitor on the time period from Mar 17th to the 21st.

0Z Wednesday GFS 500mb Chart showing -32°C temps reaching into portions of eastern CA with a cold/dry north flow pattern over NOR/CENCAL.

 

 

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300mb upper level Jet Stream diving southward from the ARCTIC region into CA on Thu, Mar 20th.

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Precip Totals past 24hrs thru midnight Wednesday include;  

4.04 Brandy Crk, 2.68 Four Trees, 2.40 Taylor Ridge, 2.37 Brush Crk, 2.32 Honeydew, Slate Crk, 2.24 Bucks Lake, 2.12 Lakeshore, Shasta Dam, 2.08 Bonanza King, Hirz, 1.80 Ruth Lake, DeSabla, 1.72 La Porte, 1.55 McCloud Dam, 1.52 Leggett, Bucks Crk, 1.46 Pit River Pwrhse #5, 1.44 Snow Mtn, 1.36 Roseville, 1.36 Trinity, 1.28 Elk Valley, Strawberry Valley,  1.20 Willits, 1.13 Somes Bar, 1.12 Fort Seward, 1.04 Miranda, Diddy Wells, 0.92 Humbug, Venado, 0.91 Mud Springs, Hayfork, 0.90 Blue Cyn, 0.88 Oroville Dam 0.84 Bridgeville, 0.76 St Helena, 0.75 Cohasset, 0.72 Angwin, 0.61 Manzanita Lake, 0.60 Clear Crk, Cottonwood Crk, Lassen, 0.56 Chico, 0.55 Marysville, 0.53 Mt Diablo, 0.52 Shingletown, 0.49 Ben Lomond, 0.47 Auburn, 0.43 Fair Oaks, 0.42 Ukiah, 0.40 Redding, Folsom, 0.39 Donner Lake, 0.37 Lincoln, Santa Rosa, 0.36 SAC, 0.31 Arcata, 0.28 Huysink, 0.27 Elk Grove, Campo Seco, 0.26 Napa, OAK, 0.24 Orick, 0.23 SF, 0.20 Weed, Walnut Grove, Soquel, 0.16 Calavaras, 0.15 Forni Ridge, 0.10 Corning, 0.06 South Lake Tahoe, 0.05 Stockton, Watsonville, 0.04 Alturas, Devils Garden, Gilroy, 0.01 Camanche, Monterey, Hernandez, Santa Rita, Buchanan Dam

 

Special Notation;        Tropical Storm  “Faxai” in the WPAC is rapidly losing strength as it ventures NNE, away from Guam.  Currently located at 22N 154E moving NNE at 14kts, with max sustained winds of 50kts with gusts of 60kts, with its extended moisture field stretching northward into the westerlies which are carrying the moisture plume eastward toward the West Coast. On Thu, Mar 6th a Mid-Pac storm which has captured much of the last portion of Faxai’s moisture plume, shifts east to near 160W with the trailing Atmospheric River (AR) originating from the decaying Tropical  Storm.  On Mar 7th the moist AR created by Faxai brings heavy rains into BC, Canada, which sag southward into the PACNW and NORCAL on the 8th and on the 9th the left-over remnants of the Faxai AR reach into portions of CENCAL.  That ends the tale of the long advertised Tropical Storm Faxai.  Congrat’s to the GFS!

 

SAC Doppler showing a narrowing frontal boundary moving thru NORCAL Wed night producing locally heavy rains along a thin frontal ribbon which is passing thru SAC and the Bay region.   The trailing southern end of the front is rapidly diminishing as it nears San Jose.  Precip efficiencies are impressively high as 1.25 inch PWAT supplies the atmospheric moisture, therefore the narrow band is producing high precip totals.

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PWAT Moisture Content feeding into the frontal boundary, showing an increasingly wet deep layer moisture reaching toward CENCAL, with a core PWAT of 1.6 inches SW of Pt Conception.

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FORECAST SUMMARIES

 

Days 1-7;

 

Thu, Mar 6th                 Early morning rain showers over the northern portions of the SJV drop may drop as much as 0.25 inch in the Northern SJV with only trace amts into Kings and Tulare Co as the weak cold front exits our region into the Great Basin and High Pressure begins to rebuild offshore.  High Winds are probable over the Tehachapi Mts up to 60mph, and up to 25mph along the Westside SJV.  The core remnants of the old Tropical Storm Faxai reach the Dateline carrying an abundance of moisture eastward toward BC, Canada and the PACNW.  Max temps may reach up to 80° at the hot spots.  Overnight the offshore ridge moves onshore and shunts all moisture out of CA.

