NASA Celebrating Earth Day with a dramatic image of our blue planet looking at the USA/Mexico;




Following the mild/warm Easter weekend, Monday concluded the final day of the 16 Day long stretch of above average temps as forecast charts show much cooler temps during the next 6 Days, then returning to above average the last 2 days of the month, April 29th/30th.   Light amts of precip are expected into NORCAL Tue/Wed with moderate amts expected on Fri/Sat which spread into CENCAL with lighter totals. Thunderstorms accompany the Friday system as far south as Kern Co. Stay tuned for an update on the Friday Thunderstorm potential to be updated tomorrow, Wednesday as SEVERE charts become available.  Shower activity diminishes on Saturday, with clearing on Sunday.  On Monday rapid warming initiates as High Pressure intensifies over the West Coast bringing a brief heat wave which peaks on Wed, Apr 30th, with max temps expected to exceed 90° at many Ag Stations.  Slight cooling on Thu, May 1st and then dramatic cooling on Fri, May 2nd.  Rainfall during the Week #2 for CA is almost non-existent.


Blowing Dust Advisoryfor Tuesday for the SJV with winds gusting up to 35mph this afternoon producing many areas with blowing dust and reduced visibility and hazardous driving conditions. 


Past 30 Days Precip Accumulation for CA     Past 60 Days Precip Accumulation for CA     Past Year Precip Accumulation for CA

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Days 1-7;                                                          


Tue, Apr 22nd               Blowing DUST!  As the trough axis pivots NE into OR and the Great Basin a NW Jet Stream enters NORCAL at 100kts along the backside of the trough advecting much cooler air into CA withgusty winds.  Expecting temp drops of -15° to as much as -20° compared to Sunday/Monday!  This will be brought about by strong WINDS associated with this system that will generate BLOWING DUST and hazardous driving conditions throughout the SJV.  Charts show most of the upper level dynamic energy will have already past to the east Monday night and are now into NV, leaving behind much cooler temps, partly cloudy skies and gusty winds for the SJV.  Orographics keep snows falling into the High Sierra with upsloping NW winds screaming across the Crest and across the higher Mojave desert region.  Post frontal convective type showers occur with Thunderstorms possible north of the Delta thru Redding.  Shower activity up north gradually diminishes overnight as the system pulls eastward into the northern Rockies and weak High Pressure moves onshore.  This cold air intrusionends the 16 Day stretch of above average temps for Fresno, which included 5 days with temps of 90° or higher.

                                    MAX                                                     MIN                                                     PRECIP

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Wed, Apr 23rd              A progressive weak High Pressure ridge moves over the West Coast providing fair skies over the lowlands of CEN/SOCAL and diminishing clouds and shower activity over the Sierra, while an onshore westerly flow remains focused over the CA/OR border region producing rainshowers as far south as the South Fork of the Eel River NE into the Shasta River basin and with partly cloudy skies from SFO to near Tahoe.  Meanwhile further west a broad trough is developing in the PAC basin at 140-150W which advances eastward overnight with heavy rains returning to the PACNW coastal region and light rainshowers spreading over most of NORCAL down to a line from the Bar area NE to near Tahoe, and with partly cloudy skies spreading southward to near Santa Maria NE into the Southern Sierra.

                                    MAX                                                     MIN                                                     PRECIP

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Thu, Apr 24th               The large broad trough axis reaches 130W as winds aloft over CA veer to the SW.  The nose of a 110kt Jet Stream points at NORCAL, as a tightening pressure gradient develops over NORCAL with increasing onshore winds.  A narrow frontal boundary brings light rains into the far northern counties by afternoon with clouds spreading rapidly southward thru NOR/CENCAL.   Overnight as the trough axis continues to approach the CA coastline, the cold front dips southward into CENCAL running from near SFO to Tahoe with light rainshowers and clouds extending inland from near Big Sur eastward to Merced, then SE into the Southern Sierra.

