High Pressure dominates with dry conditions and above average temps thru next weekend and into early next week. Long range into the Fantasyland realm shows one storm system scheduled to possibly arrive into CA around Mar 25th into the 26th which focuses primarily upon NORCAL. The rain/no rain line with this system is wavering somewhere over CENCAL. The GFS is suggesting another storm arriving at the end of Mar with a stronger/wetter storm suggest on Apr 3rd. Colder air associated with these storm systems could pose a threat of producing patchy morning frost. Close examination of the Sierra Precip Index shows the accumulated precip numbers are deceptive as compared to the current SNOW WATER CONTENT numbers issued on Friday. Why the difference? Plain and simple…evaporation… and lots of it!
GFS is increasing its optimism for a multi-storm event during the 8-16 Day time frame, with much needed precip for the Southern Sierra. Poor timing for SJV Ag activities, but nonetheless welcomed news for the Water Supply. Timing issues and trajectory issues will need to be monitored as these events could easily disappear or most certainly will alter their trajectories and intensities during the upcoming subsequent model runs. Although confidence is now low, if the next model runs appear similar then confidence will rise.
Precip Totals past 24hrs include; none
FROST ADVISORY; Mendocino Co interior for minimum temps dipping to the mid 30°’s
ABC Channel 7 News, DENVER Fire Dust Devil at the Rocky Mtn Arsenal, CO Friday, video link; copy and paste this link to your browser
Sat, Mar 22nd Shows a persistence pattern for CA with little overall change…fair/mild/dry with weak High Pressure offshore the West Coast. Meanwhile a High Pressure ridge pushes northward into the Bering Sea with a downwind flank REX configuration 528dm Low Pressure center locked into position in the GOA which carves out a cold trough into the EPAC at 150W at 45N. Above normal temps continue over CA.
Sun, Mar 23rd The 528dm Low Pressure center near 45N 150W pushes a trough further to the south which reaches as far as 35N, as the ridge of High Pressure covers the West Coast up thru the PACNW and southern BC, Canada. No changes noted for CA except for slight warming. A minor disturbance ripples thru SOCAL with a few high clouds. Overnight the trough slowly approaches 140W with winds aloft veering SW bringing rains spreading into the WA coastline, with the frontal boundary trailing southward, far offshore west of CA.
Mon, Mar 24th The main features in the EPAC show a Low Pressure storm center in the GOA with an associated trough southward which is approaching the West Coast. High Pressure over the West Coast shifts eastward into the Great Basin with increasing SW flow aloft over NORCAL. Overnight as the High Pressure ridge continues to migrate eastward the GOA Low Pressure storm pivots NE with the trailing cold front moving into the NORCAL coastline oriented north to south with diminishing amts of moisture and dynamic lift south of the Bay region. While the diminishing frontal boundary reaches into NORCAL, the main trough axis remains offshore with a cyclonic flow pattern producing a SW flow over CA.
Tue, Mar 25th Confidence regarding this storm event is quite high, as it has been on charts for at least the past 10Days! However, the QPF’s projected for CENCAL remain somewhat in question. As the offshore trough pivots NE dynamic lift moves onshore along the CA coastline from the Bay region northward with rainshowers gradually weakening and pulling northward. Cyclonic flow into the West Coast following the cold front brings the trough axis with additional rainshowers overnight into CENCAL with moderate rainfall rates into the Central Sierra from Tahoe to Kings Canyon and up to 0.2 inch for the SJV north of Fresno.
Wed, Mar 26th A quasi-zonal flow pattern behind the passage of the trough axis continues a moist onshore flow into NORCAL with gradually diminishing shower activity over CENCAL, and then with clearing skies over CENCAL as weak High Pressure moves onshore overnight, however a moist flow continues to bring occasional rainshowers into NORCAL.
Thu, Mar 27th The moist onshore westerly flow pattern continues to bring rainshowers into far NORCAL, from Cape Mendocino eastward into the Northern Sierra, while CENCAL remains partly cloudy and SOCAL stays fair. Overnight another frontal boundary approaches the PACNW with increased rains that reach SSW into far NW coastal CA.
Fri, Mar 28th The frontal boundary over the PACNW stalls out, with heavy non-stop rains from Vancouver, BC southward to Portland, OR, and showers reaching as far south a Cape Mendocino to the Shasta River basin, and with partly cloudy skies reaching into CENCAL. Overnight the stalled frontal boundary begins to diminish in intensify as the trailing end to the front weakens to the west of NORCAL. Partly cloudy skies maintain over the northern portion of CENCAL.
Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;
Sat, Mar 29th shows the remnants of the stalled cold front continue to bring heavy rainfall into the WA coast with moderate rains reaching as far south as near Cape Mendocino to the Shasta River basin, with partly cloudy skies from Monterey to Tahoe. Overnight the main trough axis approaches the CA coastline, with light rains over NORCAL down to SFO to Tahoe with partly cloudy skies from San Simeon to Kings Canyon.
Sun, Mar 30th shows the sharp trough axis approaching the CA coastline, containing a -32°C cold core storm center west of the OR coast. The SW flow aloft over CA increases with rainshowers spreading over NOR/CENCAL down to near Big Sur to Fresno to Kings Canyon and partly cloudy skies crossing the Tehachapi Mts. Preliminary QPF’s show this storm event could bring up to 0.5 inch to the SJV and up to 1+ inch to the Southern Sierra.
Mon, Mar 31st shows one spoke of the trough axis having passed thru CA, with a secondary trough axis rotating toward the CA coastline with continued rainshowers over NORCAL from the I-80 corridor northward.
