With over ½ of April gone, the month has been extremely warm…thus far. How warm? For Fresno the departure from average is currently showing an average monthly temp of a whopping +6.8° as compared to normal. Bakersfield’s departure from average is not far behind with a +6.1° increase above average. Those extreme warm departures from normal may soon diminish, as the incoming system on Tuesday brings cold air into the region and drops temps -5° to -8° below average for a few days and then is reinforced again on the 25th with more cold air from a much larger and stronger trough. The remaining days of April may counter-balance the earlier heat experienced during the first ½ of the month, as a procession of cool troughs dominate the forecast charts thru the end of the month. In fact, the temps projected for April, 26th to 29th could be down-right cold as minimum temps dip into the mid to upper 30°’s and max temps possibly only peaking in the 50°’s…more than -20° below average. Charts hint that the morning of the Mon, Apr 28th could see frost in the coldest areas…if the current charts verify. If this possible frost event does indeed verify, it would possibly set records as the latest frost in the climate history for the SJV, by beating the frosty morning of Apr 27, 1984 by one day later. This has a low confidence threshold, but should be monitored closely.
A thick blanket of clouds is holding temps unusually warm overnight, with many stations in the 60°’s and the Kern Cyn Powerhouse station reporting a 70° at 5am! Numerous Thunderstorms are expected over the Sierra Fri afternoon with less activity on Saturday. Easter Holiday is expected to be tranquil/mild and dry. Monday southerly winds ahead of an approaching storm will continue the warm spell to Day number 16. Showers may spread over the region overnight Monday and into Tuesday. The biggest impact this system will have on Tuesday is a dramatic drop in temps with reading dropping below normal into Wed. Many stations will struggle to reach 70° on Wed! A warming trend initiates on Thu. The Long Range into Fantasyland Forecast shows another cold trough of Low Pressure residing over the West Coast with unsettled conditions. The exact timing and strength issues abound on charts, but in general are holding the same trend for the past week. Therefore, look for cool wx to continue thru the end of the month with several chances of showers and/or Thunderstorms possible. It is also worthy of mentioning that several charts also show that if (big iffy) skies clear (post storm environment) that frost may be possible toward the end of the month. This should be regarded with low confidence, but nonetheless be monitored closely. The second half of April could go out with a bang if the current charts verify.
Enjoy the Easter Holiday with your friends and family. We couldn’t ask for more pleasant outdoor wx for the Easter Holiday Weekend!
The most recent CPC ENSO update shows an increasing probability of a warm phase ENSO event by this fall, with an increase in probability up to a 65% chance as illustrated in the chart below;
In addition to the increase probability chance of El Nino for next season, the CPC also shows the average intensity from models indicates a strength of less than 1.0°C, although it is noteworthy that the Scripps model places the anomaly above 1.0°C.
Fri, Apr 18th A zonal-type flow pattern is established across the PAC basin, with weak High Pressure over the PACNW and a weak trough passing thru CA which drops temps by a few degrees, with increased chances of Sierra convection. SPC has placed the Sierra and portions of the Mojave in a Categorical Outlook for Thunderstorms. Some of the Thunderstorms over the Sierra could be strong on Friday and may extend southward into the Tehachapi Mts as well. With mostly sunny skies, light winds aloft should carry the anvil blowoff eastward into the Owens Valley during the afternoon. Temps continue to run about +10° above average. Overnight the trough shifts into SOCAL and the Great Basin.
MAX MIN PRECIP
Sat, Apr 19th The Low Pressure trough weakens significantly in the Great Basin as High Pressure regains over CA with temps near persistence. The main storm track continues to bring heavy rains into BC, Canada. Residual moisture from the trough brings another afternoon of convection for the Southern Sierra but probably not as active as on Friday. Overnight High Pressure moves onshore over CENCAL.
MAX MIN PRECIP
Sun, Apr 20th EASTER SUNDAY With 576dm High Pressure running thru NORCAL on a dry westerly flow pattern, expect a beautiful, warm/dry Holiday, with Sierra convection diminishing, however the Supercell parameter is painted for the Kings River basin, so that will be interesting to see verify. Overnight a trough of Low Pressure rapidly approaches the PACNW and NORCAL with an increasingly tight pressure gradient producing a stronger onshore flow. The flow pattern across the PAC basin is becoming more amplified with 2 troughs; 1) at the Dateline and 2) at 140W.