                                    MAX                                                     MIN                                                     PRECIP   

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Fri, Apr 25th                 While the cold front dissipates, the trough axis moves onshore and is accompanied with the upper Jet Stream at 100kts aligned from the SW which advances into SOCAL.  Increasing vort energy and a moist flow aloft during the trough passage produces light to moderate convective-type showers as far south as Kern Co by afternoon.  Thunderstorms are also expected from Kern Co northward.  Due to the spotty nature of showers andThunderstorms, rainfall amts could vary widely.  Thunderstorm parameters for Friday are just barely out of range on the NAM charts, so we’ll need to examine those more closely tomorrow.  Currently the last chart valid on Thu night shows Supercell parameters popping up over the SAC Valley…at night!  So it will be interesting to see what occurs during Friday in the subsequent SEVERE charts later tomorrow.  Stay tuned for an update on Thunderstorm potential on Wednesday. As the front passes thru CENCAL it is accompanied by strong top-of-the-scale vort energy producing brief mod precip over CENCAL, especially in the North Valley and into the Southern Sierra near YNP.  700mb charts show a cold front with excellent lift producing abundant orographics into the Sierra on the SW flow.  Too bad this event is short lived.  As the -28°C cold core moves onshore near SFO, freezing levels plummet in the Sierra.  Overnight the cold trough shifts east into the Great Basin with a strong NW Jet Stream at 120kts moving over CA advecting cold air into the region.  Top-of-the-scale vort dynamics spread across the lower Mojave desert with high winds expected.

MAX                                                     MIN                                                     PRECIP   

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Sat, Apr 26th                As the trough kicks into the Rockies the tight NW flow continues to bring a moist onshore flow pattern into NORCAL with an additional cold front spreading more rains into the PACNW and NORCAL as far south as the Bay area to near Tahoe northward while CENCAL has partly cloudy skies.  Overnight the front spreads a little further south to near Monterey to near Tahoe with additional rainfall to the north. Showers are possible as far south as SLO along the coast and with scattered showers possible over the SJV with partly cloudy skies reaching into the northern portions of SOCAL.

MAX                                                     MIN                                                     PRECIP

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Sun, Apr 27th               The flat zonal-type flow pattern over the mid PAC basin begins to buckle, with a broad High Pressure ridge formation near 130W producing cooler/drier NW winds aloft with some moisture spilling into of NORCAL with possible light shower activity extending southward thru the Sierra, while most of the Great Valley is dry from Chico southward.  Overnight the storm track moves northward as 576dm High Pressure moves over CEN/SOCAL.

MAX                                                     MIN                                                    PRECIP

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Mon, Apr 28th              Models are recently trending with much stronger High Pressure building northward over CA which produces a brief heat wave!  Currently the 0Z GFS shows 582dm heights spread over CEN/SOCAL as far north as Monterey on Monday.  This produces a rapid warm up over CA with the storm track displaced far north into southern BC, Canada.   Overnight pressures continue to increase as a 586dm High Pressure circulation forms west of the LA basin as illustrated in the 500mb chart below, this is the beginning of a brief heat wave.   

                                    MAX                                                     MIN   

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Special Notation;   The recent model trend on Monday has lessened the impact of the Tuesday storm system with regards to precip, but are keeping the high winds intact.  The Friday storm system also appears somewhat weaker than previous models which is reflected with generally lighter QPF’s as well, although Thunderstorms could produce locally heavy rain and hail from Delano northward.  The largest fundamental change in model trends issued on Monday pertains to the brief heat wave which begins on Mon, Apr 28th and ends on Fri, May 2nd as strong High Pressure builds northward over CA into the PACNW with summer-like intensity.


The first 100° days in Fresno and Bakersfield occurred on April 23rd and 24th in 1910.



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


Tue, Apr 29th shows the storm track and upper Jet Stream at 135kts from the SW flowing into Vancouver, BC, Canada, while High Pressure noses into CA and NE into MT and Alberta, Canada.  582dm heights cover all of CA/NV/AZ and most of ID while a 587dmcirculation cell moves northward to a position over the SJV region, producing increasinglyhotter temps.



Wed, Apr 30th shows the axis of the High Pressure ridge narrows as a large GOA storm begins to drop SE toward the PACNW.  Temps expected to reach above 90°+ at many SJV Ag Stations.  A close monitoring of this heat wave is suggested.  This appears to be the peak day of the brief heat wave as pressures begin to fall overnight


Thu, May 1st shows the High Pressure retracting southward into SOCAL as Low Pressure becoming increasing dominant over the PACNW and NORCAL with onshore breezes bringing a cooling trend to most of NORCAL.  Overnight marine air floods inland in response to lower pressures which initiates a cooling trend.


