area forecast discussion  fxus66 khnx 132124  afdhnx  area forecast discussion  national weather service san joaquin valley - hanford ca  224 pm pdt fri jul 13 2007  .discussion...  nice afternoon across the valley with temperatures still in the   comfort range for this time of year. the 24 hour temp trends  show readings up as much as 3 degrees f across the central valley  with no change to readings up to 1 degrees f cooler across the  south valley where the marine air isn`t mixed out yet as is  typically the case. so far no clouds seen over the sierra and at  best one or two clouds may pop up here and there by later this  afternoon but that`s about it.  being it`s friday the 13th...you know something has to be up with  the forecast. well that something is lurking presently near the  northern baja peninsula in the form of an upper level low. this  low will spread in an increase in moisture into california tonight  into tomorrow as it moves northwest off the coast of socal around  an strong upper ridge centered over the western conus. this feature  doesn`t get far enough north to really bring an exceptional slug  of moisture into the area. looking at the h7 rh fields the gfs is  still by far the most moist with values as high as 55 percent  tomorrow afternoon across the kern deserts while the nam and ecmwf  only have h7 rh as high as 40 percent. have increased clouds  tonight over the kern deserts and the tehachapis as well as  tomorrow across the southern half of our cwfa to better blend in  with our neighbors` grids. however despite playing up the clouds  i am not all that impressed for much in the way of convection. the  h7 flow does turn more southerly but we still never get a really  good push of moisture. have generally targeted two areas for  convection during the afternoon...the tehachapis where something  may be triggered with the upslope flow and the sierra crest. the  nam li/s are progged to go to -1/-2 over the crest in tulare  county and h7 omega values are negative here as well. this is  typically a favored spot for convection so have tweaked pops up to  20 here. in the deserts...there is actually a good amount of  positive h7 omega values progged on the nam and the gfs brings  pwats to an inch at best near mojave and never brings the h85  dewpoints any higher than about 5c. thus opted to keep the deserts  dry and yanked out pops from here.  as we move into sunday...the upper low will drift northwest off  the coast of socal and moisture values decline across the area.  all the models turn the h7 flow southwest which will dry things  out. still with whatever moisture lingers near the crest, the nam  indicates there is just enough instability for a little afternoon  convection to fire. have kept in a low end pop here but anything  will ride across the crest given the steering flow. with an upper  ridge remaining over the western conus there is little change in  the heights across the area but any warming in the valley will be  attributed to more in the way of sunshine. look for monday to be  similarly warm to sunday as the heights don`t change much and we  should see a decent amount of sunshine. the remains of the upper  low off the coast of socal will get shunted northeast across the  cwfa monday night ahead of an approaching upper trough and bring  us some high clouds.  the aforementioned upper trough will move towards the pac nw by  monday night with the effects felt across the cwfa by tuesday as  heights begin to lower resulting in significant synoptic cooling.  expect a marine push as well as the sfo-las gradient tightens to  around 8mb per the gfs. have lowered highs some tuesday in all  areas. there is general agreement from the gfs, gem and ecmwf as  to this being a deep trough for this time of year. all three  models plunge the h5 588 height line as far south as orange  county, ca with gfs taking it just south of tijuana. as a result  figured there was enough model consensus to lower highs on  wednesday in all areas as well. some rebounding will take place  towards the end of next week as ridging tries to build back into  california from the east. other big concern with this trough could  be some locally breezy to windy conditions tuesday into wednesday  in the favored spots.  &&  .aviation...vfr conditions will prevail through 00z sunday. for  specific details...please refer to the tafs for kmce...kfat and  kbfl...and tweb routes 421 and 423.  &&  .air quality issues...  none  &&  .hnx watches/warnings/advisories...  none.  &&   __________________________________________________________________________  public...stachelski  aviation/fire wx...bean  weather.gov/hanford Boycott Internet Spam:  See <URL:http://spam.abuse.net/spam/ The National Weather Service data is made available courtesy of the National Science Foundation-funded UNIDATA Project and the University of Michigan.