Dry With Above Average Temps Through the Weekend

Generally dry and zonal-type flow pattern across CA producing mostly fair skies should continue thru the weekend.  A weak shortwave trough should provide enough instability to bring showers and Thunderstorms to the Sierra Thursday thru Easter Sunday.  Otherwise this feature should have minor sensible impact upon CENCAL wx with temps remaining well above average for this time of year.  All extended forecast models show a cold trough moving into NORCAL on Monday spreading clouds and showers across the northern portions of the State on Monday, then sliding SE overnight.  By Tuesday a closed circulation develops over CENCAL with the backside northerly flow pattern bringing clouds, showers and much cooler temps into CA.  The bulk of precip should remain concentrated into the higher terrain of NORCAL, but showers or Thunderstorms in the Great Valley are possible.  There is much uncertainty regarding this system, so confidence is low, but at a minimum… expect cooler temps.  The morning of Wed, Apr 23^rd could see a few of the favored cold spot Ag Stations reaching into the 30°’s if skies are clear overnight.  See the Special Notation regarding next Tuesday below.  A warming trend begins again on Thu, Apr 24^th as High Pressure noses into NORCAL.  Longer range into Fantasyland show several troughs pushing thru CA with varying strength and trajectories.  At this time, about all we can expect from these systems would be cooler temps, as charts show the only one to bring NORCAL some showers is on Sun, Apr 27^th, otherwise the State stays dry.  The last frame of the 384hr GFS 16Day forecast model valid on May 1^st shows a large and powerful -32°C Low Pressure trough dropping SE toward the PACNW and NORCAL, unfortunately with little in the way of moisture associated with it.

Enjoy the Easter Vacation Holiday with your kids or grandchildren.  We couldn’t ask for more pleasant outdoor wx for the Easter Holiday Weekend!  Monday could be a transitional day to a very interesting Tuesday.

Record-Setting Heat is causing snow-melt as well as evaporation in the Sierra watersheds, an unwelcomed early event.  Hydrograph for the Merced River in YNP showing diurnal fluctuations on the increase. 

Record breaking snowfall season for Detroit;

http://www.weather.com/news/weather-winter/detroit-record-snow-season-20140415

Blood Red Moon Eclipse Monday night was spectacular!  It was very strange to watch Monday night. This was the first of 4 Lunar Eclipses, called a Tetrad.  The next is on Oct 8, 2014, then again on Apr 4, 2015 and the last Lunar Eclipse of the Tetrad is during a Super Moon on Sep 28, 2015.  NASA image below taken during the peak of the eclipse.

FORECAST SUMMARIES

Days 1-7;                    

Wed, Apr 16^th              High Pressure over the West Coast produces another warm day under a light NW flow pattern.  The storm track is displaced to the north, into BC, Canada and the PACNW, with NORCAL having a few passing clouds while CEN/SOCAL remain fair and warm.

                                    MAX                                                     MIN

Thu, Apr 17^th               The High Pressure migrates east as a weak trough of Low Pressure reaches into the PACNW with a trailing cold front which extends southward offshore from Cape Mendocino, producing partly cloudy skies over CENCAL, with increasing chances of Sierra convection. Overnight the dead on arrival cold front pushes thru CENCAL with some increased marine winds.

                                    MAX                                                     MIN

Fri, Apr 18^th                 The weak trough passage thru CA drops temps by a few degrees, with increased chances of Sierra convection.  Convective Parameters show possible Supercell Thunderstorm development near the Kings/Kaweah/Kern divide region.  Overnight the trough shifts into the Great Basin.

                                    MAX                                                     MIN                                                     PRECIP

Sat, Apr 19^th                The Low Pressure trough weakens significantly in the Great Basin as High Pressure regains over CA with temps recovering a few degrees.   The main storm track continues to bring heavy rains into BC, Canada.

                                    MAX                                                     MIN                                                     PRECIP

Sun, Apr 20^th               EASTER SUNDAY  With 576dm High Pressure running thru CENCAL on a dry westerly flow pattern, expect a beautiful, warm/dry Holiday, with less Sierra convection than in previous days.  Overnight a trough of Low Pressure rapidly approaches the PACNW and NORCAL with an increasingly tight pressure gradient producing a stronger onshore flow

                                    MAX                                                     MIN                                                     PRECIP

Mon, Apr 21^st              The GFS forecast charts show a sharp trough reaching toward the CA coastline, with a piece of vortmax energy reaching SFO to Monterey by late afternoon.  Since the arrival of the disturbance occurs late in the day, the interior portions of CENCAL may have ample time to warm back up to temps similar to Easter Sunday’s readings.  However, the 700mb charts show a slug of high level subtropical moisture spreading into CENCAL ahead of the cold front which may produce variable amts of cloudiness.  Therefore the sky coverage and temp forecast for this day could likely be revised, therefore low confidence.  Overnight charts show a closed circulation developing over NORCAL containing a -28°C cold core storm center located over NW CA, with the trough axis pushing into NOR/CENCAL and approaching SOCAL offshore west of Pt Conception. The -26°C isotherm reaches into Monterey to YNP with cold air advection aloft occurring.  A top-of the-scale vortmax punches onshore near SLO aimed at the Southern Sierra on a SW flow alignment.

MAX                                                     MIN

Tue, Apr 22^nd               The developing Low Pressure circulation drops SE along the CA/NV border region with a cloudy/showery regime for NORCAL and probable convection for the Southern Sierra.  A cold north flow pattern develops over NORCAL behind the storm which advects colder/drier air from WA/OR into NORCAL.  Overnight as the system shifts into the Great Basin, if skies clear over CA, strong radiational cooling could occur. 