 

Fri, Mar 7th                  High Pressure rapidly rebuilds over the West Coast and up into western Canada, with the long-fetched Faxai enriched AR flowing NE along the backside of the ridge into BC, Canada producing heavy precip.  Under the dome of High Pressure, fair skies continue over CA and the PACNW with warming temps.  Overnight the ARwarm/heavy rains reach into the Olympic Peninsula and then trail SW back to Hawaii.

 

Sat, Mar 8th                 While High Pressure continues to protect CA, the long-fetched SW flow carries the bulk of Faxai’s AR rains into the BC, Canada and the WA coastline, while fair/mild wx continues over CEN/SOCAL.  Overnight the High Pressure over CA relaxes slightly and allows heavy rains into NORCAL from SF northward.  

 

Sun, Mar 9th                 Broad but flat High Pressure covers CA, with a moist SW flow pattern continuing to advect the AR slowly over the top of the ridge into NORCAL.   Overnight the old decaying AR reaches southward into CENCAL with possible showers as far south as Big Sur to Madera to the San Joaquin River basin. 

 

Mon, Mar 10th              The broad West Coast ridge intensifies and shunts the storm track northward into BC, Canada, as an extended dry period for CA is accompanied with above normal temps.  Overnight the ridge axis moves onshore over the West Coast.

 

Tue, Mar 11th               High Pressure offshore the West Coast has built up into the Yukon with a minor tiny disturbance possibly forming near Pt Conception which could produce NE offshore flow over CENCAL.  Overnight the strong RRR High Pressure ridge shifts onshore.

 

Wed, Mar 12th             570dm High Pressure covers all of CA/NV and OR, with the storm track into northern BC, Canada and southern Alaska.  A new trough digs southward to near 40N 140W penetrating into the western flank of the ridge.  Fair/warm conditions prevail over CA.

 

 

Days 8-16, Long Range into Fantasyland OutlookDay 8 begins;

 

 

Thu, Mar 13th shows the West Coast ridge shifting east into the Great Basin with the approaching trough being the leading edge of a long fetch of westerlies, crossing the PAC. Some moisture approaches the NORCAL coast with perhaps a few showers north of Cape Mendocino overnight and partly cloudy skies for CENCAL.

 

Fri, Mar 14th shows the High Pressure over CA flattening, as some moisture continues to flow into portions of NORCAL and mostly fair skies over CENCAL. Overnight the offshore High Pressure ridge intensifies dramatically.

 

Sat, Mar 15th shows a narrow but strong High Pressure ridge offshore CA and nosing into the PACNW, which allows a Low Pressure trough to dig into the Great Basin.  This produces a colder north flow pattern over CA. Overnight an intense Low Pressure circulation develops over the Lower Colorado River Valley, which produces a strong NE offshore flow pattern over CENCAL.

 

Sun, Mar 16th shows the Low Pressure circulation migrates east into AZ, with High Pressure continuing to nose into the PACNW, keeps the offshore NE flow pattern going over CENCAL.

 

Mon, Mar 17th shows weakening High Pressure over CA, with a strong ‘REX’ tucked Low Pressure center at 40N 140W and the AZ Low Pressure sagging into northern Mexico.   The dry flow pattern over CA veers to the north.

 

Tue, Mar 18th shows the ‘REX’ tucked Low Pressure circulation moving toward the PACNW as weak High Pressure covers CA, with dry/mild conditions continuing.

 

Wed, Mar 19th shows the ‘REX’ tucked Low Pressure reaching the PACNW with light rains.  An ARCTIC trough digs southward thru Alaska.  Fair/dry/mild conditions continue over CA. Overnight a transformation occurs in the GOA as the High Pressure ridge retrogrades westward to 160W, which allows the newly developing ARCTIC storm to begin sliding into the GOA.

 

Thu, Mar 20th shows the frigid/dry ARCTIC storm following the Alaskan coastline southward which reaches into BC, Canada overnight.  Meanwhile, the flow pattern over CA switches to NW and the pressure gradient tightens with increased cool/dry NW winds.