Tue, Apr 1st shows the trough axis moving into the Great Basin, followed by weak High Pressure nosing onshore over CA, which produces a clearing trend for NOR/CENCAL. Overnight a new-30°C cold core moves rapidly eastward toward the NORCAL coast.
Wed, Apr 2nd shows High Pressure over the GOA forces a break thru of the southern branch Jet Stream to begin intensifying the approaching -30°C cold core with strong upper dynamics as a new cold front develops west of the CA coastline which is rapidly approaching the NORCAL coast. Overnight the -30°C cold core nears Cape Mendocino with heavy rains commencing along the NORCAL coast from SFO northward, powered by a 100kt Jet Stream aloft on a SW flow pattern. With cold air aloft, if skies clear and winds calm, then patchy frost is possible in the cold spots of the SJV overnight.
Thu, Apr 3rd shows the upper Jet Stream at 100kts passes thru CENCAL on a SW flow pattern, optimizing moderate/heavy precip for the Southern Sierra and moderate lowland rains for CENCAL. Depending upon the timing of the actual frontal passage thru CENCAL, Thunderstorms could develop during the late afternoon over the SJV. The trough axis lags behind over CA overnight, which continues to produce precip for the Sierra, with diminishing amts for the lowlands of the SJV. Preliminary QPF’s show this event could bring up to 1 inch to the SJV and up to 3 inches for the Southern Sierra. Needless to say, we should monitor this storm event closely.
Fri, Apr 4th shows the trough axis moves into the Great Basin in response to a High Pressure ridge building offshore, producing brisk cool NW breezes for most of CA. Overnight the ridge moves inland with a cold north flow pattern developing over CA.
Sat, Apr 5th shows the High Pressure nosing into the PACNW with the trough to the east produces an increased cold/dry north flow pattern over CA which originates from the PACNW. The storm track is deflected northward into BC, Canada. With cold air aloft and calming winds, overnight temps in the SJV may radiate enough to produce patchy frost.
Sun, Apr 6th shows continued High Pressure over NORCAL producing a cold/dry north flow pattern over CA with a few clouds over NORCAL. Due to the cold nature of the air aloft and the dry conditions near the surface, we need to monitor this time period for the potential of possible patchy morning frost.
Latest Northern Sierra 8-Station Precip Index
Latest San Joaquin 5-Station Precip Index
The Northern Sierra and San Joaquin Precip Indexes are in stark contrast to the latest SNOW WATER EQUIVALENTS (provided by the CA Cooperative Snow Survey), which depicts amuch smaller water supply available;
SNOW WATER CONTENT CHARTS, March 21, 2014, showing the current SWC (Pink Line) at or below 1976-77 levels (Dashed Burgundy Line).
CA Regional Cities Seasonal Precip
Station New Record Old Record__
San Diego 62° 61° set in 1978 High Min
Oceanside Harbor 58° (Ties) 58° set in 1993 High Min
Day 1 – 5 QPF:
At 12Z (9am) Friday thru the period Tuesday night (Wednesday @4am);
7 Day QPF Chart; showing up to 4 inches near the CA/OR border region, with diminishing amts to the south with up to 2 inches to Cape Mendocino and into the wet spots of the Shasta River basin, with up to 1 inch from near Ukiah northward to the bulk of the Shasta River basin and into most of the Feather River basin, with up to 0.5 inch from near the Russian River basin northward into the northern SAC Valley region and to near Hwy 50, with up to 0.25 inch from near Santa Cruz to the Delta to near YNP, with up to >0.1 inch from near Big Sur to Merced to near Kings Canyon.
16-Day QPF estimates (from the 0Z GFS model) for;
Days 1-7; shows up to 4 inches near the CA/OR border region, with diminishing amts to the south with up to 2 inches to Cape Mendocino and into the wet spots of the Shasta River basin, with up to 1 inch from near Ukiah northward to the bulk of the Shasta River basin and into most of the Feather River basin, with up to 0.5 inch from near the Russian River basin northward into the northern SAC Valley region and to near Hwy 50, with up to 0.25 inch from near Santa Cruz to the Delta to near YNP, with up to >0.1 inch from near Big Sur to Merced to near Kings Canyon.
Days 8-16; shows up to 3 inch over NORCAL, with up to 2 inches near the Delta diminishing to 1 inch for the SJV and the coastal portions of SOCAL. Two primary storm periods are shown during this time frame.
GFS 384hr, 16Day QPF Chart, depicting up to 3-4+ inches of precip for a large section of NORCAL as far south as Lake Tahoe, extending into the Central Sierra with up to 2 inches of precip for portions of CENCAL, up to 1 inch for portions of SOCAL. The storm periods are spaced into 3 individual storm events; 1) on Mar 25th to 26th, 2) on Mar 31st to Apr 2nd and 3) from Apr 3rdto Apr 4th. The largest event is the last.
Weekly Evapotranspiration rates for the local 7 Counties shows up to 1.08 to 1.27 inches of evaporation along the Westside with up to 1.00 to 1.05 inches of evaporation for the Eastside SJV with up to 1.16 to 1.21 inches for the South Valley. The Sierra Crest loss is 0.69 inch up to 0.80 inch with about 0.94 inch near Lake Isabella.
Water Vapor 4KM Image of the West Coast Friday, March 21st, 2014, shows a weak disturbance moving thru NORCAL with a dry slot. Enhanced lift over the Southern Sierra by this disturbance is producing cloudiness over the Southern Sierra and Tehachapi Mts.
Visible Satellite Image of the CA Friday, March 21st, 2014, shows most of CA abundantly clear with variable cloudiness over the Sierra and Tehachapi Mts.
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Comments and suggestions always welcome.
Atmospherics Group International
Dan Gudgel Steve Johnson