                                    MAX                                                     MIN                                                     PRECIP

Special Notation;  The placement of a 546dm Low Pressure circulation with a -26°C cold core storm center over FAT next Tuesday is illustrated in the chart below.  If this chart does indeed verify it would put the SJV within the proper parameters for a SJV convective event to occur, especially from Fresno County southward.  Due to the potential instability this time of year, we could easily assume that if convection does fire up, that the storms located south and east of the Low Pressure circulation could be strong.  Stay tuned for further updates.  The consistency regarding this storm strength and trajectory has NOT been high, so we’re not too concerned just yet, but this should be monitored closely.  Forecasting an upper level ‘devil’ is most definitely problematic, especially for Day 7.

Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;

Wed, Apr 23^rd shows the Low Pressure cold core moving NE into UT with a cool/dry backside north flow pattern over CA allowing for chilly morning temps.  Partly cloudy skies clear out with the cool/dry north flow pattern continuing to advect into CA from the PACNW region.  Another chilly night could be on tap for CA as winds and clouds diminish.

Thu, Apr 24^th shows 576dm High Pressure moves onshore from SFO SE to the Imperial Valley with light winds and warming temps for all of CA, under fair skies except near the OR border region.

Fri, Apr 25^th shows a cold core Low Pressure storm dropping SE from the GOA toward the BC, Canada coastline with a trough extending southward to offshore CA.  Overnight the storm pivots NE into BC, Canada with a trailing cold front stretching SW from the Olympic region.  A southerly flow pattern develops over CA in advance of this system producing a strong warming trend.

Sat, Apr 26^th shows the offshore trough is slow to move eastward.  While the trough axis moves closer toward the CA coast, the southerly flow pattern continues to bring warmer temps to the interior of CEN/SOCAL, while NORCAL has some clouds.

Sun, Apr 27^th shows a zonal-type flow pattern over NORCAL with some moisture moving onshore north of Cape Mendocino and clouds down to Ukiah to the Feather River basin.  Precip is limited to the far northern counties near the OR border.  Overnight the active wx sags as far south as Santa Rosa to the Feather River basin, with clouds reaching down to Monterey to near Tahoe.

Mon, Apr 28^th shows the disturbance kicks eastward into northern NV and ID/MT, with a cool/dry NNW flow pattern developing over CA behind the storm.

Tue, Apr 29^th shows High Pressure nosing into NORCAL and the PACNW, while Low Pressure hangs back over SOCAL, producing a NE offshore flow pattern over CENCAL with fair skies and downsloping winds reaching into the SJV.  Meanwhile further north, a large storm is developing in the GOA.

Wed, Apr 30^th shows 576dm High Pressure moving onshore over the Central Coast with a NNW flow pattern over the region.  The large GOA storm is producing a developing trough far offshore, while High Pressure ridging covers the West Coast.

Thu, May 1^st shows a late season storm digging SE from the GOA toward the PACNW, with a 540dm Low Pressure circulation containing a large pooled-32° cold core.  At this time the storm appears to be moisture starved, but very cold with high amts of vort energy.  The final destination of this storm is unknown at this time, but due to its large size and cold nature it would be worth a close watch.

NEW  CA  RECORDS

Station                         New Record                Old Record__

Merced                          54°                               52° set in 2004  High Min

Merced                          87°                               84° set in 1999  High Max

Madera                         87°                               85° set in 1999  High Max

Hanford                         53°       Ties                  53° set in 1999  High Min

Hanford                         89°                               86° set in 1999  High Max

Bakersfield                    61°       Ties                  61° set in 1947  High Min            A 67 year old record.

PRECIPITATION FORECAST

Day 1 – 5 QPF:

At 12Z (9am) Wednesday thru the period day Sunday night (Monday @4am);

7 Day QPF Chart; shows up to 0.1 to 0.6 inch for the Southern Sierra and up to 0.1 to 0.5 inch for portions of NORCAL. The region from the Russian River basin southward remains dry as well as the Great Valley and all of SOCAL.

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

Days 1-7; shows up to 0.1 to 0.6 inch for the Southern Sierra and up to 0.1  all of SOCAL. The region from the Russian River basin southward remains dry as well as the Great Valley and all of SOCAL.

Days 8-16; shows most of CA stays DRY.  The only precip indicated is near the OR border with up to 0.2 inch.

GFS 384hr, 16Day QPF Chart shows up to 0.75 to 1 inch of precip for the far northern portions of CA near the OR border down to near Mt Shasta with diminishing amts to the south showing up to 0.5 inch possible north of Merced to YNP, with up to 0.2 inch from Kings/Tulare Co northward and up to 0.1 inch for SOCAL.  It is unusual to see that the coastal regions have far less precip than the interior, which suggests that the rainfall could be produced by upper level disturbances which are placed inland.

EVAPOTRANSPIRATION

Weekly Evapotranspiration rates for the local 7 Counties shows up to 1.42 inch near Merced up to 1.71 inch western Fresno Co and up to 1.93 inch near Ridgecrest during the next 7 Days.  The Sierra Crest evaporation loss is 0.93 inch in the upper Tuolumne River basin up to 1.57 inch near Isabella.

SATELLITE

Water Vapor 4KM Image of the West Coast Tuesday, April 15^th, 2014, shows a zonal-type westerly flow pattern across CA with a dry boundary moving thru CENCAL.  The storm track is displaced far north into WA.

Visible Satellite Image of the CA Tuesday, April 15^th, 2014, shows partly cloudy skies over CENCAL with SW winds aloft bringing occasional high cloudiness over the region. Coastal stratus has filtered into the coastal valleys and basins.  Especially noteworthy is the penetration of the stratus into the Altamont and Pacheco Passes and the Salinas Valley.

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