274  
FXUS66 KHNX 222235  
AFDHNX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA  
335 PM PDT TUE MAY 22 2018  
   
SYNOPSIS
 
 
LOW PRESSURE OVER THE REGION WILL MOVE EAST TODAY WITH A BRIEF  
RIDGE OF HIGH PRESSURE OVER THE AREA WEDNESDAY AND THURSDAY. THIS  
WEEKEND, ANOTHER PACIFIC LOW PRESSURE SYSTEM WILL MOVE INTO THE  
REGION BRINGING ADDITIONAL COOLING.  
 

 
   
DISCUSSION
 
 
ANOTHER DAY OF UNSETTLED CONDITIONS OVER THE SIERRA NEVADA AND  
MOJAVE DESERT AS THE ASSOCIATED UPPER LOW DRIFTS PASS LAS VEGAS.  
WHILE OROGRAPHIC LIFT IS SUPPORTING WIDESPREAD SHOWERS OVER THE  
MOUNTAINS, A MORE NORTHERLY ORIENTATION OF THE FLOW ALOFT IS  
KEEPING MUCH OF THE VALLEY CLEAR AS THE BLOW-OFF FROM TODAY'S  
CONVECTION HEADS SOUTHEASTWARD. IN ADDITION, WITH THE MARINE LAYER  
(AS OBSERVED ON THE FORT ORD PROFILER) WAS REACHING UP AROUND  
3000 FEET MSL AND SPILLING INTO THE SAN JOAQUIN VALLEY AS  
OBSERVED ON VISIBLE SATELLITE IMAGERY. FURTHERMORE, SURFACE  
OBSERVATION FROM THE HIGHER ELEVATIONS OF THE WESTERN SIDE THE  
DISTRICT WERE BLOWING IN THE 15 TO 25 MPH RANGE AS COOL AIR  
FILTERS IN THE REGION. THEREFORE, THE AIR-MASS OVER THE VALLEY MAY  
BE TOO STABLE FOR SIGNIFICANT AFTERNOON CONVECTION. YET, WHILE  
THUNDERSTORMS ARE NOT VERY LIKELY OVER THE SAN JOAQUIN VALLEY,  
SOME CLOUDS COULD STILL DRIFT INTO THE AREA WITH A POSSIBLE  
SPRINKLE OVER THE EAST SIDE OF THE VALLEY BEFORE SUNSET TONIGHT.  
AFTERWARD, UPPER LOW LIFTS TOWARD THE NORTHERN ROCKIES AND ALLOWS  
A WEAK SHORT-WAVE RIDGE TO PUSH IN AHEAD OF THE NEXT DISTURBANCE.  
 
MODELS CONTINUE TO SHOW HIGHER UNCERTAINTY LEVELS WITH THE NEXT  
DISTURBANCE, EVEN AT THE 48 HOUR TIME FRAME, WHILE STILL  
INDICATING THAT A DISTURBANCE WILL FORM OVER THE EASTERN PACIFIC  
AT THAT TIME. ENSEMBLE MODEL UNCERTAINTY IS MORE WITH THE  
AMPLITUDE OF THE DISTURBANCE THAN THE PHASE(TIMING). THEREFORE,  
WITH MODELS SHOWING GOOD CONSENSUS OF HAVING THE AXIS OF THE  
DISTURBANCE ABOUT 525 MILES WEST OF THE BAY AREA BY WEDNESDAY  
EVENING, THE PROBLEM IS MORE WITH HOW DEEP THE DISTURBANCE WILL BE  
BEFORE SHIFTING ONSHORE BY THE END OF THE WEEK. MODELS COME INTO  
BETTER AGREEMENT BY THURSDAY AFTERNOON AS THE POSITION OF THE LOW  
MAY BE ABOUT 300 MILES DUE WEST OF THE BAY AREA. AT THAT POINT,  
WEAK DIFLUENT FLOW ALOFT MAY SUPPORT THE SIERRA NEVADA'S  
OROGRAPHIC LIFT AS SHOWERS CONTINUE OVER THE HIGHER TERRAIN. BY  
FRIDAY, ENOUGH LIFT MAY EXIST FOR POSSIBLE VALLEY CONVECTION NORTH  
OF FRESNO COUNTY AS THE LOW MOVES CLOSER TO SHORE AND VORT MAX  
ENERGY MOVES INTO THE REGION. WITH THE GFS/ECMWF/ CANADIAN AND  
NOGAPS SHOWING REDUCED UNCERTAINTY IN THEIR SOLUTION OF THE UPPER  
LOWS POSITION TOWARD FRIDAY NIGHT, WILL HAVE HIGHER CONFIDENCE  
LEVELS HAVE PRECIPITATION MAY OCCUR OVER THE REGION UNTIL THE VORT  
MAX ENERGY EXITS THE REGION TOWARD SATURDAY.  
 
THE BULK OF THE ENERGY FROM DISTURBANCE PASSING THROUGH AROUND THE  
END OF THE WEEK WILL BE EAST OF THE DISTRICT BY SATURDAY NIGHT. BY  
THAT TIME, WILL EXPECT LINGERING SHOWERS OVER THE SIERRA NEVADA AS  
WRAP AROUND MOVES VORT LOBES THROUGH THE AREA UNTIL MONDAY  
MORNING. WHILE MODELS SHOW NO SIGNIFICANT SURGES OF MOISTURE INTO  
THE AREA, ENOUGH MOISTURE SHOULD EXIST OVER THE REGION TO POP-UP A  
FEW LIGHT TO MODERATE SHOWERS DURING EACH EVENT. AFTERWARD,  
RIDGING RETURNS TO THE REGION NEAR THE MIDDLE OF NEXT WEEK. AGAIN,  
JUST LIKE THE FIRST SHORT-WAVE RIDGE IN THE SHORT TERM, THE SECOND  
WILL BE SHORT-LIVED AS MODELS CONTINUE TO SHOW A VERY UNCERTAIN  
LONG TERM PROGNOSIS. WITH THE AMOUNT OF ERROR IN THE LONG TERM,  
WILL INTRODUCE THE RIDGE AND HOLD OFF ON ALLOWING THE RIDGE TO  
EXIT THE REGION UNTIL AFTER DAY SEVEN. IN THE MEANWHILE, WILL KEEP  
TEMPERATURES AND WINDS ON A ROLLER-COASTER RIDE OF WARM OR COOL  
AND STRONG OR LIGHT DURING THE FORECAST PERIOD.  
 

 
   
AVIATION
 
 
A SLIGHT CHANCE OF POSSIBLE THUNDERSTORMS WITH LOCAL MVFR/IFR  
CONDITIONS MAY OCCUR OVER THE HIGHER ELEVATIONS OF THE SOUTHERN  
SIERRA NEVADA UNTIL 03Z WEDNESDAY. OTHERWISE...VFR CONDITIONS  
WILL PREVAIL ACROSS THE CENTRAL CA INTERIOR DURING THE NEXT 24  
HOURS.  
 

 
   
AIR QUALITY ISSUES
 
 
NONE.  
 

 
   
CERTAINTY
 
 
THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS HIGH.  
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS MEDIUM.  
 
CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT  
WWW.WEATHER.GOV/HNX/CERTAINTY.PHP FOR ADDITIONAL INFORMATION  
AN/OR TO PROVIDE FEEDBACK.  
 

 
   
HNX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
 
PUBLIC/AVN/FW...MOLINA  
SYNOPSIS...MOLINA  
 
WEATHER.GOV/HANFORD  
 
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