MAX MIN PRECIP
Mon, Apr 21st Forecast charts are in fairly basic agreement regarding the strength and timing of the arrival of the next storm. The sharp Low Pressure trough approaches the West Coast supported with a 100kt Jet Stream reaching SFO by evening. Although the cold pool is located west of the Olympics, weak vorticity manages to reach as far south as Santa Maria to Mt Whitney which could produce showers into the northern SJV and nearby Sierra as depicted on the precip chart below. Southerly (downsloping) winds developing ahead of the storm are likely to cause SJV temps to spike in the South Valley region. Overnight the trough axis travels into CA spreading clouds and showers southward in a narrowing and weakening frontal passage.
MAX MIN PRECIP
Tue, Apr 22nd As the trough axis pivots NE into OR, a NW Jet Stream over NORCAL at 100kts advects much cooler air into CA, with the -30°Cisotherm reaching Crescent City by early morning. Charts show most of the dynamics remain north of Modesto with the heaviest target focal pointing at the Tahoe region with high winds and lowering snowlevels. Current charts do not show the isothermic barrier moving south of the Delta region. Convective type showers occur throughout the SJV with Thunderstorms possible north of Modesto. Showers gradually diminish overnight as the system pulls eastward into the northern Rockies. A cool/dry NW flow pattern develops over NOR/CENCAL with dramatically cooler temps and possible gusty winds along the Westside. This cold air intrusion ends the 16 Day stretch of above average temps for Fresno, which included 5 days with temps of 90° or higher.
MAX MIN PRECIP
Wed, Apr 23rd As High Pressure noses into the PACNW, the NNW flow aloft continues to advect cold/dry air into CA with temps in the SJV struggling to reach 70°! Partly cloudy skies gradually clear as winds diminish, leaving the area calm and clear…with strong radiational cooling overnight, which produces temps in the coldest Ag Stations into the upper 30°’s.
MAX MIN PRECIP
Thu, Apr 24th While High Pressure and warming temps dominate CA, a large Low Pressure circulation covers the entire GOA with a moist Jet Stream flowing from Japan across the PAC basin to near 140W, then curving NE into BC, Canada. Heavy rains reach southward from BC, Canada into the PACNW with the trailing cold front aligned to the SW of the OR coast. The cold trough is slowly advancing to the east, with the axis crossing 140W. Overnight the clouds reach south to Monterey and rainfall reaches south to near the North Bay region, NE into the Feather River basin.
MAX MIN PRECIP
Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;
Fri, Apr 25th shows High Pressure building near 160W which sends a surge of cold air downwind into the trough that is approaching the West Coast. A powerful Jet Stream is wrapping around the trough, racing at 140kts. The very large storm center in the GOA contains a -32°C cold core. Rains continue to spread into NORCAL down to the Bay region to Tahoe with cloudiness as far as Cambria to Fresno. Overnight the cold trough continues to develop offshore, near the CA coastline with the cold front slowly migrating SE with increasingly heavier rainfall. Noting; a long-fetched Atmospheric River (AR) has developed in the WPAC basin, stretching from near 160E to near 150W…quite a distance. The backside of the West Coast trough is beginning to pull a slug of moisture from the AR toward the West Coast.
Sat, Apr 26th shows a low level close circulation forming over the North Coast region, which intensifies rainfall rates into NORCAL. Clouds spread into SOCAL and rains reach into CENCAL and the Southern Sierra as a strong vortmax approaches the Central Coast with top-of-the-scale energy. Cold air rapidly advects into NOR/CENCAL with the cold front and isothermic barrier reaching the Tehachapi mts by afternoon. Overnight heavy rains spread into CENCAL and the nearby Sierra as illustrated in the precip chart below;
Sun, Apr 27th shows the cold trough remains stationary over CA, with -26°C temps aloft spreading over CENCAL, producing conditions favorable for Thunderstorms. With the upper Jet Stream to the south, the SJV is placed in the favored left quadrant of the flow, a region capable of producing strong Thunderstorms. Overnight another vort disturbance travels SE from the GOA into the base of the trough offshore, taking aim at the Central Coast…just as the AR moisture arrives into the Central Coast!
Mon, Apr 28th shows a powerful storm developing over NOR/CENCAL with the formation of a 546dm Low Pressure circulation, cut-off upper level ‘devil’ containing a -28°C cold core and… absolute top-of-the-scale vort energy plowing into the Central Coast at mid day. Large scale uplift may inhibit individual Thunderstorm development in favor of a broad scale heavy rain event over CENCAL. The coastal region of SLO/Santa Barbara/Ventura Counties could receive heavy rains, especially along the south facing mountain slopes. Overnight the storm center remains stationary near Monterey with mod/heavy rains continuing to reach into CEN/SOCAL. Noteworthy; the WPAC Tropical region spawns a Tropical Cyclone at 10N 150E with rapid intensification.
