533
FXUS66 KHNX 172103
AFDHNX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HANFORD CA
203 PM PDT SAT OCT 17 2026
DISCUSSION
I AM GOING TO VENTURE OUT ON A BIT OF A LIMB HERE BY SAYING
TODAY OR TOMORROW (SUNDAY) WILL BE THE LAST TIME THE CENTRAL
VALLEY HITS OR IS WITHIN A FEW DEGREES OF 90F FOR HIGH
TEMPERATURES.
WHY DO I SAY THIS?
A BIG PATTERN CHANGE WILL EVOLVE STARTING MONDAY, AND MUCH OF
CALIFORNIA CAN EXPECT TROUGHING TO DEVELOP AND REMAIN ALL THE
WAY INTO THE 8-14 DAY PERIOD. BEFORE WE GET THERE, HIGHS IN THE
UPPER 80S OR LOW 90S WILL KEEP RELATIVE HUMIDITY AT NEAR
CRITICAL LEVELS IN THE FOOTHILLS, SIERRA NEVADA AND DESERTS WITH
A MODERATE FIRE RISK. HOWEVER, UNLIKE THE PAST FEW DAYS THERE IS NO WIND TO
ACCOMPANY THE DRY CONDITIONS. THE PROBABILITY FOR MAX TEMPS AT
90F OR ABOVE DROPS TO 40-50 PERCENT AND THAT'S ACROSS THE
SOUTH VALLEY ON SUNDAY,
THE UPPER AIR PATTERN RESPONSIBLE FOR THE HOT, WINDY AND DRY
CONDITIONS WILL OPEN UP MONDAY. A FORMIDABLE STORM, DROPPING
SOUTH FROM THE PACIFIC NORTHWEST WILL FILL THAT VOID. ALTHOUGH
IT IS ANOMALOUS, IT IS NOT TOO UNCOMMON FOR THIS TIME OF YEAR.
THERE IS EXCELLENT AGREEMENT BETWEEN ENSEMBLE MEMBERS AND
CLUSTER SOLUTIONS OF ITS POSITION JUST OFF THE SOUTHERN
CALIFORNIA COAST LATE WEDNESDAY, BEFORE MOVING ASHORE THURSDAY
AND FRIDAY. THIS MEANS THE BEST CHANCE FOR A WETTING RAIN (WHICH
IS 0.10" OR GREATER) FOR THE ENTIRE REGION WEDNESDAY INTO
THURSDAY. PROBABILITIES ARE HIGHEST IN THE FOOTHILLS AND HIGH
SIERRA WITH A 40-50% CHANCE OF A HALF INCH OF RAIN OR MORE BOTH
WEDNESDAY AND THURSDAY. SINCE THIS STORM WILL BE APPROACHING
FROM THE SOUTH AND WEST, SOME OF THE ENSEMBLE SOULTIONS WHICH
PROVIDE THE WORST CASE SCENARIO (ABOUT 20% OF THE MEMBERS)
DEPICT RAIN SHOWERS WITH EMBEDDED THUNDERSTORMS TRAINING OVER
THE EASTERN KERN DESERTS FOR SEVERAL HOURS (WHICH ARE VERY
VULNERABLE TO FLOOD WITH EVEN SMALL AMOUNTS OF RAIN) AND EASTERN
TULARE COUNTY. THE BEST CASE SCENARIO (ABOUT 50% OF THE
MEMBERS) WOULD EITHER NUDGE THIS PERSISTENT LINE OF RAINFALL
JUST FAR ENOUGH EAST, SO THAT IT MISSES KERN COUNTY OR THE
REGION JUST EXPERIENCES OFF AND ON SHOWERS, WITH A THUNDERSTORM
IN THE HIGH SIERRA, SIMPLY DUE TO THE INSTABILITY CREATED BY THE
COLD AIR ALOFT. REGARDLESS, CLOUDY AND RAINY WITH TEMPERATURES
STRUGGLING TO THE 70S IS SOMETHING THE CENTRAL VALLEY HASN'T
EXPEIRNECED CONSISTENTLY SINCE LATE SPRING. THE EXPECTED OUTCOME
IS CLOSER TO THE MAJORITY OF THE ENSEMBLE MEMBERS, BUT THERE
DOES REMAIN A NOTABLE CHANCE FOR HEAVY RAIN THAT WE WILL NEED TO
WATCH.
LET'S NOT FORGET ABOUT WHAT HAPPENS IN THE HIGH SIERRA. ALTHOUGH
RAIN AMOUNTS WILL BE LESS FOR THE NORTH CENTRAL VALLEY, SAY
MERCED, SNOW WILL FALLL IN OUR HIGH SIERRA WITH SNOW LEVELS
SITTING AT A 90% PROBABILITY OF BEING NO LOWER THAN 8000 FEET.
WITH THAT WRITTEN, SNOW WILL ACCUMULATE ALONG TIOGA ROAD/PASS IN
YOSEMITE NATIONAL PARK DURING THIS PERIOD, WITH A 40%
PROBABILITY OF 4" OF SNOW OR MORE FROM WEDNESDAY 5A TO THURSDAY
5A. KEEP THIS IN MIND IF YOUR TRAVELS TAKE YOU OVER THE MOUNTAIN
PASSES OF THE SIERRA NEVADA DURING THIS TIME.
AFTER THIS STORM PASSES, ENSEMBLE MODEL MEMBERS ARE IN ABOVE
AVERAGE AGREEMENT THAT ANOTHER STORM ARRIVES OFF THE CALIFORNIA
COAST FROM THE PACIFIC NORTHWEST AGAIN LATE NEXT WEEKEND, SO
THERE WILL BE A BREAK BETWEEN ACTIVE WEATHER.
PREV DISCUSSION
/ISSUED 1039 AM PDT SAT OCT 17 2026/
KEY MESSAGES...
1. WARM CONDITIONS THROUGH THE WEEKEND WITH TEMPERATURES 5-10
DEGREES ABOVE NORMAL.
2. MODERATE FIRE RISK WITH RELATIVE HUMIDITY BELOW 20% IN THE
FOOTHILLS, SIERRA NEVADA AND DESERTS.
3. HIGH CONFIDENCE IN A PATTERN CHANGE EARLY NEXT WEEK.
4. TEMPERATURES WELL BELOW AVERAGE NEXT WEEK WITH MODERATE
CONFIDENCE OF RAIN AND HIGH SIERRA SNOW EARLY WEDNESDAY MORNING
THROUGH THURSDAY.
AVIATION
VFR CONDITIONS WILL PREVAIL FOR THE NEXT 24 HOURS. WINDS WILL
VEER TO THE EAST AT ALL TERMINALS OVERNIGHT WHILE REMAINING
LIGHT.
CERTAINTY
THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS HIGH.
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS HIGH.
CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT
WWW.WEATHER.GOV/HNX/CERTAINTY.HTML FOR ADDITIONAL INFORMATION
AND/OR TO PROVIDE FEEDBACK.
HNX WATCHES/WARNINGS/ADVISORIES
NONE.
PUBLIC...MATTAROCHIA
AVIATION....MATTAROCHIA
WEATHER.GOV/HANFORD
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