Fri, May 2nd shows the new trough axis pivoting into the PACNW and grazing the NW portion of CA with only cloudiness in the far north, otherwise fair skies and breezes bring temps back down into the 70°’s.  Overnight the trough pivots eastward into ID/MT with High Pressure rebuilding further offshore west of CA producing a gentle NW flow pattern over CA with cool/dry winds.


Sat, May 3rd shows the base of the trough configuration is over the PACNW with a weak westerly Jet Stream at 80kts over OR and lighter winds over CA with fair skies and temps near persistence to the previous day.


Sun, May 4th shows a High Pressure ridge nearing the West Coast, with a NW flow pattern over CA and the storm track flowing into southern BC, Canada. 


Mon, May 5th shows a zonal flow into the PACNW as a trough approaches BC, Canada.  Weak High Pressure offshore west of CA produces a cool/dry NW flow over CA with mild temps into the 80°’s.  Overnight pressures increase slightly over CA.


Tue, May 6th shows a moist onshore flow reaches into the PACNW and NORCAL as far south as Cape Mendocino to the Shasta River basin with rainshowers, and clouds and chances of showers extending south to near a line from the North Bay region NE into the Feather River basin.  This moist onshore flow continues overnight.  Slow warming occurs over CENCAL with fair skies.


Wed, May 7th shows a weak shortwave trough reaches into the PACNW and increases the rainfall rates over OR and the far NW corner of CA into the Smith River basin.  Cloudy skies remain over most of NORCAL with chances of showers as far south as near Santa Rosa to near Chico and the Feather River basin while mostly fair skies prevail over CENCAL.






Station                         New Record                Old Record__








Day 1 – 5 QPF:

At 12Z (9am) Tuesday thru the period day Saturday night (Sunday @5am);




7 Day QPF Chart; shows up to 4-5 inches of precip into OR.  With diminishing amts further south into NORCAL with up to 3-4 inches into the Smith River basin, and up to 2-3 inches into the Eel, Klamath and Trinity River basins, decreasing to 1.5 to 2 inches into the Shasta River basin and up to 1.5 inches into the Feather River basin, up to 1 inch near Tahoe, up to 0.5 inch for most of the Southern Sierra Crest and up to 0.25 inch for the lowlands of CENCAL, diminishing to >0.1 inch for the Transverse Range, with most of SOCAL remaining dry.



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

Days 1-7; shows up to 4-5 inches of precip into OR.  With diminishing amts further south into NORCAL with up to 3-4 inches into the Smith River basin, and up to 2-3 inches into the Eel, Klamath and Trinity River basins, decreasing to 1.5 to 2 inches into the Shasta River basin and up to 1.5 inches into the Feather River basin, up to 1 inch near Tahoe, up to 0.5 inch for most of the Southern Sierra Crest and up to 0.25 inch for the lowlands of CENCAL, diminishing to >0.1 inch for the Transverse Range, with most of SOCAL remaining dry.

Days 8-16; shows most of CA with dry conditions.  Only the far northern counties in the NW and near the OR border are expected to receive rainfall, with up to 0.3 to 0.7 inch.



GFS 384hr, 16Day QPF Chart shows reduced amts of precip expected over CA as compared to previous model runs.  With a concentration of heavy precip forecast into the NW coastal region of up to 3-4 inches with rapidly diminishing amts further south showing only 0.5 to 0.7 inches for the Sierra as far south as YNP with lighter amts southward. 





Weekly Evapotranspiration rates for the local 7 Counties shows up to 1.26 inch near Merced up to 1.52 inch in western Fresno Co and up to 1.88 inch near Ridgecrest during the next 7 Days.  The Sierra Crest evaporation loss ranges from 0.66 inch in the upper Tuolumne River basin up to 1.39 inch near Isabella.






Water Vapor 4KM Image of the West Coast Monday, April 21st, 2014, shows a dry cold front moving thru CENCAL, followed by a trough axis which is approaching NORCAL with much cooler air.




Visible Satellite Image of the CA Monday, April 21st, 2014, shows a very rare sight over the SW portion of the SJV…a standing lenticularis wave cloud which is brightly lit into western Kings and Kern Counties!  High cloudiness associated with a dry cold front passing thru CENCAL is producing obscure sunshine over CENCAL while a thicker cloud mass approaches the NORCAL coastline from the approaching trough axis.




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