Tue, Apr 29th shows a classic Thunderstorm pattern for CENCAL! A tightly wrapped 546dm Low Pressure circulation centered near Big Sur containing a-24°C cold core over CENCAL, with vorticity nearby, combined with a high speed Jet Stream over the Tehachapi Mts. Overnight the system shifts east into NV with wrap-around moisture continuing shower activity over much of CA. The WPAC Tropical Cyclone becomes a full-fledged TYPHOON which continues to intensify. Chart below illustrates the Low Pressure near the Central Coast with rainfall reaching into CENCAL and heavy rains reaching San Diego.
Wed, Apr 30th shows the storm system continues to move NE into ID, while the baggy trough pattern lags behind over CA, with clouds and some shower activity. Very cold air is in place over CA. Overnight skies become partly cloudy and winds calm, with rapid radiational cooling. The partly cloudy skies in the SJV may save the day from a potentially frosty morning. The WPAC TYPHOON continues to build.
Thu, May 1st shows flat High Pressure noses into the PACNW with a NNW flow pattern for NOR/CENCAL, with cold/dry air advecting into CA from OR. Another chilly night with less cloudiness with upper 30°’s widespread. The WPAC TYPHOON may reach SUPER TYPHOON status and has moved to near 15N 138E.
Fri, May 2nd shows weak High Pressure over CA with a light NW flow pattern, with partly cloudy skies, light winds and warming temps. The WPAC SUPER TYPHOON continues to move toward the Philippines.
Sat, May 3rd shows the absence of the Jet Stream from the Dateline east to the central CONUS. Very odd. With pressures slowly rebounding over CA, a warming trend initiates with a weak onshore westerly flow pattern. The storm track is displaced northward into BC, Canada. The WPAC SUPER TYPHOON moisture field begins to spread northward toward Japan. This feature could play an important part of the upcoming forecasts for the next 7 days, as the NPAC basin is still in a winter phase, while the WPAC Equatorial region has SST’s that are very high for this time of year. An early sign of the upcoming El Nino event… perhaps???
NEW CA RECORDS
Station New Record Old Record__
Lancaster 60° 55° set in 1989 and 1964. High Min
Indio 75° 73° set in 1947 High Min
Borrego 64° Ties 64° set in 1999 High Min
Day 1 – 5 QPF:
At 12Z (9am) Friday thru the period day Tuesday night (Wednesday @5am);
7 Day QPF Chart; shows up to 0.1 to 0.4 inch for the Southern Sierra and up to 0.1 to 0.5 inch for portions of NORCAL and up to 0.75 inch into the far NW coastal region. The region from the Russian River basin southward remains dry as well as most of the Great Valley and SOCAL.
16-Day QPF estimates (from the 0Z GFS model) for;
Days 1-7; shows up to 0.1 to 0.4 inch for the Southern Sierra and up to 0.1 to 0.5 inch for portions of NORCAL and up to 0.75 inch into the far NW coastal region. The region from the Russian River basin southward remains dry as well as most of the Great Valley and SOCAL.
Days 8-16; shows a long-wave trough setup for the West Coast which could bring significant rainfall into CA. The period from Sat, Apr 26th thru Tue, Apr 29th receives the bulk of the projected precip. Up to 3 inches of precip is possible for the Northern Sierra, 2 inches for the Southern Sierra and withThunderstorms for the SJV on the 28th and 29th.
GFS 384hr, 16Day QPF Chart shows up 3 inches of precip for portions of NORCAL, up to 2.5 inches for a vast region of CENCAL and up to 1-2 inch for the coastal region of SOCAL, diminishing to approx 1 inch for the deserts. The bulk of this precip occurs from Sat, Apr 26th initially over much of NORCAL, then spreading southward into CENCAL on Sun, Apr 27th and then into SOCAL on the 28th.
Weekly Evapotranspiration rates for the local 7 Counties shows up to 1.33 inch near Merced up to 1.55 inch western Fresno and Kings Co and up to 1.87 inch near Ridgecrest during the next 7 Days. The Sierra Crest evaporation loss is 0.83 inch in the upper Tuolumne River basin up to 1.42 inch near Isabella.
3 Month Outlook April/May/June for Precip and Temp
Water Vapor 4KM Image of the West Coast Thursday, April 17th, 2014, shows Low Pressure circulation SW of San Diego advecting subtropical moisture northward into CENCAL, while further north a cold front is moving southward thru NORCAL.
Visible Satellite Image of the CA Thursday, April 17th, 2014, shows considerable high cloudiness over portions of CA. A cold front is moving thru NORCAL, while subtropical cloudiness rotates into CEN/SOCAL.
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