 

Fri, Mar 21st show the -34°C cold core ARCTIC storm over Vancouver, BC with strong High Pressure pushing northward into Alaska.  The downwind flank of the ridge is carrying much cooler air into CA, even before the storm arrives.  Overnight the -34°C ARCTIC storm drops into WA/OR, as the ARCTIC cold front dips across the CA border.  With extremely low snowlevels forecast the storm is too cold to produce much QPF.

 

 

 

 

NEW CA RECORDS

 

Station                         New Record                Old Record__

none

 

 

 

Minimum Temps this morning at the Paramount Citrus Stations ranged from the coolest minimum of a 50° at Loma and Comanche, rising to the warmest minimum of 59° at Root Creek…due to extensive cloud coverage and light rainshowers which totaled 0.19 inch.

Maximum Temps this afternoon at the Paramount Citrus Stations ranged from the coolest maximum of 70° at Horizon and Cappello, rising to the warmest maximum of 81° at Belridge.

 

 

PRECIPITATION FORECAST

 

Day 1 – 5 QPF:

At 12Z (9am) Thursday thru the period Monday night (Monday @4am);

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7 Day QPF Chart; showing up to 5 inches near the CA/OR border region with diminishing amts to the south showing up to 3-4 inches along the NW Coastal Region, with up to 2-3 inches from Fort Bragg to near the western portions of the Shasta River basin, with up to 1-2 inches from near Willits NE into the bulk of the Shasta River basin then SE thru the Northern Sierra into the Feather River basin with up to 0.5 to 1 inch from the Bay region to near Stockton east to near YNP northward.  With up to 0.25 to 0.5 inch from near Big Sur to Modesto to the San Joaquin River basin, and >0.1 inch from Big Sur southward to Vandenberg then eastward across the Transverse Range/Tehachapi Range and across the San Gabriel’s of SOCAL.  The Southern SJV, Mojave Desert and most of SOCAL remain DRY.

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16-Day QPF estimates (from the 0Z GFS model) for;

Days 1-7; shows up to 5 inches near the CA/OR border region with diminishing amts to the south showing up to 3-4 inches along the NW Coastal Region, with up to 2-3 inches from Fort Bragg to near the western portions of the Shasta River basin, with up to 1-2 inches from near Willits NE into the bulk of the Shasta River basin then SE thru the Northern Sierra into the Feather River basin with up to 0.5 to 1 inch from the Bay region to near Stockton east to near YNP northward.  With up to 0.25 to 0.5 inch from near Big Sur to Modesto to the San Joaquin River basin, and >0.1 inch from Big Sur southward to Vandenberg then eastward across the Transverse Range/Tehachapi Range and across the San Gabriel’s of SOCAL.  The Southern SJV, Mojave Desert and most of SOCAL remain DRY.

 

 

Days 8-16; shows up to 0.2 inch into portions of the Sierra down to near Mammoth Mtn, with >0.10 inch for the remainder of NOR/CENCAL, and SOCAL completely DRY.

 

 

GFS 384hr, 16Day QPF Chart, depicting a wet NORCAL, with up to 4-5 inches in the NW Coastal Region, with up to 3-4 inches from Fort Bragg NE into the Shasta River basin with up to 2-3 inches from near Pt Arena NE into the Shasta basin, with up to 1-2 inches from Santa Rosa northward and into the Northern Sierra down to Hwy 50, with up to 0.5 inch from Santa Cruz to Modesto to YNP northward, 0.25 inch from near Big Sur to Fresno to Kings Cyn northward and >0.1 inch from Santa Barbara and the San Gabriel’s and Tehachapi Mts northward.

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SATELLITE

 

Water Vapor 4KM Image of the West Coast Thursday, March 6th, 2014, shows a disturbance moving into UT which brought showers to the region early Thursday morning, with a minor secondary disturbance moving into NORCAL, with a cluster of Thunderstorms into the northern SAC Valley.

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Visible Satellite Image of the CA Thursday, March 6th , 2014, shows diminishing cloudiness over most of CA, except for the cluster of Thunderstorms in the northern SAC Valley.

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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

559-696-9697                 559-433-7316

 

 

BenitoLink Staff